3-D numerical analysis on seismic responses of the underground large scale frame structure under near-fault ground motions

This paper mainly focuses on seismic responses of the underground large scale frame structure (ULSFS) under near-fault ground motions with the long-period velocity pulse and high-frequency components. 3-D finite models of the ULSFS with great scales along two horizontal directions are proposed by an underground supermarket under building. A representative near-fault ground motion including the long-period velocity pulse and high-frequency components is selected from the Northridge earthquake. Through parametric analyses, the distinctive seismic responses of the ULSFS under the near-fault ground motion have been highlighted. In addition, the typical near-fault ground motion is decomposed into the low-frequency motion and the high-frequency motion to investigate effects of the soil deformation and structural vibration on the ULSFS, respectively. This study reveals that there are obvious tensile damages on the outside floor slabs and walls where soil-structure interaction is great; and bottom columns have the greatest horizontal deformation and tensile damage with an increase from outside to inside of the ULSFS, and top second-columns perform the salient flexural deformation due to soil-structure interaction. Moreover, the dynamic vibration of the ULSFS not only enlarges the whole seismic responses but also causes the severe tensile damage on outside floor slabs and walls; and the soil deformation in the long-period velocity pulse is more likely to result in the increasing internal forces of bottom columns and the flexural deformations of top second-columns.