A new assessment method is proposed considering shortcomings of the current investigations for the assessment of underground structures considering seismic load. First, the dynamic elastic modulus and damping ratio of sand are studied based on the dynamic characteristic experiment of the soil. Subsequently, a series of design acceleration time history curves are obtained using the proposed methods. Finally, the seismic response of underground structures is evaluated by a three-dimensional numerical simulation. The results indicate that the dynamic elastic modulus of sand decreases with the increase of dynamic elastic strain and increases with the increase of confining pressure. The influence of confining pressure on the damping ratio of sand is slight, but it can still be seen that the damping ratio decreases with the increase of confining pressure, especially when the dynamic elastic strain is relatively low. The interlayer displacement between the top and middle plate is 2.1 mm and the interlayer displacement angle is 1/2650. The interlayer displacement between the middle and bottom plate is 1.7 mm and the interlayer displacement angle is 1/4117. Under the action of fortification earthquake, the interlayer displacement angles of Taiyuan Street station are less than 1/550, indicating that the structure meets the seismic requirements.

This article is devoted to study the axial compression behaviour of recycled concrete-filled steel tubular (RCFST) columns after high temperature. Several axial compression members’ internal mechanisms are analyzed by combining experimental and finite element analysis (FEA). Firstly, the failure mode of axial compression members is studied by experiments. Then, based on the correct constitutive relationship between recycled concrete and steel, the finite element model is established by ABAQUS software, and theoretical analysis and experimental verification are carried out, which are in good agreement. The effects of different parameters such as temperature, substitution rate, and bond strength of the coefficient on the whole load-strain curve are compared. The results show that the bearing capacity of recycled concrete-filled steel tubular columns decreases with the increase in temperature and replacement rate. The bond coefficient between steel tubular and core concrete has little effect on the specimen’s overall axial compressive mechanical properties. The interaction force P rises slightly along the height after the high temperature at the peak load, as it gradually moves away from the cover. In the square section, corners show stress concentration, and bulge deformation occurs first under the condition of axial compression.