Assessment of Perforated Unreinforced Masonry Walls Responding In-Plane

Abstract

The research presented in this thesis describes the seismic assessment of perforated unreinforced masonry (URM) walls subjected to in-plane loading through accurate analysis of the wall lateral capacity and seismic demand. Current assessment methods for determining the capacity of perforated URM walls loaded in-plane, as outlined in the New Zealand guideline document (NZSEE 2006), are based on the assumption of infinitely rigid spandrel elements. From observations of damage after the 2010/2011 Canterbury earthquake sequence, this assumption has been proven to be invalid for certain perforated wall geometries. The research reported in this thesis was conducted with the primary aim of developing a practitioner focused assessment tool that accurately captured the global and local response of a perforated URM wall, with an emphasis placed on defining the influence of the spandrel geometry on the system level response of perforated URM walls responding in-plane. Pseudo-static cyclic testing of six full-scale pier-spandrel substructures and a two storey half-scale isolated perforated URM wall was conducted to investigate the variables which control spandrel failure mode and the influence of spandrel failure on the lateral capacity of multi-storey URM walls. Testing showed that the behaviour of the spandrel has a significant effect on the failure mode of the piers and hence the strength, stiffness and energy dissipation capacity of the system. A non-linear Equivalent Frame modelling method for perforated URM walls using the structural analysis software SAP2000 was appropriately validated using modelling results and experimental data. Spandrel behaviour was included within the modelling through the use of a moment-axial failure domain and a shear-axial relationship. Finally, a modified linear elastic procedure for assessing the demand on the in_ plane loaded walls of URM buildings with flexible diaphragms was developed and validated through the use of non-linear time history modelling.