Seismic performance upgrading for underground structures by introducing sliding isolation bearings

Isolation bearings have been a widely applied seismic strengthening technique in above ground structures. Whereas, the sliding isolation bearings were seldom used in underground structures. This study aims to explore the feasibility of sliding isolation bearings reducing the seismic response of underground structures. The collapse mechanism of underground structures was firstly analyzed by taking the Daikai Station as an example. Numerical results demonstrated that the collapse of the structure was due to the poor ductility of the intermediate columns. Therefore, the sliding isolation bearing could be installed between the columns and the beam to reduce the lateral deformations of columns. In order to determine an appropriate coefficient for sliding bearings, static analyses for the capacity of columns were conducted. Moreover, the performances of a beam-bearing-column system were also investigated. Finally, seismic responses of the underground structure retrofitted with bearings were studied. Numerical results presented that the responses of both columns and the whole structure were reduced remarkably. Moreover, the frictional coefficient of bearing influencing the seismic responses of underground structures was discussed. And some interesting conclusions were also obtained for the seismic design of underground structures.