A Study on Failure Characteristics of Double Plastic Hinge of Bridge Tower of Long-Span Bridge

Within the engineering context of Runyang bridge, tower bridge of suspension bridge is discussed as the main research object of this paper. A number of nonlinear seismic response analyses have been carried out on long-span suspension bridge, and failure mode and failure characteristic of the bridge tower have been under research. Based on this, incremental dynamic analysis is conducted on the tower bridge of suspension bridge under the action of specific seismic oscillations. Also, the failure process under earthquake action has been studied. Researches show that, with continued excitation from sufficiently large seismic loads, the tower bridge of large-span suspension bridge is bound to form one pair of double plastic hinges at the tower bottom with the maximum bending moment as well as at the tower body with the maximum displacement. When double plastic hinges are formed and the next large seismic pulse arrives, the plastic curvature of cross section of the tower bottom and the tower body will simultaneously change. The stress distributed on the bridge tower makes a gradual shift to the tower body, until the curvature of cross section of the tower bottom exceeds the limit and suffers failure, with no more new plastic hinges generated. The five characteristic responses selected in the incremental dynamic analysis are compared. In terms of the IDA curve, the maximum displacement of bridge tower is set as the X-axis, and the grade of seismic load is chosen as the Y-axis, which effectively illustrates the failure process of bridge tower.