Shaking table test study on seismic behavior of underground structure with intermediate columns enhanced by concrete-filled steel tube (CFT)

Many severe damages have long been attributed to the collapse of intermediate columns in underground constructions happened in amounts of disastrous earthquake events. By virtue of a series of shaking table modelling tests, the mechanism and positive and negative effects on structural seismic behavior by means of stiffening underground structure through substituting general reinforced concrete columns with square concrete-filled steel tube (CFT) columns are elaborately studied. The viewpoint is provided from test result analysis that the balance between the safety and applicability of underground structure when stiffening intermediate columns to resist seismic actions should be achieved, as the strengthened intermediate column will not only increase structural aseismic capacity but also induce large structural acceleration responses to the same intensive earthquake. Besides, different structural deformations and load transfer conditions will emerge when changing column formations. Both the dynamic soil behavior and the interaction mechanism between soil and different stiffness underground structures are analyzed. •The working mechanism of CFT column in underground structure under earthquake is examined.•The interaction mechanism between soil and structure is analyzed based on the test data.•The safety and applicability when improving underground structure in earthquakes should be both considered.•The research also can serve well as an implication for practical engineering exercises.