Pushover method for seismic analysis of shield tunnel

The dynamic time-history analysis of shield tunnel seismic design needs long computed time and massive work. The dynamic constitutive model and damp for soils are difficult to determine. Its wide application in practical project is hindered by these problems. In order to solve these difficulties, a modified pushover method for shield tunnel which is developed from pushover method of structure on the ground is put forward; and inclination of shield tunnel is introduced to assess its seismic performance. Since the seismic responses of shield tunnel are determined by the surrounding soils; the horizontal loading model is improved. In this method, the seismic action on shield tunnel is simulated by applying the inverted-triangular lateral horizontal displacement on the model along the depth. The complex problems existed in the dynamic time-history analysis, such as the dynamic constitutive model and damp of soil, the boundary condition, are avoided; and the interaction between tunnel and soil is able to consider in this method. The seismic performance capacity curve also could be obtained by this method. The comparison results with dynamic time- history analysis show that the calculation result of the modified pushover method is reasonable and accurate in the elastic stage. It is an appropriate method for seismic design of shield tunnel.