Structural Behavior of Steel Structure Retrofitted with Bracing Systems and Nonlinear Viscous Dampers

Abstract

Introduction: A steel frame system becomes structurally less efficient when subjected to large lateral loads such as a strong wind or a severe earthquake. Several techniques could enhance the structural performance against these lateral loads, including single diagonal and X-bracing systems, moment-resisting frames, and viscous dampers. Methods: This study aimed to compare these techniques' ability to reduce the structure's dynamic and static behavior when it faces lateral loads. The structure dynamic behavior was discussed through its lateral displacement response computed from the nonlinear dynamic analyses using different seismic and harmonic excitations. The structure static behavior was investigated based on the demand capacity curves and the plastic hinges response computed from the nonlinear static analyses (Pushover) following FEMA P-1050-1 guidelines. In this paper, the viscous dampers were assumed to have a nonlinear behavior (0<α<1) and the impact of the velocity exponent α on their performance against the dynamic excitations was evaluated. Results: The results show that the X-braced frame performs better in reducing the structure displacement response and plastic hinges performance levels formed in the structural members than a single diagonal braced frame, followed by a momentresisting frame. The results also indicate that the X-braced frame has a larger base shear resistance capacity and a smaller deformation capacity than other structural configurations. Conclusion: It was also concluded that, for the same damping coefficient, the performance of nonlinear viscous dampers increased as the velocity exponent decreased.