Temporary Constraint Relief Optimization Scheme For Mixed Steel-Concrete Composite Girder Cable-Stayed Bridge And Force Analysis Of Key Parts

As a new type of bridge structure emerging in recent years,mixed steel-concrete composite girder cable-stayed bridge has become a popular choice for long-span bridges because of its advantages of improving the span capacity of cable-stayed bridge and making full use of the tensile properties of steel and the compressive properties of concrete.Temporary constraints need to be set in the construction process of bridges,and the change of constraints in the system transformation process will have an irreversible impact on the bridge.Taking Yanpingba Yangtze River Bridge in Sichuan province as the engineering background,this paper mainly studies and analyzes the lifting time and sequence of temporary constraints,and mainly carries out the following aspects of work:(1)The stress characteristics of the mixed steel-concrete composite girder cable-stayed bridge are expounded,which are different from other cable-stayed bridges,and the structural characteristics and stress characteristics of the mixed steel-concrete composite girder cablestayed bridge are pointed out.The research status and key directions of temporary constraint relief of hybrid steel-composite cable-stayed Bridges are clarified.(2)Based on the large finite element software,the establishment of a hybrid steel and mixing calculation model of composite beam cable-stayed bridge of fine construction process simulation of three-span mainly to analyze the stress and displacement during construction,found that stress distribution before and after the bridge system transformation and the linear difference obvious,hybrid steel and mixed composite beam cable-stayed bridge temporarily lifted the restriction of time and sequence has a vital role.(3)For a temporary constraint in the process of the bridge system conversion to lift the timing and order three construction schemes are put forward,based on its stress,main girder stress,deflection and girder cable tower on the basis of comparative analysis,using the finite element software ABAQUS to key parts of the system transformation,the cross local modeling and comparative study of closure segments.The results show that when the temporary consolidation of tower beams is removed after mid-span closure and the side span supports are removed,the corresponding stress of the whole bridge system is small in the transition process,the structural alignment is stable,the deflection of main beams is controllable,the deflection of cable towers is reasonable,and the stress of closure section is small.(4)Based on the above established finite element model,the dissolving sequence of the cast-in-place support of the side span was studied,and two specific dissolving schemes were proposed,and the dissolving sequence of the cast-in-place support of the side span was optimized by comprehensive evaluation of the key indicators such as deflection and stress corresponding to the two schemes.(5)To analyze the transformation system key parts-tower beam combined with the construction of the whole process of stress path,determine the most unfavorable loading state,then with the help of finite element software ABAQUS,areas of consolidation of the tower beam local research,through the maximum unbalanced stress state analysis of positive and negative bending moment conditions,optimizing the tower lift beam consolidation order.