Punching shear capacity of bridge decks regarding compressive membrane action
S. Amir1, C. van der Veen1, J.C. Walraven1, A. de Boer2
1 Department Design and Construction, Structural and Building Engineering, Concrete Structures, Faculty of Civil Engineering and Geosciences, Delft University of Technology, the Netherlands
2 Ministry of Infrastructure and the Environment (Rijkswaterstaat), the Netherlands
In the Netherlands, there are a large number of transversely prestressed concrete bridge decks that have been built in the 60’s and 70’s of the last century and are found to be shear-critical when assessed using the recently implemented EN 1992-1-1:2005 (CEN 2005). To check the safety of such bridges against the wheel print of the Eurocode Load Model 1, laboratory tests on a 1:2 scale model of a prototype bridge, consisting of a thin, transversely prestressed concrete deck slab cast in situ between the flanges of long prestressed concrete girders were carried out. The same bridge was modelled with a finite element program and several nonlinear analyses were carried out to calculate the bearing (punching shear) capacity. The theoretical analysis of the model bridge deck demonstrated that the ultimate load carrying capacity as found from the experiments and the finite element analysis was much higher than predicted by the governing codes. A possible explanation to this anomaly could be the occurrence of “Compressive Membrane Action” (CMA) in the deck slab. A combination of numerical and theoretical approach was developed to incorporate CMA in the Model Code 2010 (fib 2012) punching shear provisions for prestressed slabs to determine the ultimate bearing capacity. Results showed an adequate safety margin against the Eurocode design wheel load leading to the conclusion that the existing transversely prestressed concrete bridge decks (about 70 bridges) still have sufficient residual bearing (punching shear) capacity and considerable savings in cost can be made if compressive membrane action is considered in the analysis.
Key words: Concrete, compressive membrane action, deck slab, prestressing, punching shear