Performance-Based Seismic Assessment of RC Frames Strengthened with Steel Angle and Strap Systems

The seismic vulnerability of reinforced concrete (RC) structures designed according to outdated standards lacking seismic provisions has been widely documented through experimental investigations and post-earthquake observations. Consequently, reliable assessment of the seismic performance of such structures and the development of effective strengthening strategies remain critical objectives in earthquake engineering. This study investigates the seismic behavior of RC frames strengthened using steel angle and strap systems through analytical and numerical approaches. A novel sectional moment-curvature model is developed, incorporating confinement effects from stirrups and steel straps as well as local buckling of compressive steel angles. Sectional curvature is converted to member rotation to derive plastic hinge properties for nonlinear structural analysis. The proposed model is validated against experimental data from existing studies, demonstrating strong agreement in predicting flexural and shear behavior. Subsequently, the seismic performance of strengthened RC members and structural systems is evaluated through nonlinear pushover analysis, with emphasis on performance levels, plastic hinge development, and failure mechanisms. Results indicate that the steel angle and strap system substantially enhances load-carrying capacity and ductility, leading to improved seismic performance and reduced structural vulnerability. These findings confirm the effectiveness of the strengthening strategy and provide an analytical framework for performance-based seismic assessment and retrofit design of existing RC structures.

کلیدواژه ها:

Reinforced concrete frames ، Seismic retrofit ، Steel angles and straps ، nonlinear analysis