Seismic assessment of school buildings with short captive RC columns under subduction seismic sequences

Abstract

This paper presents the results of a study focused on evaluating the seismic performance of school buildings located in a region of high seismicity in the Pacific Coast of Mexico. For this purpose, a family of three archetype school buildings having typical plan view with one-, two-, and three-story height were designed with out-of-date 1990s seismic requirements. Detailed analytical models representative of the archetype school buildings included modelling the nonlinear behaviour of captive reinforced concrete (RC) columns and the adjacent partial-height infill masonry walls commonly found in this type of structures. The analytical models were subjected to a set of 22 as-recorded mainshock-aftershock seismic sequences gathered at stations placed on the subduction zone of the Mexican Pacific Coast. Drift-based fragility curves for captive RC columns failing in shear, which represent the probability of reaching or exceeding four damage states, based on experimental tests are introduced in this study for evaluating their seismic performance. This investigation revealed that the two- and three-story school buildings exhibit larger inter drift demands at the ground story than those exhibited by the one-storey school building, which led to a weak first-storey mechanism under some mainshock earthquake ground motions. Furthermore, it was noted that aftershocks increased the state of damage at the ground storey due to the increase of damage in the captive RC columns. Findings of this investigation highlight the priority of implementing retrofit strategies, mainly for three-storey school buildings.