Seismic response of a steel frame considering the underground subway-soft soil-steel frame interaction

The existence of the underground structures can alter the mechanical behavior of surface structures, leading to increased damage during earthquakes. Therefore, it is essential to consider the effects of underground structures. This paper presents a modeling method for soft soil-steel frame structures, with results that are well-correlated with test data, providing a reliable foundation for modeling the entire system. The subway station is introduced, and the underground subway-soft soil-steel frame finite element model is established to study the influence of soft soil and underground subway on the seismic response of the surface steel frame. Key parameters, including soil stiffness, surface structure, earthquake type, and horizontal distance between the underground and surface structures, are taken into consideration. The results show that soft soil has the ability to filter and amplify seismic waves, and its impact on the soil surface varies depending on the specific seismic wave and soil stiffness. Lower soil stiffness leads to a more pronounced amplification effect. Additionally, the presence of an underground subway can scatter and reflect seismic waves, resulting in a 10 % or so increase in peak acceleration at the soil surface under the same ground motion excitation. Finally, the maximum inter-story drift ratio of the steel frame structure increases significantly under the excitation of EL-Centro and Kobe waves, whereas its change under the Taft wave excitation depends on specific parameters.