Refined Analysis And Cable Force Optimization For The Long-span Cable-Stayed Bridge With Steel-concrete Stiffening Girder During Closing

In recent years,cable-stayed bridge with steel-concrete composite beam have been widely used in the country due to their advantages of large spanning capacity and low cross-section height of main beams.As the span of the cable-stayed bridge with steel-concrete composite beam continues to increase,the alignment during construction becomes more difficult to control;coupled with the softness of the steel-concrete composite stiffening beam makes the influence of the change of cable force on the structural alignment more obvious.Therefore,in the construction of a cable-stayed bridge with steel-concrete composite beam,the control of the closing of the mid-span steel-concrete composite beam and the optimization of the cable force on the completed bridge is particularly critical.Taking the Yanpingba Yangtze River Bridge in Yibin,Sichuan as the engineering background,this paper studies the mid-span closure and cable force optimization of the long-span cable-stayed bridge with steel-concrete composite beam.The main contents are as follows:1.Based on the large-scale finite element analysis program,the finite element modeling method of the cable-stayed bridge with steel-concrete composite beam is studied,the plat-girder models and the single girder model are established.Through the comparative analysis of the calculation results of the two models,the accuracy of the finite element model is verified and the appropriate modeling method of the cable-stayed bridge with steel-concrete composite beam is determined.The results show that the two models have high calculation accuracy and can accurately reflect the real force of the bridge.The single-beam model has a small number of elements,which can greatly save the calculation time.For a refined analysis of the construction process of composite beams,the plat-girder models has higher accuracy.2.The cable-stayed bridge with steel-concrete composite beam has many influence parameters in the mid-span closure.In this paper,the temperature field of the bridge structure is monitored,and using the finite element model combined with the monitoring results to analyze the influence of temperature on the closure construction.At the same time,the influence of construction errors and temporary loads on the bridge structure is analyzed,and the analysis results provide an important guiding basis for the construction control of the closure and the error analysis in the closure.3.Combined with the above-mentioned refined finite element model,the key research on the dynamic changes of the structure line and force during the construction of the closure is carried out,and the technical key of the closure construction is determined,mainly including the lifting of the closure section,the control of the maximum cantilever state,the continuous observation of the closing section,and determination of the length of the steel girder in the closing section,etc.Based on the calculation and analysis results and considering the construction status on site,the closing construction plan was determined,and the precise closing of the Yanpingba Yangtze River Bridge was finally realized.4.The cable force of the cable-stayed bridge is optimized based on the influence matrix method,which effectively solves the problem of the major linear deviation of the cable-stayed bridge with steel-concrete composite beam due to the load change after the mid-span closure.The field application results show that the bridge cable force obtained after the optimization of the influence matrix method enables the bridge structure to remain consistent with the original target bridge state after the load changes.Which provides an important reference for the cable force optimization of the same type of bridge structure.