Numerical analyses of seismic performance of underground and aboveground structures with friction pendulum bearings

摘要

The seismic design concept of base isolation is widely used in the aboveground structures, and the typical isolation device is friction pendulum bearing (FPB). However, there are significant differences in the seismic response characteristics between the underground structures and aboveground structures. Whether the base isolation is suitable for the underground structures remains to be further discussed. In order to shed light on the mechanism of FPB applied in the underground structures, two different seismic mitigation schemes are compared in this paper. One is the structure with FPB under the bottom of the structure and the other is the structure with FPB on the top of central column. Firstly, the FPB is equivalent to two linear springs in the horizontal and vertical directions. The influences on the natural vibration characteristic of the structures and soil-structure systems are discussed based on the linear perturbation method from the perspective of modal analysis. Secondly, the influences on the dynamic responses of aboveground and underground structures are compared based on the dynamic time history analysis of the 2D numerical model of soil-structure system. The results show that the FPB under the bottom of the aboveground structure can extend the natural vibration period of the structure and reduce the seismic response, while the mechanism is not suitable for the underground structure. The FPB under the bottom of the underground structure can only reduce the transmission of the soil shear effect at the bottom of the structure, and there is no obvious change in the seismic responses of the new structure. However, the shear force, bending moment and horizontal deformation of the key vertical support component are greatly reduced in the underground structure with FPB on the top of the central column, which can be considered as an effective seismic mitigation measure for the underground structure to avoid the shear failure of the central column under high axial compression.