During a seismic event, the walls within an unreinforced masonry (URM) building must possess sufficient capacity to withstand out-of-plane collapse. Traditionally, design against this type of failure has been performed using a force-based (FB) approach, in which the engineer must ensure that the force capacity of the wall is not exceeded during a design earthquake. In recent years, however, seismic design philosophy for ductile systems has experienced a move away from FB methods and toward displacement-based (DB) methods, where the aim is to ensure that
structural deformations are kept within acceptable displacement limits. URM walls subjected to out-of-plane actions make a prime candidate for the development of such methodology. This is particularly true for two-way spanning walls, which have significant displacement capacity as well as good energy dissipation capability during cyclic response—both highly favourable characteristics with respect to seismic performance. This thesis documents research undertaken at the University of Adelaide into the seismic response of two-way URM walls subjected to out-of-plane actions. The aims of this work were to facilitate improvements to the presently-used FB design methods and to provide a basis for the development of a reliable DB design approach.
The following outcomes have been achieved:
• Characterisation of the load-displacement behaviour of two-way walls through quasistatic cyclic testing using airbags;
• Verification of this behaviour under true seismic loading conditions by means of dynamic shaketable tests;
• Improvements to the current state-of-the-art design approach for predicting the ultimate load capacity of walls possessing tensile bond strength;
• A probabilistic approach to deal with the different modes of possible failure in horizontal bending;
• Development of analytical methodology for predicting the load capacity of walls using the assumption of zero tensile bond strength;
• A proposed model for representing the nonlinear inelastic load-displacement behaviour of two-way walls; and finally,
• Implementation of the load-displacement model into a simple DB seismic assessment procedure.
It is anticipated that this research will eventually culminate in a multi-tiered seismic design procedure incorporating both the FB and DB components, with applicability toward the design of new buildings and assessment of existing buildings alike.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 201
