An Analysis Of Wind Resistance Stability Of Long-span Railway Hybrid Beam Cable-stayed Bridge

The soft structural system and complex cross section forms of long-span Bridges makes its wind resistance design very challenging.In recent years,the construction scale of transportation infrastructure in China is becoming larger and larger,and the construction scale of hybrid beam cable-stayed bridge is growing as well.The problem of wind resistance stability is becoming more and more prominent.So it is of great technical challenge to improve the wind resistance performance of long-span hybrid beam cable-stayed bridge.Based on the engineering background of the new hybrid beam cable-stayed bridge of Guangzhou Nansha port railway crossing Longxue South waterway main bridge,this paper uses the finite element software Midas Civil to establish the finite element model of the whole bridge,and the dynamic characteristics of the bridge were calculated and analyzed.The static three-component force coefficient of the main girder section is calculated by numerical simulation technology,so as to analyze the static wind stability of the hybrid girder cable-stayed bridge.Finally,the flutter stability of the hybrid girder cable-stayed bridge is checked.The main work of this paper is as follows:(1)The finite element model of the whole bridge is established,and the dynamic characteristics of the hybrid beam cable-stayed bridge are analyzed in the completed bridge state and the largest single cantilever construction state.The vibration mode and natural frequency of the bridge structure are obtained,which provide the necessary parameters for the subsequent analysis of the wind resistance stability of the bridge,and the influence of the setting of auxiliary piers on the wind resistance performance of the bridge is also considered.(2)The calculation domain of the girder section is selected reasonably.Firstly,the grid is divided in ANSYS ICEM CFD,and then solved it in Ansys Fluent solver.Finally,the static force coefficients of the girder section in the wind axis coordinate system and the body axis coordinate system are obtained,which provides accurate data for the subsequent static wind stability analysis of the bridge girder.(3)The static wind response of the hybrid girder cable-stayed bridge is calculated at ±3° and 0° wind attack angles respectively.The lateral displacement,vertical displacement and torsional displacement of the main girder span,as well as the displacement along the bridge direction and the displacement across the bridge direction of the tower top are studied on the condition of the wind speed increases 10m/s from 10m/s to 100m/s.Moreover,the static wind displacement response under different initial wind attack angles is considered.Finally,the static wind stability of the hybrid beam cable-stayed bridge is checked.(4)The flutter stability of the hybrid beam cable-stayed bridge is checked by the approximate formula of flutter critical wind speed under the condition of completed bridge and the maximum single cantilever during construction.Then,the flutter stability of the cable-stayed bridge is checked by the empirical coefficient method according to the different wind resistance specifications of the three countries.The calculation results show that the torsional vibration mode of the hybrid beam cable-stayed bridge appears later and the torsional rigidity of the main beam is very large,so it is very beneficial to improve the wind resistance performance of the bridge;The setting of auxiliary piers can improve the wind resistance stability of the bridge;Under the design reference wind speed,whether in the stage of completion or in the stage of construction of the largest single cantilever,the critical wind speed values of static wind,torsional divergence and flutter of the hybrid beam cable-stayed bridge are far greater than their test wind speed values,which shows that the bridge will not have static wind instability and flutter instability,and the safety can be effectively guaranteed during construction and operation.