Cyclic Performance of Buckling Restrained Composite BracesComposed of Selected Materials

Concentric bracing is one of the most common lateral load resistant systems in building frames, and areapplied to many structures due to their manufacturing simplicity and economics. An important deficiency in thebracing members is their irregular hysteretic loops under cyclic loading. In order to overcome this problem, it isadvised to restrain braces against buckling under compression, since buckling restrained frames dissipate a largeamount of energy. One method to restrain braces against buckling is to cover them with concrete. Aproper coveringcan prevent the core from buckling and provide similar capacities whether in tension or compression which wouldproduce regular hysteric curves. In this study, the behavior of buckling restrained braces (BRB) has been investigatedby considering different types of surrounding covers. The steel core is encased in concrete with different coverings. Thecovering types include steel tubes, PVC pipes, and FRProlled sheets. Experimental and numerical analyses wereimplemented. According to the results, PVC pipes and FRPsheets are suitable alternatives to steel pipes. Furthermore,the behavior of several types of steel cores was assessed; since, applying steel with high ductility promotes the energydissipation of the brace. Finally, the effect of the separating layer between the steel core and the concrete on theperformance of bracing was evaluated.