عنوان مقاله [English]
The special concentrically braced frame (SCBF) is a common type of steel structural system for resisting lateral loading. This type of system provides the required stiffness and strength at relatively low cost. Design codes, based on past research, have recommended some details for connections and braces, in order to ensure sufficient ductility and energy dissipation capacity in this system for their application in seismic design. In this paper, the behavior of four SCBF specimens with different details of connections is studied using experimental and numerical models. They are single story single bay sub-assemblages of frames with a single brace that are subjected to lateral cyclic loads. In the first specimen, a 2tp straight line clearance at the end of the brace was observed, but, in the second specimen, an 8tp elliptical clearance was provided. In the third and fourth specimens, stiffeners were installed to provide enough stiffness for gusset plates, so that they can act as fixed ends for braces. The dimensions of the gusset plates in these specimens were naturally different. Measures such as stiffness, strength, ductility, energy dissipation capacity and equivalent plastic strain are used to compare the behavior of specimens in experiments and finite element analysis. The results show that all specimens satisfy code expectations with regard to seismic performance. For unstiffened gusset plates, the accumulation of plastic strain at the corners of the gusset plates and in the middle of the brace results in crack initiation and fracture in specimens in the final stages of cyclic loading. In stiffened specimens, although gussets are smaller, plastic hinges are formed in the middle and at the end of the brace element, but final cracking and fracture occurs in the middle of the element. In these specimens, higher buckling resistance and lower out of plane displacement of braces are observed.