Comparative numerical analysis on dynamic effects of underground large scale frame structures under seismic waves

In this paper, dynamic effects of the underground large scale frame structure (ULSFS) with large scales along both two horizontal directions are investigated by 3-D numerical analyses. To guarantee the accuracy of seismic inputs, seismic waves are transformed into equivalent forces adding on the truncated boundary nodes based on the viscous-spring artificial boundary. 3-D finite element models of 4-span, 8-span, and 20-span underground frame structures with surrounding foundation are proposed to simulate small, middle and large scale underground structures. For a comprehensive study of results, another two analyses of the ULSFS are proposed to evaluate the two dynamic effects of structures: structural inertial effects on inner structures, and effects of structural vibration on the whole soil-structure system, respectively. Furthermore, several soil conditions are employed to study influences of the relative stiffness between the structure and soil on the two mentioned dynamic effects of the ULSFS. The results demonstrate that dynamic effects of the ULSFS are much more significant compared with small scale underground structures which make the structural deformations and internal forces to be larger; and dynamic effects of the ULSFS would decrease with increasing elastic moduli of surrounding soils due to great soil constraints.