Seismic assessment of reinforced concrete building strengthened with CFRP sheets using non-linear static approach

Abstract. The gravity load-designed (GLD) reinforced concrete (RC) frames commonly found in Saudi Arabia have limited resistance to lateral loads and are susceptible to column-side sway or soft-story failures during earthquakes. Even in taller buildings where lateral wind loads were considered in the design, it is still crucial to perform a comprehensive seismic evaluation, as higher mode effects can sometimes lead to soft-story mechanisms in the mid to upper levels of the building. The recent seismic event in Saudi Arabia has raised concerns about the safety and vulnerability of RC buildings in the region. This paper presents a performance-based assessment of an existing eight-story RC shear wall building located in Madinah. The building is 8 stories reinforced concrete structure with dome at the top and ribbed plus flat slab system. Nonlinear static pushover analysis was conducted using SAP2000 software, accounting for the inelastic behavior of concrete and steel materials. The shear walls were modeled using mid-pier frame and user defined hinges were assigned. The nonlinear seismic analysis of existing building revealed that shear walls and columns are deficient against the lateral forces and strong beam-weak column mechanism was observed. To meet the seismic and increase the seismic load bearing capacity the building columns and shear walls of the building were retrofitted by Carbon Fiber Reinforced polymer (CFRP) sheets and the seismic performance, strength, and durability of the retrofitted building was evaluated. The study showed that the proposed retrofitting scheme increased the base shear capacity and ductility of the building as well as controlled energy dissipation and strong column-weak beam mechanism were observed in retrofitted building. Also, the load-displacement behavior of the retrofitted building demonstrates a notable enhancement in both strength and stiffness, featuring an increased ultimate base shear capacity and greater deformation capacity prior to reaching the collapse threshold as compared to the existing structure. Overall, the base shear capacity of the existing building is increased by 26% after CFRP retrofitting and performance of the structure is enhanced.