Transverse seismic performance index system of urban mass transit underground structures

摘要

The transverse seismic performance index system of urban mass transit underground structures was presented, which included both intensity index of component and overall deformation index, in order to reasonably evaluate its damage degree under seismic excitations. Intensity index of component had two grades and limit values of two levels ware provided. Overall deformation index included story drift angle for rectangular underground structures and diameter deformation rate for shield tunnels. Performance index values of urban mass transit rectangular underground structure story drift angle ware put forward by reference to modified performance index values of ground structure story drift angle, which was based on a statistical analysis for experiment data of forty-six groups concrete-filled steel tubular frames and one hundred forty-five groups steel-reinforced concrete frames and took into account similarities and differences between surface structures and underground structures. Based on relation between tunnel diameter deformation and stress state of tunnel concrete and bolts, the diameter deformation rate was derived from the analytical solution using compatibility of deformation for a segment cross section. And the diameter deformation rate was also computed by means of incremental dynamic analysis method for different sites under various earthquakes. It is found in the study that based on two performance levels, limiting value of diameter deformation rate is obtained.