Investigation of steel buildings response equipped with buckling-restrained braces against progressive collapse

In the present study, the use of buckling-restrained braces (BRBs) has been evaluated as a research innovation aimed at reducing the potential of progressive collapse in steel braced frames. These braces prevent the overall buckling of brace and provide much more energy absorption than conventional convertible bracing systems. For this purpose, three-dimensional finite element models of 4, 8, and 12-story buildings were simulated in two modes using ordinary and buckling braces and their response against progressive collapse was evaluated. The progressive collapse analysis was carried out using an alternative load path method and the response of the structures to column removal was investigated. Simulation of models was done using ABAQUS software. Also, the accuracy of the finite element method used in simulating the models was evaluated and a suitable agreement between the results was observed. The most significant results show that in steel frames that have BRBs, less stresses have been created compared with conventional steel braces. In all cases, BRBs with internal energy absorption of the structure have caused lower stresses to other structure member, thereby reducing the potential of progressive collapse. Also, the use of BRBs has reduced the rotation of the beam to column connection, compared to conventional bracing. This effect is especially noticeable in buildings with higher altitudes; the maximum amount of joint rotation corresponding to the 12-story building with BRBs has been reduced by 21% compared with the conventional braces. The reason for this is that, in buckling-restrained braces, the members are able to withstand a pressure above the tensile yield strength, and, unlike ordinary systems, the inherent ductility is due to the occurrence of yield in pressure before it begins to buckle.