Seismic fragility assessment of confined masonry houses in Colombia

Abstract

Confined masonry (CM) houses are widely used in low- and mid-rise houses worldwide, especially in countries with emerging economies. CM emerged in Latin America as a response to the severe damage observed in unreinforced masonry buildings following significant earthquakes in the early twentieth century. In Colombia, CM construction dates back to the 1930s, with houses up to five stories tall. A key challenge in seismic risk estimation is predicting the behavior of prevalent construction typologies in a region to inform risk mitigation and management strategies. As a part of a larger project called the National Seismic Risk Model for Colombia, this study presents a seismic fragility assessment of CM houses, evaluating the effects of masonry strength, masonry unit type, wall density, construction quality, and number of stories. A total of 72 archetype houses, representative of Colombian CM structures, were analyzed across low, intermediate, and high seismicity zones. Nonlinear models were proposed and calibrated using quasi-static cyclic tests on confined masonry walls and shaking table tests on scaled buildings. For each archetype, nonlinear time history analyses were conducted in OpenSees, using approximately 370 hazard-consistent ground-motion records to represent the hazard at each site of interest. The results from these structural analyses are then combined with damage information to obtain fragility curves for this building typology. The fragility results of this study, combined with vulnerability functions, will serve as inputs to calculate risk metrics later on as part of the National Seismic Risk Model for Colombia. The present work provides a region-specific fragility assessment, calibrated with local experimental data, which enhances its applicability within Colombia and potentially to other Latin American countries with similar construction practices and standards. These findings can contribute directly to national seismic risk mitigation initiatives.