Typical Collapse Modes of Confined Masonry Buildings under Strong Earthquake Loads

Abstract

Confined masonry structures are a widely applied structural system in many developing countries. During the past Wenchuan Earthquake in 2008, numerous confined masonry buildings collapsed, while many others suffered damage. This study reviews the construction practices of confined masonry buildings in China. Simple models and hand calculation methods are proposed for quantifying the tearing failure of diaphragms, the tensile failure of tie-columns and the sway-mode strength of masonry buildings. The results indicate very good agreement with field observations. The seismic measures that are stipulated in the seismic design codes are very effective for increasing the strength and integrity, but not the ductility of masonry buildings. For those buildings that survived the earthquake, strength rather than ductility protected the confined masonry from collapse or serious damage. Design recommendations are suggested for preventing various types of premature failures and enhancing the lateral strength of masonry buildings.