Experimental and computational study into the onset of light damage of Dutch masonry structures

P.A. Korswagen, M. Longo, J.G. Rots

Delft University of Technology, Faculty of Civil Engineering and Geosciences, the Netherlands

In recent decades, extraction of natural gas in the northern part of the Netherlands has resulted in low-magnitude, shallow earthquakes. Besides assessing the safety and 'near collapse' state of the structures in the region, the lower damage state or Damage State 1, is important. Light, repeating, seismic events may cause cracks in masonry houses. This has led to societal unrest, serviceability losses and troubled claiming procedures against the government and the companies involved.

An experimental and computational campaign, ongoing at the Delft University of Technology over the past years, aimed to improve the knowledge of the underlying physics of crack initiation and propagation in typical, unreinforced masonry structures, ubiquitous in the Netherlands. Herein is an overview of this study. First a scalar damage parameter is matched to a damage scale to objectively quantify cracking damage and its progression as a function of crack width, length and number. Next, cracking is observed experimentally in walls and spandrels subjected to in-plane loading using high-resolution Digital Image Correlation to detect the formation and evolution of cracks. The experimental results are then interpreted to establish drift intervals for which light damage can be expected.

Subsequently, orthotropic composite continuum models were calibrated against the test results. Modelling and constitutive improvements were made in these 2D models. Then, the validated models were extrapolated to real building cases, also included herein. The combination of existing damage due to e.g. differential settlement, and new damage due to the seismicity is evaluated with these extrapolation models. Finally, the models provide a relationship between the variability in e.g. material strength, earthquake intensity, and damage; this is then employed to determine probabilities for light damage.

Key words: Damage, unreinforced masonry, nonlinear finite element analysis, cracking, experimental tests

HERON
Home Back issues Search Information for authors About HERON	To the contents of Vol. 66, issue 1 To full-text article (pdf 1.15 MB)
	Experimental and computational study into the onset of light damage of Dutch masonry structures P.A. Korswagen, M. Longo, J.G. Rots Delft University of Technology, Faculty of Civil Engineering and Geosciences, the Netherlands In recent decades, extraction of natural gas in the northern part of the Netherlands has resulted in low-magnitude, shallow earthquakes. Besides assessing the safety and 'near collapse' state of the structures in the region, the lower damage state or Damage State 1, is important. Light, repeating, seismic events may cause cracks in masonry houses. This has led to societal unrest, serviceability losses and troubled claiming procedures against the government and the companies involved. An experimental and computational campaign, ongoing at the Delft University of Technology over the past years, aimed to improve the knowledge of the underlying physics of crack initiation and propagation in typical, unreinforced masonry structures, ubiquitous in the Netherlands. Herein is an overview of this study. First a scalar damage parameter is matched to a damage scale to objectively quantify cracking damage and its progression as a function of crack width, length and number. Next, cracking is observed experimentally in walls and spandrels subjected to in-plane loading using high-resolution Digital Image Correlation to detect the formation and evolution of cracks. The experimental results are then interpreted to establish drift intervals for which light damage can be expected. Subsequently, orthotropic composite continuum models were calibrated against the test results. Modelling and constitutive improvements were made in these 2D models. Then, the validated models were extrapolated to real building cases, also included herein. The combination of existing damage due to e.g. differential settlement, and new damage due to the seismicity is evaluated with these extrapolation models. Finally, the models provide a relationship between the variability in e.g. material strength, earthquake intensity, and damage; this is then employed to determine probabilities for light damage. Key words: Damage, unreinforced masonry, nonlinear finite element analysis, cracking, experimental tests