Mahdi BANAZADEH - Assistant Professor, Department of Civil and Environmental Engineering,Amirkabir University of Technology, Tehran, Iran
Ali GHANBARI - M.Sc. student of Earthquake Engineering, Department of Civil and Environmental Engineering,Amirkabir University of Technology, Tehran, Iran
Massoud HOSSEINALI - M.Sc. student of Structural Engineering, Department of Civil and Environmental Engineering, Sharif University of Technology, Tehran, Iran

In this paper, the performance of relatively high-rise steel moment resisting frame (MRFs) under far field earthquakes is investigated with and without supplemental fluid viscous dampers. In this order, three structures of six, eight and twelve stories are designed according to ASCE 7-10 with and without damper, and the characteristics of linear and nonlinear dampers (α = 0.5) are also calculated with equal damping ratios (20% for the models of six and eight stories, 25% for the model of twelve stories). Then, the structures with and without dampers are modeled in Opensees with plastic hinges. Afterwards, the probability of structure collapse is investigated using Incremental Dynamic Analysis (IDA) under far field records, and the probability of collapse of structures are extracted from fragility curves. The results show that the higher the height is, the higher the probability of collapse is due to the effects of P-Delta. Moreover, use of damper improves performance of the structure and reduces its collapse probability in comparison with structure without damper. On the other hand, it was observed that structure with linear damper shows better performance and it has less collapse probability, in comparison against structure with nonlinear damper with equal damping ratio.

Steel MRFs, Linear and Nonlinear Fluid Viscous Damper, Far Field Ground Motion, Incremental Dynamic Analysis (IDA), Fragility Curve