A Spectral Intensity Index of Ground Motions for Input Selection With Consideration of Higher Modes Effect for Super High-Rise Buildings

Abstract eng:
The selection of ground motion is a critical problem which can influence the structural response in seismic design and analysis. Nevertheless, the proposed intensity indexes are unable to consider the influence of higher modes (HM) on seismic response of super tall building structures reasonably. The effect of HM is measured by sufficient number of modes that modal participating mass ratio (MPMR) more than 90% generally. In this study, some spectral intensity indexes are summarized. The MPMR of the first three order vibration mode are counted. Meanwhile, the base shear error of 5 different super high-rise buildings are analyzed when structures with different MPMR. And then, a ground motion spectral intensity index（S90）which MPMR more than 90% for considering the HM is put forward. The correlation between it and super high-rise structural seismic response is studied, and the incremental dynamic analysis (IDA) method is adopted to evaluate its discreteness. The results show that the statistics value of MPMR of the first three orders generally amounted to less than 80%. Only considering the first three order vibration modes of the ground motion intensity indexes to reflect the structural response features is insufficient. There are more than 5% error for the structural base shear due to keeping down vibration modes, and it cannot meet the requirement of the structural base shear errors control according to the MPMR requirements of 90%.The correlation between the response of super high-rise building and S90 is good and the discreteness is also in a reasonable range. It can therefore be taken as a significant reference index when selecting the ground motions input for the analysis of super high rise buildings.

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