大跨度钢-混混合梁斜拉桥施工过程动力特性分析OA

To investigate the dynamic properties of long-span steel-concrete hybrid cable-stayed bridges throughout the construction phase,a construction phase finite element model was developed using MIDAS/Civil,with the Liulv Yongjiang Bridge as the technical background for this model.The subspace iteration method was used to investigate the dynamic characteristics of the bridge during the construction phase.The effect of cable installation and modification on the dynamic characteristics of the structure was investigated,and then the finite element calculation values were compared with the field measurements.The results show that as the cantilever end elongates,the natural frequency of the structure gradually de-creases.The installation of the stay cables significantly influences the fundamental frequency of the the main beam's vertical vibration mode,while its effect on the transverse vibration mode is relatively minor.However,as the cantilever elongates,the additional stiffness provided by the cable gradually weakens.The auxiliary and side columns exert a certain damping effect on the vertical and lateral vibration of the main beam.After system transformation,the vertical stiffness of the main beam decreases significantly.The difference between the measured and calculated values is less than 10%.The safety of the structure is more vulnerable during the maximum double cantilever and maximum single cantilever states than in the completed bridge state.Therefore,the construction organization scheme should take this stage into account and speed up the installation of the auxiliary pier supports and the centre span closure.