Shaking Table Study on Displacement-Based Design for Seismic Retrofit of Existing Buildings Using Nonlinear Viscous Dampers

Abstract

This paper presents the experimental and analytical results of a shaking-table study on the elastic and inelastic behavior of a 2/3-scale three-story steel structure retrofitted by the nonlinear viscous dampers. The properties of the dampers used in the test are designed based on the displacement-based design procedure. The retrofitted frame exhibits moderate inelastic behavior under the design ground motion of the 275% El Centro earthquake. The lateral floor displacements, story drifts, floor accelerations, story shears, and damper axial forces measured from the frame tested are compared with those obtained from the displacement-based method as well as the nonlinear time-history analysis. It is shown from the study that the addition of nonlinear viscous dampers to the structure results in displacement and force reduction by about 68 to 80% under the 30% El Centro earthquake (PGA ≈ 0.1 g). Higher-mode responses are significantly diminished. In addition, the displacement and acceleration responses of the structure with dampers are appropriately captured by analytical models in the elastic range. The differences between the experimental and analytical results become noticeable in the inelastic range. The displacement-based evaluation procedure tends to underestimate the responses of the damped structure in the elastic range and overestimate them in the inelastic range.