Analysis Of Mechanical Performances And Influence Factors Of Steel-Concrete Composite Continuous Beam Bridge In Construction Process

With the development of the national infrastructure business,how to make the performance of building materials more reasonable has become the development trend of bridge projects.The appearance of steel-concrete composite beams just meets the engineering community's pursuit of the performance of building materials and is increasingly being applied to the engineering field.In recent decades,Chinese scholars have been working on the design calculation method and foundation of composite girder bridges.A lot of research has been done in theory and other aspects.However,there are relatively few studies on the mechanical properties and construction influencing factors during the construction process of composite girder bridges,especially composite continuous beam bridges.Based on the composite beam bridge of Binhe West Road in Linfen City,this paper systematically analyzes the mechanical performance of composite continuous girder bridges using the fulcrum lifting method.The main contents of the analysis are as follows:(1)The model of the whole bridge is established through Midas Civil software,using different lifting height of the construction process stress has carried on the detailed analysis of the performance;(2)By quantitative analysis of some factors which are easy to error in construction,the influence of them on the lifting effect is analyzed;(3)The influence of the concrete time effect on the bearing jacking effect was explored by establishing the finite element modelThe main results are as follows:(1)The use of the method of pivot movements compared to not using the construction method,the stress of the concrete plate at the fulcrum position changes from tensile stress to compressive stress;the fulcrum jacking height is within a reasonable range,and the height is higher,which is used to slow the cracking of concrete and steel beams.The better the pressure instability effect.At the same time,the height of the crown increases,and the shrinkage and creep of the concrete weakens the prestress generated by the method of pivot movements.The method of pivot movements will increase the displacement of the bridge and it is necessary to consider the influence on the displacement when laying the steel beam.(2)For the three span composite beam bridge with the method of pivot movements,the construction method of lifting two supports separately is more effective than lifting them together to reduce the cracking of fulcrum location concrete slab.(3)Considering the effects of shrinkage and creep,the displacement of the composite beam's side span becomes larger,and the displacement of the middle span becomes smaller.At the same time,the stress of the composite beam section will also be redistributed.In the ten years after the completion of the bridge,the compressive stress of the concrete top and bottom slab at the cross-section of the bearing was reduced by 82.80% and 114.6%,respectively,and tensile stress occurred at the bottom plate position.Shrinkage and creep are unfavorable to the combined continuous beam,which must be considered in the structural design and construction.(4)The increase in the age of the deck will slow down the Shrinkage and creep effects on the pre-stress applied by the method of pivot movements.In the actual project,the age of the bridge deck can be increased to reduce the decrease of the pre-stress and the cracking time of the concrete slab.