SEISMIC PERFORMANCE EVALUATION OF STEEL BUILDINGS WITH STRUCTURAL MODIFICATION TECHNIQUES

Abstract

Steel buildings are widely used as multi-story buildings due to their high strength and ductility. However, they remain vulnerable to seismic forces, especially in seismically active regions. This study conducted a 3D nonlinear time-history analysis using ABAQUS to evaluate the impact of structural modifications on the overall real-life constructed building. Every model was examined using the El Centro earthquake 0.32g. The results showed that weakened columns and higher ground floors exhibited longer natural time periods due to the decrease in stiffness. In contrast, strengthened columns decreased the time period, reflecting enhanced rigidity. Top floor maximum displacements were increased by 26.4% and 16.5% in the weakened column and higher ground floor, and reduced by 26.4% and 0.433% in the strengthened column and joint reinforcement, respectively. Inter-story drift was most pronounced in the model with weak column sections, while the higher ground floor showed soft-story behavior, and the stronger column sections showed a considerable decrease in drift. In weakened columns, strengthened columns, and ground floor height increased the timing of peak displacements by 1.8%, 15.4%, and 3.9%, respectively, while joint reinforcement experienced a reduction of 0.36%. Base shear was increased by 7.6% in thickening column sections, while weakening columns, joint reinforcement, and raising the ground floor experienced decreases of 8.0%, 0.99%, and 8.5%, respectively. Acceleration amplification was the largest at the roof in weakened columns and the smallest in the referenced model. Overall, column strengthening proved to be the most effective technique, while column weakening and increasing floor height significantly compromised seismic safety.