Seismic design considerations for underground box structures

Underground structures have generally performed well during seismic events. Nevertheless the design of these structures has to consider seismic loading. Unlike above ground structures, the response of undergound structures to seismic loading is dominated by the seismic deformations of the surrounding soil. Seismic loading is characterized in terms of deformations imposed by the soil on the box structures and the interaction between them. This paper describes seismic analysis approaches for underground structures. The paper reviews available simplified solutions and describes procedures to conduct numerical analyses using pseudo-static and dynamic soil-structure interaction approaches. The paper describes some of the limitations associated with pseudo-static analyses for shallow structure and the need for dynamic soil-structure analyses under these conditions.