iAn Evaluation of Seismic Energy Demand: An Attenuation Approach

iii As a first step for the development of an energy-based procedure for seismic design and verifica-tion, establishing seismic demand in the form of absorbed energy spectra for an inelastic single-degree-of-freedom system was the main objective of this research. The absorbed energy (Ea), not the input energy or hysteresis energy, was selected as the key demand parameter because it is not only related to the yield strength but also directly attributed to the damage of the structure. Further-more, expressing Ea in its equivalent velocity form (Va = mEa /2, where m = mass), Va converges to pseudo-velocity (V) in the special case when the structure responds elastically. Thus, the pro-posed Va parameter bridges the seismic demands for both the energy-based and force-based design methods. Based on 273 strong ground motion records from 15 earthquakes in California, an attenua-tion relationship was used to relate Va to the earthquake magnitude, source-to-site distance, and site class. Va, which represents the equivalent velocity of the geometric mean of Ea values for two randomly oriented components of each record, was computed at 27 periods (0.1 sec to 3.0 sec) fo