Elastic and post-elastic response of structures to hybrid broadband synthetic ground motions

In this paper, a statistical comparison between seismic demands of single degree of freedom (SDOF) systems subjected to past events using simulations and actual recordings is provided. A number of SDOF systems are selected considering: (1) eighteen oscillation periods between 0.1s and 8s, (2) elastic case and four non - linearity levels, from mildly inelastic to severely inelastic structures, and (3) two hysteretic behaviors, namely non - degrading and non - evolutionary, and both degrading and evolutionary. Demand spectra in terms of peak and cyclic response and theirs statistics are derived for four historical earthquakes: 1979 M w = 6.5 Imperial Valley, 1989 M w = 6.8 Loma Prieta, 1992 M w = 7.2 Landers, and 1 994 M w = 6.7 Northridge. Results of this study show that both elastic and inelastic demands to simulated and recorded motions are generally similar. However, for some structural systems, the inelastic response to simulated accelerograms may produce demand s that are different from that obtained using corresponding recorded motions. In the case of peak response, these discrepancies are due to differences in the spectral shape while the differences in terms of cyclic response can be explained by some int egral parameters of ground motion (i.e., duration - related). Moreover, the intra - event standard deviation values of structural response calculated from the simulation are generally lower than those given by recorded ground motions. The amount of such d ifferences strongly depends on the SDOF period and nonlinearity level, and to a lesser extent depends on the hysteretic model used. Assessment of the results using formal statistical hypothesis tests indicat es that in most cases the differences are not statistically significant.