Seismic risk of aging asymmetric reinforced concrete buildings

Reinforced concrete (RC) buildings located in corrosion-laden aggressive environments experience progressive deterioration over time that adversely affects their strength, stiffness, and ductility. While the interaction between corrosion and earthquake has been investigated in the past, most existing studies are limited to plan-symmetric structural systems. In practice, however, a large proportion of buildings exhibit plan asymmetry arising from architectural and functional constraints that lead to coupled lateral–torsional seismic response and elevated damage potential of building components. The current study, therefore, investigates the combined influence of corrosion-induced deterioration and plan irregularity on seismic performance and risk of six-story RC buildings. Building asymmetry is introduced through mass eccentricities of 5%, 10%, and 20%, representing realistic levels of plan irregularity commonly observed in practice. Time-dependent material degradation due to corrosion is explicitly incorporated, and nonlinear time-history analyses of symmetric and asymmetric buildings are performed at multiple stages of their service lives. Damage of both structural (drift sensitive) and nonstructural (drift and acceleration sensitive) components is considered, and their relative contributions towards overall seismic risk of buildings are quantified. Comparative assessments among various cases of asymmetry levels and life-cycle years quantified the amplification of seismic vulnerability and risk of the buildings resulting from individual and combined effects of corrosion deterioration and torsional effects. Results indicate that neglecting the combined influence of plan asymmetry and corrosion may provide unconservative estimates of seismic risk.