Unreinforced masonry (URM) walls with sufficient anchorage to the diaphragms will crack above mid-height when subjected to out-of-plane ground motions. This study investigates the sensitivity of the out-of-plane response to varying height-to-thickness ( h/ t) ratios for URM walls connected to rigid diaphragms. ASCE 41, Seismic Rehabilitation Standard, provides guidelines for permissible h/ t ratios for out-of-plane URM walls. To assess these limits, a rigid-body numerical model, calibrated to full-scale shake table tests, was used. The focus of the analysis was to identify the minimum h/ t ratio that would cause collapse of the wall when subjected to seismic shaking. The analysis was performed for 80 input motions and accounted for variability in the crack location. The results of the study suggest that the probability of collapse is dependent on the site class and that walls with limited overburden and satisfying the h/ t limits in ASCE 41 have a very low probability of collapse.

Given sufficient anchorage to the diaphragms, out-of-plane walls in unreinforced masonry (URM) buildings have been shown to crack above midheight and then rock as two rigid bodies. This study investigates the sensitivity of the rocking response to the type of ground motion and the quality of the wall construction. Shake table tests were conducted on four full-scale multi-wythe walls, all with a height to thickness (h/t) ratio of 12 but of varying construction quality and subjected to three different ground motions. All walls experienced cracking at less than one half of the 2005 National Building Code of Canada (NBCC) level for Vancouver, but exhibited a stable rocking behaviour without collapse beyond a ground motion 1.5 times the 2005 NBCC level.

The 26 December 2004 earthquake and tsunami resulted in over 100,000 damaged or destroyed homes and over 500,000 internally displaced people in northern Sumatra. Reconstruction and recovery from these massive losses requires the coordination of many stakeholders, including multiple levels of government, nongovernment relief organizations, donors, and the people of northern Sumatra. Although efforts have been taken by the Government of Indonesia to develop standards for the reconstruction of houses and establish a coordinating body, the reconstruction effort in Sumatra still faces many challenges. A broad range of housing types, with varying degrees of construction quality, have been constructed as part of the recovery effort. A field study team visited Banda Aceh, Meulaboh, and Nias seven months after the December event and documented the process of reconstruction, the interaction of the stakeholders, and the types of housing construction.

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