Probabilistic Seismic Analysis of Steel Structures Equipped with Nonlinear Viscous Dampers

During the recent two decades, many structures have become in need for seismic retrofit due to changes in either requirements of relevant seismic codes or the building usage. Viscous dampers are increasingly employed for seismically retrofitting various structures thanks to their easy installation and minimum intervention into the existing structure while significantly improving the seismic performance of the building. The main objective of this paper is to present a new design procedure for the evaluation of probabilistic seismicity of steel structures equipped with nonlinear viscous dampers. For this purpose, numerical investigation was conducted on, as benchmark structures, three steel-made moment-resistant frames with 3, 9, and 20 stories. Due to significant differences in their dynamic characteristics, these three structures represented low-rise, mid-rise, and high-rise buildings, respectively. Nonlinear time history analysis was performed using two near-field and two far-field accelerograms at various intensities (making up a total of 10 accelerograms). Moreover, nondimensional analysis was done to evaluate the uncertainties associated with velocity exponent of the nonlinear viscous dampers. Next, probabilistic estimation of damages occurred to the benchmark structures was performed and the effect of the uncertainty associated with the dimensionless power intensity of the damper on the seismic response of the structure. Investigating the results of the seismic analysis for viscous dampers at power intensities of 0.2, 0.3, and 0.4, it was found that although the seismic retrofit had significantly improved the seismic performance in all model structures but the proposed design procedure was more effective in the retrofitted high-rise structures at the power intensity of 0.4.