Seismic design of multistory reinforced concrete structures requires rigorous evaluation of structural behavior under dynamic earthquake loading. This paper presents a comprehensive comparative analysis of two widely adopted seismic analysis methodologies: Equivalent Static Analysis (ESA) and Response Spectrum Analysis (RSA). Two building models with identical plan configurations (33 m × 30 m) but different heights—a 10-story and 25-story structure—were analyzed according to Indian Standard IS 1893:2016 provisions for seismic zone III. Computational analysis using STAAD PRO V8i was conducted to evaluate critical engineering demand parameters including lateral displacements, inter-story drifts, story stiffness, base shear, and support reactions. The investigation reveals that RSA consistently produces 17-18% lower displacement estimates and inter-story drifts compared to ESA, while generating 18-19% lower overturning moments at the foundation level. These systematic differences have significant implications for design efficiency, material optimization, and foundation design. The study demonstrates that RSA provides more realistic structural response estimates for flexible buildings, particularly when higher vibration modes contribute significantly. The findings indicate that method selection should be based on structural configuration, building period, and design requirements. Results confirm that modern computational capabilities make dynamic analysis methods equally practical as static approaches, supporting their preferential use in seismic design practice.
Rathore et al. (Thu,) studied this question.