SEISMIC RESILIENCY ASSESSMENT OF STEEL MOMENT FRAMES WITH NONLINEAR VISCOUS DAMPERS UNDER SECONDARY EARTHQUAKE

Incidents such as earthquakes have led to the formation of a new concept in the analysis of structures and response to events. Resilience is the ability of a system to maintain the desired level of performance and return to service when facing the risks that occur in the structural life cycle. The research process is based on resiliency and calculation of its parameters through maximum structural drift. Three steel moment frames are analyzed based on nonlinear time history analysis under two primary and secondary earthquake records. For damaged frames, viscous dampers with different damping percentages are installed and the intensity of seismic records is increased to the point of structural collapse. It is observed that the presence of dampers in the structure under secondary earthquake results in reduced drift and relative displacement in the floors. Resiliency diagrams of frames are drawn and values of resiliency parameters are calculated. Decreasing the alpha coefficient for each damping percentage increases the robustness coefficient and also increases the level below the resilience diagram for the final performance of the frames. Based on the comparison between alpha coefficient and damping percentage, it has been found that the effect of damping percentage on drift reduction is greater than damping alpha coefficient. It can also be said that the 9-story structure has shown lower resistance to earthquakes and 3-story structure has the best resilient performance.