Study On Mechanical Properties Of Steel-concrete Hybrid Continuous Girder Bridge In Completion And Construction

The steel-concrete hybrid continuous girder bridge is different from the traditional prestressed concrete girder bridge and the steel box girder bridge.It requires that the steel box girder and the concrete girder be joined into a continuous structural system under common loads so as to smoothly transfer various loads.Its structural form is that the steel box girder is used in the mid-span part of the main girder and the concrete girder is used in the rest of the main girder.Hybrid beam bridge reduces the weight of the bridge as a whole,optimizes the stress state of the bridge to a large extent,increases the span of the bridge,and overcomes the shortcomings of the traditional long-span concrete continuous beam in the midspan deflection and cracking.At present,the structural form of hybrid girder bridge is widely used,and the research on hybrid girder bridge is more and more.Although some achievements have been made,the research on hybrid girder bridge is only the beginning with the continuous innovation of bridge materials and the continuous optimization of construction technology.In this paper,a steel-concrete hybrid continuous girder bridge is taken as the background,and the main research contents include the following three parts:Firstly,the steel-prestressed concrete composite continuous beam bridge is built by Midas Civil finite element software.In the process of modeling,the structure of steel-concrete composite section is simplified,the steel-concrete composite section is replaced by the same volume concrete beam,and the stress and deflection of the bridge under the combined effect of load in the construction stage and the use stage are obtained by dividing the function of the construction stage.According to the requirements of the code,the stress and deflection of the bridge are analyzed.At the same time,the internal force of the local model of the steel-concrete composite section under the most unfavorable load combination in the overall model is extracted in the overall model,which paves the way for the analysis of the solid force of the steel-concrete composite section.Secondly,the influence of the change of sensitivity parameters and structural parameters on the mechanical properties of hybrid girder bridges is analyzed.Considering the six situations of prestressing standard tension,over-tension(5%,10%)and loss(5%,10%,15%),it is concluded that the change of prestressing parameters has little effect on the stress of steel box girder,and has the greatest influence on the deflection of cantilever end of concrete girder,which shows a linear change.Considering five working conditions of temperature effect,it is concluded that the temperature gradient has great influence on the deflection and stress of the main girder.The positive temperature gradient reduces the midspan deflection by 16.0 mm,while the negative temperature gradient increases by 8.0 mm.The system temperature has little effect on the stress and deflection of the main girder.By changing the length of steel box girder and the ratio of side to mid span,the deflection and internal force of the main girder under dead load and live load are analyzed.It is concluded that when the ratio of side to mid span is 0.5,the unbalanced negative moment on both sides of pier top is the smallest.Finally,the solid model of steel-concrete bonding section is established by finite software.First,the force transfer mechanism of steel-concrete bonding section under single load is analyzed.Then,the force effect of steel-concrete bonding section during construction is analyzed.Finally,the Civil model is loaded into the solid model to calculate the internal force value under the most unfavorable load combination effect,and the stress value and force transfer effect of steelconcrete bonding section are coMPared.The mechanism of force transmission and the local stress distribution in the steel-concrete bonding section are summarized.It is concluded that steel fiber concrete should be used to increase the tensile capacity of concrete in the construction of the bonding section.