Dynamic Response Spectrum Analysis of Irregul...

Dynamic Response Spectrum Analysis of Irregular Reinforced Concrete Structures Using SAP2000: A Comprehensive Review

Author Name : Ramjan Mohammad, Prof. Narayan Malviya

ABSTRACT Irregular reinforced concrete (RC) buildings are increasingly prevalent in modern urban environments due to architectural, functional, and economic constraints. However, such structural configurations exhibit complex dynamic behaviour under seismic excitation, characterized by torsional coupling, higher-mode participation, and localized deformation. These features significantly influence seismic demand distribution and structural vulnerability. Accurate evaluation of the seismic response of irregular RC structures is therefore essential for ensuring structural safety and performance. This paper presents a comprehensive review of research on the dynamic analysis of irregular RC buildings using the response spectrum method, with particular emphasis on studies employing SAP2000 and similar finite element platforms. The review systematically examines the influence of plan and vertical irregularities, including torsional eccentricity, soft storeys, mass and stiffness discontinuities, and setback configurations, on modal characteristics and seismic response. Modelling strategies, material representation, mass distribution, diaphragm behaviour, and modal combination techniques adopted in previous investigations are critically analysed. Furthermore, this study compares response spectrum analysis with alternative dynamic approaches such as nonlinear time-history analysis and modal pushover methods, highlighting their respective advantages and limitations. The findings indicate that while response spectrum analysis offers computational efficiency and practical applicability, it may underestimate seismic demands in highly irregular structures, particularly under combined irregularity conditions. Modelling uncertainties, limited experimental validation, and neglect of soil–structure interaction are identified as major challenges in current research.