Investigating the effect of infill walls on the behavior of building with eccentrically braced frame in the Sarpol-e Zahab earthquake through nonlinear analysis

The most important goal in designing eccentrically braced frame (EBF) is that only link beam yields during the earthquake and other structural members remain elastic. Field survey after the Sarpol-e Zahab earthquake shows that despite several defects in structural design and construction of EBFs, due to positive effects of infill walls, they have remained stable. In this study, one three-story steel building with EBF system that was damaged in the Sarpol-e Zahab earthquake, was studied. This building was nonlinearly analysed as a three-story four-bay frame with and without infill walls in Etabs. In the condition that infill walls are not connected to the structure, three cases including case one: design of braces and link beams according to the code, case two: only design of link beams according to the code, and case three: neither design of braces nor design of link beams according to the code were studied. In the condition that infill walls are connected to the structure the existing structure, in which neither the braces nor the link beams are designed according to the code, was considered as case four. Based on the pushover diagram of all four cases, it can be concluded that connecting the infill walls to the structure causes increase in stiffness, strength and energy absorption and it almost compensates the weakness of link beams and braces. In this condition, if there were not infill walls, there would be a possibility of structural collapse.