Research On Cable Force Optimization And Reasonable Construction State Of Hybrid Composite Girder Cable Stayed Bridge Based On Step By Step Algorithm

The structural analysis of the ideal bridge state and the reasonable construction state of the cable-stayed bridge is the key and difficult point of its design.The two are in a complementary relationship.When the structural system layout and dead load distribution of the cable-stayed bridge are determined,the cable force of the cable stayed It has become the core of controlling the stress state of the full bridge,that is,how to determine and optimize the bridge cable force so that the cable-stayed bridge achieves a reasonable bridge stress state,and how to determine a reasonable construction state,including safe and economical construction process design And construction control the value of the tension cable force,so that the cable-stayed bridge can reach a predetermined reasonable completion state,and the purpose is to realize the final reasonable state of the cable-stayed bridge.For the hybrid composite girder cable-stayed bridge with steel-concrete composite beam in middle span and prestressed concrete beam in side span,it not only has the commonness of cable-stayed bridge,but also has its own characteristics.Taking a long-span hybrid composite girder cable-stayed bridge as the engineering research background,this paper studies the determination of reasonable cable force and reasonable construction state.The main research contents and conclusions are as follows:1.The lattice beam element is used to simulate the steel main beam and the plate element to simulate the concrete bridge deck and the wet joint.The two are linked by elastic connection to accurately simulate the composite beam,and the finite element analy sis model of the whole bridge is established.2.In view of the unique structural characteristics of the hybrid composite beam cablestayed bridge,a simple and effective step-by-step algorithm for optimizing the cable force in the completed state of the bridge is proposed.That is,the dead load balance method is used to initially simulate the dead load cable force of the cable-stayed bridge.The cable force is further adjusted according to the influence matrix of the cable force on the displacement of the main girder.Finally,considering the combined action of dead load and live load,combined with Midas Civil’s cable internal force amplitude modulation module to determine that the hybrid composite beam cable-stayed bridge is satisfied The cable force required by the force and deformation of each member in a reasonable bridge state.The calculation results of the actual bridge show that the algorithm is simple and effective,flexible in adjustment,high in calculation accuracy,and better in the fitting of the bridge alignment.3.On the basis of the design and construction method of the main girder of the composite beam,three optimized construction methods that can improve the construction efficiency of the main girder are drawn up,and the reasonable construction status of these three methods is solved based on the upside-down and forward-installation iteration method.According to the analysis and calculation results of the finite element model of each optimized construction method during the whole construction process,the bridge line shape of each optimized construction method is less than the bridge line shape control error,and the stress of the cable tension during the bridge completion stage and the construction process is safe The coefficients are above 2.80,that is,the stay cables have sufficient safety reserves;The construction method with two segments of wet joint lag has the maximum stress of steel girder in the bridge completion stage and the construction process,followed by the construction method with one segment of wet joint lag.The stress of steel girder with two segments of wet joint lag is the minimum and is close to the design scheme.However,the tensile stress of bridge deck is too large in the construction process of the construction method with two segments of wet joint lag,which exceeds the allowable strength of the material.The tensile stress of bridge deck is the minimum in the construction process of the construction method with two segments of wet joint lag,which has sufficient tensile stress safety reserve.4.According to the calculation results of the three optimized construction methods,one of them is determined to be adopted after comprehensively considering the construction period of the main girder of the composite beam,the completion stage of the bridge and the safety of the structure during the construction process,the feasibility of cable tension,and the safety.This optimized construction method and optimized and adjusted its tension cable force is regarded as the optimal construction method of the bridge,that is,iteratively takes the stress of the upper and lower edges of the main girder during the construction process as the optimization target on the basis of the iterative calculation results of the formal installation Try calculations to ensure that the stresses of the steel main girder and the bridge deck are within a larger safety range.Then,before the completion of the bridge construction,the pre-determined ideal bridge state is used as the goal,and the influence matrix is used to adjust the full bridge cable force,and finally Meet the requirements of the ideal bridge state.