Deformation-capacity of unreinforced masonry elements – from empirical to analytical models

Abstract eng:
Unreinforced masonry (URM) is a brittle construction material and known to be rather vulnerable to seismic loading. In regions of low to moderate seismicity they might however have a sufficient seismic safety if local out-of-plane mechanisms are avoided. Demonstrating this would enable us to maintain stone masonry buildings that shape the image of many cities all over the world and build new buildings using the rather sustainable construction material of burnt clay bricks. However, by means of conventional force-based design methods it is often difficult to demonstrate the seismic safety of URM buildings. Displacement-based design methods are known to lead to more realistic and less conservative results, opening up hence new opportunities for structural masonry. An effective implementation of displacement-based design approaches requires reliable estimates of the structure’s force and displacement capacity. This presentation takes a fresh look at the in-plane drift capacity of URM walls and discusses in particular the influence of the boundary conditions, the size of the test unit and the applied loading history on the drift capacities of URM walls. Starting from the idea of the simple plastic hinge models for reinforced concrete elements, the first mechanical models for the in-plane drift capacities of unreinforced brick masonry walls are presented and compared to the empirical approaches implemented in current codes. The presentation continues with outlining the challenges that are related to stone masonry and points out new parameters that could play a role when determining the displacement capacity of stone masonry walls.

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