Enhanced Seismic Efficiency and Resiliency of Steel-Frame Buildings Using Viscous-Dampers

The focus of this paper is on quantifying and assessing the seismic response of a steel building consisting of moment-resisting frames (MRFs) and damped braced frames with nonlinear viscous dampers. Three MRF designs were studied for 100%, 75%, and 60% of the required base shear design strength according to the ASCE 7 code. The braced frame with nonlinear viscous dampers was designed to control the lateral drift demands. Large-scale experiments were performed, where the structure was subjected to an ensemble of ground motions using earthquake real-time hybrid simulations. In the experiments the ground motions were scaled to the design basis earthquake (DBE) and the maximum considered earthquake (MCE) hazard levels to investigate structural system performance under different earthquake intensities. The experimental program is described, including the real-time hybrid simulation approach, the performance-based design objectives for the structure, and the outcomes of the experiments. The results show that the effects of elastic flexibility in the damper force path of the system can be significant, where larger column axial forces develop than those predicted using current design procedures. In addition, it is shown that MRFs with nonlinear viscous dampers can be designed for a reduced base shear strength that is lower than that prescribed in the ASCE 7 code and achieve a high performance between immediate occupancy and life safety under DBE ground motions, while having a low probability of collapse under the MCE.