Click on this page and type Ctrl+F to search for key words in titles and summaries.
Volume 48 - 2003
Volume 47 - 2002
- C. Both, Tunnel Fire Safety, Heron, Vol. 48 (2003) No. 1, pp. 3-16.
Summary: In forthcoming years, public and private transport in Europe requires large investments in infrastructural works. A significant part of the infra-structural works will consist of tunnels and other underground structures. Such structures have specific safety aspects. The safety of underground structures such as tunnels, is a point of increasing concern, both in Europe and elsewhere. Main reason is the increasing road and rail traffic and increasing tunnel lengths. New innovative safety measures have to be defined to avoid an increasing incident frequency in tunnels and to avoid increasing consequences of the incidents both in terms of causalities and material damage, including traffic obstruction. This paper briefly reviews the various aspects involved in the assessment of the structural integrity. Results of extensive research into three major infra-structural works are be presented: the fire safety of the tunnels in the High Speed Link, Betuweroute and the Western Scheld tunnel in the Netherlands. The results incorporate full scale fire tests investigating the structural integrity of high strength concrete tunnel linings.
Key words: Tunnels, Fire Safety, Concrete, Structural Integrity
- C.B.M. Blom, The Structural (Un)safety of Tunnels Explained by Analytical Approach, Heron, Vol. 48 (2003) No. 1, pp. 17-32.
Summary: From soft soil tunnelling practice it has been observed that the segmental thickness of the tunnel lining has a constant ratio to the tunnel diameter. Nevertheless many engineering models are published in literature and used in practice, which describe the structural behaviour of the tunnel lining. These models are used to analyse the structural safety of the tunnels. In this paper a new analytical approach is described which clearly reveals the influence on structural behaviour of longitudinal joints and lateral interaction between adjoining rings of the lining. Furthermore it is explained that a common missing parameter in today's models is the influence of the construction of the tunnel, and especially the influence of grouting. In this paper the influence of the grouting is assessed. It turns out that the observed lining thickness can be dominated by the influence of grouting.
Key words: Tunnel, Analytical, Structural, Safety, Soft Soil, Grout
- K.J. Bakker, Structural Design of Linings for Bored Tunnels in Soft Ground, Heron, Vol. 48 (2003) No. 1, pp. 33-63.
Summary: The increase of bored tunnels in the Netherlands has raised the question how to design the tunnel structure in an efficient way. As a large part of the cost of a bore tunnel is related to the cost of the lining, it is important to design the lining in a cost-effective way. In the Netherlands it is customary to base the structural design of tunnel linings, on the use of models, validated models. Due to the increased flexibility in modelling quite often in engineering practice these models are numerical. Numerical models however are sometimes difficult to interpret, this contrary to the clarity of most empirical and analytical models. In this paper a number of, these simple models are used to evaluate different design aspects of the tunnel lining. These models are discussed in a comparison with measurements and results of more elaborate numerical analysis. The purpose of which is to show that tunnel lining behaviour can be understood, with relatively simple models. The advantage of simple models is that these can be used for a 1st order covering of the dominant mechanisms and for preliminary design. Empirical relations and analytical solutions generally give a good insight in the relevant issues. However to take into account the complexity of geometry, geology and construction method, in practice for a final design numerical models are necessary. Finally, a number of special issues, such as 3D effects, creep and longitudinal effects in the tunnel tube, and in addition to that, the effects of fire as well as some aspects of durability, are discussed.
Key words: Underground, Construction, Tunnels, Soft Ground Models
- G.P.C. van Oosterhout, Recent Dutch Experiences in Developing Structural Monitoring Systems for Shield Driven Tunnels, Heron, Vol. 48 (2003) No. 1, pp. 65-78.
Summary: This paper discusses two major structural monitoring programs that have been recently conducted in the Netherlands in the Second Heinenoord tunnel and Botlek Railway tunnel respectively. The Second Heinenoord tunnel was the first large diameter shield driven tunnel in The Netherlands. It was constructed in the period March 1997 to July 1998. Because of to its novel construction technique for the Dutch building community, a large monitoring program accompanied the construction of the lining. This paper focusses on the structural monitoring program at the Second Heinenoord tunnel. The monitoring concept, the execution of the monitoring and the lessons learned are discussed. Subsequently, the enhanced monitoring program for the Botlek Railway tunnel, that was conducted in 2000, is presented. Finally, some future developments in monitoring the structural behaviour of shield driven tunnels are discussed.
Key words: Shield Driven Tunnels, Structural Behaviour, Monitoring
- J.C.D. Hoenderkamp, M.C.M. Bakker and H.H. Snijder, Preliminary Design of High-Rise Outrigger Braced Shear Wall Structures on Flexible Foundations, Heron, Vol. 48 (2003) No. 2, pp. 81-98.
Summary: This paper presents a graphical method to optimise the position of outriggers on shear walls with flexible foundations. This location for the outriggers will cause a maximum reduction in lateral deflection at the top of the building. The method can be used for preliminary design of high-rise structures subjected to horizontal loading. The method requires the calculation of six structural parameters: bending stiffnesses for the shear wall and outrigger structure, an overall bending stiffness contribution from the exterior columns, rotational stiffnesses for the shear wall and column foundations in addition to a newly suggested bending stiffness parameter representing the structural behaviour of the flexible foundation beam connecting the foundation of the shear wall to the exterior column foundations. These parameters allow the derivation of two compatibility equations for rotations at the intersections of the neutral lines of the shear wall with the outrigger and foundation structures. They yield expressions for the restraining moments at outrigger and foundation levels that act in the opposing direction to the bending moment from the horizontal loading on the structure. Maximising the influence of the restraining moments on the horizontal deflections leads to the optimum location of the outrigger structure. Combining all stiffness parameters into two non-dimensional characteristic structural parameters allows the optimisation procedure for this type of structure to be represented by a single graph that directly gives the optimum level of the outrigger. It is concluded that all six stiffness parameters need to be included in the preliminary analysis of a proposed tall building structure as the optimum location of the outrigger as well as the reductions in horizontal deformations and internal forces in the structure can be significantly influenced by all the structural components.
Key words: Tall Buildings, Outrigger Structures, Shear Walls, High-Rise, Design Method
- E.M.P. Huveners, F. van Herwijnen and F. Soetens, Load Sharing in Insulated Double Glass Units, Determination of the Air Pressure in the Cavity due to Mechanical and Thermo-Mechanical Loads., Heron, Vol. 48 (2003) No. 2, pp. 99-122.
Summary: Glass is an indispensable building material because of the special properties. Glass has a low heat resistance and therefore it is a thermal leakage in the outer wall. Insulated double glass reduces the heat transfer tremendously. The closed air in the hermetically closed cavity is a good insulator. The magnitude of the pressure in a hermetically closed cavity is an unknown parameter. What is the cavity pressure if the temperature changed, ambient pressure changed, under a uniformly distributed load, under a concentrated load and the like? These influences were investigated by an analytical model and were verified by experimental research.
Key words: Glass, Insulated Double Glass Unit, Hermetically Closed Cavity, Load Sharing
- G.E. González, F. van Herwijnen, J.J.A. Janssen, S.P.G. Moonen and J.A. Gutiérrez, Lateral Resistance of Plybamboo Wall-Panels, Heron, Vol. 48 (2003) No. 2, pp. 123-144.
Summary: This paper deals with the experimental and theoretical behavior of plybamboo (kind of plywood made out of bamboo) wall-panels subjected to lateral load. The wall-panels are part of a house design method proposed in the author's PhD thesis for prefabricated social housing in developing countries. Sixteen fullscaled wallpanels with or without window and door openings were tested and their theoretical capacities estimated. Design wind and seismic loads were determined according to the International Building Code 2000. The results showed that all the specimens present ductile behavior adequate for expected wind and seismic loads. The theoretical models for calculating lateral capacities of timber framed walls gave lower values than the experimental ones. The wall-panels sheathed with plybamboo and traditional plywood showed similar behavior and hence, plybamboo could be used as an alternative sheathing material in timber frame construction.
Key words: Shear-Walls, Plybamboo, Timber Framed Walls, Structural Panels, Bamboo Structures
- T.G. Nijland and R.P.J. van Hees, Editorial, Heron, Vol. 48 (2003) No. 3, pp. 147,148.
- T.G. Nijland, S. Brendle, R.P.J. van Hees and G.J.L.M. de Haas, Decay of Rhenish Tuff in Dutch Monuments. Part 1: Use, Composition and Weathering, Heron, Vol. 48 (2003) No. 3, pp. 149-166.
Summary: Rhenish tuffs from the volcanic Eifel region, Germany, have widely been used as building stone in the Netherlands. Different kinds of tuff (Römer, Weiberner, Ettringer, Riedener) show different kinds of decay, and also within each group, remarkable differences in weathering behaviour occur. In the present study, a short introduction is given to the historic use of tuff in the Netherlands, and a survey of weathering patterns is presented. Fresh quarry samples and material removed from several Dutch monuments have been studied by polarization-and-fluorescence microscopy (PFM) and X-ray diffraction analysis (XRD). So far, no relationship between mineral assemblages and durability could be established.
Key words: Natural Stone, Tuff, Römer, Ettringer, Hasenstopler, Weiberner, Hohenleie, Weathering Patterns, Damage, Mineralogy, Zeolites, Analcime, Chabazite, Philipsite, Merlinoite
- R.P.J. van Hees, S. Brendle, T.G. Nijland, G.J.L.M. de Haas and H.J. Tolboom, Decay of Rhenish Tuffs in Dutch Monuments. Part 2: Laboratory Experiments as a Basis for the Choice of Restoration Stone, Heron, Vol. 48 (2003) No. 3, pp. 167-177.
Summary: Rhenish tuffs (Eifel, Germany), have been used as building material in the Netherlands since Roman times. They were the most important natural building stone in the Netherlands in early medieval times. In addition, tuff was used as raw material for production of trass, that served as a pozzolanic addition for mortars. Rhenish tuffs, notably Römer, Weiberner and Ettringer, show remarkable differences in decay. Ettringer tuff applied during late 19th -early 20th century restorations often shows severe deterioration, whereas, for example, most 14th century Römer in rampant arches on top of St. John's cathedral, 's Hertogenbosch, resisted weathering reasonably well, as do sculptures out of the more fine-grained Weiberner tuff on top of these. In order to obtain a better understanding of the processes underlying the decay of these tuffs and the compositional factors controlling them, a research project was started that includes both on site investigations of major monumental buildings in the Netherlands (partly) built with tuff and laboratory research. Fresh quarry samples of Römer, Ettringer and Weiberner tuff were used for selected physical characterization and testing, including a.o. hydric dilation, drying behaviour and frost resistance. One type of Römer showed a remarkably high resistance against frost. The results of the laboratory experiments on quarry samples are reported. The experiments provide a sound basis for the choice of restoration stone.
Key words: Natural Stone, Tuff, Römer, Weiberner, Ettringer, Damage, Laboratory Research, Drying Behaviour, Frost Resistance, Salt Crystallization
- T.G. Nijland, C.W. Dubelaar, R.P.J. van Hees and T.J.M. van der Linden, Black Weathering of Bentheim and Obernkirchen Sandstone, Heron, Vol. 48 (2003) No. 3, pp. 179-195.
Summary: Black weathering of sandstone in monuments is widespread. Some objects owe their name to it, like the Porta Nigra in Trier (Germany). Other than the black gypsum crusts common on limestone, the black weathering layer on sandstone is rather thin and well adherent. Formation of such layers on Bentheim and Obernkirchen sandstone, both widely used in the Netherlands, has been investigated by microscopy and whole rock chemistry. Samples were obtained from several monuments in the Netherlands, amongst them the Old and New Church (Delft), St. John's cathedral ('s Hertogenbosch) and St. Plechelmus' basilica (Oldenzaal). Microscopically, the layers are composed of algae and fungi, gypsum, airborne particles such as fly ash, and iron (hydr)oxides, present on the surface and in directly adjacent pores. Gypsum is present in all samples, algae are not, but typically occur in the most blackish layers. Black layers show significant increases in loss on ignition (LOI), total and organic carbon, total sulfur and iron, as well as Pb, Cu, Zn and Sn. Formation of thin black layers is evidently not due to a single process, but involves formation of gypsum, deposition of airborne material, microbiotic activity and dissolution and redeposition of Fe-(hydr)oxides.
Key words: Natural Stone, Bentheim Sandstone, Obernkirchen Sandstone, Black Weathering, Algae, Gypsum, Microscopy
- T.G. Nijland and T.J. Wijffels, Laser Cleaning of Rakowicze Sandstone, Heron, Vol. 48 (2003) No. 3, pp. 197-205.
Summary: Decisions about the cleaning of natural stone should always be made within the awareness of direct and indirect damage that may be the result of cleaning. During the last decade, laser cleaning of objects and monuments of natural stone has become increasingly popular. Whereas a considerable amount of literature has been devoted to the effect of laser cleaning on marble and limestone, research into the effects on sandstone is limited. In the present paper, the effect of two cleaning methods, viz. the combination of dry microblasting and laser and laser alone, on Rakowicze sandstone that had developed a thin black weathering layer, are reported and evaluated. Results of visual inspection, microscopic investigation and determination of water absorption and evaporation behaviour are enigmatic.
Key words: Natural Stone, Rakowicze Sandstone, Laser Cleaning, Black Weathering, Damage, Microscopy
- J.A. Larbi, R.P.J. van Hees and S. Naldini, Microscopic Study of Weathering of White Flemish Stone from the Monumental Church of Our Lady in Breda, The Netherlands, Heron, Vol. 48 (2003) No. 3, pp. 207-219.
Summary: This paper deals with the use of an integrated microscopic method to assist in the investigation of the causes and the extent of decay of the stones and ornaments in the gothic Church of Our Lady in Breda, The Netherlands. The purpose of the study was to determine whether conservation measures were necessary. As part of the investigation 8 fluorescent thin sections were prepared from cores removed from the Flemish sandy limestone, used to build parts of the church and 4 from cores of an oolitic limestone, used for some of the architectonic ornaments and examined by means of fluorescent microscopy. The results showed that the processes and extent of decay vary for the two types of stone, although the causes of decay were similar. In the case of the sandy limestone, the decay processes, mainly conversion of calcite to gypsum and the formation of black crusts, were found to be largely restricted to the fine-grained calcite matrix. With regard to the oolitic limestone, the processes of decay were found not only to be confined to the microcrystalline calcite matrix, but also to the calciticoolites. In both cases, however, the occurrence, distribution and interconnectivity of cracks and micropores seemed to play an important role in the decay processes. In general, the stones that had always been exposed to outdoor weather were found to be more severely decayed than those in sheltered areas.
Key words: Natural Stone, White Flemish Stone, Gobertange, Lede, Conservation, Microscopic Investigation
- C.W. Dubelaar, S. Engering, R.P.J. van Hees, R. Koch and H.-G. Lorenz, Lithofacies and Petrophysical Properties of Portland Base Bed and Portland Whit Bed Limestone as Related to Durability, Heron, Vol. 48 (2003) No. 3, pp. 221-229.
Summary: This study focuses on the differences in lithofacies and petrophysical properties of Base Bed and Whit Bed Portland limestone and the presumed relationships between these characteristics and the durability of this building stone. As Portland limestone probably will be used as a stone for several restoration projects in the Netherlands in the near future, it is of great importance to know the weathering behaviour, especially its resistance against freeze/thaw decay. Samples of Portland limestone were analyzed by means of thin section microscopy, X-Ray fluorescence spectroscopy, and measurements of petrophysical properties such as watersaturation, porosity, permeability and specific surface area. Distribution of pore throat diameters were analyzed by mercury porosimetry. Results of a freeze/thaw test performed on Whit Bed limestone were also taken in account. The Whit Bed consists of a medium grained, fine to coarse bioclastic oolific limestone (oobiosparite; oolitic grainstone). Generally the fabric is grain supported showing a large amount of open inter-particle pores. High effective porosity combined with high permeability (1000 - 1400 milliDarcy), predominantly reflect the open interparticle porosity. The Base Bed is also a coarse bioclastic oolitic grainstone, but the oolitic fabric shows a tighter, matrix-rich compacted texture. Samples from the Base Bed show differences in primary matrix contents compared to the Whit Bed and differences in diagenesis, resulting in different physical properties. For example, a lower effective porosity (15.11 - 15.99 vol.%) and a lower permeability (35.0 - 80.1 milliDarcy). It is concluded that a thorough study of lithofacies (especially microfacies) and analysis of microporosity reveal basic data for selecting the most durable type of limestone. In this particular case, using only samples from one quarry, the Whit Bed samples are thought to be the most durable ones.
Key words: Building Stone, Portland Limestone, Base Bed, Whit Bed, Lithofacies, Microfacies, Durability, Freeze/Thaw Decay, Microscopy, Mercury Intrusion Porosimetry
- J.A. Larbi, Effect of Stylolites on the Durability of Building Stones: Two Case Studies, Heron, Vol. 48 (2003) No. 3, pp. 231-247.
Summary: The mechanical properties and the durability of natural building stones are influenced to a large extent by inherent inhomogeneities. One of such inhomogeneities is a stylolite, particularly when it occurs in carbonate-rich rocks. Stylolites are irregular surfaces in which small tooth-like projections on one side of the surface fit into cavities of like shape on the other side. Many stylolitic carbonate rocks are generally dense and sound, and may perform excellently when used as facing stones or tiles. However, there are other types that are of inferior quality due to the type of materials filling the stylolites To the naked eye, such rocks may appear dense, homogenous and impermeable, but on a microscale, the stylolites may contain porous, permeable and water-sensitive materials, such as smectites that can adversely affect the durability of such rocks when exposed to the atmosphere. Experience shows that the use of an integrated method, consisting of traditional physical, non-destructive and durability tests, in combination with optical microscopy and X-ray diffraction analysis, often offers an invaluable means of evaluating the quality of such materials. In this paper, the use of such an integrated method to assess damage due stylolites in two separate natural stones is presented and discussed.
Key words: Building Stones, Stylolites, Inicroscopy, Inhomogeneities, Durability
- G. Ye and K. van Breugel, Three-dimensional Microstructure Simulation Model of Cement Based Materials, Heron, Vol. 48 (2003) No. 4, pp. 251-275.
Summary: This paper describes a computer-based numerical model for the simulation of the development of microstructure during cement hydration. Special emphasis is on the algorithm for characterizing the pores. This includes the porosity and the pore size distribution and the topological properties of the porous network. In order to do so, a serial sectioning algorithm and an overlap criterion were employed for the determination of the microstructure. The algorithm for calculating the pore size distribution was also developed. The thus obtained information about the microstructure during cement hydration was further checked against experiments.
Key words: Microstructure, Porosity, Percolation, Modeling, Cement-Based Materials
- M.C.M. Bakker and F.B.P. de Jong, Ultrasonic Underside Inspection for Fatigue Cracks in the Deck Plate of a Steel Orthotropic Bridge Deck, Heron, Vol. 48 (2003) No. 4, pp. 277-295.
Summary: Due to an unexpected increase of heavy traffic large fatigue cracks appeared through the deck plate of orthotropic steel bridge decks in the Netherlands. Visual inspection revealed that this particular type of crack initiates where a weld joins the deck plate, a rib and a girder. These critical points are commonly inspected from the roadside, which necessitates that the road is closed down for all traffic and that the wear layer is first removed. To overcome these costly drawbacks a new method is proposed that enables ultrasonic inspection of the deck plate from the underside of the bridge deck. The method requires a combination of two special measurement techniques, which are optimised for the bridge problem at hand. To detect the maximum crack depth an angled pitch-catch technique is employed. The crack length can be detected along the rib weld by employing the simpler pulse-echo technique. The crack depth and crack length are determined from the respective ultrasonic data sets by a calibration, which relates the number of detected waves to the actual crack size. The calibration is determined by ultrasonically monitoring the various crack stages during a fatigue test that is conducted on a bridge deck specimen. The original, uncracked state and the final state where the cracks can be visibly detected in the deck plate determine the extremes. The tests show that a reasonable accurate detection of crack size is quite possible, while the visual inspections prove to be useless until the crack has already grown completely through the deck plate. The new method provides a crack depth and crack length estimate with an accuracy of ±15 %.
Key words: Ultrasonic Inspection, Fatigue Crack, Orthotropic Bridge Deck, Steel
- T. Vrouwenvelder and E. Calle, Measuring Spatial Correlation of Soil Properties, Heron, Vol. 48 (2003) No. 4, pp. 297-311.
Summary: The probability of geo-technical failure depends for a significant part on random system effects, i.e. parallel system effects due to averaging of fluctuations along failure surfaces and series system effects due to partial correlation among potential failure modes. Decisive for these effects is the structure of spatial correlation of soil properties or, equivalently, the so-called scales of fluctuation. Although much is known about the implications of scales of random fluctuation, very little is known about its magnitudes in practice. Classical geo-statistical methods to evaluate the scale of fluctuation of a soil property are only effective if a large range of sample values is available. As the determination of mechanical soil properties may be quite expensive, the number of sample points in routine soil investigation is usually very limited. Consequently, classical geostatistical method may be of little help in the assessment of spatial correlation of mechanical soil properties. In this paper a new approach, based on Bayesian statistical inference, will be discussed. It will be demonstrated that this approach leads to fairly accurate estimates of scale of fluctuation in the case of limited number of measurements.
Key words: Soil Mechanics, Geo-statistics, Spatial Correlation, Bayesian Inference
Volume 46 - 2001
- C.M. Steenhuis, A.C.W.M. Vrouwenvelder, F. van Herwijnen, H.H. Snijder, Definitions of Resistance and Deformation Capacity for Non-Sway Steel and Composite Structures, Heron, Vol. 47 (2002) No. 1, pp. 3-27.
Summary: Resistance, stiffness and deformation capacity are three characteristics describing the behaviour of (statically loaded) structures. The stiffness relates mostly to the serviceability of the structure. The resistance and deformation capacity relate to the safety of the structure. Nowadays, the safety of structures is checked explicitly with help of probabilistic methods. Studies using these methods focus very much on the resistance (strength and stability) of structures. Normally the objective of such studies is the probabilistic assessment of partial safety factors for design standards. The item discussed in this paper is the definition of deformation capacity from the viewpoint of structural reliability. This definition cannot be seen independently from the definition of resistance. This paper presents the results of a deterministic parametric study on the definitions of resistance and deformation capacity. The structural system under consideration is a steel-concrete beam with two joints connecting the beam to a rigid core. The work presented in this paper should be seen as a step towards an understanding of the reliability of structures in relation to deformation capacity. The next step of this study will be a parameter study based on a reliability approach'). The objective of this work is to assess influencing parameters of the effect of deformation capacity on the reliability of structures. This study is carried out at Eindhoven University of Technology.
Key words: Steel, Composite, Resistance, Deformation Capacity, Definition, Reliability
- A.W.M. Kok, Artificial Orthotropy, Heron, Vol. 47 (2002) No. 1, pp. 29-51.
Summary: An homogeneous orthotropic plate model is presented for the idealisation of composed plate structures with orthotropy properties. The model requires the specification of 14 material parameters and couples membrane and bending forces. To find these parameters a finite element procedure is proposed that calculates these parameters with the help of a plane strain analysis and a simple potential analysis for a series of basic load cases. These parameters are substituted into the orthotropy model for the analysis of the homogeneous orthotropic plate. Both analysis steps can be performed with simple 2D finite element programs such as KOLA. Two examples show the performance of these models.
Key words: Orthotropic Plates, Finite Element Method, Bending of Plates, Twisting of Plates, Composed Structures, Hollow Core Slabs
- A. Bigaj and J.C. Walraven, Size Effects in Plastic Hinges of Reinforced Concrete Members, Heron, Vol. 47 (2002) No. 1, pp. 53-75.
Summary: Reasons for size dependence of rotation capacity of plastic hinges are discussed. The increase of ductility with decreasing member size is interpreted from the viewpoint of fracture mechanics of concrete. The results of the introductory test series on simply supported slender beams loaded in three-point bending are discussed. A new model for the calculation of the rotation capacity is described, which takes into consideration the strain localisation in the damage zones in the hinge region. In particular, the way of implementing the Fictitious Crack Model, the Compressive Damage Zone Model and a new fracture mechanics based bond model that takes into account the steel stress level (e.g. the yielding of reinforcement) is explained. The results of parameter studies on size effects in plastic hinges are described. Special attention is given to the influence of reinforcement arrangement and of the flexural crack pattern. In conclusions the importance of the size effect in practical design situations is examined and the need for altering the existing design rules in the light of the possible member size dependence of the rotation capacity of plastic hinges is evaluated.
Key words: Reinforced Concrete, Plastic Hinge, Rotation Capacity, Size Effect, Strain Localisation, Damage Zone, Bond, Yielding
- J.A. Larbi, Editorial, Heron, Vol. 47 (2002) No. 2, pp. 79-80.
- T.G. Nijland and A.J.M. Siemes, Alkali-silica Reaction in the Netherlands: Experiences and Current Research, Heron, Vol. 47 (2002) No. 2, pp. 81-85.
Summary: In 1992, the first structure with deleterious ASR was diagnosed in the Netherlands, followed by the publication of the first Dutch guideline on the prevention of ASR in 1994. Since, ASR has been demonstrated in 40 to 50 structures over the country. Development of ASR in a series of structures on a major Dutch motorway, built in the late sixties - early seventies of last century, has provoked new research and discussions, aiming at the revising of guidelines on ASR-prevention and development of guidelines dealing with ASR-affected structures. In the present paper, an overview is given of experiences with ASR in the Netherlands, and current research is introduced.
Key words: ASR, Assessment, Regulations, The Netherlands
- T.G. Nijland and W.A. de Bruijn, New Dutch Guideline on ASR-prevention, Heron, Vol. 47 (2002) No. 2, pp. 87-93.
Summary: In I994, the first Dutch guideline on the prevention of ASR was published. Since, deleterious ASR has been diagnosed in several structures. This diagnosis prompted the revision of preventive guidelines. In the current paper, an overview is given of preventive measures and aggregate testing methods required by the new Dutch guideline on ASR-prevention, CURRecommendation 89, which became effective in June 2002.
Key words: ASR, Preventive Measures, Regulations, The Netherlands
- H. Borsje, W.H.A. Peelen, F.J. Postema and J.D. Bakker, Monitoring Alkali-silica Reaction in Structures, Heron, Vol. 47 (2002) No. 2, pp. 95-109.
Summary: A large number of structures along motorway A59 are experiencing cracking due to alkali-silica reaction, ASR. From recent investigations, it appears that this cracking varies from innocuous to cracking that has led to structurally undesirable situations. For this reason, some structures have been structurally reinforced. With regard to the remaining structures, a range of measures are currently being taken to ensure that the amount of ASR-induced cracking will not increase.
Current experiences of rehabilitation of structures affected by ASR are rather limited. Therefore, the Civil Engineering Division of the Netherlands Ministry of Transport, Public Works and Water Management decided to monitor the structural behaviour of two viaducts on highway A59. This paper summarizes the final results of this pilot project, which started in 1998.
Key words: Alkali-silica Reaction, Monitoring, Structures
- T. Siemes, N. Han and J.H.M. Visser, Unexpectedly Low Tensile Strength in Concrete Structures, Heron, Vol. 47 (2002) No. 2, pp. 111-124.
Summary: During an extensive investigation of some 25 concrete bridges and other structures suffering from alkali-silica reaction it has been found that the uniaxial tensile strength of the concrete was extremely low in relation to both the compressive strength and the splitting tensile strength. It is known that concrete with damage due to ASR has reduced mechanical properties. The literature indicates that with an expansion of 1 ‰ a reduction of 30 % may occur. The reduction found in some of the bridges was, however, up to 82 % with an expansion between 0.5 and 1.0 ‰ There was no clear reduction of the tensile splitting strength and the compressive strength.
Previous research on older concrete structures without ASR showed that low tensile strength is not exclusively connected to the presence of ASR. Although not conclusive, Petrographic Fluorescence Microscopy (PFM) research and visual inspection of the structural damage of the concrete structures with ASR indicate that at least part of the damage must be due to ASR. The structural damage due to ASR and due to other causes cannot be distinguished.
Tests on reinforced beams taken from two of the ASR affected structures and tested in shear proved that the concrete had a reduced tensile strength, though the reduction was less than indicated by the uniaxial tensile tests. The orientation dependency of the tensile strength as found for these two structures can partly account for this difference. On the other hand, positive structural effects of ASR such as prestressing of the concrete due to the swelling within the reinforcement net can also explain this difference.
Key words: ASR, PFM, Tensile Strength
- J.A. den Uijl and N. Kaptijn, Structural Consequences of ASR: An Example on Shear Capacity, Heron, Vol. 47 (2002) No. 2, pp. 125-139.
Summary: Since the beginning of the nineties of the last century numerous viaducts in the Netherlands have been traced that suffer from ASR. Uniaxial tensile tests on cores drilled from the bridge decks sometimes showed a dramatically low tensile strength. Since these decks are not provided with shear reinforcement, the question was raised whether the residual shear strength would still satisfy the requirements, the more so as in large parts of the decks mainly horizontally orientated cracks had developed.
To answer this question six beams, sawn from two 35 years old viaducts, were subjected to shear tests in the Stevin Laboratory at Delft University of Technology. The observed crack development and shear strength could be explained by taking into consideration the influences of a longitudinal compressive stress due to the restraint of ASR induced expansion and an orientation dependent tensile strength.
Key words: Concrete, ASR, Tensile Strength, Shear, Anisotropic Material
- J.A. Larbi and J.H.M. Visser, A Study of the ASR of an Aggregate with High Chert Content by Means of Ultra-accelerated Mortar Bar Test and Pore Fluid Analysis, Heron, Vol. 47 (2002) No. 2, pp. 141-159.
Summary: Various studies have indicated that the use of some ultra-accelerated mortar bar expansion test methods for assessing the alkali-silica reactivity of concrete aggregates (particularly those using 1 M NaOH solution at 80 ºC) can give rise to misleading results causing certain types of aggregates to be inappropriately accepted. This is the case if the aggregates contain more than 2 % by mass of reactive constituents, in the form of porous chert or flint and chalcedony. To date, no explanations have been given for this anomaly. This paper deals with a study aimed at investigating this anomaly. A sample of crushed sea gravel, dredged from the southeast coastal waters of England, containing 12.5 % of reactive constituents, was used for the study. Fractions of the crushed sea gravel amounting to 0, 25, 50, 75 and 100 % of the total aggregate fraction and corresponding to 0, 3.1, 6.3, 9.4 and 12.5 % reactive constituents, were incorporated in mortar bars, which were subsequently subjected to RILEM ultra-accelerated mortar bar expansion test. At the end of the test, the bars were examined by means of concrete petrography to establish whether or not attack due to ASR had taken place. The study was designed in this way in order to examine whether or not North Sea gravel from the southeast coastal waters of England exhibits a pessimum effect.
Key words: Alkali-silica Reaction, North Sea Gravel, Chert, Mortar Bars, Pessimum, Pore Fluid
- J. Bisschop and J.G.M. van Mier, Drying Shrinkage Microcracking in Cement-based Materials, Heron, Vol. 47 (2002) No. 3, pp. 163-184.
Summary: In this paper the nature of drying shrinkage microcracking in a variety of model cementbased materials, as well as in more practical types of concrete is described. The model mixtures were studied to elucidate the mechanisms of drying shrinkage microcracking and the factors that influence these mechanisms. This fundamental knowledge is important for the development of microstructural models that predict concrete behaviour. The degree and evolution of drying shrinkage microcracking in concrete have been determined with an eye on the durability of drying concrete. It has been determined however, that under the given experimental conditions, drying shrinkage microcracking remained superficial and did not occur in the bulk of the dried concrete.
Key words: Drying Shrinkage, Microcracking, Concrete, Microscopy, Durability
- A.T. Vermeltfoort, Deformation of the Brick Mortar Interface in Compression and the use of ESPI, Heron, Vol. 47 (2002) No. 3, pp. 185-209.
Summary: For masonry loaded in compression, the interaction between brick and mortar is of main interest. Tests showed that the deformation-properties of the mortar itself could be measured with ESPI. With the usual measuring techniques this turns out to be difficult as only small gauge lengths are applicable. This paper discusses the ESPI measuring technique and shows some of the effects of joint imperfections on the behaviour of masonry loaded in compression. Precise quantitative information about the deformation of brick and mortar separately was obtained. It may be concluded that the load is mainly transmitted through the central 60 to 70 mm of the specimen. ESPI measurements under various stages of testing confirm the linear behaviour of the specimen up to 80% of failure load. The bottom load platen of the used moving seating arrangement had too much freedom of movement in relation to the bending stiffness of the specimen around the weak axes and caused unintended deformations. Lateral deformation could be measured quite simply with ESPI but only provided a general idea of the behaviour of the specimen.
Key words: Laser-speckle Pattern Interferometry, Masonry in Compression, Brick-mortar Interface Behaviour
- R.B. Polder and A.W.M. van den Hondel, Laboratory Investigation of Electrochemical Chloride Extraction from Concrete with Penetrated Chloride, Heron, Vol. 47 (2002) No. 3, pp. 211-220.
Summary: Chloride extraction of concrete is a short-term electrochemical treatment against corrosion of reinforcing steel. The aim is to remove chloride ions from the concrete cover in order to reinstate passive behaviour. Physically sound concrete is left in place. To make this method more predictable and reliable, a laboratory study was carried out. Concrete specimens with penetrated chloride were subjected to electrochemical chloride extraction. The influence on chloride extraction was studied of: cement type (Portland, blast furnace slag), water-cement-ratio, cover to the reinforcement, steel geometry, amount of charge passed and type of electrolyte. Additionally, some potential 'killing' factors and the effect of the treatment on corrosion pits were studied. Chloride profiles before and after treatment were measured. The durability of the final situation is predicted from calculation of the redistribution by diffusion of the remaining chloride ions. For various cement types and cover depths, the minimum amount of electrical charge was determined to obtain corrosion protection for at least 10 years. The presence of bending cracks in the specimens or tie wires close to the concrete surface did not have a significant effect on the extraction result. The test results suggest that active corrosion pits are extinguished by the treatment.
Key words: Concrete, Reinforcement Corrosion, Chloride Extraction, Desalination, Durability
- K. De Proft, G.N. Wells, L.J. Sluys and W.P. De Wilde, Combined Experimental-Computational Study to Discrete Fracture of Brittle Materials, Heron, Vol. 47 (2002) No. 4, pp. 223-241.
Summary: In this paper, a combined experimental-computational study of a double-edge notched specimen subjected to tensile loading is presented. In the experimental part, the loaddeformation response and the displacement field around the crack tip are recorded. An Electronic Speckle Pattern Interferometer (ESPI) is used to obtain the local displacement field. The experimental results are used to validate a numerical model for the description of fracture using finite elements. The numerical model uses displacement discontinuities to model cracks. The discontinuities are able to pass through finite elements. At the discontinuity, a plasticity-based and a combined damage-plasticity cohesive zone model are used, while the continuum remains elastic. Both local and global results from the numerical simulations are compared with experimental data.
Key words: Discontinuous Model, Monotonic and Cyclic Loading, ESPI
- M. Shamalta and A.V. Metrikine, Comparison of the Dynamic Response of One- and Two-Dimensional Models for an Embedded Railway Track to a Moving Load, Heron, Vol. 47 (2002) No. 4, pp. 243-262.
Summary: In this paper, the steady-state response of an embedded track to the axle loading of a moving train is studied theoretically using two models. The first and the second models are one-dimensional (1D) and two-dimensional (2D), respectively, and differ by the fact that the latter model accounts for the lateral flexibility of the concrete slab of the track. The loading is modelled by a harmonically varying load that uniformly moves along the track. The response to this load is studied analytically with the help of the Fourier integral transforms. The study is accomplished performing the following steps, every of which is accompanied by comparison of two models under consideration. Firstly, the dispersion curves are calculated and critical parameters (frequency and velocity) of the load are found that could lead to resonance in the structure. Secondly, displacements of the rails and stresses in the concrete slab are studied for various velocities and frequencies of the load. The results obtained from both models are compared to that one calculated using a Finite Element program. On the basis of a comparative analysis of results obtained from the 1D and 2D models it is concluded that in engineering calculations, the 1D model can be employed for a quick and sufficiently accurate assessment of the dynamic behaviour of the embedded track under a high-speed train.
Key words: Embedded Railway Track, High-speed Train, Moving Load, Dynamic Response, Radiation of Elastic Waves
- IJ.J. van Straalen and M.J.L. van Tooren, Development of Design Rules for Adhesive Bonded Joints, Heron, Vol. 47 (2002) No. 4, pp. 263-274.
Summary: This article deals with the development of design rules for structural adhesive bonded joints. In daily practice engineers are confronted with the problem to verify the reliability of their designs. This can be done with use of an experimental programme, but for the marine, transport, building and civil engineering sectors this will not be an option, because it is too expensive and time consuming. The use of design rules might be an alternative, but current guidelines for structural adhesive bonded joints do not guarantee the reliability. To develop design rules that meet the required level of reliability, new approaches have to be used. Such a systematic approach is presented in this article. It is based on the current structural adhesive bonding technology and on structural reliability methods. Partial factors are used to take the required reliability level into account. Additional conversion factors are introduced to cover the effects of ageing. Methods are discussed how to calibrate these factors. To illustrate the developed approach, examples of calibrating design rules for metal overlap joints with epoxy and polyurethane adhesives are presented.
Key words: Adhesive Bonded Joints, Reliability, Design Rules
Volume 45 - 2000
- G.F.J. Kruijtzer, A Stoneley-Gibson-Varga Elastic Stratum, Heron, Vol. 46 (2001) No. 1, pp. 3-25.
Summary: Non-linear governing equations and some special non-linear static solutions. The influence of geometrical non-linearity on the linear theory of staic subgrade reaction and surface wave motion of a Gibsion soil.
Key words: Non-Linear Elasticity, Geometrically Non-Linear Gibson Stratum, Subgrade Reaction, Indentation Excavation
- G.F.J. Kruijtzer, A Comparative Treatise on the Vertical Vibration of Rigid Bodies on Deep Elastic Strata, Heron, Vol. 46 (2001) No. 1, pp. 27-48.
Summary: Deep water, Gibson soil, Homogeneous (water saturated porous) isotropic elastic half-space. Compressible versus incompressible strata. Low frequency versus high frequency factors.
Key words: Lumped Parameters, Dynamic Subgrade Reaction, Floating Bodies, Resting Footings
- Y.M. de Haan and G.M. Sluimer, Standard Linear Solid Model for Dynamic and Time Dependent Behaviour of Building Materials, Heron, Vol. 46 (2001) No. 1, pp. 49-76.
Summary: Vibrations in building structures are almost always undesirable. Whether in the form of low frequency oscillations, or droning of the structure, or as audible noise, they may effect the comfort of the user. They may even effect the safety and the integrity of (parts of) the structure. Damping of mechanical vibrations has always been a point of consideration for the engineer. Presently, it is of increasing interest and importance for the building industry. There are several reasons for this: (1) increasing use of high quality materials which exhibit very low material damping, (2) tendency towards "slender" designing requiring a lower volume of (high quality) materials, thus offering less capacity for absorption of vibration energy, (3) excessive noise and vibration hindrance and interference in highly populated area's (particularly city centers), due to high concentration of structures including high rise buildings, surface- or underground infrastructure, combined with replacement of natural soil between them by low damping solid material; (4) necessity to meet higher performance standards and environmental requirements as to vibration hindrance and noise, (5) necessity to apply high vibration-absorbing materials and systems. Study and careful description of various sources and forms of damping, including the internal damping of materials, is a requirement for meeting these developments. This paper discusses the merits of a three parameter rheological model for modeling time dependent behaviour of materials in general and dynamic behaviour in particular, with emphasis on damping of free vibrations. This model is known in litterature as the standard linear solid (SLS). Damping of vibrations in materials is normally anticipated on the basis of the damping modes of the standard mechanical model for damping: viscous damping element parallel with a elastic element (spring). It is shown that these modes are not the general free damping modes for linear materials. When the three-parameter (SLS) model is adopted, the general damping modes do appear. The agreement between model and actual time-dependent material behaviour is acceptable for a wide range of materials with low as well as high damping under both free and forced vibration, over a wide frequency (or time) domain. Parameters can be adapted according to specific materials, including composite materials. The standard (springdamper) model retains its applicability for low-damping materials.
Key words: Internal Damping, Solid Damping, Free Damped Vibrations, Dynamic Modulus, Loss Factor, Relaxation, Standard Linear Solids, Composite Materials
- Ch.F. Hendriks and G.M.T. Janssen, Construction and Demolition Waste: General Process Aspects, Heron, Vol. 46 (2001) No. 2, pp. 79-87.
Key words: Recycling Options, Demolition, Seperation of Waste
- K. van Dijk, P. Boedianto, B.J.H. te Dorsthorst and T. Kowalczyk, Strategy for Reuse of Construction and Demolition Waste Role of Authorities, Heron, Vol. 46 (2001) No. 2, pp. 89-94.
Key words: Role of Authorities, Delft Ladder, Building Materials Decree, Landfill Ban
- Ch.F. Hendriks and G.M.T. Janssen, Application of Construction and Demolition Waste, Heron, Vol. 46 (2001) No. 2, pp. 95-108.
Key words: Reuse of Concrete, Reuse of Mixed Concrete and Masonry, Recycled Aggregates in Roads, Recycled Aggregates in Concrete, Reuse of Asphalt
- Ch.F. Hendriks and G.M.T. Janssen, Reuse of Construction and Demolition Waste in the Netherlands for Road Constructions, Heron, Vol. 46 (2001) No. 2, pp. 109-117.
Key words: Reuse of Concrete, Reuse of Mixed Concrete and Masonry, Reuse of Asphalt, Technical Requirements, Environmental Conditions
- F. Felix, A.L.A. Fraaij and Ch.F. Hendriks, Comparison of Stabilisation/Solidification-Treatments of Hazardous Waste Materials, Heron, Vol. 46 (2001) No. 2, pp. 119-133.
Summary: In this paper the advantages en disadvantages of three different Stabilisation/Solidification-treatments are discussed. The first treatment, cement based S/S-treatment, is based on the hydration reaction of cement by which heavy metals chemically and or physically are bound. Cement based S/S-treatment is more critical with regard to the used waste materials than most of the other S/S-treatments. For that reason, research particularly is directed on the enlargement of the chemical and physical bounding by adding additives. The compressive strength of the material is usually below the compressive strength of concrete, near 5 to 50 MPa. Moreover the materials are sensitive to moisture and fluctuation in temperature which can result in the formation of cracks.
The second treatment is based on the addition of organic binding agents. Bitumen is the most frequently used. In addition experience has been gained with S/S-treatments on the basis of styrene. Organic solidified waste materials show a slight leaching of components that mainly are implied physically. The materials show a high grade of impermeability in comparison with cement based solidified waste materials. Through this, not many requirements are set for the waste material. The compressive strength of the material is near 15 to 100 MPa. The materials are insensitive with regard to external influences. An exception comprises the presence of oxygen and UV radiation. The expenses, related to S/S-treatments with organic binders, are significantly higher than these of cement based stabilized waste materials. An aspect concerning the environmental benefit is possibly a waste-to-waste approach. Harmful influences for the environment are the emission of volatile components and the consumption of energy.
The third treatment is thermal S/S-treatment of waste materials. This technique falls into three groups: sintering, glazing and crystallisation. The difference with the three preceeding techniques is that the waste material is transferred into a crystalline, amorphous or ceramic material by raising the temperature. For the sintering, producing a ceramic material, a temperature between 800°C and 1150°C is required. Crystallisation and glazing takes place at melting temperature, approximately 1450°C. Gradual cooling of the melt at a temperature between 800°C and 1400°C provides an crystalline material whereas a rapid cooling provides a amorphous material. The leaching behaviour of the three materials is mostly favourable compared to the other two treatments. Little requirements are set for the waste material, but a high content of oxides and silicates is favourable. The stability of the products under the influence of external influences is reasonable. Possibilities of utilisation therefore are rather big. Expenses are between $75 and $350 per ton product depending on the possibilities of regenerating energy from the waste material. The high consumption of energy and the possibly created flue gas is, in certain cases, environmentally harmful. In general, there is a lot of uncertainty about the actual quality of S/S-waste materials. Some adequate information and an assessment method is missing. In addition, an assessment tool for the long term release of components due to application conditions is desired. Therefore, more research is needed towards the long term behaviour of the different S/S-waste materials. Because dumping capacity is more and more a problem, carefully controlled application of these materials in practice should be stimulated.
Key words: Immobilisation, Durability, Leaching
- Ch.F. Hendriks and C.M.T. Janssen, Testing Regulations and Procedures for Environmental Auditing of Recycled Aggregates, Heron, Vol. 46 (2001) No. 2, pp. 135-143.
Key words: Quality Certification, Testing, Environmental Conditions
- J.G.M. van Mier, J.C. Walraven, L.J. Sluys, A.L.A. Fraay and K. van Breugel, Experimental and Numerical Research Programme for the Design and Optimization of Various Aspects of Concrete Behaviour, Heron, Vol. 46 (2001) No. 3, pp. 147-150.
- X. Xiong and K. van Breugel, Isothermal Calorimetry Study of Blended Cements and its Application in Numerical Simulations, Heron, Vol. 46 (2001) No. 3, pp. 151-159.
Summary: Apparent activation energy (Ea) is generally used to consider the effect of temperature on the kinetics of cement hydration in the numerical simulation of cement hydration processes. This paper deals with an experimental study on the kinetics of Portland cement and blast furnace slag cement using isothermal calorimetry at 20, 30, and 40 ºC. Two different water/cement ratios were used, viz. 0.4 and 0.6. Based on the experimental data, Ea a for Portland cements and blast furnace cement was calculated dynamically with the progress of hydration. It was found that Ea a exhibits dependence on degree of hydration, water/cement ratio, and temperature. Variation of Ea along with degree of hydration may suggest a change in the mechanisms of hydration. Numerical simulation was done using HYMOSTRUC model with a new expression of Ea and good agreement with experimental data was found.
Key words: Isothermal Calorimetry, Apparent Activation Energy, Numerical Simulation, Blended Cements
- G. Ye, K. van Breugel and A.L.A. Fraaij, Experimental Study on Ultrasonic Pulse Velocity Evaluation of the Microstructure of Cementitious Material at Early Age, Heron, Vol. 46 (2001) No. 3, pp. 161-167.
Summary: This paper describes an ultrasonic experimental set-up to monitor the development of the microstructure of fresh concrete at different temperatures (isothermal curing at 10, 20, 30 and 50 ºC and water/cement ratios (0.40, 0.45 and 0.55). The Ultrasonic Pulse Velocity (UPV) is used as an indication for microstructure development of concrete at early age. The results indicate that the ultrasonic pulse velocity largely depends on the water/cement ratio and state of hydration during the first 24 hours. The numerical cement hydration simulation model HYMOSTRUC is used for investigating the relation between the change of microstructure and the evolution of ultrasonic pulse velocity. The relation between ultrasonic pulse velocity and compressive strength is almost linear at early stage. The ultrasonic pulse velocity method is proved to be applicable in the recording and monitoring the microstructure development and strength at early stage.
Key words: Ultrasonic Pulse Velocity, Cementitious Material, Early Age, Microstructure
- D. Jankovic and J.G.M. van Mier, Crack Development in Concrete due to Moisture Flow, Heron, Vol. 46 (2001) No. 3, pp. 169-179.
Summary: The goal of this study is to develop a numerical model for the simulation of crack growth due to moisture flow in the porous zone between aggregate and matrix (interfacial transition zone, ITZ), where cracking in concrete originates. Two models are coupled based on similarities in their mesh shape: a Lattice Gas Automaton for moisture flow and a Lattice Fracture Model for crack growth. The results of coupling analyses are presented for several cases.
Key words: Moisture Flow, Lattice Gas Automaton, Lattice Fracture Model, Interfacial Transition Zone, Concrete
- G.N. Wells and L.J. Sluys, On the Conceptual Equivalence of Embedded Strong Discontinuity and Smeared Crack Formulations, Heron, Vol. 46 (2001) No. 3, pp. 181-189.
Summary: Embedded discontinuity formulations have been recently presented as a method of incorporating displacement discontinuities in standard finite elements. These elements allow inelastic deformations to be modelled using discrete constitutive models at an internal interface. However, the actual formulation of these models is identical in concept to more traditional fracture energy regularised smeared crack models. Rather than adjusting the hardening modulus depending on element size, the inelastic strain itself is made dependent on element size. It is shown here that the embedded discontinuity idea and smeared crack models are conceptually identical.
Key words: Embedded Discontinuity, Smeared Cracks, Concrete Fracture
- I. Markovich, J.G.M. van Mier and J.C. Walraven, Single Fibre Pullout from Hybrid Fiber Reinforced Concrete, Heron, Vol. 46 (2001) No. 3, pp. 191-200.
Summary: Hybrid fiber reinforcement can be very efficient for improving the tensile response of the composite. In such materials, fibers of different geometries can act as bridging mechanisms over cracks of different widths. The fiber bridging efficiency depends on the interface properties, which makes interface characterization very important.
Therefore, single-fiber pullout tests from conventional matrices as well as from the fiber reinforced mortar matrices are performed. The composition of the mortar matrix has been varied as well.
The pullout response of single fibers generally improves with increasing percentage of fibers in the mortar. Moreover, pullout forces are generally higher when the matrix has a higher strength. In all these cases, intensive microcracking of the surrounding matrix can be observed during fiber pullout.
Together with single-fiber pullout tests, standard compression tests and splitting tensile tests, as well as workability studies have been performed, in order to provide experimental data for further research of the high-performance hybrid fiber reinforced concrete.
Key words: Fiber Reinforcement, Mix Design, Mechanical Properties, Fiber Pullout, Microscopy
- S. Grünewald and J.C. Walraven, Self-Compacting Fibre-Reinforced Concrete, Heron, Vol. 46 (2001) No. 3, pp. 201-206.
Summary: The project 'self-compacting fibre-reinforced concrete (SCFRC)' is part of the Dutch STW/PPM program -'cement-bonded materials'- DCT.4010. Subproject III to which the project 'SCFRC' belongs deals with the development of new high performance concretes. The project 'SCFRC' aims at investigating the effect of type and content of fibres on the characteristics of self-compacting concrete in order to optimise the mixture composition. Fibres are able to bridge cracks and to improve the ductility of otherwise brittle cementitious materials. Therefore, the addition of fibres might extend the possible fields of application of self-compacting concrete. Besides the properties in the fresh state, while the concrete still flows, the mechanical behaviour will be investigated. This paper aims at introducing the reader to the goals, methods of research, and first experimental results of the project 'SCFRC'.
Key words: Self-Compacting Concrete, Fibres, Mix Design, Mechanical Behaviour
- S.J.H. Meijers, J.M.J.M. Bijen, R. de Borst and A.L.A. Fraaij, Computational Modelling of Chloride Ion Transport in Reinforced Concrete, Heron, Vol. 46 (2001) No. 3, pp. 207-216.
Summary: Exposure to a saline environment is a major threat with respect to the durability of reinforced concrete structures. The chloride ions, which are present in seawater and de-icing salts, are able to penetrate the concrete up to the depth of the reinforcement. They can eventually trigger a pitting corrosion process. The assessment of a corrosion-free service life of concrete structures is of paramount economic interest. However, the modelling of the ingress of chloride ions is complicated due to various influencing factors and transport mechanisms. Here a computational model for chloride ion transport through a porous material is presented. Chloride ion transport in reinforced concrete is modelled by focusing on centimeter-level and setting up three coupled equations for heat, moisture and chloride ion transport respectively. Three quasi-homogeneous components are distinguished: mortar, aggregates and interfacial transition zones. The model is handled computationally by discretising in space according to the finite element method and discretising in time according to the finite difference method. Stationary and transient, linear and non-linear, homogeneous or heterogeneous calculations can be performed. By applying the model a number of examples have been elaborated; one of these is presented. This example focuses on the coupling between chloride ion and moisture flow.
Key words: Chloride Penetration, Reinforced Concrete, Corrosion, Coupled Transport, Porous Media
- E.L.J. Goossens, W.H. van der Spoel and E.L.J. Banchen, Moisture Transport in Coated Plaster, Heron, Vol. 46 (2001) No. 3, pp. 217-222.
Summary: In the framework of the research project: 'Water balance of water-borne paint systems on plaster substrates in relation to fungal growth', a study is carried out to moisture transport mechanisms in coated gypsum plaster. In this contribution, the set-up of the study is described. Besides a description of the experiments to investigate the moisture transport properties of the plaster, coating and coated plaster, attention is given to the effect of slight alterations of the paint formulation on the moisture transport characteristics of the final paint.
Key words: Wall Paint, Gypsum Plaster, Moisture Transport, Fungi, Moulds
- R.B. Polder, H. Borsje and H. de Vries, Prevention of Reinforcement Corrosion by Hydrophobic Treatment of Concrete, Heron, Vol. 46 (2001) No. 4, pp. 227-238.
Summary: Corrosion of reinforcement in concrete bridge decks may occur due to penetration of deicing salts, even in the presence of an asphalt overlay. This paper reports a laboratory study into additional protection of concrete by hydrophobic treatment. It was found that hydrophobic treatment strongly reduces chloride ingress, both during semi-permanent contact and under wetting/drying exposure. The water repellent effect remains effective for at least five years under full exposure to outside conditions. After five years, carbonation of concrete was found to be similar for non-treated and hydrophobised concrete. Under wet conditions, hydrophobic treatment does not stop ongoing corrosion that has been initiated by chlorides before the treatment. Methods and criteria for testing hydrophobic products are available. Hydrophobic treatment is an effective, low cost preventative measure against corrosion of reinforcement in chloride contaminated environment. In The Netherlands, it has become standard for all new concrete bridge decks.
Key words: Concrete, Reinforcement Corrosion, Hydrophobic Treatment, Chloride, Durability, Preventative Measures
- P.M. Esser, H.A. van der Sloot and W.L.D. Suitela, Harmonization of Leaching Tests: Leaching Behaviour of Wood, Heron, Vol. 46 (2001) No. 4, pp. 239-252.
Summary: The leaching behaviour of preservative treated wood was studied, using three existing leaching methods. This study was part of a European project "Harmonization of Leaching / Extraction Tests " (EU project SMT4-CT96-2066). The leaching methods were: 1. A diffusion tank test of 3 months with medium sized samples of 200 mm length (NEN7345), 2. A laboratory protocol of 3-4 days stirring in water with small samples of about 50 mm length (ENV 1250-2), and 3. A leaching protocol of five days with large samples of one metre length (shower test). Milled wood samples were used for assessment of the total potential of leachable preservative at different pH (pH-stat test). The wood samples were taken from CCA-C treated Norway spruce and Scots pine treated with a Cu-quat. From the results it was concluded that the leaching behaviour of wood is very similar to that of other materials containing organic matter. The pH has a significant effect on leaching of preservatives from wood. The leaching behaviour of the small samples (ENV 1250-2) showed much wider variations in results. It is concluded that the NEN7345 diffusion tank test method, which was developed for inorganic building materials, is also suitable for assessment of the leaching behaviour of preservative treated wood. An adaptation of the acidic pH conditions to neutrality of the leaching water used is recommended.
- T.G. Nijland and J.A. Larbi, Unraveling the Temperature Distribution in Fire-damaged Concrete by Means of PFM, Microscopy: Outline of the Approach and Review of Potentially Useful Reactions, Heron, Vol. 46 (2001) No. 4, pp. 253-264.
Summary: Concrete is a poor conductor of heat. Nevertheless, heating of concrete results in physico-chemical conditions shifting in or out the thermodynamic stability field of specific phases (minerals) in the concrete, effectuating their (dis)appearance. Metamorphic petrology is a branch of geology that deals with the study of such changes; as a basic approach to unravel the heating history of rocks, domains with phases (minerals) specific for a set of discrete physico-chemical conditions are delineated (mapped). Unravelling the heating history of concrete is important to forensic research or to determine whether a concrete structure subjected to fire and its components are still structurally sound. Analogous to metamorphic petrology, thermally triggered reactions in concrete result in changes in specific phases which may be used to trace isograds. In the case of heated concrete, these occur in response to temperature alone, and may hence be used to trace temperature variations in concrete with depth (isograds). The method involves a combination of visual inspection and the use of microscopic methods in a systematic way to study the thermally affected concrete. It is a powerful diagnostic tool that has successfully been applied in research and testing of concrete linings in tunnels, assessment of firedamage to structures and evaluation of fireproofing in waste incinerators.
Key words: Fire-Damaged Concrete, Concrete Petrography, Phase Changes, Analysis of Heating History
- P. Stroeven and M. Stroeven, SPACE Approach to Concrete's Space Structure and its Mechanical Properties, Heron, Vol. 46 (2001) No. 4, pp. 265-289.
Summary: Structural properties of particulate materials can be described in densities of the particle packing, more generally denoted as particle composition. Obviously, this global measure does not offer information on the way particles are mutually arranged in space. This is associated with particle configuration. This terminology and the associated categories of material behaviour that rely on either one of these extremes of structural properties are elaborated in this paper. The range of such properties will be between structure-insensitive ones, like mass or stiffness (Young's modulus), and structure-sensitive properties like crack initiation and tensile strength. The establishment of an experimental basis for the dependence of a mechanical property on certain structural features (and the associated micro-mechanical properties) would require extensive, cumbersome and complicated testing: mechanical testing for defining the very property, quantitative (section) image analysis and stereological three-dimensional assessment of the relevant structural features. 'Realistic' simulation of material structure by computer would therefore offer an interesting alternative. This paper introduces the SPACE system (Software Package for the Assessment of Compositional Evolution) as the most recent development in this field. It has been developed to assess the composition as well as configuration characteristics of dense random packing situations in opaque materials. This paper presents an introduction to the system and will thereupon highlight by means of illustrative examples of typical applications on different levels of the microstructure the system's capabilities. Although only a single application can be presented in this framework, they all concern areas of major engineering interest.
Key words: Composition, Configuration, Interfacial Transition Zone, Material Model, Particle Packing, SPACE, Stereology, Structure-Sensitivity.
Volume 44 - 1999
- C. Esveld, Editorial, Heron, Vol. 45 (2000) No. 1, p. 2.
- C. Esveld, Jettisoning Ballast en Route to the Next Millennium, Heron, Vol. 45 (2000) No. 1, pp. 3-8.
Summary: Railway engineering has been a traditional discipline for over hundred years. Most developments were based upon experience and progressed thus very slowly. Recent proposed new railway structures and new applications make the traditional empirical approach ineffective. To support the new developments much more research, both experimental and numerical, is required. This paper gives an overview of the role of TU Delft in the projects that were carried out in this field.
Key words: Railway Research, HSL, Slab Track, DYNATRACK, Noise Reduction
- D. Vermeij, Design of a High Speed Track, pp. 9-23.
Summary: With the increase of train speeds, requirements to the track geometry become more and more important in the design of a new high speed line, since safety should be guaranteed and a high level of comfort is desired. Contrary to safety, which can be indicated by the wheel-rail forces in the track plane, the level of passenger ride comfort is determined by the motions of the passenger within the vehicle. Current geometry standards are based on a quasistatic consideration of a vehicle in a horizontal curve and do not take into account the characteristics of the rolling stock, track and substructure. A three-dimensional simulation program was built in order to simulate the dynamic behaviour of a high-speed train as a result of the track alignment and to determine the level of passenger ride comfort by calculating the accelerations of the coach. When evaluating track alignment and the influence of the rolling stock, these simulations show that the dynamic behaviour of the vehicle is not only determined by the amount of noncompensated lateral accelerations or cant deficiency / excess, but also by the geometry of superelevation ramps and the type of transition curves.
Key words: Design, Alignment, Computer Modelling, Passenger Comfort, Transition Curve, Cant
- K.H. Oostermeijer and A.W.M. Kok, Dynamic Behaviour of Railway Superstructures, Heron, Vol. 45 (2000) No. 1, pp. 25-34.
Summary: Railways have always been designed on the basis of experiences from previous designs. With the coming of new types of superstructures, i.e. ballastless track, combined with a new field of application, i.e. high speed lines, the empirical design method is no longer applicable. The use of computer models which predict the dynamic behaviour of the track and the vehicle have become necessary for designing this kind of track to ensure a save and trouble free exploitation. In this paper a ballastless track with continuous support, the embedded rail structure Or ERC, is modelled with the use of the computer program 'Rail', a program which has been developed at the Delft University of Technology. Laboratory tests are carried out for the validation of the computer model. The dynamic behaviour of the ERC is compared to that of a classic ballasted track. The frequency response functions and the distance damping as well as the accelerations of a simplified vehicle are determined and compared. Furthermore a simulation of a complete Thalys high speed train running at high speed over the ERC is made giving information on the dynamic behaviour of the track and the comfort level for the passengers, the latter determined as acceleration levels in the vehicle.
Key words: Dynamic Track Analysis, Distance Damping, Vehicle Track Interaction
- A.P. de Man, Pin-Pin Resonance as a Reference in Determining Ballasted Railway Track Vibration Behaviour, Heron, Vol. 45 (2000) No. 1, pp. 35-51.
Summary: Pin-pin resonance is one of the most significant preferred vibration modes of beams, which are supported at equal distances, such as rails at sleepers in railway track structures do. Pin-pin resonance is a vibration that appears in one basic (first) mode and several higher modes, however the basic mode will have the highest amplitudes. In operational conditions of railways, pin-pin resonance only partly influences wheel-rail contact of the train while the speed dependent sleeper-passing frequency is more important. Among other track resonances, pin-pin resonance plays an important role in noise and vibration radiation of the rails and can be used as a meaningful instrument in track system dynamics recognition and optimization. However, existing simple analytic approximations are not sufficiently reliable to perform these recognitions. This will be shown in this paper by means of new tests and simulations that are based on improved models and methods but restricted to ballasted track structures.
Key words: Railwaytrack, Dynamics, Vibration modes, Simulation
- A.W.M. Kok, Finite Element Models for the Steady State Analysis of Moving Loads, Heron, Vol. 45 (2000) No. 1, pp. 53-61.
Summary: The analysis of structures subjected to fast moving loads is a subject of growing interest in railway and pavement engineering. The applications of transient analyses using finite element models, however, are still very limited. The faster a load moves the more elements we need to model the structure. Even at fast workstations and main frame computers a moderate accurate analysis requires a huge amount of computer time. Many problems can be solved more efficient by application of a steady state analysis using a moving reference system. Based upon this formulation we will develop finite element models that travel together with the moving loads. Such an analysis can be performed with the computer power and execution time necessary for the solution of a common static problem, thus at a normal PC. Especially in the design phase such an analysis is very attractive.
Key words: Moving Loads, Finite Elements, Railway Engineering
- V.L. Markine, A.P. de Man and C. Esveld, Optimization of an Embedded Rail Structure using a Numerical Technique, Heron, Vol. 45 (2000) No. 1, pp. 63-74.
Summary: This paper presents several steps of a procedure for design of a railway track aiming at the development of optimal track structures under various predefined service and environmental conditions. The structural behavior of the track is analyzed using a finite element model in which the track and a moving train are incorporated. Parameters of the optimum track are determined by applying a numerical optimization technique. The optimization method employed here uses Mutipoint Approximations based on Response Surface fitting (MARS). To demonstrate the robustness of the procedure, it is applied to a problem of optimal design of an innovative railway track for high-speed trains - a socalled Embedded Rail Structure. Requirements for the optimal design are related to the wear of the rails and wheels and the level of acoustic noise produced by a moving train. To obtain the optimal design, component dimensions and mechanical properties of the track are varied. Results of the optimization are presented and discussed.
Key words: Railway Engineering, Numerical Optimization, Dynamics
- A.S.J. Suiker, A.V. Metrikine and R. de Borst, Steady State Response of a Granular Layer to a Moving Load - A Discrete Model, Heron, Vol. 45 (2000) No. 1, pp. 75-87.
Summary: This paper discusses the steady state response of a rigidly supported, granular layer to a moving load. Accordingly, the dynamic behaviour of a ballast layer under an instantaneous train axle passage is simulated, where the rigid support reflects a substratum that is much stiffer than the ballast layer, e.g. ballast in a concrete railway tunnel or on a concrete railway foundation. The discrete nature of the layer is captured via a 9-cell square lattice. After deriving the equations of motion for the lattice, the long-wave approximation of the equations of motion is compared with the equations of motion for a continuum model. This leads to relations between the macroscopic constitutive parameters of the continuum and the microscopic constitutive parameters of the discrete lattice. Next, the boundary value problem is formulated and solved. The influence by the particle size, the damping characteristics and the load velocity on the layer response is demonstrated via a parametric study.
Key words: Railway Track, Ballast Behaviour, Discrete Lattice, Moving Load, Wave Propagation
- M.R.A. van Vliet and J.G.M. van Mier, Size Effect of Concrete and Sandstone, Heron, Vol. 45 (2000) No. 2, pp. 91-108.
Summary: A series of uniaxial tension experiments has been conducted to investigate the size effect on strength and fracture energy of concrete and sandstone. The experiments were carried on specimens of six different sizes in a scale range of 1:32. Depending on the material and the curing conditions a stronger or weaker size effect on the nominal strength occurred in the tests. The observed size effect was attributed to a combination of statistical size effect and strain gradients in the cross section of the specimens, which were caused by the specimen shape, load eccentricity and material inhomogeneity. The fracture energy was, irrespective of the type of material, found to increase with size going towards a horizontal asymptote for large sizes.
Key words: Size Effect, Concrete, Sandstone, Weibull Theory, Stress/Strain Gradients
- R.B. Polder and A. Hug, Penetration of Chloride from De-Icing salt into Concrete from a 30 Year Old Bridge, Heron, Vol. 45 (2000) No. 2, pp. 109-124.
Summary: This paper presents the analysis of chloride profiles obtained from a reinforced concrete bridge. It was the bicycle part of the Berkumer bridge near Zwolle, The Netherlands. For about 30 years, this bridge was exposed to de-icing salts. The bicycle lane was coated with an epoxy coating. The parapets (side walks) were left uncoated. A total number of 36 chloride profiles were analysed using a diffusion model. The chloride diffusion coefficient is typical for Portland cement concrete in wet conditions, about 3e-12 m2/s.
In the cycle-lane part of the bridge, a diffusion coefficient of 3e-12 m2/s and surface contents of about 2-4 % describe the penetration of chloride rather accurately. This is unexpected in the presence of an epoxy coating. It appears that the protective effect of the coating was practically lost after about 15 years of service. The presence of the damaged coating has however caused the concrete to remain relatively wet, so allowing quick chloride transport.
The non-coated parapets on the other hand, have not shown quick chloride penetration despite significant chloride loads (as demonstrated by significant surface contents). The calculations give quite low apparent diffusion coefficients for the parapet, which are not in agreement with typical values for Portland cement concrete (assuming near water saturation). Apparently the absence of a coating has allowed the concrete of the parapets to dry out substantially, so slowing down chloride transport. These results suggest that the protective effects of (epoxy) coatings in these types of structures should be reconsidered. It is suggested to improve the protective effect by applying hydrophobic treatment of the concrete before applying this type of coatings and it may be useful to monitor coating integrity. There appears to be a need for improved coatings for this type of applications, ideally combining high chloride penetration resistance, high water evaporation, good mechanical resistance and a long effective service life. Alternatively, the cover to the steel should be increased and/or a blast furnace slag cement (with higher resistance to chloride penetration) should be chosen.
Key words: Concrete, Reinforcement Corrosion, Chloride, Diffusion, Bridge, Coating
- G.K. van der Wel and O.C.G. Adan Moisture Transport and Equilibrium in Organic Coatings, Heron, Vol. 45 (2000) No. 2, pp 125-152.
Summary: Improving coating performance in regard of protection of substrates and structures against moisturerelated degradation requires detailed knowledge of underlying transport mechanisms. In this paper a review is given on transport and equilibrium sorption of moisture in polymer films and organic coatings. Polymeric material forms the continuous phase of a coating and is therefore important for transport properties. Besides polymer, coatings consist of pigments (colouring agents) and fillers (cheap minerals) and various additives, each of them affecting moisture transport. Firstly, in this paper typical transport and equilibrium characteristics of pure polymer films are covered, and secondly those of coatings, assimilating the impact of pigments, fillers and additives. Discrimination between Fickian and non-Fickian effects is usually made based on the appearance of kinetic absorption curves. Several types of curve are dealt with, and models that describe these curves are discussed. These include "two-stage" sorption, "sigmoidal" sorption and "Case II" sorption. The common practice of fitting Fick's law to kinetic data by means of relaxation parameters is criticised. Transport kinetics is modelled on the basis of kinetic plots, thereby introducing relaxation parameters in Fick's diffusion law. Although these models describe moisture transport in polymers reasonably, these models imply a lot of "curve-fitting", without a clear mechanistic foundation. Equilibrium sorption of moisture in polymeric systems is reflected by their sorption isotherms. Type 11 and III isotherms of the BET classification are commonly encountered, together with linear isotherms according to Henry's law. The suitability of porous media adsorption models for polymeric systems is discussed. These models are treated in relation to interactions of water in polymers, since localised binding of water to specific groups may justify the use of these models. Finally, the substantial - effects of pigments and fillers, as well as coating additives on moisture transport and solubility in coatings are dealt with. Pigments may lower moisture permeation, but nonideality of pigmentation reduces this effect. Coating additives increase moisture solubility, but only little is known in detail.
Key words: Polymer Films, Organic Coatings, Transport, Equilibrium Sorption, Moisture
- J.G.M. van Mier, Editorial, Heron, Vol. 45 (2000) No. 3, p. 154.
- T.O. Medani and A.A.A. Molenaar, Estimation of Fatigue Characteristics of Asphaltic Mixes using Simple Tests, Heron, Vol. 45 (2000) No. 3, pp. 155-165.
Summary: A simplified procedure for estimation of fatigue characteristics of asphaltic mixes is presented. The procedure requires the determination of the so-called master curve (i.e. the relationship between the mix stiffness, the loading time and the temperature), the asphalt properties and the mix composition. It is shown that the master curve does not only give information about the variation of the mix stiffness, the loading time and the temperature, but also on the fatigue behaviour of asphaltic mixes. This information can reliably be obtained from rather simple tests, which can be performed in any road-engineering laboratory. Procedures of the determination of the fatigue characteristics of asphaltic mixes from simple tests are of special interest in mix design procedures where the quality of various mixes with respect to fatigue and crack resistance has to be evaluated. It is obvious that such a procedure is also extremely attractive for specification and pavement evaluation purposes. An insight is provided as to how the fatigue parameters for an asphaltic mix can be estimated using the Wöhler approach.
Key words: Fatigue, Master Curve, Wöhler Approach, Simple Tests
- K.J. Jenkins, A.A.A. Molenaar, J.L.A. de Groot and M.F.C. van de Ven, Developments in the uses of Foamed Bitumen in Road Pavements, Heron, Vol. 45 (2000) No. 3, pp. 167-176.
Summary: Following the lapse in patent rights on foam-producing nozzles, the use of foamed bitumen for the improvement of road construction materials has become more accessible and as a result, it's use increased considerably in the 1990's. In addition, the applications of foamed bitumen process have diversified. No longer is the process only used for the production of cold bituminous mixes with good quality aggregates, but it is being applied to marginal materials including crushed building rubble, recycled materials such as reclaimed asphalt pavement (RAP), contaminated materials, surface dressings and even pre-warmed aggregates. Each application has its own requirements in terms of optimal foamed bitumen properties and mix requirements. This paper provides an overview of the applications of foamed bitumen, highlighting some of the fundamental differences between desired foam characteristics and typical mix properties.
Key words: Foamed Bitumen, Coldmix, Marginal Materials
- A.F.H.M. Visser and D. Priambodo Koesrindartono, Towards a Mechanistic Analysis of Benkelman Beam Deflection Measurements, Heron, Vol. 45 (2000) No. 3, pp. 177-195.
Summary: This paper introduces and describes the Benkelman beam deflection test. Furthermore Benkelman beam tests are simulated using two multi-layer programs, based on an elastic and visco-elastic material model for asphalt. The results of these two programs are compared with each other. Finally, using the model based on visco-elasticity as a benchmark, the limiting conditions for elastic analysis are indicated.
Key words: Benkelman Beam, Visco-Elasticity, Non-Destructive Testing, Lintrack
- A.A. van Niekerk, J. van Scheers, P. Muraya and A. Kisimbi, The Effect of Compaction of the Mechanical Behaviour of Mix Granulate Base Course Materials and on Pavement Performance, Heron, Vol. 45 (2000) No. 3, pp. 197-218.
Summary: The results of large scale triaxial tests (d x h=300*600 mm) as performed on a specific mix granulate compacted to four degrees of compaction (D.o.C.) are presented in terms of measured and modelled failure, resilient and permanent deformation behaviour. In addition finite element design calculations have been conducted on the basis of the measured mechanical behaviour to demonstrate the influence of the D.o.C. of the base course layer on the performance of different pavements. Thus in addition to the conventional design criteria of asphalt and subgrade strain (fatigue cracking and permanent subgrade deformation), safety against base shear failure and permanent deformation in the base course and sub-base layers, resulting in rutting at the pavement surface, have also been considered. The results clearly demonstrate the importance of adequate base course compaction on pavement performance and of considering design criteria for the base course and sub-base especially when dealing with pavements in which an important structural contribution is required from the base course and sub-base (thinner toplayers and small-element pavements). In such pavements stresses in the base should be limited to prevent base failure and to limit permanent deformation under repeated loading.
Key words: Mechanical Behaviour, Granular Base Course Materials, Compaction, Triaxial Testing
- S.M.J.G. Erkens and M.R. Poot, Determining and Modeling Asphalt Concrete Response (ACRe), Heron, Vol. 45 (2000) No. 3, pp. 219-236.
Summary: In road engineering research and design the principles of material mechanics have not yet become a standard tool. In this contribution a project aimed at applying these principles to asphalt concrete is presented. Attention is paid to the differences between the standard test procedures and those based on mechanics considerations, presenting examples of the disturbances that can occur to illustrate the need for mechanically sound testing. The general approach in the ACRe project is introduced, showing the material model utilised and the parameters that have to be determined. The physical meaning of the model parameters is mentioned the tests used for the model parameter determination, uniaxial tension and compression tests and four-point shear tests, are introduced. The uniaxial compression test is discussed in more detail, to illustrate the approach used in the test programme. The results from this test are also presented, as well as the way in which a general expression for the compressive strength of the material was determined on the basis of these results. Finally, an example of the application of the model for damage predictions in road engineering constructions is presented. In this example two different pavement structures are analysed, illustrating that this kind of analyses can show the different damage patterns that will occur. In current day road engineering design approaches for every structure the same location is considered normative. From observations in practise it is known that this is not the case and the differences observed in the simulations agree rather well with these observations.
Key words: Asphalt Concrete, Testing, Material Model, Finite Elements
- H. ter Huerne, Possibilities for Material Characterisation and FEM Simulation of Compaction Processes of Asphalt Pavements, Heron, Vol. 45 (2000) No. 3, pp. 237-252.
Summary: Scientific knowledge about how compaction processes of asphalt roads can best be managed in order to achieve homogeneous compaction results hardly exists. In particular when road construction takes place under poor external weather conditions this can be problematic. During these circumstances the workmen experience and professionalism have to be relied upon for realising quality in compaction. The research discussed here attempts to fill a lacuna in knowledge by simulating the compaction process with help of FEM methods. Because there is no model for the description of the mechanical behaviour of non-compacted asphalt concrete, a "Critical State" model out of soil mechanics is adopted. In the paper results of a first roller pass, based on an ALE approach, will be discussed. The calculations show a realistic stress and strain pattern in the asphalt mixture. For quantifying the parameters of the FEM material model, material measurements have to be carried out. For this activity standard laboratory equipment is not sufficient and therefore modifications of an existing piece of equipment will be proposed. In the project, a field experiment has been set up to validate the model.
Key words: Asphalt Concrete Material Model Compaction, FEM Simulation
- G.P.A.G. van Zijl, R. de Borst and J.G. Rots, Time-Dependent Fracture of Cementitious Materials, Heron, Vol. 45 (2000) No. 4, pp. 255-273.
Summary: The response of cementitious materials is highly time dependent. On the one hand, it can lead to delayed collapse of structures fabricated of such materials. On the other hand, the time dependence is associated with the relaxation of peak stresses, which avoids, or postpones damage. A finite element formulation is presented for the analysis of the time-dependent cracking of cementitious materials. The constitutive law incorporates continuum plasticity and linear visco-elasticity. The former accounts for crack initiation and propagation, while the latter describes the bulk creep via an aging Maxwell chain. The cracking velocity dependence, which considers the additional viscous effect in the fracture process zone, is also included. This contribution to the cracking resistance regularises the localisation process and also introduces the correct time scale. The simple framework of the model allows the inclusion of other important phenomena in cementitious materials, such as stress-dependent hygral and thermal shrinkage.
Key words: Concrete, Fracture, Creep, Shrinkage, Crack Rate
- A.G. Kooiman, C. van der Veen and J.C. Walraven, Modelling the Post-Cracking Behaviour of Steel Fibre Reinforced Concrete for Structural Design Purposes, Heron, Vol. 45 (2000) No. 4, pp. 275-307.
Summary: With the increasing number of applications in practice, the demand for standardised test methods and design rules for Steel Fibre Reinforced Concrete (SFRC) arises. Test methods need to be practical, which means that they have to be relatively cheap and simple to carry out. Design models should be easy to use and reliable. This paper presents a procedure to develop a post-cracking material relation for SFRC by means of inverse analysis. It shows that mean experimental results from three-point bending tests can be simulated with high accuracy using a bilinear stress-crack width relation. After determining the correct procedure to calculate the characteristic values, material safety factors are proposed dependent on the scatter in the post-cracking behaviour. Finally, a material relation is proposed that can be used for structural design purposes.
Key words: Design Relation, SFRC, Scatter, Softening Behaviour, Reliability
- H. Hofmeyer, J.G.M. Kerstens, H.H. Snijder and M.C.M. Bakker, Post-Failure Modes for Steel Sheeting Subject to Concentrated Load (Web Crippling) and Bending Moment, Heron, Vol. 45 (2000) No. 4, pp. 309-336.
Summary: Cold-formed trapezoidal sheeting of thin Steel plate is a very popular product for building construction. It combines low weight and high strength and is economical in use. To increase the insight into the behaviour of the sheeting, this article presents new experiments in which first-generation sheeting behaviour is studied under combined concentrated load and bending. The experiments show that after ultimate load, three different post-failure modes occur. Mechanical models have been developed for the three post-failure modes. These models can help to explain why a certain postfailure mode occurs.
Key words: Steel Sheeting, Concentrated Load, Web Crippling, Bending Moment, Post-failure.
Volume 43 - 1998
- A. van Beek and M.A. Hilhorst, Dielectric Measurements to Characterize the Microstructural Changes of Young Concrete, Heron, Vol. 44 (1999) No. 1, pp. 3-17.
Summary: The dielectric properties of concrete can be used to characterize the development of the microstructure of the cement paste. During hydration the microstructure changes and so does the amount of water in the pore structure. The different dielectric properties of the pore water and the solid phases can be measured with microwave frequencies. In this paper the dielectric properties of cement and concrete during hydration are discussed. The interpretation of the measurements to microstructure-related properties is shown. The connectivity of the pore system has been related to the conductivity of the cement paste. The conductivity versus strength relationship has been used for a practical application. This application concerns the strength development in young concrete in a non-destructive way. This method of monitoring the strength development has proved to be successful. The practical application is now tested on site.
Key words: Young Concrete, Dielectric Properties, Hydration, Pore Water, Strength Development
- A.C.W.M. Vrouwenvelder and P. Schießl, Durability Aspects of Probabilistic Ultimate Limit State Design, Heron, Vol. 44 (1999) No. 1, pp. 19-29.
Summary: An example calculation is given to demonstrate the various steps in a probabilistic approach of the durability aspects of structural reinforced concrete design. The results are translated into a verification procedure based on code type limit state formulations, characteristic values and partial factors. This way the durability aspect is a natural extension of the classical resistance verification where deterioration effects normally are neglected. The paper draws attention to a recent BRITE EURAM project on this topic.
Key words: Reliability, Durability, Concrete, Chloride Ingress
- B.T.J. Stoop and R.B. Polder, Redistribution of Chloride after Electrochemical Chloride Removal from Reinforced Concrete Prisms, Heron, Vol. 44 (1999) No. 1, pp. 31-44.
Summary: Electrochemical chloride removal (ECR) of reinforced concrete is an innovative repair technique gaining widespread acceptance. By removal of 1/3 to 2/3 of the chloride penetrated into the concrete cover it is possible to suppress chloride-induced corrosion of the reinforcement. A non-stationary distribution of the remaining chloride will remain in the concrete cover. This chloride will diffuse back to the reinforcement, which may reinitiate corrosion. In this paper the chloride redistribution inside concrete specimens over one year after removal is described. Based on these findings the redistribution of chloride over a period of 10 years was assessed by numerical calculations. It was found that in concrete with a low total initial chloride content and low chloride mobility (Blast Furnace Slag Cement, low water cement ratio), chloride removal treatment will suppress corrosion of the reinforcement over an extended period of time. In concrete with a relatively high average initial chloride content and high chloride mobility (Ordinary Portland Cement, high water cement ratio), reinforcement corrosion may be reactivated due to redistribution of chloride within a ten year period.
Key words: Reinforcement Corrosion, Durability, Electrochemical Chloride Removal, Desalination, Chloride Redistribution, Numerical Simulation, Concrete
- M.S. de Wit, Uncertainty in Wind Pressure Coefficients for Low-Rise Buildings, Heron, Vol. 44 (1999) No. 1, pp. 45-59.
Summary: This paper reports on an analysis of the uncertainty in wind pressure (difference) coefficients, which are assessed on the basis of generic knowledge and experimental data rather than with a specific (wind tunnel) experiment. The analysis is carried out on time averaged pressure coefficients in a specific case, concerning a low-rise building in an urban environment. To assess the uncertainty, structured elicitation of expert judgment is employed. Method and results are described here. The acquired uncertainty is compared to an estimate of the uncertainty that could be attributed to wind pressure difference coefficients obtained in a wind tunnel experiment. This comparison serves as input to a discussion whether expert judgment studies could develop as an alternative for wind tunnel tests.
Key words: Wind Pressure Coefficients, Wind Tunnel, Low-Rise Buildings, Uncertainty, Expert Judgement
- C.J.W.P. Groot and J. Larbi, The Influence of Water Flow (Reversal) on Bond Strength Development in Young Masonry, Heron, Vol. 44 (1999) No. 2, pp. 63-78.
Summary: Water loss from the fresh mortar is believed to be related to mortar-brick bond strength development in masonry. Recent research on mortar-brick bond has shown that, particularly, effects of water flow on the composition and the hydration conditions of the mortar-brick interface have to be taken into account to explain bond strength development. However, many cases of unexpected bond behaviour are still registered, and apparently the insight into this complex phenomenon is still incomplete. In this paper an attempt is made to increase the understanding by analysing in more detail the hydration conditions of the mortar at the interface. To this end, models of capillary water pressure and water transport for cylindrical capillaries (bricks) and water-containing particle systems (mortars) are analysed and applied to the evaluation of a series of bond strength tests. To enhance the potential for a more extensive analysis of the test results much attention is paid to the 'hygric' characterisation of bricks and mortars of the test series. It is concluded, that not only the water flow from mortar to brick (which takes place immediately after mortar-brick contact) but also a reversed water flow from brick to mortar (occurring after compaction and initial hydration of mortar) may significantly influence the bond strength development.
Key words: Masonry, Bond Strength, Moisture Transport, Porosity, Polarising and Fluorescent Microscopy
- M.R. de Rooij and J.M.J.M. Bijen, 'Active' Thin Section, Heron, Vol. 44 (1999) No. 2, pp. 79-90.
Summary: Optical microscopy using thin sections has become more and more important over the last decade to study concrete. Unfortunately, this technique is not capable of studying actually hydrating cement paste. At Delft University of Technology a new technique has been developed using 'active' thin sections. This technique allows microscopic observations of physicochemical processes during the first hours of hydration. This paper describes the construction of active thin sections and its development during a research project on the occurrence of syneresis, a known phenomenon from the field of colloid chemistry, in cement paste.
Key words: Active Thin Sections, Syneresis, Early Hydration, Chemical Admixture, Mineral Addition
- A.V. Metrikine, A.R.M. Wolfert and A.C.W.M. Vrouwenvelder, Steady-State Response of Periodically Supported Structures to a Moving Load, Heron, Vol. 44 (1999) No. 2, pp. 91-107.
Summary: Steady-state vibrations of periodically supported structures under a moving load are analytically investigated. The following three structures are considered: an overhead power line for a train, a long suspended bridge and a railway track. The study is based on the application of so-called 'periodicity condition', which implies that the shape of a structure is repetitive in time with space translation equal to the distance between neighboring supports. Main attention in the paper is paid to the effect of the load velocity on dynamic response of the structures. It is shown that the higher the load velocity, the wider the deflection field. Deflection of structures grows as the load velocity increases. This grow, however, can be not monotonical due to appearance of critical velocities related to resonances on subharmonics of a periodic structure.
Key words: Dynamics, Moving Load, Periodicity Condition, Waves, Resonance
- A.M.A.M Abdelkarim, A.C.W.M. Vrouwenvelder and M.D. Verweij, Analysis of the Dynamic Response of Layered, Elastic Media by Means of the Fast Fourier Transform, Heron, Vol. 44 (1999) No. 2, pp. 109-125.
Summary: A straightforward method is presented to calculate the three-dimensional response of layered, elastic half-spaces to a dynamic surface loading. The derivation of the method is performed in the wavenumber-frequency domain. Spacefrequency domain results are subsequently obtained through the application of the Fast Fourier Transform. The results show good agreements with the static solutions of Boussinesq and the dynamic solutions of Lamb.
Key words: Dynamics, Wave Propagation, Layered Media, FFT
- L.A.G. Wagemans, Editorial, Heron, Vol. 44 (1999) No. 3, pp. 129,130.
- A.J.M Leijten, Locally Reinforced Timber Joints with Expanded Tube Fasteners, Heron, Vol. 44 (1999) No. 3, pp. 131-161.
Summary: The study presented focuses on the development of a novel timber joint. Traditional timber joints with mechanical fasteners, particular dowel type fasteners, such as bolts exhibit a low strength and an unreliable stiffness and ductility caused by the presence of hole clearance and the unpredictable splitting of timber. The novel joint tackles all of these shortcomings. Local reinforcement glued to the timber members in the jointed area prevents unexpected splitting and results in the enhancement of the strength. By choosing a steel (gas) tube instead of a solid fastener, that fit in an over-sized hole, and by expanding the diameter after assembly of the joint, easy assembly and no hole clearance is insured. Due to the ductile behaviour of the reinforcement and the plastic deformation capacity of the tube the ductility of the joint is guaranteed. To assess the performance of this joints a comprehensive study was performed and reported in this article.
Summarising the experimental results, it can be stated that densified veneer (ply)wood is an excellent material to reinforce the timber joint. It possesses a high embedding strength and stiffness compared to softwood and is able to sustain the high concentrated loads imposed by the tubes. It is demonstrated that the new joint possess a reliable and high strength and stiffness capacity in monotonic loading. When certain requirements are fulfilled the joint shows a superior behaviour in cyclic loading. Design examples show that when used in portal frames a considerable amount of timber can be saved, up to about 40%, compared to joints with traditional dowel type fasteners, without a loss of safety.
Key words: Timber, Joints, Reinforcement, Testing
- A. Jorissen, Double Shear Timber Connections with Dowel Type Fasteners, Heron, Vol. 44 (1999) No. 3, pp. 163-186.
Summary: For the design of single fastener connections with dowel type fasteners Johansen's Yield Model [11, extended by Meyer [21 is generally adopted. However, since this model gives a poor prediction of the load carrying capacity of single fastener connections with rigid fasteners, an extension based on fracture mechanics considerations was developed . The strength of multiple fastener connections does not equal the strength of the single fastener connection multiplied by the number of fasteners. Generally the connection fails at a lower load because the timber splits and/or because of softening of the wood, which can be explained by the complicated stress distribution around the fastener position. The stiffness of multiple bolted connections is lower than the stiffness of the single bolted connection multiplied by the number of bolts, which can be explained by the individual hole clearances. Both the strength and stiffness of multiple fastener connections and the strength of single fastener connections with dowel type fasteners were studied.
Key words: Timber, Connections, Bolts, Dowels, Rracture, Model
- J.W.G. van de Kuilen, The Residual Load Carrying Capacity of Timber Joints, Heron, Vol. 44 (1999) No. 3, pp. 187-214.
Summary: Timber joints that have been preloaded for 2 to 8 years have been short term tested in accordance with EN 26891. The applied load levels varied between 30% and 50% of the average short term strength. The study comprised nailed, toothed-plate and split-ring joints. All joints were made of spruce and loaded in tension. The test results indicated no strength loss during this period. The strength of the preloaded joints was at least equal to the average short term strength of joints with no preloading prior to testing. Actually, the results indicate a slight increase in strength. The development of the strength of the joints in time is modelled with an exponential damage equation. The parameters of the damage equations have been determined on the basis of time to failure tests on the same types of joints.
Key words: Timber Joints, Residual Strength, Damage Accumulation
- M.L.R. van der Linden, Timber-Concrete Composite Beams, Heron, Vol. 44 (1999) No. 3, pp. 215-239.
Summary: In this paper an easy-to-use design model for timber-concrete composite beams is discussed. The model is applicable for computer simulations as well as for hand calculations. A research programme was started in 1992 in cooperation with the University of Karlsruhe, to study the loadbearing capacities of timber-concrete composite beams that are subject to bending. This research programme also included shear tests, creep tests, Monte Carlo simulations on floor systems and short term tests on a platelike timber-concrete structure, that are not included in this publication.
The load-slip characteristics of three different connector types were determined and thirty bending tests, ten for each connector type, were carried out on beams constructed with these connectors. The bending testspecimens failed due to combined bending and tensile failure of the timber, that is near knots or at a fingerjoint. Depending on the configuration of the beam and behaviour of the connectors, other phenomena could occur first. These phenomena however never initiated total collapse of the beam. Although timber beams normally exhibit brittle failure in the tensile zone, the composite beams showed a plastic behaviour before total collapse occurred. This behaviour was caused by plasticity of the connectors.
Hardly any plasticity was observed at the 5-percentile characteristic strength values for single T-beams and systems, when timber representing the Dutch strength class K17 was modelled. An elastic calculation model thus proves to be correct for most timber-concrete composite beam configurations, provided that timber beams of ordinary strength classes have been installed. This observation is no longer valid if glulam or timber from the highest strength classes is used. It shifts the characteristic strength values upwards and plasticity of the concrete compression zone or plasticity of the connectors occurs before the timber beam with characteristic strength collapses.
Key words: Timber-Concrete Composites, Connector, Bending, FEM, Plasticity, Monte Carlo, Failure, Strength, Slip, Stiffness
- J.A. Larbi, Editorial, Heron, Vol. 44 (1999) No. 4, p. 243.
- J. Bisschop and J.G.M. van Mier, Quantification of Shrinkage Micro-Cracking in Young Mortar with Fluorescence Light Microscopy and ESEM, Heron, Vol. 44 (1999) No. 4, pp. 245-255.
Summary: In this paper a method is described to quantify shrinkage microcracking in young mortar by means of crack mapping. Visualisation of the microcracks is realised with two techniques: Fluorescence Light Microscopy (FLO and Environmental Scanning Electron Microscopy (ESEM). The preliminary results obtained with the microcrack mapping method showed an increase in extent of shrinkage microcracking as a function of the hardening time of the young mortar, probably due to autogenous shrinkage. In the ESEM it was observed that microcracks in the young mortar open upon drying from relative humidities of about 25% to 1%. It is concluded in this paper that quantitative microcrack mapping at constant magnification should be done as a function of relative humidity of the sample and its environments.
Key words: Young Mortar, Shrinkage Microcracking, Fluorescence Light Microscopy, ESEM, Crack Mapping
- H.J.P. Brocken, J.A. Larbi, L. Pel and N.M. van der Pers, Composition of Mortar as a Function of Distance to the Brick-Mortar Interface: A Study on the Formation of Cured Mortar Structure in Masonry using NMR, PFM and XRD, Heron, Vol. 44 (1999) No. 4, pp. 257-270.
Summary: The formation of cured mortar structure in masonry was studied using multiple experimental techniques. Starting with fresh mortar, nuclear magnetic resonance (NMR) was used to measure the water extraction during brick laying. After curing, the composition of cured mortar was investigated with polarizing and fluorescent microscopy (PFM) and X-Ray diffraction (XRD).
Two typical mortars were investigated: a cement-lime mortar and a cement mortar with air entraining agent. The measurements indicate that the mortar composition (i.e. the contents of sand, cured binder and voids) and the contents of chemical substances of the cured binder (i.e. the contents of calcite and portlandite) change with distance to the brick-mortar interface. For the cement mortar with air entraining agent, the observations are explained by the enrichment of binder towards the brick-mortar interface, resulting from the local compaction and compression of the fresh mortar. In the cement-lime mortar such an enrichment of binder hardly occurs and the observations are explained by the intense carbonation that takes place. As a result, the chemical composition of the binders is very much different in both mortars. In the cement mortar with air entraining agent, near the brick-mortar interface the enrichment of cement and the low water content (resulting from the low water retentivity of this mortar), lower the water-to-cement ratio and as a consequence the cement is not fully hydrated. In the cement-lime mortar, because the Ca(OH)2 content and the water content is higher, near the brickmortar interface, a carbonated zone is formed which is hardly permeable for CO2. (and probably water). The latter does not occur in the cement mortar, it remains permeable.
The analysis of the experimental results have lead to the formulation of a conceptual model for the formation of cured mortar structure in masonry. Such a model may be helpful in analysing and predicting the durability of mortars.
Key words: Masonry, Mortar Characteristics, Mortar Composition, Moisture Transport, Curing, Carbonation
- J.A. Larbi and R.P.J. van Hees, Investigation of the Conservation-Treatment Methods of the Dutch National Monument: The Role of Microscopy, Heron, Vol. 44 (1999) No. 4, pp. 271-284.
Summary: The Dutch National Monument in Amsterdam, a World War-II memorial structure, was built with an outer face consisting of slabs of travertine. In 1995, the masonry structure forming the core of the monument showed severe deterioration. In order to determine the actual cause of deterioration and to advise on the most suitable method of restoration, an extensive investigation was carried out on the monument itself and on samples removed from it. The action of frost was found to be the primary cause of the deterioration to the brick structure. The travertine slabs and sculpture showed decay in the form of cracks and of smoothening of the sculptural details (superficial loss of material). For purposes of restoration, the monument was completely dismantled and the inner masonry structure was replaced with prefabricated concrete. The sculptures (statues and reliefs) were treated with a special acrylic resin (polymethyl metha-acrylate, PMMA) in order to conserve them. Polarising and Fluorescent Microscopy (PFM) was used in all phases of the investigation. The technique was found to be an excellent tool for such investigations. This article deals with various aspects of the investigation where PFM played a key role, such as the diagnosis of the cause of the surface deterioration of the travertine and the evaluation of the effectiveness of impregnation treatment methods of the sculptures.
Key words: Microscopy, Travertine, Conservation Treatment
- W.M.M Heijnen and J.A. Larbi, Preventive Measures against Concrete Damage to ASR in The Metherlands: Current State of Affairs, Heron, Vol. 44 (1999) No. 4, pp. 285-298.
Summary: In CUR-Recommendation 38, various vital measures that need to be taken during design of new concrete-mixtures in order to prevent damage due to ASR in the concrete have been outlined. The most important of these measures are:
- the use of blast furnace slag cement (with a high slag content: > 50 % by mass of cement as slag);
- or the use of portland fly ash cement (containing at least 25 % by mass of cement as fly ash).
If one of these cement types is used, then the potential reactivity of the aggregates is assumed to be of no concern. These measures were cautiously adopted on the basis of several years of experience with the performance of these cements, especially blast furnace slag cement. Although, to date, no cases of damage due to ASR have been found in concrete structures prepared with such cements, various questions have been raised recently as to whether these measures are adequate enough, especially in cases such as large infrastructures.
This paper is intended to throw more light onto the current state-of-affairs concerning these measures with a view to answering the most commonly asked questions.
- H.S. Pietersen, Application of TEM to Characterise Fly Ash - and Slag Cements, Heron, Vol. 44 (1999) No. 4, pp. 299-312.
Summary: A Portland fly ash cement containing 20 % of a fine fly ash and a blast furnace slag cement of approximately 290 days old were examined with analytical transmission electron microscopy, in order to examine the (local) microstructure in these cements in detail. In the Portland fly ash cement the fly ash reacted with CH resulting from the cement hydration. Due to this pozzolanic reaction, initially a dense C-S-H reaction rim precipitates around the fly ash glass spheres. In course of time, a radially fibrillar and more porous zone of C-S-H is formed in between the dense C-S-H zone and the fly ash surface. The dense C-S-H notably contains aluminium and potassium, elements which are likely to originate from the fly ash.
The microstructure of the blast furnace slag cement is also marked by a local chemical differentiation; a zoned structure is formed surrounding the original slag grain. Chemical analyses and element maps indicate that notably Si and Ca, and also some of the Al, is transported out of the slag grain interior. The driving force for this element transport is accounted for by a postulated gel-layer, creating a chemical potential gradient for water. Hydrophillic elements, such as Si and Ca will migrate out of the slag, and will cause a gradual paste densification, responsible for the low permeability in blast furnace slag cements. Within the gel-layer, a water poor region is formed in which a hydrotalcite-like phase precipitates, possibly together with minor amounts of C-S-H like material at its inner edge.
Key words: Transmission Electron Microscopy, Fly Ash, Slag, Microstructure, Pozzolanic Reaction, Element Distribution, Chemical Gradient
Volume 42 - 1997
- R.B. Polder, Cathodic Protection of Reinforced Concrete Structures in The Netherlands - Experience and Developments, Cathodic Protection of Concrete - 10 Years Experience, Heron, Vol. 43 (1998) No. 1, pp. 3-14.
Summary: Cathodic protection (CP) of reinforcing steel in concrete structures has been used successfully for over 20 years. CP is able to stop corrosion in a reliable and economical way where chloride contamination has caused reinforcement corrosion and subsequent concrete damage. To new structures where corrosion is anticipated, cathodic prevention can be applied. Recently the state-of-the-art was described and a draft European standard has been published. In The Netherlands, CP was introduced in 1987 and since then 20 full scale projects were executed. In all cases, alternatives such as replacement of the elements or conventional repair were considered, but CP was preferred for reasons of practicability, safety and durability. Most structures with CP in The Netherlands concern mixed in chloride and relatively small precast concrete elements. In 1996, CP was applied to parts of a post-tensioned bridge. Based on practical experience, a National Technical Recommendation was published. This paper describes the history, the principles and three examples.
Key words: Concrete, Corrosion, Cathodic Protection
- A. Taheri, Durability of Marine Concrete under Thermal Cycling Loads, Heron, Vol. 43 (1998) No. 1, pp. 15-28.
Summary: Data on chloride penetration into concrete exposed to a simulated aggressive marine environment are presented. Concrete specimens, large beams and small cubes, are subjected to 90 complete exposure cycles of wetting and drying plus heating and cooling. The applied exposure condition consists of a drying period of 42 hrs followed by a wetting phase of 6 hrs with salt water containing 5% NaCl. The drying phase itself is a thermal regime characterised by a temperature swing from 20 OC to 60 oC within a period of 12 hrs. This simulates, with some accelerations, the aggressive marine environmental condition in hot regions with varying daily temperature including direct solar radiation. Totally 315 temperature cycles and 90 cycles of wetting/drying were applied to specimens in this experiment. It was observed that temperature and humidity variations promote chloride penetration into marine concrete significantly. This particular study shows that thermally-induced microcracks increase, but slightly, the permeability of concrete in "restrained" beams compared to the relatively "stress free" small specimens. Effect of two other significant parameters, i.e. type of curing and type of cement, on chloride ingress rate is also investigated.
Key words: Chloride, Cracking, Curing, Heating/Cooling, Marine Concrete, Portland Cement, Restraint, Slag Cement, Temperature, Thermal Stresses, Wetting/Drying
- A. Sariyildiz, Ö. Ciftcioglu, S. Durmisevic, Architectural Pattern Generation by Discrete Wavelet Transform and Utilisation in Structural Design, Heron, Vol. 43 (1998) No. 1, pp. 29-45.
Summary: Since computers were introduced in architectural design as a valuable tool, there was a growing need to develop tools that would support the designer from the initial phase of the design till the detailing. In a computer aided architectural design environment it is feasible to stimulate the spatial design ideas and create alternatives in an efficient way. Pattern Grammar approach is one of the design alternatives where patterns, based on complex spatial geometry, are used as an underlayer for a design. In this research, the wavelets techniques are used as pattern grammar and applied to spatial information processing for the generation and analysis of the architectural patterns as well as for supporting decision-makings in structural realisations.
Key words: Pattern Grammar, Architecture, Wavelets, Multiresolution, Space-Frame
- A. van Hal, Sustainable Housing in Europe, Heron, Vol. 43 (1998) No. 1, pp. 47-60.
Summary: There is considerable variation in the extent to which environmental measures are adopted in housing construction in various European countries. Whereas sustainable housing is clearly part of day-to-day building practice in some countries, in others the topic seldom receives serious attention. None of the environmental measures which are considered as such in the Netherlands are adopted frequently in all countries. On the other hand, various measures are adopted regularly everywhere. An overall comparison of 24 countries shows that Denmark is currently the country where the greatest number of sustainable housing measures are actually adopted, followed (some way behind) by countries such as Austria and Sweden.
Key words: Sustainable Building, Europe, Housing, Comparison
- F. Hashagen and R. de Borst, Numerical Assessment of Failure Mechanisms in Fibre Metal Laminates, Heron, Vol. 43 (1998) No. 2, pp. 63-84.
Summary: In this contribution numerical models are discussed for describing failure mechanisms in fibre metal laminates. Fibre metal laminates form a new class of materials which are considered for a possible application to the fuselage of future aircraft generations. The intensive experimental analyses of these materials are focused on the assessment of their residual strength and on the assessment of new design methods. To support the experimental analyses numerical models are used to describe cracking and delamination in fibre metal laminates. A special continuum element and a corresponding interface element are introduced. Furthermore, loading functions are applied which account for cracking and delamination. Subsequently, results are discussed which are obtained from numerical analyses of the residual strength of plates made of GLARE TM. Finally, the splicing technique as a new design method is assessed by a comparison between numerical and experimental results.
Key words: Fibre Metal Laminates, Solid-Like Shell, Interface Elements, Crack Growth, Residual Strength, Delamination, Splices
- C. Geurts, Validation of Wind Loading Codes by Experiments, Heron, Vol. 43 (1998) No. 2, pp. 85-98
Summary: Between 1994 and 1997, full scale measurements of the wind and wind induced pressures were carried out on the main building of Eindhoven University of Technology. Simultaneously, a comparative wind tunnel experiment was performed in an atmospheric boundary layer wind tunnel. In this paper, the transition from wind velocity into wind loading is studied from both experiments. This transition is expressed by three quantities: the pressure coefficient, the pressure admittance and the coherence. The results of the experiments show that the wind loading, defined in building codes, is based on assumptions, which are generally not valid for buildings. The errors, made in these assumptions, work in opposite direction, thus giving an unknown, but generally small error.
Key words: Wind Loading, Dynamic Response, Full Scale Testing, Wind Tunnel Tests
- E.A.B. Koenders and K. van Breugel, Numerical Modelling of Self-Desiccation of Hardening Cement Paste, Heron, Vol. 43 (1998) No. 2, pp. 99-118.
Summary: In this paper a numerical model is presented with which it is possible to predict the non-thermal hydration-induced volume changes that develop during hardening of a cement-based material. The model equilibrates the relative humidity in the pore system with the free surface energy in hardening cement past. From a certain state of equilibrium, the deformation of a cementitious material can be determined. The numerical simulations are in good agreement with a limited number of experimental results considered in this paper.
Key words: Modelling, Pore Structure, Self-Desiccation, Autogenous Shrinkage, Cement Hydration
- J.G.M. van Mier, Special Issue on Compressive Failure of Concrete and Rock, Heron, Vol. 43 (1998) No. 3, pp. 123-125.
- M. Küntz, A. Dyskin and P. Lavallée, The Stress-Strain State and Potential Crack Trajectories in 2D Elastic Brittle Materials from Steady-State Flow Experiments, Heron, Vol. 43 (1998) No. 3, pp. 127-136.
Summary: A steady-state flow method is used to examine micromechanisms of brittle failure in 2D elastic cracked media submitted to uniaxial compressive stress. The steady-state flow experiments were conducted with an incompressible Newtonian fluid in a Hele Shaw cell. Thin linear rubber inclusions were inserted in the cell to model preexisting cracks and flow was visualised by a continuous injection of methylen blue dye. Several experiments with different configurations of inclusions were conducted: 1) one single inclusion inclined at different angles b to the flow direction, 2) left lateral shear of right or left-stepping en échelon inclusions with various overlapping and 3) several randomly-distributed inclusions. The flow lines around the inclusions show very strong similarity with the trajectories of growth of similarly arranged cracks in uniaxially compressed brittle plates. Although the similarity between Hele shaw flow and elastic deformation is not fully understood yet, the method may be used to visualise both crackinduced perturbation of the stress field and crack interaction and allows accurate predictions of the potential crack's trajectories for one or several pre-existing cracks in two dimensions.
Key words: Elasticity, Stress Field, Brittle Failure, Crack-Induced Perturbations, Elastic Interactions, Mode I Crack Growth, Hele Shaw Cell, Steady-State Flow.
- A.V. Dyskin, Stress Fluctuation Mechanism of Mesocrack Growth, Dilatancy and Failure of Heterogeneous Materials in Uniaxial Compression, Heron, Vol. 43 (1998) No. 3, pp. 137-158.
Summary: The fracture process in heterogeneous materials (e.g., concrete, rock, aggregate composites) under uniaxial compression proceeds in three stages differing in the scale levels involved. Stage 1 is the accumulation of wing cracks formed under compression from pre-existing defects. The wing cracks themselves cannot grow to an extent sufficient to cause failure. However, they produce an additional self-equilibrating and, in general, spatially random stress field. Therefore, some places can be found in the sample subjected to tensile stress components acting in the direction perpendicular to the direction of the applied compression and hence not getting suppressed by it. The magnitude of these tensile stresses increases as a square root of the wing crack concentration and, as the wing cracks accumulate, becomes sufficient to produce new tensile fractures. This starts Stage 2 in which these tensile fractures grow in a stable manner parallel to the direction of compression and become mesocracks (i.e., their sizes are now larger than the ones of the wing cracks, but still small compared to the sample dimensions). It is assumed that mesocracks grow in such a way to avoid wing cracks. Thus, the mean value of the part of the wing crackproduced random stress field that affects each mesocrack is positive (tensile), which eventually initiates the unstable grows of mesocracks and causes failure. This constitutes Stage 3 of the fracture process.
Key words: Spatially Random Stress Field, Gaussian Field, Stress Intensity Factor, Correlation Radius
- J.P.W. Bongers and H.S. Rutten, Concrete in Multiaxial Compression - A Multilevel Analysis, Heron, Vol. 43 (1998) No. 3, pp. 159-180.
Summary: The macroscopic mechanical behaviour of concrete, observed in multiaxial compression tests, is classified according to four typical stages in crack formation. At these stages, the behaviour is analysed at three different scale levels. It appears that most of the observed macroscopic features can be explained by quite simple phenomena when the concrete structure is analysed at the level of aggregate grains embedded in a matrix of cement paste. Based on this analysis, a 2D meso-mechanical model is presented aiming at describing the pre-peak mechanical behaviour of concrete in multiaxial compression tests.
Key words: Multiaxial Compression, Numerical Modelling, Scale Levels, RVE Approach
- P. de Vries and W.F. Gard, The Development of a Strength Grading System for Small Diameter Roundwood, Heron, Vol. 43 (1998) No. 4, pp. 183-197.
Summary: Roundwood as a construction material is becoming more and more interesting to users. Using this wood in construction will increase the value of the material and may open new opportunities for construction design. In order to use roundwood for this application, suitable connectors and/or joints have to be developed, but before all, the strength characteristics of roundwood must be determined and grading systems should be established. This investigation deals with the determination of the modulus of elasticity and the bending strength. The wood species concerned are Larch, grown in The Netherlands, and Douglas fir, grown in France, with diameters between 80 mm and 140 mm. The modulus of elasticity is determined by static and dynamic test methods. The data were included in a multiple regression model in order to predict the bending strength. The resulting model is compared with models for sawn timber that are nowadays used in practice.
Key words: Roundwood, Strength Grading, Testing
- G.M. Sluimer, Ultimate Performance of GRP-Laminates under In-Plane Biaxial Loading, Heron, Vol. 43 (1998) No. 4, pp. 199-225.
Summary: Widespread acceptance and utilisation of composite laminates requires confidence in their loadbearing capacity. The ability to accurately predict the stiffness and strength of laminates composed of glass-fibre reinforced polyester (GRP) is necessary for a sound design when laminates are used in structural applications. In this paper an easily accessible computational tool has been described that is able to deal with the phenomenon of progressive failure. Because loading in structural applications is merely biaxial, we designed experiments to test the biaxial capacities of GRPlaminates. The final computational results show an excellent agreement with the biaxial test results.
Key words: Biaxial Testing, Progressive Failure, Composite Laminates, Glass-Fibre Reinforced Polyester
- T. Siemes, R. Polder and H. de Vries, Design of Concrete Structures for Durability - Example: Chloride Penetration in the Lining of a Bored Tunnel, Heron, Vol. 43 (1998) No. 4, pp. 227-244.
Summary: This paper is based on a presentation for the 1998 Workshop of the European programme COST 521 "Corrosion of steel in reinforced concrete structures", 30 September - I October, 1998, Utrecht, The Netherlands. Further it is based on a paper presented at a post doctoral course at Delft University PATO Lessen uit de Tweede Heinenoord Tunnel', authored by Ton Siemes and Hans de Vries.
The present design method for durability of concrete is based on a set of rules that do not give objective insight in the service life to be expected from a concrete structure. Therefore an objective comparison between different durability measures is not possible. Especially if the lack of durability can lead to loss of human life and high economic losses, this situation is not acceptable. In addition, lack of serviceability and premature repair are not acceptable if methods are available to avoid them.
Designing for a distinct service life means that we have to define all relevant performances that the structure has to fulfil and that can be influenced by degradations. Further we have to define the probability (reliability) that a given performance must be delivered within the design service life. In structural design this approach has been already developed and is followed in practice. That approach is characterised by keywords like performance, ultimate limit state, serviceability limit state and reliability index. To a large extent this approach can be adopted for a performance based service life design.
One of the consequences of the required reliability in the service life design of a structure is the fact that between the design service life and the mean service life a margin must be present. This margin depends on the required level of reliability, the type of service life distribution and its mean value and scatter. Some examples for this margin have been presented in this paper.
In an example of a reinforced concrete lining of a bored tunnel it has been demonstrated how the service life design should be approached. The example shows clearly that the quantified performance approach gives a stronger base for service life design than the conventional approach of durability.
Key words: Concrete, Design, Durability, Service Life, Reliability, Chloride, Corrosion
Volume 41 - 1996
- A.W.M. Kok, Lumped Impulses, Discrete Displacements and a Moving Load Analysis, Heron, Vol. 42 (1997) No. 1, pp. 3-23.
Summary: Finite element models are usually presented as relations between lumped forces and discrete displacements. Mostly finite element models are found by the elaboration of the method of the virtual work - which is a special case of the Galerkin's variational principle -. By application of Galerkin's variational principle to time dependent problems, considering elements bordered by geometry and time boundaries, we obtain relations between lumped impulses and discrete displacements. The analogy with respect to static models which formulates relations between lumped forces and discrete displacements is striking. Models are formulated using linear and quadratic displacement fields with respect to time. Free model parameters are used to manipulate numerical stability, accuracy and numerical damping. These numerical tools are used for the numerical simulation of a moving vehicle at a rail track structure. The analysis shows the natural way of modelling a moving structure (the train) with respect to a fixed supporting structure (the rail track).
Key words: Direct Integration Methods, Finite Element Models, Impulses, Nonlinear Dynamics, Rail Wheel Interaction, Moving Loads
- R. van der Pluijm, Non-Linear Behaviour of Masonry under Tension, Heron, Vol. 42 (1997) No. 1, pp. 25-54.
Summary: For the micro-modelling of masonry in numerical programs that take non-linear behaviour into account, a complete description of the behaviour of masonry components has to be available. "Complete" means that, apart from the initial stiffness and the strength, the behaviour beyond the peak in the s-e diagram is described. This article gives an overview of deformation controlled tensile and flexural tests that have been carried out since 1990 by the author to establish the behaviour prior and beyond the maximum load under tension. All tests were carried under a monotonic increase of a deformation measured on the specimen itself. The behaviour of units and mortar-joints under tension showed a great similarity to that of concrete. Experience in describing the non-linear behaviour of concrete under tension could be applied to the masonry components. The mode I fracture energy of units is of the same magnitude as that of concrete. The mode I fracture energy of mortar-joints is approximately one order of magnitude smaller and showed a great scatter.
Key words: Units, Mortar-Joints, (Post Peak) Behaviour, Mode I Fracture Energy, Deformation Controlled Tests
- H.J.P. Brocken, O.C.G. Adan and L.Pel, Moisture Transport Properties of Mortar and Mortar Joint: A NMR Study, Heron, Vol. 42 (1997) No. 1, pp. 55-69.
Summary: The moisture transport in mortar and mortar joint often is an important parameter in degeneration of brick masonry and other block constructions. In this study, the influence of single additives on the moisture transport properties of mortar is investigated. Due to water extraction during brick laying, curing conditions of mortar in mortar joint differ from curing conditions of separately cured mortar. Consequently, the moisture transport properties of mortar joint differ. In addition to the moisture transport in mortar and mortar joint, the moisture transport in brick masonry is investigated. Experimental moisture profiles of water absorption in brick masonry indicate that there is no perfect hydraulic contact at the brick-mortar interfaces.
- J. Kullaa, Finite Element Modelling of Fibre-Reinforced Brittle Materials, Heron, Vol. 42 (1997) No. 2, pp. 75-95.
Summary: The tensile constitutive behaviour of fibre-reinforced brittle materials can be extended to two or three dimensions by using the finite element method with crack models. The three approaches in this study include the smeared and discrete crack concepts and a multi-surf ace plasticity model. The tensile relation represents the crack normal stressnormal strain behaviour. Depending on the fracture mode single or multiple - different modelling strategies must be considered. Applications in this study include a short steel fibre-reinforced densified small particles (DSP) beam, kevlar fibre-reinforced beams with and without ordinary reinforcing bars, and a steel fibre-reinforced concrete pipe. The increase of the peak load due to fibres could be reproduced, which supports the validity of the proposed method. All the tensile relations have been computed from micromechanical. properties. Some micromechanical properties have been obtained by trial and error by fitting to experimental results. Once the micromechanical properties are fixed, a parametric study is possible by varying e.g. the fibre content or fibre length.
Key words: Composite, Fibre, Brittle, Finite Element Method, Smeared Crack Model, Discrete Crack Model
- G.P.C. van Oosterhout, Evaluation of the Voorhof II Building Reburbishment: A Dynamic Behaviour View-Point, Heron, Vol. 42 (1997) No. 2, pp. 97-111.
Summary: The paper discusses the effectiveness of stiffening an existing building to improve the dynamic behaviour. The evaluation was part of a Ph.D. studies on the wind-induced dynamic behaviour of tall buildings. Sensitivity analyses by means of a computer model suggested that stiffening tall buildings may not be effective to increase human comfort in relation to wind-induced vibrations. The dynamic behaviour of the test-case building was assessed by measurements before and after a major refurbishment, that included stiffening the existing steel frames. The evaluation of the measurement confirmed increasing the stiffness of tall buildings is an ineffective measure to increase human comfort.
Key words: Tall Buildings, Dynamic Behaviour
- M.J. Vaessen and J.J.A. Janssen, Analysis of the Critical Length of Culms of Bamboo in Four-Point Bending Tests, Heron, Vol. 42 (1997) No. 2, pp. 113-124.
Summary: Bamboo is a remarkable engineering material: it is a tapered tube with nodes, and the material is a composite with fibres in one direction. The bending behaviour has to be studied with a four point bending test. For pure bending a minimum length of the free span is essential. This minimum length is being discussed theoretically; the outcome is verified by tests.
Key words: Bamboo, Bending Test
- J.A. Larbi and W.M.M. Heijnen, Determination of the Cement Content of Five Samples of Hardened Concrete by Means of Optical Microscopy, Heron, Vol. 42 (1997) No. 2, pp. 125-138.
Summary: This article presents the results of a microscopic analysis to determine the cement content of five samples of hardened concrete prepared with portland pozzolanic cement and crushed limestone as part of the aggregate. The volume fraction of the coarse aggregate was determined macroscopically from polished plates of the concrete samples. The volume fractions of the cement paste, the fine aggregate and the air voids were determined microscopically from thin sections. Both analyses were carried out by means of point-counting. The mass by volume of the samples was determined according to RILEM Recommendation CPC 11.3. The cement content of the concrete samples was calculated from the point-counting results combined with the estimated water-cement ratio, the estimated mass by volume of the cement paste and the measured mass by volume of the concrete samples. Corrections were made for the resulting value concerning part of the very fine aggregate material (≤ 63 mm) that may have been counted as part of the cement paste during the point-counting analysis.
Key words: Concrete, Cement Content, Optical Microscopy, Point-Counting Analysis, Water-Cement Ratio
- A.C.W.M. Vrouwenvelder, Editorial, Heron, Vol. 42 (1997) No. 3, p. 143.
- C. Both, J.H.H. Fellinger and L. Twilt, Shallow Floor Construction with Deep Composite Deck: From Fire Tests to Simple Calculation rules, Heron, Vol. 42 (1997) No. 3, pp. 145-158.
Summary: This paper deals with an international research project into the fire behaviour of a particular, economically appealing, type of composite steel concrete beams: the shallow floor beams with composite slabs using deep deckings. The results of 3 full scale fire tests are briefly summarised. Based on these fire tests, advanced numerical models have been established enabling accurate simulation of the fire tests as well as a parametric study into relevant factors affecting the overall fire behaviour of this type of composite structures. The outcome of the parametric study is transformed into economic, yet easy to handle calculation rules for engineering practice.
Key words: Shallow Floor, Deep Composite Deck, Fire Behaviour, Finite Element Analysis, Calculation Rules
- J. Blaauwendraad and P.C.J. Hoogenboom, Discrete Elements in Structural Concrete Design, Heron, Vol. 42 (1997) No. 3, pp. 159-168.
Summary: In the sixties Prof. J. Witteveen introduced a discrete model for the elastic analysis of slabs (Heron 1966). This article presents a similar approach for the design of reinforced concrete walls and deep beams, with holes or otherwise. The model - which is called stringer-panel model - combines the advantages of the popular strut-and-tie method and the standard finite element method. It has the same geometry as the plastic model proposed by Prof. M.P. Nielsen in the seventies (Kærn 1979). However, the stringer-panel model accurately uses the non-linear behaviour of reinforced concrete. So, it encompasses both the elastic and plastic states. The method provides crack width information in the serviceability limit state and allows for redistribution of forces in the ultimate limit state. A design example shows the usability of the model in engineering practice.
Key words: Wall, Structural Concrete, Stringer-Panel, Strut-and-Tie, Computer Aided Design
- P. Waarts and A.C.W.M. Vrouwenvelder, Probabilistic Analysis of the Stüssi-Kollbrunner Paradox, Heron, Vol. 42 (1997) No. 3, pp. 169-180.
Summary: In most text books on Plasticity Theory a reference is made to the famous tests performed by Stüssi and Kollbrunner in 1935. The test object was a continuous beam on four supports, loaded by a concentrated point load halfway the central span. According to a straight forward application of the theory of plasticity the load carrying capacity of this beam is independent of the length of the outer spans. However, if the length of the outer span approaches infinity, the stiffness of the outer beam parts goes to zero. The centre span is then to be considered as a simply supported beam, having only half the load carrying capacity of the continuous beam. As usual, such a paradox can only be solved by using a more advanced theory, including both elastic and plastic deformations, as well as the real stress strain
relationship. This of course has been done in the past successfully and the theoretical results were confirmed by tests.
The present paper intends to reconsider this problem, however including also the random nature of the material properties. This way an adequate approach to the reliability aspects of the problem can be
achieved. Such an approach is considered especially useful for high strength steel and concrete
materials that are used nowadays. For these materials aspects of deformation capacity become more and more important
Apart from some simplified calculations, the numerical results in this paper have been attained using a special purpose computer program that combines the standard Finite Element Method and First Order Reliability Methods. Some attendance will be given to the possibilities and limitations of the present program and the techniques that are used to reduce the computation time.
Key words: Reliability, Rotation Capacity, Plasticity, Steel Structure
- A.E. Groen and R. de Borst, Three-Dimensional Finite Element Analysis of Tunnels and Foundations, Heron, Vol. 42 (1997) No. 4, pp. 183-214.
Summary: An increasing need for underground infrastructure in The Netherlands requires knowledge about the behavior of construction in soft soils. In this contribution, attention is focused on three-dimensional numerical simulation of construction works in soils, i.e. tunneling and foundations. In order to perform such simulations, robust numerical tools are a first requirement. The development of such numerical tools will be presented, as well as some typical threedimensional test cases such as a guided pipe-jacking and the leaning tower of Pisa.
Key words: Finite Element Method, Element Locking, Clay, Sand, Soil Mechanics
- R.J. van Eijk and H.J.H. Brouwers, Study of Hydrated Portland Cement Composition in Regard to Leaching Resistance, Heron, Vol. 42 (1997) No. 4, pp. 215-229.
Summary: The present paper addresses cement compositions that have an optimal resistance against acid attack and hence, low leaching rates and optimal waste containment. To this end a shrinking core leaching model is used that describes the leaching of metals from a cement sample. This process is directly related to the calcium hydroxide removal from the sample by the acidified leachant. Effective diffusion coefficients in this so-called leached shell were calculated using the equations derived from a cement hydration model. This results in equations in which leaching rates were dependent on cement composition, especially the calcium hydroxide fraction. Optimizing the calcium hydroxide fraction yields cement compositions possessing the optimal leaching resistance as a function of the water porosity. The results were also used for the determination of optimal amounts of silica fume.
Key words: Immobilization, Shrinking Core Model, Leaching, Acid Attack, Hydration, Waste
- M. Küntz and J.G.M. van Mier, Field Evidences and Theoretical Analysis of the Gravity-Driven Wetting Front Instability of Water Runoffs on Concrete Structures, Heron, Vol. 42 (1997) No. 4, pp. 231-244.
Summary: A series of field observations of the evolution of water runoffs over several vertical concrete walls directly exposed to rain falls is reported in this note. In all the cases, the main water flow originated from the top horizontal surface of the walls. The observations show that the gravity-driven wetting front may propagate in a very unstable way by developing well defined and quite regularly spaced vertical finger-like features. The mean width < d > and the mean growth's velocity < v > of the fingers appear locally constant, but may vary from a wall surface to another. A simple relationship between < d > and < v > is deduced from the field data and the narrower the fingers the higher the growth's velocity. The fingering process is tentatively interpreted by using the theoretical analysis developped by Glass et al (1989b) for the wetting front instability of infitration in unsaturated homogeneous layered soils. It is shown the model accounts qualitatively well for our observations. The variation in the geometry and kinematics of the instabilities from a wall surface to another may therefore be related to variations of the concrete structure at the microscopic scale. The relationship between < d > and < v > reflects the effects of the microstructure. The gravity driven-wetting front instability provides a powerful mechanism for a fast and over large distance moisture transfer along concrete constructions. It also leads to an heterogeneous distribution of the moisture content along the wall surface, which may eventually result in large spatial variations of the moisture-induced damages of the building structures.
Key words: Moisture Transport, Gravity Instability, Porous Media, Building Materials
Volume 40 - 1995
- A.A.A. Molenaar, ROADS: Constructions under Increasing Loads, Heron, Vol. 41 (1996) No. 1, pp. 3-4.
- A. Scarpas and A.H. de Bondt, Finite Elements Simulation of Reflective Cracking in Asphaltic Overlays, Heron, Vol. 41 (1996) No. 1, pp. 5-28.
Summary: Overlaying is one of the most popular and cost effective techniques of rehabilitation of cracked pavements. The placing of reinforcement between the overlay and the top layer of the cracked pavement is currently being utilised as a possible technique for delaying the development of cracks into the overlay. In order to assist the road designer with his attempt to determine the factors leading to the development of cracks into the overlay and in order to enable him to quantify the contribution of reinforcement in carrying tensile forces across cracks in overlayed pavements, CAPA, a user-friendly, PC based, finite elements system has been developed. A variety of options enable the simulation of discrete cracks in the pavement and their interaction with the surrounding materials. Starting from an initial crack length in the pavement, the system can automatically propagate the crack all the way to the surface computing at the same time the relevant fracture mechanics parameters at successive crack tip positions. A user friendly graphical screen input facility, together with a fully fledged mesh generator and extensive pre- and post-processing graphic facilities allow the designer to quickly evaluate the efficiency of various overlay techniques. By means of an example of an actual Dutch pavement profile it is shown that adequately bonded reinforcement can reduce the speed of crack propagation into the overlay and hence prolong the economic life of the structure.
Key words: Pavement Rehabilitation, Reflective Cracking, Pavement Reinforcement, Discrete Cracking, Barsoum Elements, Interface Elements
- M. Huurman, Development of Traffic Induced Permanent Strain in Concrete Block Pavements, Heron, Vol. 41 (1996) No. 1, pp. 29-52.
Summary: Concrete block pavements (c.b.p.) commonly consist of concrete blocks placed over a granular substructure. As a result of wheel load passages permanent strains will slowly develop in the substructure and cause rutting. This paper is about the prediction of the permanent strain development in the substructure and the associated rutting on the basis of the results of repeated load triaxial tests and analytical models. By discussing the behaviour of three c.b.p.'s it is shown that insight into c.b.p. behaviour is obtained and that the effects of various substructure designs can be evaluated without the construction of real c.b.p.'s.
Key words: Concrete Block Pavements, Granular Materials, Stress Dependent Behaviour, Permanent Strain, Rutting, Theoretical Modelling
- S.M.J.G. Erkens and J. Moraal, Cracking in Asphalt Concrete, Heron, Vol. 41 (1996) No. 1, pp. 53-70.
Summary: Fatigue resistance of asphalt concrete is usually evaluated by means of fatigue tests, like repeated load four point bending tests. These tests are rather time consuming and, therefore, not suited for performance based specifications. In this article a new, faster procedure to determine the fatigue characteristics is introduced. The procedure is based on a combination of theory and experiments. Both the theorectical background and the experiments that were used are discussed in this article. Furthermore, fatigue relations that were developed using the new procedure and relations developped using classical fatigue tests, are compared.
Key words: Fatigue Cracking, Asphalt Concrete, Fracture Mechanics, Frequency Sweep Tests, Direct Tensile Tests, Stress Intensity Factor
- P.C. Hopman, The Visco-Elastic Multilayer Program VEROAD, Heron, Vol. 41 (1996) No. 1, pp. 71-91.
Summary: The mathematical principles and derivation of a linear visco-elastic multilayer computer program are described. The mathematical derivation is based on Fourier Transformation. The program is called VEROAD, which is an acronym for Visco-Elastic ROad Analysis Delft. The program allows calculation of physical quantities like time-dependent displacements, stresses and strains, permanent deformations and dissipated energies in a multi-layer system built of visco-elastic materials. All the quantities thus depend on the velocity of the traffic, which explicitly comes into the calculations. The material model assumes the bulk modulus to be elastic and the shear modulus to be visco-elastic. The latter follows the Burgers' model. For illustrative purposes, some mechanical analyses of asphaltic road structures are shown.
Key words: Multilayer Programs, Linear Visco-Elastic, (Permanent) Deformation, Stress, Strain, Dissipated Energy
- L. Pel, K. Kopinga and H. Brocken, Moisture Transport in Porous Building Materials, Heron, Vol. 41 (1996) No. 2, pp. 95-105.
Summary: The isothermal moisture transport in various porous building materials during absorption and drying was studied by nuclear magnetic resonance (NMR). It is shown that the moisture diffusivity can be determined directly from measured transient moisture profiles. NMR appears to be an accurate and reliable method to determine these moisture profiles. For both water absorption and drying it is found that, within the experimental accuracy, a single unambiguous relation exists between the moisture diffusivity and the moisture content, which is dependent on the type of material. Preliminary absorption measurements on brick/mortar samples suggest that the hydraulic contact between mortar and brick may not be perfect.
Key words: Moisture Transport, Moisture Diffusivity, Nuclear Magnetic Resonance, Drying, Absorption, Brick/Mortar Interface
- J.J.W. Gulikers, Experimental Investigations on Macrocell Corrosion in Chloride-Contaminated Concrete, Heron, Vol. 41 (1996) No. 2, pp. 107-123.
Summary: Chloride-induced reinforcement corrosion in concrete is characterised by the action of so-called macrocells. The associated localised form of corrosion results from the strong electrochemical interaction between the relatively small pitting sites acting as anodes and the large passive steel areas acting as cathodes. The existence of macrocell corrosion poses severe problems in the interpretation of results obtained from corrosion experiments, especially regarding corrosion potential and galvanic current. To elucidate the mechanism of macrocell corrosion experimental investigations were conducted on reinforcement steel embedded in chloride-contaminated concrete. The macrocells were provoked by shortcircuiting actively corroding mild steel bars to passivated stainless steel, thereby intensifying the corrosion process. The experiments included measurement of corrosion potential, ionic concrete resistance, potential difference, corrosion rate and galvanic current. The magnitude of the galvanic current is significantly influenced by the resistance of passive steel to polarisation, and to a much lesser degree by the ionic concrete resistance. Results from potential mapping demonstrated that due to macrocell action the rest potential of the passive steel was shifted towards very negative values that, according to many codes of practice, would suggest active corrosion to take place.
Key words: Concrete, Reinforcing Steel, Chloride, Durability, Corrosion, Macrocell Testing
- W. Tijhuis and G.J. Maas, Construction-Process: Fragmentation or Integration? Some International Experiences, Heron, Vol. 41 (1996) No. 2, pp. 125-138.
Summary: Recent projects of contractors and project-developers are increasingly realized in an international scope. Also the Dutch construction industry becomes more active in Europe and other parts of the world, while companies from abroad become more active in the Dutch construction market. Although several Dutch companies had already activities and experiences in other parts of the world, several of these companies encountered specific problems when working in Germany. After falling of the Berlin Wall in 1989 it became clear there would be an enormous construction marktet, and also the other East-European countries became interesting. But it seems that the entering of the German market by Dutch contractors was and is still quite difficult. The research, described in this article, is part of a Ph.D project, which searches for possible backgrounds for differences between the Netherlands and Germany in the construction-management process. To get a more practical view on the research-area, there has been created a possibility for a partly-continuous investigation inside some contractors and project-developers in Germany, which are from Dutch origin. One specific case-study according the realization of two hotel-projects in Germany is being described shortly in this article. The comparison is being made by investigating theory and practical experience, mainly according problems in construction-management and working with people.
Key words: Managing the Project, Project-Control, Conflict-Management, Information, Win-Win-Situation
- S. van Baars, Discrete Element Modelling of Granular Materials, Heron, Vol. 41 (1996) No. 2, pp. 139-157.
Summary: A new model is developed by the author, which does not use the equations of motion but the equations of equilibrium to describe granular materials. The numerical results show great similarities with reality and can generally be described by an advanced Mohr-Coulomb model. However, many contacts between the grains will collapse not due to shear deformation as Coulomb suggests, but due to tension failure. These micro cracks occur always in the direction of the major principal stress, which might be a different direction than the observed failure surface.
Key words: Discrete Elements, Shear Bands, Crack Growth
- F. Beetstra, Building Related Environmental Diagnosis, Towards a Broad and Practical Method for a Comprehensive Sustainability Analysis of a Building, Including its sites' Aspects on the Basis of a Limited Set of Objectively Computable Indicators, Heron, Vol. 41 (1996) No. 3, pp. 161-174.
Summary: On a global level it is known that the environmental impact of the construction sector is huge. But how much of an environmental burden is a building? And what is the impact of an "environmentally friendly" measure on the environmental load? The lack of a tool that indicates how much of a burden a building induces is an important obstacle in making better designs and maintenance decisions from an environmental standpoint.
For products, the impact of all the material flows and other inputs and outputs on the environment could be determined in principle by means of an environmental life-cycle assessment methodology LCA. With the LCAS' there are however still many problems regarding the assessment of the use and consumption of (nature) space and land, and the acquiring of objective input data. Furthermore the environmental impact induced by a building is far more than the sum of the materials. In view of the problems surrounding the definition of physical, quantifiable environmental measures for many relevant effects, a broad environmental assessment of a building is - for the time being - not possible with LCA.
For clients and designers in the building trade, it would be useful if the environmental impact induced by a building could be represented in a well-organized environment profile. Such a profile has to be composed of a limited set of objective, quantitative and verifiable indicators, each of which encompasses a certain part of the sustainability spectrum or environmental impact. We believe that such a profile could consist of a set of eight indicators: 3 site oriented, 3 building oriented, and 2 aimed at building parts. A. Site oriented: use of space; oxygen balance; and accessibility. B. Building oriented: water balance; energy balance; and Sick Building Syndrome. C. Building part and material oriented: material-use balance; and reuse balance.
A comparison between the proposed set and LCA indicates that all relevant LCA aspects have been incorporated into the set. However, by contrast, the environmental aspects that are connected to four indicators, i.e. use of space, oxygen balance, accessibility, and water balance, cannot be worked out adequately in a LCA for buildings. Furthermore, the LCA pays no attention to the physical aspects that influence human well-being in a building. An environmental valuation with the proposed method therefore: has a larger assessment area than that which is covered by LCAS' nowadays; gives more insight in the environmental load aspects, and is more practical.
Key words: LCA, Indicators, Material Flows, Environmental Impact, Sustainable Building
- M.A. Van, Buckling Analysis of Continuous Welded Rail Track, Heron, Vol. 41 (1996) No. 3, pp. 175-186.
Summary: Continuous welded rail track, compared to jointed track not only reduces maintenance costs, but also increases life time of track components and the comfort of passengers. Since expansion of the rails is hardly possible in CWRtrack, a temperature increase will result in high compressive stresses and track buckling may occur. Therefore the 'European Railway Research Institute' commissioned Delft University of Technology to develop a computer program, by which the stability Of CWR on plain track and on bridges can be modelled and calculated in three directions. The computer program is called CWERRI and will be a major tool for railway companies for the implementation of new safety concepts. It further will be used for the revision of the Leaflet 720R, which code prescribes the laying and maintenance of CWR-track.
In this paper the stability of a track model is investigated. It is shown how the parameters of this track model can be derived from measurements. A sensitivity analysis is performed to determine the most significant parameters affecting the stability. It is concluded that the curvature, the horizontal ballast strength and the misalignment are the important buckling parameters. Only the very stiff fasteners improve the track stability considerably. Low fastener stiffnesses and the longitudinal and lateral ballast stiffness are less significant.
Key words: CWR-Track, Buckling, Safety Concept, Measurements, Sensitivity Analysis
- K. Both, Fire-exposed Continuous Span Composite Steel-concrete Slabs, Heron, Vol. 41 (1996) No. 3, pp. 187-199.
Summary: From experimental evidence, it was concluded that existing rules for the calculation of the behaviour of fire-exposed composite beams and slabs often lead to conservative solutions. Furthermore, the range of common applications had grown beyond the limits of existing calculation rules. It was felt that existing rules lacked a fundamental basis, in order to optimally design and evaluate fire-exposed composite beams and slabs. Therefore, a research project was started in 1989, in which CTICM (F), TNO (NL) and ARBED (L), together with both Delft and Eindhoven Universities of Technology, shared numerical and experimental research activities with respect to the behaviour of fire-exposed composite beams and slabs. The project aimed at gaining more insight into the behaviour -failure mechanisms in particular- of fire-exposed composite beams and slabs by means of the development of numerical models and their validation based upon a limited number of full-scale well-instrumented fire tests. The final goal of this research project was to establish simple calculation rules, which would allow for easy and fast assessment of the fire-behaviour of composite beams and slabs. The project was co-sponsored by the ECSC; the part on composite slabs was conducted in the Netherlands, the part on composite beams in France. In the paper, the results of the Dutch part of the research project are described. After a brief introduction, the experimental programme is outlined. A total of 21 full-scale fire tests was performed on unloaded as well as loaded test specimens. These experiments have successfully been modelled using a general purpose finite element programme, with some pilot extensions. With the numerical model, a parameter study was performed. The results of this study were translated into a proposal for new simple calculation rules.
Key words: Finite Element Analyses, Fire-Exposure, Composite Steel/Concrete Slabs, Continuous Span, Calculation Rules
- J.A. den Uijl and A.J. Bigaj, A Bond Model for Ribbed Bars Based on Concrete Confinement, Heron, Vol. 41 (1996) No. 3, pp. 201-226.
Summary: A new bond model for ribbed bars embedded in concrete has been developed. The model is based on the confining capacity of the concrete surrounding the bar. This confinement capacity is evaluated with the help of a thick-walled-cylinder model with which the relation between the radial displacement and the radial compressive stress at the steel-to-concrete interface is described. Next, the slip of the ribbed bar is linked to the radial displacement of the interface, treating the two modes of bond failure, splitting of the cover and pull-out of the bar, in a different way. The model takes into account the effect of concrete softening in tension and of bar contraction connected to yielding. It has been tuned and verified on the basis of a broad range of experimental results.
Key words: Bond, Ribbed Bars, Concrete Confinement, Splitting Failure, Pull-Out Failure, Concrete Softening, Poisson Effect, Steel Yielding
- A.G. Dorée, Tendering for Co-operation Municipality-contractor, Heron, Vol. 41 (1996) No. 4, pp. 229-240.
Summary: The European Union (EU) has strongly influenced the perspective on the way public organisations (should) utilise markets. The EU directives on procurement, and the battle against cartels, resulted in extra attention towards the relationships between municipalities and construction contractors. Figures suggest that municipalities prefer limited tendering procedures, and avoid public tender procedures. This paper reports on the research into the reasons for such behaviour. Analysis of municipalities' procurement and tendering practice uncovered an intricate mechanism for project control. Municipalities implicitly use the prospect of futures assignments to restrain contractors' misbehaviour. By doing so municipalities reduce uncertainties and risks. Contractors' demeanour becomes more flexible, co-operative and quality orientated because of this mechanism. Through the use or this mechanism the relationship municipality-contractor has developed to a kind of co-makership relation. Bending the procurement and tendering practice towards more public tendering is expected to make project control more troublesome.
- J.H.M. Visser and J.G.M. van Mier, Dry and Hydraulic Extensile Fracturing of Porous Impermeable Materials, Heron, Vol. 41 (1996) No. 4, pp. 241-266.
Summary: Extensile hydraulic fracturing of mortar is investigated and compared to extensile dry fracturing of sandstone. The extensile fracture experiments have been performed in a Hookean cell in deformation control. The cell allows for axial loading and radial fluid pressure loading of cylindrical specimens. Variables in the experiments are the load path and the degree of saturation. In the dry fracturing tests, the sandstone specimens are sleeved. In the hydraulic fracture experiments, the mortar specimens are not sleeved so that the radial fluid pressure is free to enter the notch and the fracture once it is initiated. In the dry fracturing experiments, the sandstone becomes more ductile for increasing hydrostatic fracture experiments are very similar for the unsaturated mortar (degree of saturation 69%) and the saturated mortar (degree of saturation 100%) . The saturated mortar behaves stiffer and has higher failure stresses due to the effect of pore pressures. Fracture propagation in the saturated mortar requires lower stresses, although the difference with fracture propagation in the unsaturated mortar is minor.
Key words: Extensile Dry Fracturing Experiments, Extensile Hydraulic Fracturing Experiment, Load Path, Degree of Saturation, Sandstone, Mortar, Pore Pressure
- H. Sadouki and J.G.M van Mier, Analysis of Hygral Induced Crack Growth in Multiphase Materials, Heron, Vol. 41 (1996) No. 4, pp. 267-286.
Summary: In this paper a numerical model for simulation crack growth processes caused by moisture movement in a porous multiphase material like concrete is proposed. In the model, the material is schematized as a regular triangular network of beam elements. The meso-material structure of the material is projected on top of the lattice and different properties are assigned to the different phases. In the hygral analysis the lattice elements are considered conductive pipes. In the mechanical analysis, the lattice elements are beams which are characterised by a modulus of elasticity, Poisson's ration, tensile strength and fracture energy. In contrast to the previously developed lattice model by Schlangen and van Mier 1992, a softening relationship was used in the fracture analysis. Examples of shrinkage cracking in normal concrete containing dense natural aggregates and in lightweight concrete containing low modulus impermeable aggregate particles are given. Moreover, a comparison between a continuum based hygral/mechanical approach and the lattice type model is presented. The model seems a useful tool for estimating the effect of hygral shrinkage cracking on the mechanical properties of concrete.
Key words: Concrete, Cracking, Lattice Model, Transient Moisture Flow, Shrinkage
- R.B. Polder, The Influence of Blast Furnace Slag, Fly Ash and Silica Fume on Corrosion of Reinforced Concrete in Marine Environment, Heron, Vol. 41 (1996) No. 4, pp. 287-300.
Summary: Chloride penetration from sea water may cause corrosion of reinforcement in concrete structures. Adding reactive inorganic materials such as blast furnace slag, fly ash or silica fume to the cement matrix improves the resistance against chloride penetration as compared to Portland cement concrete. A relatively simple laboratory procedure was proposed to test concrete mixes for their expected service live in sea environment. The assumption is that chloride diffusion and cover depth determine the time-to-initiation of corrosion and electrical resistivity determines the corrosion rate and so the time-to-cracking. The sum is the total "service life".
The proposed testing procedure was applied to five concrete mixes. The contained ordinary Portland cement; OPC + fly ash + silica fume; blast furnace slag cement, all with gravel aggregate; OPC and lightweight coarse aggregate. The predicted time-to- initiation and the time-to-cracking in marine splash zone were calculated from the test results.
The calculated service lives range from 10 to 80 years, increasing in the order: OPC-lightweight aggregate < OPC-gravel < OPC + silica fume-gravel < OPC + fly ash + silica fume-gravel < blast furnace slag cement-gravel. The ranking and the numerical results are in general agreement with data from exposure research and with practical experience. The addition of blast furnace slag, fly ash and/or silica fume may significantly increase the resistance against chloride penetration and consequently the time-to-initiation of corrosion. Once corrosion has started, steel in concrete with additional cementing materials may have a decreased rate of corrosion.
The proposed set of laboratory tests appears suitable for evaluating the effect on corrosion protection in marine environment of new and/or supposedly improved concrete compositions.
Key words: Concrete, Reinforcement Corrosion, Marine Environment, Diffusion, Resistivity, Service Life, Durability
- A.C.W.M. Vrouwenvelder, New Scope and New Formula, Editorial, Heron, Vol. 40 (1995) No. 1, p. 3.
- J.C. Walraven, J. den Uijl, J. Stroband, N. Al-Zubi, J. Gijsbers and M. Naaktgeboren, Structural Lightweigth Concrete: Recent Research, Heron, Vol. 40 (1995) No. 1, pp. 5-30.
Summary: As a result of a number of reasons new interest developed into the use of lightweight aggregate concrete. Within the scope of this development, a modernized code for lightweight concrete had to be written. In order to support this development, a number of research projects have been carried out. The aim of the research was to verify the appropriateness of a number of design methods for lightweight concrete. The behaviour of various types of lightweight concrete has been studied.
Key words: Lightweight Concrete, Material Properties, Concentrated Loading, Splitting, Bond, Crack Width, Shear
- R.B. Polder and J.A. Larbi, Investigation of Concrete Exposed to North Sea Water Submersion for 16 Years, Heron, Vol. 40 (1995) No. 1, pp. 31-56.
Summary: In 1976 concrete specimens were submerged in the North Sea. Ordinary portland cement (OPC) with two water-tocement ratios and blast furnace slag cement (BFSC) were used. After 2, 8 and 16 years specimens were investigated.
The mechanical properties of the concrete appeared not to have changed importantly due to the exposure. The microstructure and the density of microcracks were found to be normal. Sulphate, magnesium and carbonation had penetrated only the outermost few millimetres. Chloride had penetrated strongly in 16 years, depending on the cement type. Diffusion coefficients, calculated from the chloride profiles, were ten times lower for BFSC concrete than for OPC concrete. Consequently, in OPC concrete depassivation of rebars may occur within a few decades; in BFSC concrete loss of passivation can be prevented for 100 or more years.
In the specimens, reinforcement corrosion was practically absent due to lack of oxygen. Corrosion in submerged concrete can only occur in hollow air-filled structures (macrocell corrosion). In such situations the corrosion rate is probably determined by the electrical resistivity of the concrete. The resistivity was found to be much higher for BFSC concrete than for OPC concrete. This would reduce the corrosion rate in BFSC concrete macrocells significantly compared to OPC concrete.
Key words: Concrete, Marine Environment, Mechanical Properties, Microstructure, Chloride, Sulphate, Magnesium, Diffusion, Reinforcement Corrosion, Resistivity, Cracks
- C.J.W.P. Groot, Effects of Water on Mortar-Brick Bond, Heron, Vol. 40 (1995) No. 1, pp. 57-70.
Summary: The quality of bond in masonry is, to a large extent, a function of the (i) the hydration conditions and (ii) the mortar composition of the mortar-brick interface. For insight into the effects of these parameters on bond performance it is essential to dispose of quantitative information about water content changes and flow rates, occurring immediately after brick laying. This quantitative information is preferably to be obtained by means of a non-destructive testing. The paper describes the test set-up, the potentiality and the limitations of two measuring methods, using thermal neutrons, with which the required data can be acquired. Furthermore, an attempt is made to explain differences in bond performance of various brick-mortar-brick combinations, using the results from neutron transmission measurements and X-ray diffraction testing.
Key words: Mortar-Brick Bond, Masonry, Non-Destructive Testing, Neutron Transmission Techniques
- J. Pamin and R. de Borst, Numerical Simulation of Localization Phenomena using Gradient Plasticity and Finite Elements, Heron, Vol. 40 (1995) No. 1, pp. 71-92.
Summary: A gradient plasticity theory is proposed, which includes dependence of the yield function on the Laplacian of an invariant plastic strain measure. The theory preserves well-posedness of the governing equations in the presence of strain softening and prevents the pathological mesh sensitivity of numerical results. An internal length scale incorporated in the theory determines the size of localization bands. Adopting a weak satisfaction of the yield condition, mixed finite elements are developed, in which plastic strains are discretized in addition to the standard discretization of the displacements. A gradient-dependent Drucker-Prager yield function is used to solve a twodimensional problem of shear slip in a soil mass. A gradient-dependent Rankine failure function is used in continuum modelling of two concrete fracture experiments. The regularizing effect of the gradient dependence is demonstrated.
Key words: Softening, Strain Localization, Higher-Order Continuum, Finite Element Analysis, Soil Instability, Concrete Fracture.
- R.A. Chandansingh, The Economic Value of CAD Systems in Structural Design and Construction, A Modelling Approach, Heron, Vol. 40 (1995) No. 2, pp. 95-123.
Summary: A modelling approach is provided for the analysis of cost-effects Of CAD systems. It aims to support strategic management Of CAD systems in structural design and construction. The approach is based on the production digraph model of production processes, and the value-added model of information commodities. It has been verified in three case-studies: two concerning the cost-effects in the structural design process at engineering consultants, and one concerning the cost-effects in the production process at a reinforcement-subcontractor. The results of two cases are provided, together with conclusions based on all three case-studies.
Key words: Modelling, Information Commodity, Production Digraph, Cost-Effects, CAD Systems, Structural Design, Construction
- D.A. Hordijk, G.M. Wolsink and J. de Vries, Fracture and Fatigue Behaviour of a High Strength Limestone Concrete as Compared to Gravel Concrete, Heron, Vol. 40 (1995) No. 2, pp. 125-146.
Summary: In the Netherlands river gravel as traditional coarse aggregate for concrete is increasingly being replaced by other types of (natural) aggregate. After some more cracking was encountered during pile driving with limestone concrete as compared to gravel concrete, a comparative investigation into a number of material parameters was performed. For approximately equal compressive strength (85 to 90 MPa) differences in Young's modulus, fracture energy and brittleness were found. With respect to the application of limestone concrete in slender concrete bridge girders, the fatigue behaviour was also studied. No significant differences were found between both concrete types, while the S-N curves as previously determined for concrete with normal strength appeared to apply also reasonably well to the investigated more brittle high strength concrete types. Attention is also paid to the influence of a moisture gradient on the material properties as determined in fracture tests.
Key words: Limestone Aggregate, High Strength Concrete, Fracture Mechanics, Fatigue, Moisture Gradient
- J.G.M. van Mier, Fracture Mechanics of Concrete: Will Applications Start to Emerge?, Heron, Vol. 40 (1995) No. 2, pp. 147-162.
Summary: Fracture mechanics of concrete has developed into an active field of research in the past decades. It promises a rational solution technique to structural problems in reinforced concrete in the limit state. Numerical tools have been developed on the basis of fracture mechanics theories. The question to be addressed is how much of the early promise, i.e. the promise of a powerful rational numerical tool having predictive capabilities, has come true, and whether additional research is needed in order to further extend the range of applicability of the new tools. Essential for new applications, both at the structural and the materials engineering level seems a combined experimental and numerical approach. Both experimentation and numerical simulation have grown to a level where highly advanced techniques are applied, often too complex and of a scope too wide to be comprehended by a single researcher. Structural engineering applications of fracture mechanics must be sought in problems where the concrete reaches its limit state, and where knowledge of softening becomes eminent. Examples are the minimum reinforcement ratio in reinforced concrete structures, or structural details like anchor pull-out. Other recent developments point towards applications at the material level, where numerical models at the meso-level (particle level) of the concrete are used to develop materials for specific structural applications. At best numerical analyses and testing should be carried out in close cooperation. A meaningful development seems one where the softening response of the material (for example by adding fibres to increase the ductility) is optimised in conjunction with new structural applications. The development of a SIFCON truss systems is a recent example.
Key words: Fracture Mechanics, Concrete, SIFCON, 3-Level Approach, Fracture Energy, Meso-Modelling, Numerical Materials Science, Applications
- M. Asin and J.C. Walraven, Numerical Analysis of Reinforced Concrete Continuous Deep Beams, Heron, Vol. 40 (1995) No. 2, pp. 163-178.
Summary: The structural behaviour of deep beams is still not completely understood, since, for example, plane sections do not remain plane and no uniform shear flow can develop because of the small ratio between depth and shear span. If in addition, the supporting system is also statically indeterminate, the number of difficulties increases. In order to investigate the behaviour of statically indeterminate deep beams, a series of fourteen tests has been carried out. Variables were the slenderness, the ratio between top and bottom reinforcement, and the amount of shear reinforcement. Complementary to these experiments numerical simulations have been carried out. This paper focuses on the computational aspects. A good match between experimental behaviour and numerical simulation was found over the entire range, which increases the confidence in the predictive capacity of non-linear finite element analysis. Extrapolation was the next step: calculations were made for cases in which either a material or a structural parameter was varied beyond the tested range. For this study, the amount of compressive strength reduction by transverse tension was chosen as a material parameter. In general this appeared to have a negligible effect on the behaviour. Only in the case of large reductions, however, a change in failure mechanism and a decrease in failure load were found. The orientation and the amount of web reinforcement was chosen as a structural parameter. Compared to the original calculation with vertical reinforcement only, a decrease in failure load is found when only horizontal web reinforcement was present. A combination of both horizontal and vertical reinforcement proved to be the most effective: at the expense of more reinforcement, it resulted in a strength increase as well as in small crack widths.
Key words: Experiments, Non-Linear Finite Element Analysis, Continuous Deep Beams, Compressive Strength Reduction, Web Reinforcement
- M.M.J. Jacobs, P.C. Hopman and A.A.A. Molenaar, The Crack Growth Mechanism in Asphaltic Mixes, Heron, Vol. 40 (1995) No. 3, pp. 181-199.
Summary: The crack growth mechanism in asphalt concrete (AC) mixes is studied. In cyclic tests on several asphaltic mixes crack growth is measured, both with crack foils and with COD-gauges. It is found that crack growth in asphaltic mixes is described by three processes which are parallel in time: cohesive crack growth in the mortar, adhesive crack growth between the mortar and the aggregates and a crack stoppers process. Differences in overall crack growth in asphalt concrete are due to differences in the contributions of each individual process to the overall process.
Key words: Asphalt Concrete, Fracture, PRINCALS Analyses, Micro Crack Zone, Cohesive Crack Growth, Adhesive Crack Growth, Crack Arresters, Uniaxial Tensile Test, Absolute Rate Theory
- O.C.G. Adan, Determination of Moisture Diffusivities in Gypsum Renders, Heron, Vol. 40 (1995) No. 3, pp. 201-215.
Summary: It is generally recognised that the water transport in monolithic porous materials can be described using a macroscopic diffusion-type equation. Until now, the determination of the diffusion coefficients in this equation was a major problem. Two new non-destructive measuring techniques based on neutron beam attenuation and nuclear magnetic resonance, respectively, were applied to determine the isothermal moisture diffusivity directly from transient moisture content profiles. The experiments concerned a gypsum render. For the first time, moisture content profiles in a dry material responding to transient relative humidities below saturation could be measured. The results show that the moisture diffusivity to be used in the modelling of moisture transfer strongly depends on the initial conditions of the material, underlining the complex interaction of liquid and vapour phases in the porous system. The moisture diffusivity for drying of the wet gypsum may exceed the moisture diffusivity of the dry gypsum exposed to transient RH's by a factor of 100. As a consequence, the experimental results refute the common estimations of hygroscopicity effects on the basis of the apparent diffusivity derived from the sorption isotherm and the water vapour permeability.
Key words: Moisture Transport, Diffusivity, Nuclear Magnetic Resonance, Neutron Radiography, Hysteresis, Gypsum
- J.S. Leendertz and M.H. Kolstein, The Behaviour of Trough Stiffener to Crossbeam Connections in Orthotropic Steel Bridge Decks, Heron, Vol. 40 (1995) No. 3, pp. 217-259.
Summary: This article describes the behaviour and stress analysis of the crossbeams in orthotropic steel decks with continuous trapezoidal closed stiffeners. The trough stiffener to crossbeam. connections, with or without cope holes, influence the behaviour of the crossbeam. The effects can be transferred to effective properties of a beam without cut outs. The deformations of the crossbeam and the stiffeners cause secondary stresses in the stiffeners and the web of the crossbeam. The sensitivity of these stresses with respect to various web depths and shapes of cut out is also investigated. The objective of this study is to improve the knowledge of the fatigue design of these structures.
Key words: Orthotropic Steel Bridge Deck, Trapezoidal Closed Stiffener, Trough Stiffener, Crossbeam, Stress Analysis, Fatigue, Effective Bending Stiffness, Effective Shear Stiffness
- Zhao Su, Microstructure and Properties of Styrene Acrylate Polymer Cement Concrete, Heron, Vol. 40 (1995) No. 4, pp. 263-284.
Summary: The paper systematically describes the evolution of the microstructure of a styrene acrylate polymer cement concrete in relation to its mechanical properties and durability. The results presented and discussed at the present paper involve the interaction of the polymer dispersion with portland cement, the effect of the polymer modification on the hydration of cement, the evolution of the microstructure of polymer cement pastes at the early stage, the interface, pore structure, mechanical properties and freeze-thaw (F-T) resistance of polymer cement concrete (PCC). The objective of this investigation is to arrive at a better understanding of the microstructure of PCC and the way in which the microstructure develops. Furthermore, an attempt has been made to relate the micro-structure of concrete to its mechanical properties and durability aspects, such as F-T resistance.
Key words: Microstructure, Polymer Dispersion, Cement Concrete, Mechanical Properties, Freeze/Thaw
- A. Vervuurt, B. Chiaia and J.G.M. van Mier, Damage Evolution in Different Types of Concrete by Means of Splitting Tests, Heron, Vol. 40 (1995) No. 4, pp. 285-311.
Summary: A new splitting test has been used for evaluating damage in different types of concrete. The set up was developed at the Stevin Laboratory of Delft University of Technology and comprises a completely new loading device in which a perfectly horizontal splitting load can be applied to concrete specimens. In addition to classical mechanical measurements, a high resolution optical microscope has been adopted for crack detection at the surface of the thin specimens. Microscale information was obtained on the topological characteristics of the damage patterns. Fractal dimensions were computed. In total, three cement paste mixtures, four mortars and four different types of concrete will be discussed in this paper. The concretes contained either river gravel with different maximum aggregate size (2 and 16 mm), phosphorous-slag aggregates or Lytag lightweight aggregates. To obtain a better understanding of the failure mechanisms at the interface between matrix and composite, tests were performed where a single (cylindrical) aggregate was embedded in a matrix of cement paste or mortar. It will be shown that the concrete mixture with phosphorous-slag aggregates yields the highest peak load and the most brittle post-peak behavior whereas the concrete with large river gravel aggregates shows the most ductile load-displacement response. Furthermore the interfacial strength is affected substantially by the density of the aggregates. This provides a different failure mechanism for the lightweight concrete as indicated by the microscopic observations. The fractal analysis of the different damage patterns confirmed different behaviors, strictly related to peculiar microscopic mechanisms.
- P.B. Lourenço, J.G. Rots and J. Blaauwendraad, Two Approaches for the Analysis of Masonry Structures: Micro and Macro-Modelling, Heron, Vol. 40 (1995) No. 4, pp. 313-340.
Summary: Two models for the micro- and macro-analysis of masonry structures are presented. For the micromodeling of masonry, an interface failure criterion that includes a straight tension cut-off, the Coulomb friction law and an elliptical cap is proposed. The inelastic behavior includes tensile strength softening, cohesion softening, compressive strength hardening/softening and coupling between tensile and shear failure. It is shown that the model is capable of describing the local interaction of both masonry components and of reproducing, in a detailed manner, observed experimental behavior. For the macro-modeling, an anisotropic continuum model that includes a Rankine type yield surface for tension and a Hill type yield surface for compression is proposed. Anisotropic elasticity is combined with anisotropic plasticity, in such a way that totally different behavior can be predicted along the material axes, both in tension and compression. It is shown that, for sufficiently large structures, the global response of masonry can be well predicted even without the inclusion of the local interaction between the masonry components.
Key words: Plasticity, Composite Yield Criteria, Softening, Finite Element Analysis, Masonry Modeling
- E. Panjeh Shahi, Stress Concentration Factors for Multiplanar Joints in RHS, Heron, Vol. 40 (1995) No. 4, pp. 341-352.
Summary: Hollow sections are most suitable for welded connections between members. The welding procedure is fairly straightforward in RHS, because they do not require profiling which is necessary for circular hollow sections. Although many multiplanar and uniplanar joints in structures are present, limited evidence is available for the fatigue behaviour of joints made of rectangular hollow sections. This is especially for the fatigue behaviour of multiplanar joints in square hollow sections which is the reason for setting up this research programme. An extensive experimental and numerical investigation was carried out for the determination of Stress and Strain Concentration Factors in Square Hollow Sections. This paper presents the numerical results for KK-multiplanar joints to demonstrate the influence of other braces.
Key words: Fatigue, Square Hollow Sections, Stress (Strain) Concentration Factors, Multiplanar Joints, Influence Factors
Volume 39 - 1994
Volume 38 - 1993
- D.J. Chinn, Long-Distance Ultrasonic Testing of Steel Structures, Heron, Vol. 39 (1994) No. 1, pp. 1-72.
- A.C.W.M. Vrouwenvelder, Inspection and Maintenance Strategies, Preface, Heron, Vol. 39 (1994) No. 2, pp. 1-2.
- A. van der Toorn, The Maintenance of Civil Engineering Structures, Heron, Vol. 39 (1994) No. 2, pp. 3-34.
- O.D. Dijkstra, S.E. van Manen and F.B.J. Gijsbers, Probabilistic Maintenance Planning for the Tubular Joints in the Steel Gates in the Eastern Scheldt Storm Surge Barrier, Heron, Vol. 39 (1994) No. 2, pp. 35-63.
- D.J.D. Wijnmalen and J.A.M. Hontelez, A Model for Determining Strategies to Maintain Single Components of a System at Minimal Costs, Heron, Vol. 39 (1994) No. 2, pp. 65-83.
- P.J. van Gestel, KEMA Maintenance Optimization Support System, Heron, Vol. 39 (1994) No. 2, pp. 85-96.
- H.K.T. Kuijper and J.K. Vrijling, Economical Optimization of the Maintenance of a River Bed Protection Construction, Heron, Vol. 39 (1994) No. 2, pp. 97-107.
- A. Romeijn, The Fatigue Behaviour of Multiplanar Tubular Joints, Heron, Vol. 39 (1994) No. 3, pp. 1-82.
- G.J. van der Vegte, The Static Behaviour of Axially Loaded Uniplanar and Multiplanar Tubular X-Joints, Heron, Vol. 39 (1994) No. 4, pp. 1-96.
Volume 37 - 1992
- J.A. Larbi, Microstructure of the Interfacial Zone around Aggregate Particles in Concrete, Heron, Vol. 38 (1993) No. 1, pp. 1-69.
- E. Schlangen, Experimental and Numerical Analysis of Fracture Processes in Concrete, Heron, Vol. 38 (1993) No. 2, pp. 1-117.
- R.A. Vonk, A Micromechanical Investigation of Softening of Concrete Loaded in Compression, Heron, Vol. 38 (1993) No. 3, pp. 1-94.
- P.H. Feenstra and R. de Borst, Aspects of Robust Computational Modeling for Plain and Reinforced Concrete, Heron, Vol. 38 (1993) No. 4, pp. 1-76.
Volume 36 - 1991
- D.A. Hordijk, Tensile and Tensile Fatigue Behaviour of Concrete; Experiments, Modelling and Analyses, Heron, Vol. 37 (1992) No. 1, pp. 1-79.
- A.M. van Wingerde, The Fatigue Behaviour of T- and X-Joints Made of Square Hollow Sections, Heron, Vol. 37 (1992) No. 2, pp. 1-181. Erratum
- K. van Breugel, Numerical Simulation of Hydration and Microstructural Development in Hardening Cement-Based Materials, Heron, Vol. 37 (1992) No. 3, pp. 1-62.
- R. de Borst, Computational Mechanics of Composite Materials, Preface, Heron, Vol. 37 (1992) No. 4, pp. 1-2.
- L.J. Sluys and R. de Borst, Computational Modelling of Impact Tests on Steel Fibre Reinforced Concrete Beams, Heron, Vol. 37 (1992) No. 4, pp. 3-15.
- M.H.J.W. Paas and J. van den Eikhoff, Numerical Analysis of Degradation Processes in Laminated Composite Materials, Heron, Vol. 37 (1992) No. 4, pp. 17-32.
- J.C.J. Schellekens and R. de Borst, Micromechanical Analysis of Delamination, Fracture and Debonding in Advanced Composites, Heron, Vol. 37 (1992) No. 4, pp. 33-69.
Volume 35 - 1990
- J.L. Bijnagte, P. van den Berg, N.F. Zorn and H.A. Dieterman, Laterally Loaded Single Pile in Soft Soil, Theory and Reality, Heron, Vol. 36 (1991) No. 1, pp. 1-78.
- R. de Borst and D.G. Roddeman, Computational Mechanics: Recent Developments in DIANA, Editorial, Heron, Vol. 36 (1991) No. 2, p. 2.
- L.J. Sluys and R. de Borst, Rate-Dependent Modelling of Concrete Fracture, Heron, Vol. 36 (1991) No. 2, pp. 3-15.
- M.A.N. Hendriks, Identification of Elastic Properties by a Numerical-Experimental Method, Heron, Vol. 36 (1991) No. 2, pp. 17-26.
- A. Bout and F. van Keulen, A Mixed Element for Geometrically and Physically Nonlinear Shell Problems, Heron, Vol. 36 (1991) No. 2, pp. 27-35.
- J.C.J. Schellekens and R. de Borst, Application of Linear and Nonlinear Fracture Mechanics Options to Free Edge Delamination in Laminated Composites, Heron, Vol. 36 (1991) No. 2, pp. 37-48.
- J.G. Rots, Numerical Simulation of Cracking in Structural Masonry, Heron, Vol. 36 (1991) No. 2, pp. 49-63.
- D.G. Roddeman, Some Aspects of Artificial Diffusion in Flow Analysis, Heron, Vol. 36 (1991) No. 2, pp. 65-71.
- P. van den Berg, Numerical Analysis of Soil-Structure Interaction, Evaluation and Application to Cofferdam Construction, Heron, Vol. 36 (1991) No. 2, pp. 73-85.
- P. Liu, An experimental and Numerical Study on Jack-Up Dynamic Behavior, Heron, Vol. 36 (1991) No. 3, pp. 1-128.
- J.G.M. van Mier, M.B. Nooru-Mohamed and G. Timmers, An Experimental Study of Shear Fracture and Aggregate Interlock in Cementbased Composites, Heron, Vol. 36 (1991) No. 4, pp. 1-104.
Volume 34 - 1989
- J.W. Frénay, Theory and Experiments on the Behaviour of Cracks in Concrete Subjected to Sustained Shear Loading, Heron, Vol. 35 (1990) No. 1, pp. 1-80.
- C. van der Veen, Theoretical and Experimental Determination of the Crack Width in Reinforced Concrete at Very Low Temperatures, Heron, Vol. 35 (1990) No. 2, pp. 1-104.
- M.C.M. Bakker, Yield Line Analysis of Post-Collapse Behaviour of Thin-Walled Steel Members, Heron, Vol. 35 (1990) No. 3, pp. 1-50.
- C.R. Braam, Control of Crack Width in Deep Reinforced Concrete Beams, Heron, Vol. 35 (1990) No. 4, pp. 1-106.
Volume 33 - 1988
- J.G. Rots and J. Blaauwendraad, Crack Models for Concrete, Discrete or Smeared? Fixed, Multi-Directional or Rotating?, Heron, Vol. 34 (1989) No. 1, pp. 1-59.
- J.M.J.M. Bijen, Maintenance and Repair of Concrete Structures, Heron, Vol. 34 (1989) No. 2, pp. 1-82.
- A.G.T.J. Heinsbroek and J. Blaauwendraad, Reinforced Concrete Beams under Shock Loading, Linear and Nonlinear Response, Heron, Vol. 34 (1989) No. 3, pp. 1-73.
- J.W.B. Stark, Composite Steel and Concrete Beams with Partial Shear Connection, Heron, Vol. 34 (1989) No. 4, pp. 1-63.
Volume 32 - 1987
- R. de Borst, P.A.J. van den Bogert and J. Zeilmaker, Modelling and Analysis of Rubberlike Materials, Heron, Vol. 33 (1988) No. 1, pp. 1-57.
- R.S. Puthli, J. Wardenier, C.H.M. de Koning, A.M. van Wingerde and F.J. van Dooren, Numerical and Experimental Determination of Strain (Stress) Concentration Factors of Welded Joints between Square Hollow Sections, Heron, Vol. 33 (1988) No. 2, pp. 1-50.
- A.J.M. Siemes, Fatigue Evaluation of Concrete Structures, Preliminary Studies, Procedure and Examples, Heron, Vol. 33 (1988) No. 3, pp. 1-75.
- A.F. Pruijssers, Theoretical and Experimental Analysis of the Behaviour of Cracked Concrete under Monotonic and Cyclic Shear Loading, Heron, Vol. 33 (1988) No. 4, pp. 1-72.
Volume 31 - 1986
- F. Soetens, Welded Connections in Aluminium Alloy Structures, Heron, Vol. 32 (1987) No. 1, pp. 1-48.
- A.S.G. Bruggeling, Structural Concrete, Science into Practice, Heron, Vol. 32 (1987) No. 2, pp. 1-67.
- J.G.M. van Mier, Examples of Non-Linear Analysis of Reinforced Concrete Structures with DIANA, Heron, Vol. 32 (1987) No. 3, pp. 1-147.
- A.L. Bouma, H.W. Loof and J. Witteveen, Special Issue on the Retirement of ir. F.K. Ligtenberg, Editorial, Heron, Vol. 32 (1987) No. 4, pp. 1-4.
- F.K. Ligtenberg, Reports and Publications, Heron, Vol. 32 (1987) No. 4, pp. 5-8.
- A.C.W.M. Vrouwenvelder and A.J.M. Siemes, Probabilistic Calibration Procedure for the Derivation of Partial Safety Factors for the Netherlands Building Codes, Heron, Vol. 32 (1987) No. 4, pp. 9-29.
- G.J. Gantvoort, A.J. Wubs, L.H.J. Goossens, P.V. Heimplaetzer, Safety in and around the House with Particular Reference to Stairs, Heron, Vol. 32 (1987) No. 4, pp. 31-54.
- W.J. Beranek, The Prediction of Damage to Masonry Buildings caused by Subsoil Settlements, Heron, Vol. 32 (1987) No. 4, pp. 55-93.
- L. Twilt and J. Witteveen, Trends in Fire Safety Design of Buildings, Heron, Vol. 32 (1987) No. 4, pp. 95-114.
- I.M. Mortelhand, Heron's Fountain, What shoulder, and what art, Heron, Vol. 32 (1987) No. 4, pp. 115-121.
Volume 30 - 1985
- F.K. Ligtenberg, J. Witteveen, Special Issue on the Retirement of prof. ir. A.L. Bouma, Editorial, Heron, Vol. 31 (1986) No. 1, pp. 3,4.
- H.S. Rutten, Forty Years of Theory, Design and Construction of Thin Cells, Heron, Vol. 31 (1986) No. 1, pp. 5-31.
- J. Blaauwendraad, Axisymmetry in Elasticity, Old Wine in New Bottles, Heron, Vol. 31 (1986) No. 1, pp. 33-47.
- A.W.M. Kok, The Numerical Calculation of Shear Properties of Members, Heron, Vol. 31 (1986) No. 1, pp. 49-57.
- C. Hartsuijker and H.W. Loof, Geometrically Non-Linear Behaviour of a Bar with Shear Deformation, Heron, Vol. 31 (1986) No. 1, pp. 59-71.
- H. van Koten, Cross-Wind Movements of Chimneys, Heron, Vol. 31 (1986) No. 1, pp. 73-84.
- A.C.W.M. Vrouwenvelder and E.M. Gostelie, Reliability Analysis for the Fatigue Limit State of the ASTRID Offshore Platform, Heron, Vol. 31 (1986) No. 1, pp. 85-98.
- H.J. Grootenboer, Stressanalysis of Implanted Knee Joint Prostheses with and without Metal/Cement Bonding, Heron, Vol. 31 (1986) No. 1, pp. 99-108.
- I.M. Mortelhand, Heron's Fountain, Frames with Fearful Symmetry, Heron, Vol. 31 (1986) No. 1, pp. 109-116.
- J. Witteveen, Fracture Mechanics and Structural Aspects of Concrete, Editorial, Heron, Vol. 31 (1986) No. 2, p. 2.
- Y.M. de Haan, Micro Reinforcement of Cement Composites, Short Introduction to the Theme of the Symposium, Heron, Vol. 31 (1986) No. 2, pp. 3,4.
- J. Kasperkiewicz, Fracture and Crack Propagation Energy in Plain Concrete, Heron, Vol. 31 (1986) No. 2, pp. 5-14.
- P. Stroeven, Stereology of Concrete Reinforced with Short Steel Fibres, Heron, Vol. 31 (1986) No. 2, pp. 15-28.
- R. Babut, Structural Investigation of Steel Fibre Reinforced Concrete, Heron, Vol. 31 (1986) No. 2, pp. 29-43.
- H.A.W. Cornelissen, D.A. Hordijk and H.W. Reinhardt, Experimental Determination of Crack Softening Characteristics of Normalweight and Lightweight Concrete, Heron, Vol. 31 (1986) No. 2, pp. 45-56.
- J.G.M. van Mier, Fracture of Concrete under Complex Stress, Heron, Vol. 31 (1986) No. 3, pp. 1-90.
- A.M. Gresnigt, Plastic Design of Buried Steel Pipelines in Settlement Areas, Heron, Vol. 31 (1986) No. 4, pp. 1-113.
Volume 29 - 1984
- J.G. Rots, P. Nauta, G.M.A. Kusters and J. Blaauwendraad, Smeared Crack Approach and Fracture Localization in Concrete, Heron, Vol. 30 (1985) No. 1, pp. 1-48.
- G.M. van Erp, The Stability of Timber Portal Frames and Arch Frames, An Investigation into the Twist-Bend Buckling Stability of Structural Frames of Constant Rectangular Cross-section, Resiliently Supported by Bracings, Heron, Vol. 30 (1985) No. 2, pp. 1-53.
- A.J.M. Siemes, A.C.W.M. Vrouwenvelder and A. van den Beukel, Durability of Buildings, A Reliability Analysis, Heron, Vol. 30 (1985) No. 3, pp. 1-48.
- R.J. van Foeken and H.H. Snijder, Steel Column and Frame Stability Analysis Using Finite Element Techniques, Heron, Vol. 30 (1985) No. 4, pp. 1-29.
- J.M.M. Out, Yield Surface for Bending Moment, Shear Force and Normal Force, Heron, Vol. 30 (1985) No. 4, pp. 30-58.
Volume 28 - 1983
- W.J. Beranek, Wind Environment around Single Buildings of Rectangular Shape, Heron, Vol. 29 (1984) No. 1, pp. 1-31.
- W.J. Beranek, Wind Environment around Building Configurations, Heron, Vol. 29 (1984) No. 1, pp. 2,33-70.
- H.W. Reinhardt, Fracture Mechanics of an Elastic Softening Material like Concrete, Heron, Vol. 29 (1984) No. 2, pp. 1-42.
- P.A. Vermeer and R. de Borst, Non-Associated Plasticity for Soils, Concrete and Rock, Heron, Vol. 29 (1984) No. 3, pp. 1-64.
- H.A.W. Cornelissen, Fatigue Failure of Concrete in Tension, Heron, Vol. 29 (1984) No. 4, pp. 1-68.
Volume 27 - 1982
- C. van der Veen and J. Blaauwendraad, Dynamic Elasto-Plastic Model for Reinforced Concrete Members, Heron, Vol. 28 (1983) No. 1, pp. 1-54.
- J. Blaauwendraad and A.K. de Groot, Progress in Research on Reinforced Concrete Plane Frames, Application of the Non-Linear Program STANIL to the Overall Safety of Frames with Imperfect Connections, Heron, Vol. 28 (1983) No. 2, pp. 1-59.
- J.C. Walraven and W.P.M. Mercx, The Bearing Capacity of Prestressed Hollow Core Slabs, Heron, Vol. 28 (1983) No. 3, pp. 1-46.
- S. Lenos, The Analysis of Reinforced Concrete Flat Slabs by Plastic Theory, Heron, Vol. 28 (1983) No. 4, pp. 1-33.
Volume 26 - 1981
- A. de Kraker, J.W. Tichler and A.C.W.M. Vrouwenvelder, Safety, Reliability and Service Life of Structures, Heron, Vol. 27 (1982) No. 1, pp. 1-87.
- S.E. van Manen, Plastic Design of Braced Frames allowing Plastic Hinges in the Columns, Heron, Vol. 27 (1982) No. 2, pp. 1-19.
- A.J. Kolvoort and T Woestenburg, Investigation of the Stresses in Rails, Secondary Effects Associated with the Bending of a Centrically Loaded Rail, Vol. 27 (1982) No. 2, pp. 21-35.
- H.W. Reinhardt, Concrete under Impact Loading, Tensile Strength and Bond, Heron, Vol. 27 (1982) No. 3, pp. 1-48.
- F.S.K. Bijlaard, The Design of Transverse and Longitudinal Stiffeners for Stiffened Plate Panels, Heron, Vol. 27 (1982) No. 4, pp. 1-91.
Volume 25 - 1980
- J.C. Walraven and H.W. Reinhardt, Theory and Experiments on the Mechanical Behaviour of Cracks in Plain and Reinforced Concrete Subjected to Shear Loading, Heron, Vol. 26 (1981) No. 1A, pp. 1-68.
- A.K. de Groot, G.M.A. Kusters and Th. Monnier, Numerical Modelling of Bond-Slip Behaviour, Heron, Vol. 26 (1981) No. 1B, pp. 1-90.
- H.J. Grootenboer, S.F.C.H. Leijten and J. Blaauwendraad, Numerical Models for Reinforced Concrete Structures in Plane Stress, Heron, Vol. 26 (1981) No. 1C, pp. 1-83.
- R.S. Puthli, Geometrical Non-Linearity in Collapse Analysis of Thick Shells with Application to Tubular Steel Joints, Heron, Vol. 26 (1981) No. 2, pp. 1-31.
- C.F. Etienne, D.C. Binnekamp, W.J. Copier, R. Hendrickx and C.L. Smit, Corrosion Protection of Unbounded Tendons, Heron, Vol. 26 (1981) No. 3, pp. 1-74.
- H. van Koten and P. Middendorp, Testing of Fondation Piles, Heron, Vol. 26 (1981) No. 4, pp. 1-42.
Volume 24 - 1979
- A.K. de Groot and G.M.A. Kusters, General Derivation of Hardening Formulas, Heron, Vol. 25 (1980) No. 1, pp. 1-42.
- R.S. Puthli, Collapse Analysis of Three Dimensional Assemblages of Eccentrically Stiffened Hot Rolled Steel Plates and Shallow Shells, Heron, Vol. 25 (1980) No. 2, pp. 1-45.
- H. Mihashi and F.H. Wittmann, Stochastic Approach to Study the Influence of Rate of Loading on Strength of Concrete, Heron, Vol. 25 (1980) No. 3, pp. 1-54. Errata
- A.W. de Jongh, A Simplified Approach to Creep Buckling and Creep Instability of Steel-Concrete Columns, Heron, Vol. 25 (1980) No. 4, pp. 1-41.
Volume 23 - 1978
- J. van Leeuwen and A.J.M. Siemes, Miner's Rule with respect to Plain Concrete, Heron, Vol. 24 (1979) No. 1, pp. 1-34.
- W.J. Copier, The Spalling of Normalweight and Lightweight Concrete on Exposure to Fire, Heron, Vol. 24 (1979) No. 2, pp. 1-92.
- M.G.M. Pat and H.W. Reinhardt, Erosion of Concrete, Heron, Vol. 24 (1979) No. 3, pp. 1-24.
- P. Stroeven, H.W. Reinhardt and H.A. Körmeling, Fibre Concrete, Foreword, Heron, Vol. 24 (1979) No. 4, pp. 3-6.
- P. Stroeven, Micro- and Macromechanical Behaviour of Steel Fibre Reinforced Mortar in Tension, Heron, Vol. 24 (1979) No. 4, pp. 1,7-40.
- H.W. Reinhardt, A Concrete Beam reinforced with Bars and Steel Fibres in Pure Bending, Heron, Vol. 24 (1979) No. 4, pp. 1,41-47.
- H.A. Körmeling, Experiments on Concrete Beams reinforced with Conventional Reinforcement and Steel Fibres subjected to Fatigue Loading, Heron, Vol. 24 (1979) No. 4, pp. 1,48-65.
Volume 22 - 1977
- A.S.G. Bruggeling, S.H. Brunekreef and J.C. Walraven, Partially Prestressed Concrete, Theory and Experiments, Heron, Vol. 23 (1978) No. 1, pp. 1-A4.4.
- A. van den Beukel, Composite Beams, Heron, Vol. 23 (1978) No. 2, pp. 1-47.
- H. Stoffers, Cracking due to Shrinkage and Temperature Variation in Walls, Heron, Vol. 23 (1978) No. 3, pp. 1-68.
- J. Dekker, J. Kuipers and H. Ploos van Amstel, Buckling Strength of Plywood, Results of Tests and Design Recommendations, Heron, Vol. 23 (1978) No. 4, pp. 1-59.
Volume 21 - 1976
- P.C. Kreijger, Research into the Embrittlement of Prestressing Steel (Stress Corrosion), Heron, Vol. 22 (1977) No. 1, pp. 5-12.
- W.L. Sluijter and P.C. Kreijger, Potentio Dynamic Polarization Curves and Steel Corrosion, Heron, Vol. 22 (1977) No. 1, pp. 13-27.
- W.L. Sluijter and P.C. Kreijger, Corrosion of Reinforcement in Concrete due to Calcium Chloride, Heron, Vol. 22 (1977) No. 1, pp. 28-45.
- F. Bergsma, J.W. Boon and C.F. Etienne, Endurance Tests for Determining the Susceptibility of Prestressing Steel to Hydrogen Embrittlement, Heron, Vol. 22 (1977) No. 1, pp. 46-76.
- A. van den Beukel, Non-Linear Analysis of Concrete Members, Heron, Vol. 22 (1977) No. 2, pp. 1-24.
- A.C.W.M. Vrouwenvelder, Optimum Fire Resistance, Heron, Vol. 22 (1977) No. 3, pp. 1-19.
- H. van Koten, Structural Damping, Heron, Vol. 22 (1977) No. 4, pp. 1-74.
Volume 20 - 1974, 1975
- J. Boon and Th. Monnier, Fire Resistance of Prestressed Concrete Beams, Heron, Vol. 21 (1976) No. 1, pp. 1-46.
- A.S.G. Bruggeling, Th. Monnier and H.W. Reinhardt, Editorial Betonforschung unterwegs, Beiträge zum 6. Forschungskolloquium des Deutschen Ausschusses für Stahlbeton, gehalten am 5. Oktober 1976 in Delft, Niederlande, (18 contributions of IBBC-TNO and Delft University to a meeting of the DAfStb in Delft at Oct. 5, 1976), (In German), Heron, Vol. 21 (1976) No. 2, pp. 1-7.
- Th. Monnier, Durchlaufträger (In German), Heron, Vol. 21 (1976) No. 2, pp. 9-17.
- F.B.J. Gijsbers, Rotationsfähigkeit (In German), Heron, Vol. 21 (1976) No. 2, pp. 19-27.
- J.C. Walraven, Spannungs-Dehnungsverhalten von gerissenem Beton (In German), Heron, Vol. 21 (1976) No. 2, pp. 29-40.
- A.K. de Groot, Stabilitätsnachweis van Rahmensystemen (In German), Heron, Vol. 21 (1976) No. 2, pp. 41-49.
- W.J. Copier, Spannbeton ohne Verbund (In German), Heron, Vol. 21 (1976) No. 2, pp. 51-60.
- J.A. den Uijl, Verbundeigenschaften von Litzen unter einmaliger und wiederholter Beanspruchung (In German), Heron, Vol. 21 (1976) No. 2, pp. 61-69.
- S.H. Brunekreef, Teilweise vorgespannter Beton (In German), Heron, Vol. 21 (1976) No. 2, pp. 71-81.
- J. Bednář, Spannungsumlagerung infolge Schwinden und Kriechen inzentrisch belasteten Stahlbetonprismen (In German), Heron, Vol. 21 (1976) No. 2, pp. 83-85.
- H.W. Reinhardt, Einige Fragen zum Fertigteilbau (In German), Heron, Vol. 21 (1976) No. 2, pp. 87-89.
- J. Stroband, Verbindungen im Fertigteilbau, I (In German), Heron, Vol. 21 (1976) No. 2, pp. 91-101.
- M. Dragosavić, Verbindungen im Fertigteilbau, II (In German), Heron, Vol. 21 (1976) No. 2, pp. 103-108.
- A. van den Beukel, Kranzkonsolen (In German), Heron, Vol. 21 (1976) No. 2, pp. 109-115. Errata
- W.A. Eisma Rationalisierung der Bewehrung (In German), Heron, Vol. 21 (1976) No. 2, pp. 117-134.
- P.J. van Stekelenburg, Bewehren von Rahmenecken mit negativem und positivem Moment (In German), Heron, Vol. 21 (1976) No. 2, pp. 135-140.
- L. Huibregtse, Qualitätskontrolle (In German), Heron, Vol. 21 (1976) No. 2, pp. 41-46.
- G.J. Gantvoort, Probleme bei der Ausführung van Betonplattformen (In German), Heron, Vol. 21 (1976) No. 2, pp. 147-152.
- A.S.G. Bruggeling, Umfang und Möglichkeiten der Mitarbeit van Studenten in der Forschung (In German), Heron, Vol. 21 (1976) No. 2, pp. 153-155
- J. Brakel, Laufende Arbeiten in der Fachgruppe Betonkonstruktionen der TU Delft (In German), Heron, Vol. 21 (1976) No. 2, pp. 157-162.
- A. van den Beukel, Punching Shear at Inner, Edge and Corner Columns, Heron, Vol. 21 (1976) No. 3, pp. 1-30.
- A.L. Bouma, H. van Koten, F.G. Koch and J. Meek, Experimental Investigation of the Effect of varying the Reinforcement upon the Behaviour of Circular Slabs, Heron, Vol. 21 (1976) No. 4, pp. 1-38.
Volume 19 - 1973
- P. Zoetemeijer, A Design Method for the Tension Side of Statically Loaded, Bolted Beam-to-Column Connections, Heron, Vol. 20 (1974) No. 1, pp. 1-59.
- M. Dragosavić and A. van den Beukel, Punching Shear, Heron, Vol. 20 (1974) No. 2, pp. 1-48.
- M. Dragosavić, A. van den Beukel and F.B.J. Gijsbers, Loop Connections between Precast Concrete Components Loaded in Bending, Heron, Vol. 20 (1975) No. 3, pp. 1-36.
- A. Vrouwenvelder and J. Witteveen, Lower Bound Approximation for Elastic Buckling Loads, Heron, Vol. 20 (1975) No. 4, pp. 1-27.
Volume 18 - 1972
- D. Bartels and C.A.M. Bos, Investigation of the Effect of the Boundary Conditions on the Lateral Buckling Phenomenon, Taking Account of Cross Sectional Deformation, Heron, Vol. 19 (1973) No. 1, pp. 1-26.
- J. Strating and H. Vos, Computer Simulation of the E.C.C.S. Buckling Curve using a Monte-Carlo Method, Heron, Vol. 19 (1973) No. 2, pp. 1-38.
- P.D. Steijaert, Underwater Concrete, Heron, Vol. 19 (1973) No. 3, pp. 1-52.
- M. Dragosavić, Structural Measures Against Natural-Gas Explosions in High-Rise Blocks of Flats, Heron, Vol. 19 (1973) No. 4, pp. 1-51.
Volume 17 - 1970, 1971
- L.J.M. Nelissen, Biaxial Testing of Normal Concrete, Heron, Vol. 18 (1972) No. 1, pp. 1-90.
- Th. Monnier, Cases of Damage to Prestressed Concrete, Heron, Vol. 18 (1972) No. 2, pp. 1-75.
- Th. Monnier and P.J.H. Schnackers, Model Research on a Prestressed Concrete Pressure Vessel for a Nuclear Power Station, Heron, Vol. 18 (1972) No. 3, pp. 1-44.
- J. Blaauwendraad, Realistic Analysis of Reinforced Concrete Framed Structures, Heron, Vol. 18 (1972) No. 4, pp. 1-31.
- F.K. Ligtenberg, Introduction, Heron, Vol. 17 (1970) No. 1.
- Th. Monnier, The Behaviour of Continuous Beams in Reinforced Concrete, Results of Experimental and Theoretical Investigation, Heron, Vol. 17 (1970) No. 1, pp. 1-83.
- Th. Monnier, The Moment-Curvature Relation of Reinforced Concrete, Heron, Vol. 17 (1970) No. 2, pp. 1-101.
- P. Stroeven, Poissons' Ratio in Uniaxial Tension and Anticlastic Bending of Micro Concrete and Perspex, Heron, Vol. 17 (1970, 1971) No. 3, pp. 1-23.
- A.M. Haas and H. van Koten, The Stability of Doubly Curved Shells having a Positive Curvature Index, Heron, Vol. 17 (1970, 1971) No. 4, pp. 1-48.
Jaargang 16 - 1968
Jaargang 15 . 1967
- C.C. Veerman, Plasticiteits- en vermoeiingsonderzoek bij metalen met behulp van exo-elektronen (Vervolg en slot), Heron, Jaargang 16 (1968) No. 1, pp. 1-19.
- S.C. Haagsma, Oriënterend onderzoek naar de wringsterkte van beton, Heron, Jaargang 16 (1968) No. 1, pp. 20-26.
- In Onderzoek 5, Licht beton voor toepassing in voorgespannen constructies, Stevin-laboratorium, Heron, Jaargang 16 (1968) No. 1, pp. 27-32.
- De Heronsfontein 12, Heron, Jaargang 16 (1968) No. 1, pp. 33-35.
- H. van Koten, Spanningsgolven in een axiaal aangestoten prismatische staaf, Heron, Jaargang 16 (1968) No. 2, pp. 37-59.
- P. Stroeven en H. Voorsluis, Optische methode ter bepaling van zeer kleine vervormingen, Toegepast voor de meting van de dwarscontractie van beton, Heron, Jaargang 16 (1968) No. 2, pp. 60-69.
- De Heronsfontein 13, Heron, Jaargang 16 (1968) No. 2, pp. 71-73.
- J. Kuipers, Structural Safety, Heron, Vol. 16 (1968) English edition No. 5, pp. 1-41.
- R. Soerjadi, On the Computation of the Moments of a Polygon, with some Applications, Heron, Vol. 16 (1968) English edition No. 5, pp. 43-58.
Jaargang 14 . 1966
- J. Witteveen, Het gedrag van in de hoeken door puntlasten belaste platen, met toepassingen op het gebied van experimenteel spannings- en materiaalonderzoek, Heron, Jaargang 15 (1967) No. 1, pp. 1-15.
- J.H.J. Almering, Over de berekening van momenten van willekeurige orde voor een veelhoek, Heron, Jaargang 15 (1967) No. 1, pp. 16-20.
- De Heronsfontein 9, Jaargang 15 (1967) No. 1, pp. 21-23.
- C.C. Veerman, Plasticiteits- en vermoeiingsonderzoek bij metalen met behulp van exo-elektronen, Heron, Jaargang 15 (1967) No. 2, pp. 25-43.
- L.J.M. Nelissen, Over de invloed van beugels en geribde staven op de scheurvorming in op buiging belaste gewapend-betonbalken, Heron, Jaargang 15 (1967) No. 2, pp. 44-57.
- In Onderzoek 4, Triplex als element in draagconstructies, stevin-laboratorium, Heron, Jaargang 15 (1967) No. 2, pp. 58-62.
- De Heronsfontein 10, Jaargang 15 (1967) No. 2, pp. 63-64.
- A.K. de Groot en A. C. van Riel, De stabiliteit van kolommen en wanden van ongewapend beton, Heron, Jaargang 15 (1967) No. 3/4, pp. 65-112.
- J. Boon, De ontwikkeling van een nieuw type afneembare rekmeter, Heron, Jaargang 15 (1967) No. 3/4, pp. 113-117.
- De Heronsfontein 11, Jaargang 15 (1967) No. 3/4, pp. 118-119.
Jaargang 13 . 1965
- R. Filarski, Invloedsvlakken voor de berekening van buigende momenten in de dekplaat van een orthotrope plaatconstructie, Heron, Jaargang 14 (1966) No. 1, pp. 1-14.
- G. Meesters, Benaderingsmethode voor het overgangsmoment van doorgaande liggers met vele velden, Heron, Jaargang 14 (1966) No. 1, pp. 15-22.
- J. Blaauwendraad, Het Elektronisch berekenen van ruimtelijke staafconstructies met bijzondere toepassing op een hoge wand, Heron, Jaargang 14 (1966) No. 1, pp. 23-52.
- Heronsfontein 6, Heron, Jaargang 14 (1966) No. 1, pp. 53-54.
- Bij Professor Vreedenburgh's afscheid, Heron, Jaargang 14 (1966) No. 2, pp. 56-62.
- C.G.J. Vreedenburgh, Ervaring, intuïtie en vernuft in de mechanica en de techniek, Diës-rede 1951, Heron, Jaargang 14 (1966) No. 2, pp. 63-82.
- R.J. Schor, Tien jaren onderzoek op lasgebied in commissie XV-NVL-TNO, Heron, Jaargang 14 (1966) No. 2, pp. 83-89.
- J.G. Hageman, Het onderzoek van paddestoelvloeren, Heron, Jaargang 14 (1966) No. 2, pp. 90-96.
- F.K. Ligtenberg, Vreedenburg en het experimenteel onderzoek, Heron, Jaargang 14 (1966) No. 2, pp. 97-104.
- H.W. Loof, De ontwikkeling van schaalconstructies, Heron, Jaargang 14 (1966) No. 2, pp. 105-112.
- De Heronsfontein 7, Jaargang 14 (1966) No. 2 pp. 113-115.
- Bibliografie C.G.J. Vreedenburgh, Heron, Jaargang 14 (1966) No. 2, pp. 117-120.
- R. Soerjadi, Over de berekening van de profielgrootheden van veelhoekige doorsneden, Heron, Jaargang 14 (1966) No. 3, pp. 123-148.
- In onderzoek 3: Dragende kunststofconstructies, Heron, Jaargang 14 (1966) No. 3, pp. 149-153.
- Heronsfontein 8, Heron, Jaargang 14 (1966) No. 3, pp. 154-156
- J. Witteveen, The Analysis of Plates of Abruptly Varying Thickness with the Aid of the Method of Differences, Heron, Vol. 14 (1966) English edition No. 4, pp. 1-29.
- L.P. Bouwman, The 'Creep' of Rotating Structural Components, Heron, Vol. 14 (1966) English edition No. 4, pp. 30-43.
Jaargang 12 . 1964
- A.S.G. Bruggeling, De spanningsverdeling in een preflexconstructie, Heron, Jaargang 13 (1965) No. 1, pp. 1-27.
- J. Kuipers en P. Vermeyden, De veiligheid van houtverbindingen, Heron, Jaargang 13 (1965) No. 1, pp. 28-44.
- T.T. Lie, Bekledingsmaterialen en bouwconstructies bij brand, Heron, Jaargang 13 (1965) No. 2, pp. 45-81.
- M. Dragosavić, Toepassing van de Moiré-methode ter bepaling van de hoofdspanningsrichtingen in platen, Heron, Jaargang 13 (1965) No. 2, pp. 82-90.
- De Heronsfontein 4, Heron, Jaargang 13 (1965) No. 2, pp. 91-93.
- J. Witteveen, Het berekenen van platen met sprongsgewijs veranderende dikte met behulp van de differentiemethode, Heron, Jaargang 13 (1965) No. 3/4, pp. 95-122.
- In Onderzoek 1, Duurproeven op houtverbindingen, Heron, Jaargang 13 (1965) No. 3/4, pp. 123-127.
- In Onderzoek 2, De toepassing van kunstharslijmen in staalconstructies, Heron, Jaargang 13 (1965) No. 3/4, pp. 127-128.
- De Heronsfontein 5, Heron, Jaargang 13 (1965) No. 3/4, pp. 129-131.
- Lijst van verschenen rapporten IX, I.B.B.C. Instituut T.N.O. voor Bouwmaterialen en Bouwconstructies, Heron, Jaargang 13 (1965) No. 3/4, pp. 132-133.
- Lijst van verschenen rapporten 4, Stevin-laboratorium van de afdeling der Weg- en Waterbouwkunde van de Technische Hogeschool te Delft, Heron, Jaargang 13 (1965) No. 3/4, pp. 134-136.
- F.K. Ligtenberg, Stability and Plastic Design (1), Heron, Vol. 13 (1965) English edition No. 3, pp. 1-12.
- F.K. Ligtenberg, Stability and Plastic Design (2), Heron, Vol. 13 (1965) English edition No. 3, pp. 13-28.
- H.W. Loof, The Theory of the Coupled Spring Foundation as Applied to the Investigation of Structures Supported on Soil, Heron, Vol. 13 (1965) English edition No. 3, pp. 29-49.
Jaargang 11 . 1963
- L.P. Bouwman, Het "kruipen" van roterende constructiedelen, Heron, Jaargang 12 (1964) No. 1, pp. 1-24.
- F.K. Ligtenberg en F. van Melle, Onderzoek naar de vervorming van statisch belaste hoeklassen, Heron, Jaargang 12 (1964) No. 1, pp. 25-41.
- De Heronsfontein 2, Heron, Jaargang 12 (1964) No. 1, pp. 43-44.
- Lijst van verschenen rapporten VIII, I.B.B.C. Instituut T.N.O. voor Bouwmaterialen en Bouwconstructies, Heron, Jaargang 12 (1964) No. 1, pp. 45-47.
- Lijst van verschenen rapporten 3, Stevin-laboratorium van de afdeling der Weg- en Waterbouwkunde van de Technische Hogeschool te Delft, Heron, Jaargang 12 (1964) No. 1, pp. 48-50.
- M. Dragosavić, Stabiliteit van wanden in systeembouw, Heron, Jaargang 12 (1964) No. 2, pp. 51-70.
- H.W. Loof en medewerkers, De programmabibliotheek van het Stevin-laboratorium voor het berekenen van schaalconstructies, Heron, Jaargang 12 (1964) No. 2, pp. 71-98.
- De Heronsfontein 3, Heron, Jaargang 12 (1964) No. 2, pp. 99-101.
Jaargang 10 . 1962
- F.K. Ligtenberg, Analogie-model ter bestudering van knikverschijnselen in het elasto-plastische gebied, Heron, Jaargang 11 (1963) No. 1, pp. 1-13.
- G. Offringa, Spiraaltrappen, Heron, Jaargang 11 (1963) No. 1, pp. 14-27.
- W.R. de Sitter, Theoretisch en experimenteel onderzoek naar het gedrag van een voorgespannen tonschaal, Heron, Jaargang 11 (1963) No. 1, pp. 28-47.
- Lijst van verschenen rapporten VII, I.B.B.C. Instituut T.N.O. voor Bouwmaterialen en Bouwconstructies, Heron, Jaargang 11 (1963) No. 1, pp. 48-49.
- Lijst van verschenen rapporten 2, Stevin-laboratorium van de afdeling der Weg- en Waterbouwkunde van de Technische Hogeschool te Delft, Heron, Jaargang 11 (1963) No. 1, pp. 50-53.
- J. Kuipers, De veiligheid van constructies, onderworpen aan combinaties van verschillende belastingen, Heron, Jaargang 11 (1963) No. 2/3, pp. 55-72.
- A.L. Bouwma, Over benaderingsmethoden bij de berekening van schalen, Heron, Jaargang 11 (1963) No. 2/3, pp. 73-93.
- F.K. Ligtenberg, Stabiliteit en bezwijkanalyse (2), Heron, Jaargang 11 (1963) No. 2/3, pp. 94-109.
- De Heronsfontein, Heron, Jaargang 11 (1963) No. 2/3, pp. 111-113.
- F.K. Ligtenberg, A.C. van Riel, H.J. Vader, J. van Leeuwen, Analogy Model for Studying Buckling Phenomena in the Elasto-Plastic Range, Heron, Jaargang 11 (1963) English edition No. 2, pp. 1-13.
- J. van Leeuwen, A.C. van Riel, Ultimate-Load Design of Axially and Eccentrically Compressed Structural Members, Heron, Jaargang 11 (1963) English edition No. 2, pp. 14-40.
- P. Vermeyden, A Loading Procedure for Testing Timber Joints, Heron, Jaargang 11 (1963) English edition No. 2, pp. 41-51.
Jaargang 9 . 1961
- C.G.J. Vreedenburgh, J. Juipers, J. de Back, P. Warmenhoven, H.W. Loof, G.A.F. van de Sande en H.M. de Haas, Het Stevin-Laboratorium, 1957 - 11 januari - 1962, Heron, Jaargang 10 (1962) No. 1, pp. 1-45.
- P.C. Kreijger, Enige eigenschappen van gesorteerde metselstenen, Heron, Jaargang 10 (1962) No. 1, pp. 46-49.
- J. van Leeuwen, Over de scheurvorming in platen en balken, Heron, Jaargang 10 (1962) No. 1, pp. 50-62.
- H.W. Loof, De theorie van de gekoppeld verende ondersteuning, Heron, Jaargang 10 (1962) No. 2, pp. 63-79.
- W.J. Beranek, Modellen van polystyreenschuim, Heron, Jaargang 10 (1962) No. 2, pp. 80-119.
- A.L. Bouma en H. van Koten, Berekening van gewapend betonplaten onder gelijkmatig verdeelde belasting, Toelichting op art. 40 G.B.V. 1962, Heron, Jaargang 10 (1962) No. 3/4, pp. 121-135.
- J. van Leeuwen en A.C. van Riel, Berekening van centrisch en excentrisch gedrukte constructiedelen volgens de breukmethode, Toelichting op art. 47 en 48 G.B.V. 1962, Heron, Jaargang 10 (1962) No. 3/4, pp. 136-205.
- H.W. Loof, Aanvullende mededelingen op het artikel: De theorie van de gekoppeld verende ondersteuning (Heron 10, No. 2), Heron, Jaargang 10 (1962) No. 3/4, p. 206.
- Introduction, Heron, Jaargang 10 (1962) English edition No. 1, p. 1.
- C.G.J. Vreedenburgh, The Shell with Double Curvature Considered as a Plate on an Elastic Foundation, Heron, Jaargang 10 (1962) English edition No. 1, pp. 2-19.
- J. Boon & A.C. van Riel, Investigation of a Model of the Nabla Girder, Heron, Jaargang 10 (1962) English edition No. 1, pp. 20-40.
- C.G.J. Vreedenburgh en F.K. Ligtenberg, Ten geleide, Heron, Jaargang 9 (1961) No. 1, p. 1.
- Heron van Alexandrië, Heron, Jaargang 9 (1961) No. 1, pp. 2,3.
- C.G.J. Vreedenburgh, De dubbelgekromde schaal beschouwd als een plaat op elastische bedding, Heron, Jaargang 9 (1961) No. 1, pp. 4-21.
- F.K. Ligtenberg, Windtrillingen in hoge gebouwen, Heron, Jaargang 9 (1961) No. 1, pp. 22-43.
- J. Boon en A.C. van Riel, Modelonderzoek van de nabla-ligger, Heron, Jaargang 9 (1961) No. 2, pp. 45-64.
- P. Vermeyden, Sterkte en stijfheid van houten balklagen, Heron, Jaargang 9 (1961) No. 2, pp. 65-96.
- Lijst van verschenen rapporten VI, I.B.B.C. Instituut T.N.O. voor Bouwmaterialen en Bouwconstructies, Heron, Jaargang 9 (1961) No. 2, pp. 97-98.
- Lijst van verschenen rapporten, Stevin-laboratorium van de afdeling der Weg- en Waterbouwkunde van de Technische Hogeschool te Delft, Heron, Jaargang 9 (1961) No. 2, pp. 98-99.
IBC Mededelingen Jaargang 8 - 1960
IBC Mededelingen Jaargang 7 - 1959
- Ter introductie, IBC Mededelingen, Jaargang 8 (1960) No. 1, pp. 1,2.
- Enkele beschouwingen over de veiligheid in constructies, IBC Mededelingen, Jaargang 8 (1960) No. 1, pp. 3-30.
- Veiligheid en catastrofe, IBC Mededelingen, Jaargang 8 (1960) No. 1, pp. 31-51.
- Lijst van verschenen rapporten V, IBC Mededelingen, Jaargang 8 (1960) No. 1, pp. 52-54.
- Aanvulling op: Proeven op een gelaste verbinding (Jaargang 7, No. 1), IBC Mededelingen, Jaargang 8 (1960) No. 1, pp. 55,56.
IBC Mededelingen Jaargang 6 - 1958
- De krimp en de strekte van beton wanneer bij de vervaardiging calciumchloride en een luchtbelvormer worden toegevoegd, IBC Mededelingen, Jaargang 7 (1959) No. 1, pp. 1-5.
- J.F. Rijsdijk, Onderzoek naar het vochtgehalte in vurehouten buitenkozijnen, ramen en balkondeuren van verwarmde gebouwen en woningen, IBC Mededelingen, Jaargang 7 (1959) No. 1, pp. 6-15.
- Proeven op een gelaste verbinding, IBC Mededelingen, Jaargang 7 (1959) No. 1, pp. 16-33.
- Lijst van verschenen rapporten IV, IBC Mededelingen, Jaargang 7 (1959) No. 1, pp. 34-36.
- Modelonderzoek van tonschalen vervaardigd van gewapend microbeton, IBC Mededelingen, Jaargang 7 (1959) No. 2/3, pp. 37-100.
IBC Mededelingen Jaargang 5 - 1957
- Randstoringen bij axiaal-symmetrisch belaste omwentelingsschalen, IBC Mededelingen, Jaargang 6 (1958) No. 1, pp. 1-35.
- De berekening van buigende momenten in rechthoekige gewapend-betonplaten, IBC Mededelingen, Jaargang 6 (1958) No. 2, pp. 37-49.
- Over de invloed van de vorm van enkele knoopplaten op de spanningsverdeling in een knooppunt, IBC Mededelingen, Jaargang 6 (1958) No. 2, pp. 50-55.
- Stabiliteit en bezwijkanalyse, IBC Mededelingen, Jaargang 6 (1958) No. 2, pp. 56-67.
- Lijst van verschenen rapporten II, IBC Mededelingen, Jaargang 6 (1958) No. 2, pp. 67-68.
- Ter introductie, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, p. 69.
- Waarom in hout bouwen en construeren, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 71-74.
- Methode toegepast bij het opstellen van sorteervoorschriften voor naaldhout, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 75-82.
- Enkele beschouwingen over het vervaardigen van gelijmde dragende houtconstructies, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 83-89.
- De invloed van de kruip op gelijmde houten bogen, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 90-96.
- Onderzoek naar het draagvermogen van ringdeuvelverbindingen, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 97-116.
- Lijst van verschenen rapporten III, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 116-118.
- Errata en aanvulling op: De berekening van buigende momenten in rechthoekige gewapend-betonplaten, IBC Mededelingen, Jaargang 6 (1958) No. 3/4, pp. 119,120.
IBC Mededelingen Jaargang 4 - 1956
- Controle van de kwaliteit van beton door middel van akoestisch onderzoek, IBC Mededelingen, Jaargang 5 (1957) No. 1, pp. 1-44.
- Problemen inzake het verband tussen spanningen en vervormingen in beton, IBC Mededelingen, Jaargang 5 (1957) No. 2/3, pp. 45-51.
- Het gedrag van betonconstructies onder invloed van kortstondige belastingen, IBC Mededelingen, Jaargang 5 (1957) No. 2/3, pp. 52-62.
- Onderzoek op het gebied van de bezwijkanalyse, IBC Mededelingen, Jaargang 5 (1957) No. 2/3, pp. 63-76.
- De kubusdruksterkte als maatstaf voor de betonkwaliteit, IBC Mededelingen, Jaargang 5 (1957) No. 4, pp. 77-103.
- Een voorbeeld van modelonderzoek, IBC Mededelingen, Jaargang 5 (1957) No. 4, pp. 104-122.
- Errata voor IBC Mededelingen 4 (1956) No. 2.
- Erratum voor IBC Mededelingen 3 (1955) No. 4.
IBC Mededelingen Jaargang 3 - 1955
- Oriënterend onderzoek naar de corrosie van staal in beton, IBC Mededelingen, Jaargang 4 (1956) No. 1, pp. 1-13.
- Over de verbinding van balken met kolommen, IBC Mededelingen, Jaargang 4 (1956) No. 1, pp. 14-17.
- F.K. Ligtenberg, Onderzoekingen over de spanningsverdeling in kophoeklassen, IBC Mededelingen, Jaargang 4 (1956) No. 1, pp. 18-33.
- De berekening van de spanningsverdeling in cirkelcilindrische schaaldaken volgens de D.K.J.-methode met behulp van een rekenschema, IBC Mededelingen, Jaargang 4 (1956) No. 2, pp. 35-101.
- Het bepalen van de treksterkte van beton - De traditionele methoden en een nieuwe indirecte methode met behulp van een splijtproef op cilinders of kuben, IBC Mededelingen, Jaargang 4 (1956) No. 3, pp. 103-119.
- Over de berekening van kraanrailconstructies II, IBC Mededelingen, Jaargang 4 (1956) No. 3, pp. 120-123.
- De invloed van vocht op versteend beton - Proeven op betontegels, IBC Mededelingen, Jaargang 4 (1956) No. 3, pp. 124-132.
- Lijst van verschenen rapporten, IBC Mededelingen, Jaargang 4 (1956) No. 3, pp. 133, 134.
- De waarschuwing van de breuk bij op buiging belaste, éénzijding gewapende, rechthoekige betonbalken, IBC Mededelingen, Jaargang 4 (1956) No. 4, pp. 135-143.
- De berekening van statisch onbepaalde constructies door het meten van grote verplaatsingen aan kleine, eenvoudige modellen, IBC Mededelingen, Jaargang 4 (1956) No. 4, pp. 144-156.
- Erratum voor IBC Mededelingen 4 (1956) No. 3, p. 157.
WGS Mededelingen - Jaargang 2 - 1954
- D. Dresden, Het nieuwe instituut T.N.O. voor Bouwmaterialen en Bouwconstructies, IBC Mededelingen, Jaargang 3 (1955) No. 1, pp. 1,2.
- C.A. Lobry de Bruyn, Het onderzoek van bouwmaterialen, IBC Mededelingen, Jaargang 3 (1955) No. 1, pp. 3-7.
- De afleiding van een stelsel niet-lineaire differentiaalvergelijkingen voor cirkelcylindrische schalen bij grote doorbuigingen, IBC Mededelingen, Jaargang 3 (1955) No. 1, pp. 8-17.
- Schaaldakmodel - Experimentele toetsing van enkele analytische berekeningsmethoden, IBC Mededelingen, Jaargang 3 (1955) No. 1, pp. 18-32.
- De meewerkende breedte bij platen onder geconcentreerde belastingen, IBC Mededelingen, Jaargang 3 (1955) No. 2, pp. 33-49.
- Het meten van temperaturen in constructies van gewapend beton, IBC Mededelingen, Jaargang 3 (1955) No. 2, pp. 50-55.
- Over de berekening van kraanrailconstructies, IBC Mededelingen, Jaargang 3 (1955) No. 2, pp. 56-64.
- Secundaire spanningen bij geknikte flenzen, IBC Mededelingen, Jaargang 3 (1955) No. 2, pp. 65-68.
- Inleiding over de kruip van beton, IBC Mededelingen, Jaargang 3 (1955) No. 3, pp. 69-79.
- Over de invloed van de kruip en de relaxatie op de spanningen en vervormingen in constructies, in het bijzonder bij excentrisch gedrukte staven en bogen, IBC Mededelingen, Jaargang 3 (1955) No. 3, pp. 80-107.
- Over mechanische modellen bij de beschrijving van het niet-elastische gedrag van materialen en over de structuur van beton, IBC Mededelingen, Jaargang 3 (1955) No. 3, pp. 108-116.
- Modelproeven, Enige beschouwingen en toepassingen, IBC Mededelingen, Jaargang 3 (1955) No. 4, pp. 117-136.
- Controleberekening voor de breukveiligheid van enkelzijdig gewapende en van voorgespannen betonconstructies, die op buiging worden belast of op buiging en normaalkracht, IBC Mededelingen, Jaargang 3 (1955) No. 4, pp. 137-147.
WGS Mededelingen - Jaargang 1 - 1953
- Het nieuwe laboratorium van de werkgroep gewapend beton- en staalconstructies T.N.O., WGS Mededelingen, Jaargang 2 (1954) No. 1, pp. 1-3.
- Onderzoek naar de invloed van geconcentreerde lasten op platen, WGS Mededelingen, Jaargang 2 (1954) No. 1, pp. 4-33.
- Het gebruik van weerstandsrekstrookjes bij het verrichten van metingen, WGS Mededelingen, Jaargang 2 (1954) No. 1, pp. 34-44.
- Over de spanningsverdeling in cirkelcylindrische schalen, WGS Mededelingen, Jaargang 2 (1954) No. 2, pp. 45-57.
- Over knik van gekoppelde staven, WGS Mededelingen, Jaargang 2 (1954) No. 2, pp. 58-61.
- Inleiding over statisch onbepaalde balkconstructies in voorgespannen beton, WGS Mededelingen, Jaargang 2 (1954) No. 2, pp. 62-76.
- n-Methode of n-vrije methode bij de berekening van op buiging belaste liggers? WGS Mededelingen, Jaargang 2 (1954) No. 3, pp. 77-90.
- Brandproeven op voorgespannen betonliggers, WGS Mededelingen, Jaargang 2 (1954) No. 3, pp. 91-94.
- Theoretisch en experimenteel onderzoek van flanklassen, WGS Mededelingen, Jaargang 2 (1954) No. 3, pp. 95-107.
- Erratum, Jaargang 2 (1954) No. 3, p. 108.
- Verankeringssystemen bij voorgespannen beton, WGS Mededelingen, Jaargang 2 (1954) No. 4, pp. 109-118.
- Discussie over de beoordeling van de betrouwbaarheid van op buiging belaste gewapend betonbalken, WGS Mededelingen, Jaargang 2 (1954) No. 4, pp. 119-128.
- Errata, Jaargang 2 (1954) No. 4, p. 128.
- De spanningsverdeling in een knoopplaat, WGS Mededelingen, Jaargang 2 (1954) No. 4, pp. 129-143.
- Summaries of the Articles of Volume 1 and 2, WGS Mededelingen, Jaargang 2 (1954) No. 4, pp. 144-148.
- C.G.J. Vreedenburg, Ten geleide, WGS Mededelingen, Jaargang 1 (1953) No. 1, pp. 1,2.
- A.L. Bouma, De werkgroep gewapend beton- en staalconstructies, taak - inrichting - arbeidsveld, WGS Mededelingen, Jaargang 1 (1953) No. 1, pp. 3-20.
- Het experimentele onderzoek van constructies, WGS Mededelingen, Jaargang 1 (1953) No. 2, pp. 21-33.
- Het breukmoment bij voorgespannen betonliggers, WGS Mededelingen, Jaargang 1 (1953) No. 2, pp. 34-36.
- Eigen spanningen en scheurvorming in stalen profielen, WGS Mededelingen, Jaargang 1 (1953) No. 2, pp. 37-44.
- Mededelingen van de redactie, WGS Mededelingen, Jaargang 1 (1953) No. 2, p. 44.
- De afleiding van een differentiaalvergelijking voor cirkelcylindrische schalen, WGS Mededelingen, Jaargang 1 (1953) No. 3, pp. 45-52.
- Metingen aan een schaaldak te Rotterdam, WGS Mededelingen, Jaargang 1 (1953) No. 3, pp. 53-62.
- De beoordeling van de betrouwbaarheid van op buiging belaste gewapend betonbalken, WGS Mededelingen, Jaargang 1 (1953) No. 3, pp. 63-72.
- Een hypothese ter verklaring van vermoeiings-verschijnselen, optredend in taaie staalsoorten, WGS Mededelingen, Jaargang 1 (1953) No. 3, pp. 73-88.