Inelastic Spectra to Predict Constant-Damage Energy Factor of Structures Under Near-Fault Pulse-Type Ground Motions

A simple relationship is proposed to construct constant-damage energy factor (gamma DI) spectra of single-degree-of-freedom (SDOF) oscillators with different levels of damage, expressed by the Park-Ang damage index. gamma DI is computed for SDOF oscillators with four hysteretic models when subjected to 80 pulse-like ground motions. The statistical dependence of gamma DI on initial period, damage index, postyield stiffness ratio, and ultimate ductility factor is investigated. In comparison with the non-pulse-type ground motions, the near-fault pulse-type ground motions can significantly increase the gamma DI of structures, and the magnitude of the increase can reach about 200%. Conservative estimates of mean gamma DI of SDOF oscillators are proposed taking into account the combined effect of period, damage level, and ultimate ductility factor.