Collapses of Masonry Structures under Non-Extreme Loads

During moderate seismic events, it is local masonry failures rather than global building responses that provide the bulk of damage. The paper suggests that one can understand the vulnerability to these local failures by analyzing collapses of vernacular structures, especially those that had occurred under non-extreme conditions. Four cases of collapse of unreinforced masonry buildings are presented in the context of the history of building accidents and empirical classifications of collapse mechanism. These accidents occurred in the absence of significant environmental loads and were the result of the walls’ geometric instability that had developed after adjoining demolitions interrupted the continuity of the building block. Aging, shortcuts during erection and especially the plane shape of the buildings’ structure contributed to the failures and should be given a larger weight in seismic risk analysis. Evaluations of non-extreme condition may help lead to efficient solutions of retrofit of large classes of buildings.