Seismic performance of multi-story underground subway stations subjected to vertical earthquake excitations

To investigate effects of vertical earthquake on seismic performance of multi-story underground subway stations, a series of shaking table tests and pushover analyses conducted by ABAQUS were carried out. Dynamic responses of central column induced by vertical earthquake were focused, especially the variation of axial force, story drift, and the relationship between responses and bearing capacity. Results from shaking table tests show that vertical ground motion increases central column axial force by up to 26.4% and raises the dynamic axial force proportion borne by central columns to 23.5%. And vertical excitation has negligible effect on column story drift, but large story heights result in drift exceeding 1/200 at 0.333 g horizontal acceleration. Results from pushover analyses show that under high axial compression ratio, column drift capacity decreased up to nearly 50%.