大跨混凝土斜拉桥施工过程中结构的断索动力响应

In order to study broken cable-induced dynamic response of long-span concrete cable-stayed bridge during construction, the accident of 9 cables breaking after fire of Chishi Bridge in Hunan Province was taken as background, the nonlinear dynamic finite element analysis model of Chishi Bridge was established by using the finite element software. Cable forces, displacements and crack development of its main girder and tower actually measured after fire were compared with those computed with the finite element model to verify the model's effectiveness. Based on the verified finite element model, the dynamic response of the cable-stayed bridge structure in process of multiple cables fracture was analyzed. The results showed that (1) the static fracture of cable only affects section internal forces and cable force near the broken cable area, while the impact caused by the sudden break of the cable can lead to larger changes of internal forces of the whole bridge structure; (2) partial cables' rupture at one side of cable plane causes a large number of cracks on top plate and web of main girder under the joint action of torque and two-way bending moment, and cracks appear after the fifth cable is broken; (3) dynamic amplification coefficients of the most unfavorable cross-sections of main girder torque, vertical bending moment and transverse bending moment are 1.09-1.55, 1.21-2.05 and 1.21-1.76, respectively, and the dynamic amplification coefficient of the maximum principal compressive stress is 1.02-1.58; (4) dynamic amplification coefficients of the maximum tensile stresses of prestressed tendons and cables are 1.0-1.9 and 1.05-1.4, respectively; (5) the dynamic amplification coefficient of tower top displacement is 1.23-1.65.