Stochastic seismic analysis of MDOF structures with viscous damper devices

Fluid damper devices in civil structures such as buildings or bridges are commonly used as energy absorbers for seismic protection. The problem in the response analysis of structures with filled dampers mainly consists in the fact that, due to the strongly nonlinear behavior of such equipments, the response spectrum technique fails. In this paper by using the concept of power spectral density function compatible with the elastic response spectrum and the stochastic linearization technique, the equivalent damping ratio is obtained. It is shown that once the system is linearized results obtained by Monte Carlo simulation and those obtained by stochastic analysis are in good agreement. Response spectrum technique based on the linearized equations of motion and simplified analysis useful for design purposes are discussed in detail.