Project Abstract
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The objective is to assess the applicability of simulated ground motions in engineering practice. We have used Single Degree of Freedom (SDOF) and Multi Degree of Freedom (MDOF) systems for this assessment; both linear and nonlinear systems are considered. We focused our efforts on assessing the similarity between simulated and recorded motions from historic events; four events from broadband simulations were investigated: 1979 Mw 6.5 Imperial Valley, 1989 Mw 6.8 Loma Prieta, 1992 Mw 7.2 Landers, and 1994 Mw 6.7 Northridge. Results 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 median demands and dispersions that differ from those obtained using corresponding recorded motions. The magnitude of differences in seismic response depends on the period and the nonlinearity level and, to a lesser extent, on the hysteretic model used. In the case of peak response, these discrepancies are likely due to differences in the spectral shape, while the differences in terms of cyclic response can be explained by some integral parameters of ground motion (i.e., duration-related). Moreover, the intra-event standard deviation values of structural demands calculated from the simulations are generally lower than those given by recorded ground motions, especially at short periods. Assessment of the results using formal statistical hypothesis tests indicates that in most cases the differences found are not significant, increasing the confidence in the use of simulated motions for engineering applications. Caution is warranted given the limited number of SDOF and MDOF models used in this study, plus ground motions were all from historic events where simulations have a high likelihood in matching the recordings. |
