Simultaneous optimization of placement and parameters of rotational friction dampers for seismic-excited steel moment-resisting frames

The present paper proposes the simultaneous optimization of the placement and parameters of rotational friction dampers (RFDs) for the seismic protection of a nonlinear steel moment-resisting frame (SMRF). In that respect, the placement and parameters of RFDs in the framework of an optimization problem is simultaneously optimized for a ten-story SMRF subjected to an artificial earthquake. In the optimization problem, the placement of RFDs and their frictional moment and the length of their vertical rigid beam are considered as the design variables, and the ratio of the maximum seismic input energy to the maximum cumulative dissipated energy by the RFDs is selected as the objective function. The mixed discrete-continuous optimization problem is solved by a hybrid of binary and real-coded modified particle swarm optimization (BRPSO). Furthermore, the effect of the number of RFDs is investigated on the seismic performance of the SMRF. The optimization results reveal that a significant portion of the input seismic energy is dissipated by the RFDs and at the same time reducing the amount of the cumulative hysteretic energy of the structure. Therefore, the seismic damage in the structure is significantly reduced. Furthermore, the appreciable reduction of the seismic responses of the structure is not observed by increasing the number of the RFDs. Finally, the results of the seismic assessment indicate that the optimized RFDs obtained for the artificial earthquake can guarantee the structure subjected to real earthquakes.