Earthquake response of reinforced concrete buildings retrofitted with inverted-v and zipper braces

Steel bracing system is one of the structural systems used to resist the earthquake. Many existing non-ductile reinforced concrete (RC) structures need to be retrofitted to improve the lateral load carrying capacity. The use of steel bracing for retrofitting is one of the convenient solutions for increasing the earthquake resistance of the structure. In this thesis, 4 and 8 storey existing RC buildings having the same plan and three bays on each direction were considered as a case study. For the rehabilitation of the structures, inverted-V and zipper braces were used. The seismic performance of the retrofitted structures was investigated and compared with the existing ones. In this regard, the effectiveness of using inverted-V and zipper bracing in strengthening the building was examined under different earthquake accelerations. The structures were modeled using a finite element method and evaluated by both nonlinear static and time history analyses. Capacity curves, interstorey index, variation of storey displacement, and roof drift time history were computed for each structural system. The results indicated a considerable enhancement in the earthquake performance of the retrofitted structures and it was observed that the zipper braced systems had more lateral load carrying and energy absorption capacity than the inverted-V braced systems. Keywords: Inverted-V brace; Nonlinear analysis; Reinforced concrete building; Seismic performance; Zipper brace.