Plastic energy evaluation of bilinear SDOF systems with fluid viscous dampers

Current seismic practices are more concerned with dissipating a significant portion of seismic input energy than with lateral load resistance, as well as with determining seismic demands of structures using response spectra. This study aims to improve the knowledge of the plastic energy spectra ( EP ) of single‐degree‐of‐freedom systems (SDOF) equipped with fluid viscous dampers (FVDs). This type of dampers is characterized by its supplemental damping ratio ξadd and velocity power α . Using nonlinear dynamic analyses, the EP and its ratio to the input energy ( EP/EI ) are determined using near‐field‐pulse, near‐field‐non‐pulse and far‐field ground motions. Parametric studies are conducted to investigate the effect of ground motion types, original system features and FVD characteristics on EP/EI spectra. The results show that ground motion types have a considerable influence on the EP/EI for systems with FVDs, while they are not effective for systems without FVDs. Increasing FVD nonlinearity (decreasing α) is more effective to reduce the EP/EI under near‐field‐non‐pulse and far‐field motions than under near‐field‐pulse ground motions for structures with Tn > 1 s. The paper further developed a prediction equation for estimating EP/EI for SDOF systems without and with FVDs, which can serve as a useful tool to analyse structural damage for energy‐based seismic design.