SUMMARYRecent improvements in performance-based earthquake engineering require realistic description of seismic demands and accurate estimation of supplied capacities in terms of both forces and deformations. Energy based approaches have a significant advantage in performance assessment because excitation and response durations, accordingly energy absorption and dissipation characteristics, are directly considered whereas force and displacement-based procedures are based only on the maximum response parameters. Energybased procedures mainly consist of the prediction of earthquake input energy imposed on a structural system during an earthquake and energy dissipation performance of the structure.The presented study focuses on the prediction of earthquake input energy. A large number of strongground motions have been collected from the Next Generation Attenuation (NGA) project database, and parametric studies have been conducted for considering the effects of soil type, epicentral distance, moment magnitude, and the fault type on input energy. Then prediction equations for input energy spectra, which are expressed in terms of the equivalent velocity (V eq ) spectra, are derived in terms of these parameters. Moreover, a scaling operation has been developed based on consistent relations between pseudo velocity (PS V ) and input energy spectra. When acceleration and accordingly velocity spectrum is available for a site from probabilistic seismic hazard analysis, it is possible to estimate the input energy spectrum by applying velocity scaling. Both of these approaches are found successful in predicting the V eq spectrum at a site, either from attenuation relations for the considered earthquake source or from the results of probabilistic seismic hazard analysis conducted for the site.

A practical implementation of generalized multi-mode pushover analysis is presented in this study where the number of pushovers is reduced significantly in view of the number of modes contributing to seismic response. It has been demonstrated on two case studies that the reduced procedure for generalized pushover analysis is equally successful in estimating the maximum member deformations and forces under a ground excitation with reference to nonlinear response history analysis. It is further shown that the results obtained by using the mean spectrum of a set of ground motions are almost identical to the mean of the results obtained from separate generalized pushover analyses. These results are also very close to the mean results of the nonlinear response history analyses, hence motivate the implementation of generalized pushover analysis with design spectrum.

The main purpose of this study is to develop a reliable model for predicting the input energy spectra of near-fault ground motions for linear elastic and inelastic systems, and to evaluate the effect of damping and lateral strength on energy dissipation demands. An attenuation model has been developed through one-stage nonlinear regression analysis. Comparative results revealed that near-fault ground motions have significantly larger energy dissipation demands, which are very sensitive to earthquake magnitude and soil type. The effect of damping on elastic and inelastic near-fault input energy spectra is insignificant. Near-fault input energy spectra for inelastic systems is dependent on lateral strength ratio R for short period systems, however, there is almost no dependency on lateral strength for intermediate and long period systems, recalling an equal energy rule. This is a significant advantage for an energy-based design approach.

An attenuation model for input energy spectra under near fault ground motions is developed in this study. The ultimate objective is developing an energy based seismic performance assessment procedure under near fault ground motions. The presented study presents the first phase of this endeavor. The main purpose of this study is to develop a reliable model for predicting the input energy spectra of near-fault ground motions for linear elastic and inelastic systems, and to evaluate the effect of damping and lateral strength on energy dissipation demands. An attenuation model has been developed through one-stage nonlinear regression analysis. Comparative results revealed that near-fault ground motions have significantly larger energy dissipation demands, which are very sensitive to earthquake magnitude and soil type. The effect of damping on elastic and inelastic near fault input energy spectra is insignificant. Near fault input energy spectra for inelastic systems is dependent on lateral strength ratio R for short period systems, however, there is almost no dependency on lateral strength for intermediate and long period systems, recalling an equal energy rule. This is a significant advantage for an energy-based design approach.

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