Comparative Case Study of RC Frame Using Finite Element Modeling Under NBC 105:2020 and IS 1893 (Part 1):2016

Nepal’s high seismic vulnerability necessitates stringent design codes to mitigate infrastructure risks. This study compares a regular reinforced concrete frame under Nepal’s NBC 105:2020 and India’s IS 1893 (part 1):2016 using finite element modeling in ETABS and SAP2000 commercial software, incorporating stiffness modifiers prescribed in the codes. Seismic parameters are compared in both ETABS and SAP2000, and for design forces and reinforcement requirements, only ETABS is used. Seismic analyses employed Equivalent Static and Response Spectrum methods. Results reveal NBC 105:2020 mandates double the base shear compared to IS 1893:2016, with lateral displacements surging by 50.6–66.6% under static analysis and 106–108% under dynamic analysis. Drift patterns mirrored displacement trends, showing similar percentage increases. Double base shear, amplified lateral displacements and drifts, consistent across both software analysis approaches, underscore NBC 105:2020’s heightened design forces and reinforcement demands, particularly in lower floors. For beams, NBC 105:2020 required 12.7% more reinforcement, 11.6% higher moments, 110% lower torsion while maintaining comparable shear forces. Columns under NBC exhibited 79.78% higher axial forces, Floor-wise fluctuation in biaxial moments and 10.6% more reinforcement, with lower floors disproportionately impacted. This study suggests that municipalities and engineers in Nepal to follow the NBC code. While NBC 105:2020’s stricter seismic provisions—requiring more robust structural systems, amplified design forces, and higher reinforcement demands compared to IS 1893 (Part 1):2016—escalate construction costs, its conservative approach ensures enhanced seismic resilience, critical for high-seismic-risk regions like Nepal.