Simplified method for the assessment of the nonlinear seismic response of structures equipped with viscous dampers

In this paper a simplified direct assessment method for nonlinear structures equipped with nonlinear fluid viscous dampers is proposed. The effect of this typology of damping system is usually identified with an equivalent supplemental damping ratio which depends on the maximum displacement of the structure, so that iterative procedures are required. The method proposed in this study is composed by two steps. The first one requires the direct estimate of the supplemental damping ratio under elastic conditions. The second step extends the procedure to structures with nonlinear behaviour. The method has then been verified through several applications and comparisons with nonlinear dynamic analyses. Finally it has been extended and ap-plied for probabilistic evaluations.