Abstract:
It is well established and routinely observed that unreinforced masonry buildings perform poorly in large earthquakes. This knowledge directly points to the need for a detailed procedure for the seismic assessment and retrofit of unreinforced masonry buildings. Pivotal to the entire assess-ment and retrofit process is the accurate treatment of the dynamic characteristics of flexible timber floor diaphragms, and the development of a straightforward and accurate method for determining the in-plane seismic loads on walls when accounting for both excitation due to self weight, and seismic demand transmitted via wall-diaphragm connections. Pertinent details of the M7.1 2010 Darfield (Canterbury) earthquake are presented, followed by a re-view of results from a large scale experimental program that investigated the strength and stiffness characteristics of timber diaphragms. Next, details are provided of a procedure for determining dia-phragm dynamic characteristics recognizing that diaphragm deformations are primarily associated with shear rather than flexure. Finally, details are summarised of a methodology now adopted in New Zealand for determining the in-plane seismic demand on unreinforced masonry walls.