Characterisation and Seismic Assessment of Unreinforced Masonry Buildings

Abstract

This thesis describes the characterisation and seismic assessment of unreinforced masonry (URM) buildings. The research in this thesis was conducted with the primary aim of developing a deeper understanding of the response of URM buildings, with an emphasis on the response of URM walls responding in-plane, and in particular, a comprehensive inspection of the in-plane response of flanged URM walls. Most previous expressions for determining the lateral strength capacity of URM walls responding in-plane have not taken into account the effect of flanges, and consequently have underestimated the expected capacity. This thesis identified that in order to accurately account for the strength inherently available in URM buildings, the effect of flanges should be incorporated into the seismic assessment procedure. The New Zealand URM building stock was analysed to determine typical building characteristics, and URM buildings were classified into seven typologies on the basis of building height and building footprint. Further analysis of the building stock determined that most URM buildings in New Zealand are one and two storeys in height. The characterisation of the New Zealand URM building stock was used to form the basis of the experimental programme reported in this thesis, such that specimens accurately reflected construction characteristic of existing New Zealand URM buildings. Testing of URM walls showed that the presence of flanges has a significant effect on the behaviour of walls responding in-plane. Flanges increase the force and displacement capacity of in-plane loaded walls, when compared with in-plane loaded walls without flanges. The results from the experimentation that was conducted in order to determine the limiting strength of the shear walls were compared with analytical results from other research, with a high level of correlation. Consequently, equations were recommended for determining the in-plane lateral strength limits of URM walls both with and without flanges. Drift limits and energy dissipation characteristics were also proposed. Finally, a procedure was developed for assessing the performance of URM buildings, based on displacement based design principles. The procedure was demonstrated using an example.