The assessment of fragility curves of the Application of diagonal and chevron viscous damper in steel structures using a metaheuristic algorithm for modification of ground motions

A proper design of viscous fluid dampers can assure us more efficiency and improvement of structural frames performance. For this purpose, these two common types of steel bracing frames of chevron and diagonal, equipped with viscous fluid dampers, are going to be analysed in this essay. All dimensional specifications, as well as the specifications of the cross sections and materials used for the beams, columns, and braces of the frame models, are considered as similarities. With the assist of the powerful Open-Sees software, considered frames are modelled in a two-dimensional form and loaded under 15 ground motions of the near-fault and far fault earthquake. These ground motions are modified by a metaheuristic algorithm. Since the viscous dampers depend on the speed of the excitement as a result of the motion of the earth and having a non-linear force-displacement relationship, they require performing nonlinear dynamic analysis, so Incremental Dynamic Analysis is selected for obtaining fragility curves. The results of this study show that using the viscous dampers in conventional steel frames would cause significant reductions in structural responses (such as base shear forces, displacements, accelerations and rate of plasticity of the main members of the structure) and also noticeable increase in dissipated energy in a viscous form. This system could also be suggested for immediate occupancy performance level.