Stress Performance Analysis Of Negative Moment Region In Prestressed Continuous Steel Girder

China's steel structure industry has a considerable scale.The steel structure with high strength and light weight is suitable for the large-span bridge structures.The support section of the continuous steel beam will have a large negative moment region under the load,of which the upper edge is subjected to tension.The negative moment inevitably has an influence on the mechanical property of the continuous girder bridge in the practical engineering.Besides,the stress in the negative moment region is relatively complex and there are many influencing factors,which is rarely studied at present.Therefore,it is necessary to analyze the stress mechanical characteristics and influencing factors in the negative moment region of the continuous steel girder.In this paper,after consulting domestic and foreign paper literatures on the prestressed steel structure and the negative moment region of the continuous girder bridge,the development background of prestressed steel structure and the research status of the mechanical performance of negative moment region were summarized,and the main factors influencing mechanical performance of negative moment region were introduced.On the basis of the bending performance experiment of a three-span prestressed continuous steel girder without pavement,the nonlinear analysis model was established by the finite element software ANSYS to analyze the mechanical performance of the negative moment region.Besides,the main factors affecting mechanical performance of the negative moment region were studied further by controlling parameters.The research results are as follows:(1)After applying prestress to continuous steel beam,the neutral axis of negative moment section moves up.The top and bottom normal stress and the deflection in the negative moment region are reduced,which depends on the initial tension of the prestressed steel cable.(2)Under the test loading condition,the lower edge stress of the support section floor firstly reaches the yield stress,and the beam reaches the elastic flexural capacity.At the later stage of loading,the section deformation greatly develops,and the test beam cannot continue to take more load due to the large deflection.(3)Considering the tension increment of prestressed steel cable,the yield moment of the negative moment region is calculated,which is in good agreement with the test results;Considering the elastic core height coefficient of the support section,the ultimate flexural capacity of the negative moment region is calculated.(4)The yield moment and ultimate flexural capacity of prestressed continuous steel girder are positively correlated with initial tensile force of prestressed steel cable and the height of steel cable in negative moment region.With the increase of initial tensile force,the yield moment increases with a decreasing trend,and the ultimate flexural capacity increases with a decreasing trend to be constant.The yield moment and ultimate flexural capacity increase linearly as the steel cables move up.