Stress Analysis Of Long-span Cable-Stayed Bridge In The Cantilever Erection State At Wind Action

With the span of bridge increasing,the stiffness of the bridge decreases continuously.As a result,the wind-induced vibration response of the structure becomes more and more sensitive,which causes great hidden danger to the bridge safety and needs to be paid attention to.Up to now,the static wind and buffeting responses of long-span bridges have been extensively researched,and fruitful results have been achieved.But most of them are based on the displacement and internal force of the overall bridge model.The analysis of local windinduced stress state of the beam is rarely reported,which leads to the lack of in-depth understanding of the strength of steel box girders under wind loads by engineers.In practice,there may be a risk of damage caused by excessive local stress of the beam under wind load,especially under the most unfavorable construction conditions,such as the maximum single cantilever and double cantilever construction state of cable-stayed bridge.Therefore,in order to ensure the wind-resistant safety of the main girder in the construction of long-span cable-stayed bridge,this thesis takes a super-long-span cable-stayed bridge as the research object,and carries out finite element analysis of the wind-induced stress of the steel box girder in the maximum cantilever construction state.The work carried out and the conclusions obtained are as follows:(1)Through wind tunnel tests,the tri-component force coefficients and flutter derivatives of the main girder section are obtained.(2)The finite element analysis software ANSYS is used to establish the maximum single cantilever construction model of long-span cable-stayed bridge,calculate the static wind and buffeting response,get the internal force of the main girder section,and make comprehensive comparative analysis to determine the most disadvantageous position.(3)Simply supported boundary conditions are used to simulate the local model,and the mixed finite element model is used to establish the segment plate-shell model.At the same time,the corresponding internal forces of the beam section are extracted from the whole bridge frame model and added to the segment model.The stress level and stress distribution of the beam section under wind load are obtained through detailed analysis.(4)The analysis results show that the stress level of steel box girder is low under the condition of designed wind speed.The fatigue performance and stability of steel box girder meet the requirements of specifications and have sufficient safety reserves.Based on the preliminary study in this thesis,the stress distribution of steel box girder in the maximum cantilever construction state of extra-long-span cable-stayed bridge under design wind load is grasped,and a sub-model boundary condition simulation method is provided to analyze the stress of local beam section.