Earthquakes pose significant threats to reinforced concrete (RC) buildings, necessitating accurate performance evaluation methods beyond traditional linear elastic approaches. This study comprehensively evaluates the seismic behavior of RC buildings employing nonlinear analysis techniques, including pushover analysis and nonlinear time-history analysis. A ten-story RC frame structure was modeled and subjected to varying seismic intensities to assess performance levels—Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP)—as defined by FEMA-356 guidelines. Material nonlinearity encompassing concrete cracking, crushing, and steel reinforcement yielding was incorporated to capture realistic structural response mechanisms.

The results demonstrate that nonlinear static pushover analysis effectively estimates structural capacity curves, plastic hinge formation sequences, and identifies weak story mechanisms. However, nonlinear dynamic time-history analysis provides superior accuracy in capturing time-dependent behavior, including displacement demands, inter-story drift distributions, and cumulative damage effects under actual ground motion records. Key performance indicators evaluated include base shear capacity, roof displacement, inter-story drift ratios, and plastic hinge rotation demands. Buildings designed according to modern seismic codes (ASCE 7-16, Eurocode 8) exhibited significantly enhanced performance with stable hysteresis and ductile behavior compared to older structures lacking seismic detailing. Furthermore, vertical and plan irregularities were found to adversely affect performance, inducing torsional responses and localized damage concentrations.

This research underscores the critical importance of nonlinear analysis in performance-based seismic design frameworks, providing actionable insights for enhancing RC structural resilience. The findings contribute to safer design methodologies and effective retrofitting strategies for existing vulnerable buildings.