Abstract
This study proposes a capacity spectrum Method (CSM)-based procedure to estimate the maximum seismic performance of steel buildings passively controlled with bilinear oil dampers. In the proposed CSM, the maximum seismic response of a building was estimated, in the acceleration-displacement response spectrum, as the intersection between the capacity curve and the damping-adjusted demand curves, using the equivalent linearization method. The building equivalent damping ratio was determined by the sum of the inherent damping, and the square root of sum of squares (SRSS) of the hysteretic damping and the viscous damping of the supplemental oil devices. The calculation steps of the proposed CSM are explained in detail based on the equivalent single degree of freedom (ESDOF) system, and its accuracy was examined by comparison with time history analysis (THA) results. Two model steel buildings of 4 and 10 stories, uniformly equipped with oil dampers along the height, were subjected to six selected earthquake ground motions scaled to be compatible with Level-2 earthquakes, as defined in the Japanese Building Standard Law. The seismic performance of the buildings was estimated by the proposed CSM procedure and compared with the results of nonlinear THA in terms of the maximum story displacements and the shear forces. It was observed that the proposed CSM scheme provided a satisfactory accuracy to assess the maximum nonlinear response of steel buildings passively controlled with oil dampers.
Highlights
The maximum responses of the target buildings under the earthquake ground motions were estimated by the proposed capacity spectrum method (CSM), and compared with the results of nonlinear time history analysis (THA)
A CSM-based procedure to estimate the maximum seismic response of steel buildings equipped with bilinear-type oil dampers was proposed, adopting a simple formula to calculate the effective damping ratio as the sum of the inherent damping and the square root of sum of squares (SRSS)
The required steps for the proposed CSM were given for the equivalent single degree of freedom (ESDOF) system equipped with the equivalent oil dampers
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The seismic performance of buildings with hysteretic and viscous dampers are studied extensively, few studies have been conducted on the CSM methods for passively controlled buildings with bilinear-type oil dampers. This study proposes a CSMbased method to estimate the maximum responses of passively controlled buildings with bilinear-type oil dampers, and the results are compared with those of nonlinear THA. Standard Law of Japan [3], the effective damping ratio, heff , of a seismically isolated building is defined by the direct sum of three types of damping ratios as given in Equation (6). The current research study proposed a formula to calculate the effective damping ratio from the sum of the inherent damping, and the SRSS of the equivalent hysteresis and viscous damping ratios as given in Equation (8). The proposed heff,SRSS , which is obtained from Ceq , is used to evaluate the maximum seismic performance of a steel building by CSM
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