Collapse assessment of a Chilean code-conforming reinforced concrete office building

Abstract

Chilean buildings are periodically subjected to earthquakes and their satisfactory performance preventing collapse is widely known. Yet, as a result of the Mw 8.8 2010 Chile earthquake, one reinforced concrete building collapsed and many others were severely damaged, raising concerns about the collapse margin of these structures. Modifications to the Chilean codes were introduced after this earthquake, but Chilean codes are still prescriptive and assessments of the collapse risk of current Chilean buildings is limited. This study evaluates the collapse potential of a code-conforming reinforced concrete office building in Santiago, Chile, whose structural system has a core of two cantilever C-shaped walls surrounded by intermediate moment frames. The architectural layout was designed based on a statistical analysis of the building inventory in Santiago. Incremental dynamic analyses using 45 Chilean earthquakes were performed over a nonlinear model of the building to estimate its collapse fragility, which was combined with a site specific seismic hazard analysis to estimate the mean annual frequency of collapse (lc), and the probability of collapse in 50 years (Pc(50)). Results of lc and Pc(50) were 1.2×10-4 and 0.6%, respectively, and deaggregation of lc is dominated by small to medium earthquake intensities.