Seismic retrofit of framed structures using a steel frame with springs and friction dampers

In this research, a seismic retrofit device was proposed and its performance was tested under cyclic loading. The developed damper is composed of a steel frame with friction hinges and springs at corners to provide stiffness and restoring force. Theoretical formulas for its mechanical behavior and its analytical model were developed and verified by comparing them with the results of an experimental test. To further evaluate the applicability of this retrofit system, it was applied to the seismic retrofit of a case study structure designed without considering seismic load. The structure was retrofitted to satisfy a given performance objective and its seismic behavior was compared using nonlinear time history analysis before and after retrofit. The seismic performance of the structure was assessed in terms of maximum interstory drift ratio, residual displacement, and energy dissipation. It was observed that the installed retrofit frames could properly dissipate the seismic energy and reduce both inter-story drifts and residual displacements of the case study structure.