Out-of-Plane Seismic Performance of URM Walls with Retrofitted Parapets and Flexible Diaphragms

A full-scale multi-wythe unreinforced masonry (URM) wall constructed with a parapet and a flexible diaphragm was subjected to out-of-plane loading on a shake table to investigate the seismic behavior and vulnerability of older existing URM buildings. Several common retrofit techniques were implemented in the specimens to assess their effectiveness. This paper describes the testing program and presents key experimental results, including the hysteretic behavior of the parapet and demands in the floor-to-wall connections. The URM wall sustained shaking consistent with the 2011 Virginia earthquake with minor damage but failed when subjected to a ground motion recorded in the 2011 New Zealand earthquake scaled to a peak ground acceleration of 0.36g. An unexpected sliding failure was observed at the connection of the floor diaphragm to the wall. A comparison of the experimental data and results of analysis of numerical models of the timber diaphragm, floor-to-wall connections and masonry walls indicates the out-of-plane response of URM assemblies can be well predicted.