Comparison between predicted URM wall out-of-plane displacement-based performance and in situ proof test results

The current study addresses the final stage of a three-part research program in which a variety of unreinforced masonry (URM) walls were physically tested in situ to measure out-of-plane (OOP) behaviour, were assessed for force-based (i.e., strength) performance, and finally were assessed for displacement-based performance. Predictive assessments were carried out using previously published predictive models, and the comparison of experimental to predictive displacement-based performance is the focus of the study reported herein. Displacement-based criteria were applied at selected points on the force-displacement backbone curve. Other researchers have found weak correlation between the results of experimental data sets and the predictive model that is incorporated within multiple internationally recognised standards such as ASCE 41 and FEMA 356 for URM infill wall drift performance. Furthermore, in situ conditions for URM walls rarely reflect the idealised conditions assumed in analytical predictive models, leading to practicing engineers being uncertain as to which analytical models and inputs are most appropriately applied. In the current study, the predictive results were compared to previously reported experimental results of twelve tests on existing URM walls performed in situ, representing a variety of geometries, boundary conditions, pre-test damage states, and material properties. In general, use of the existing predictive methods results in the over-prediction of the measured displacement parameters, which is likely due to most of the predictive methods being based on historical walls tests in one-way spanning conditions and without rigid restraints capable of effectuating arching action in the wall, in contrast to the wall test conditions in the current study.