Seismic risk evaluation of non-ductile low-rise RC buildings in Brazil: Time-based and intensity-based assessments considering different performance metrics

Abstract

Brazil is located in a stable continental region where earthquakes are infrequent and, as such, there is a scarcity of studies on seismic risk assessment and a current need to make the risk more transparent, which can be helpful to code provisions development and rational decision-making. This paper is a natural progression from previous performance-based studies in the country, and assesses the seismic risk associated with low-rise non-ductile reinforced concrete buildings in Brazil. The risk is estimated as a function of building typology, site location, soil type and capacity criteria. The risk is quantified in terms of limit states’ exceedance probability, fatality rates, monetary losses and downtime using time-based and intensity-based approaches. First, fragility functions are developed using cloud analysis for the three- and five-story buildings settled as case study. The fragility is then combined with consequence models and hazard curves from the national hazard model to estimate the risk in ten sites countrywide and considering five different soil classes. Finally, the results are compared with acceptance criteria found in the literature. The results demonstrate that the collapse risk is generally within the range enforced by codes worldwide in the most critical sites, and the fatality rates are mostly below reasonable thresholds. However, considerable losses and downtime can be expected in some cases for ground motions of engineering importance. Moreover, similar risk is observed between some sites that are in the current seismic design zones of the code and some that are not. We therefore conclude that seismic design could bring benefits in the country and should not be neglected, while also presenting estimates that may be useful for future decision making studies.