Optimum placement of supplementary viscous dampers for seismic rehabilitation of steel frames considering soil–structure interaction

In this paper, the significance of soil-structure interaction (SSI) in optimal placement of viscous dampers in steel frames is studied. Optimal placement of dampers is determined with the purpose of achieving performance objectives at three hazard levels using genetic algorithm optimization. Endurance time method is used for seismic nonlinear response analysis of the fixed-base and SSI included frames. The soil beneath the structures is considered as a homogeneous elastic half-space, and the soil-structure systems are modeled by the substructure method. Results indicate that at low excitation intensities, consideration of SSI results in maximum drift ratio reduction at all stories of the frames. At higher intensity levels, more drift is observed in the upper stories of the soil-structure systems in comparison with the fixed-base frames. Higher damping in the upper stories is required to optimally rehabilitate soil-structure systems as compared with the corresponding fixed-base ones. In most of the frames, SSI leads to the reduction of total required damping. However, the optimal damper placement based on the analysis of fixed-base frames can be unconservative due to changes in damping distribution patterns.