The ability of structural elements to absorb input energy through inelastic deformation and supplemental damping is a primary factor in determining structural damage during earthquake excitation. This study proposes an energy methodology for the seismic evaluation of single-degree-of-freedom (SDOF) systems, considering the effect of fluid viscous dampers (FVDs). The FVD is characterized by supplemental damping ratio, [Formula: see text], and velocity power [Formula: see text]. A computer algorithm is developed for the numerical simulation of SDOF systems using nonlinear time history analysis, which is verified through a number of validation examples. This study focuses on issues related to input and hysteretic energies [Formula: see text] with particular emphasis on near-field records and their interrelationship with seismic response demand, which is defined as non-dimensional indices for SDOF systems without FVD and those equipped with FVD. The energy indices ([Formula: see text] and [Formula: see text]) are the ratios of input and hysteretic energies to maximum displacement demand, respectively. The results show that the natural period [Formula: see text], ductility level [Formula: see text], [Formula: see text], and [Formula: see text] have a significant effect in the determination of energy spectra [Formula: see text]. The non-dimensional [Formula: see text] is a more stable and reliable indicator than [Formula: see text] to quantify the damage potential of ground motion. Finally, the observations of the energy approach provided in this study indicate that it can be used as a useful tool for developing energy-based guidelines for structures incorporating FVDs.

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Summary 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 ξadd0.25em 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/EI0.25emfor SDOF systems without and with FVDs, which can serve as a useful tool to analyse structural damage for energy‐based seismic design.