Comparative Study On Mechanical Behavior Of Steel-Concrete Joint Section Of New Hybrid Continuous Girder Bridge

Medium-span hybrid girder bridge has been widely used in plain lake area because of the smaller section height of the main girder,the lower elevation of the bridge deck,the shorter length of approach bridges and the faster bridge construction while it meets the requirement of navigable height under the bridge.The steel box girder of traditional medium-span hybrid girder bridges that across plain lakes is an integral steel box,the welding work in the box is heavy,and the section height is usually small.So,the welding work is difficult for workers,and in the enclosed space,the construction condition is bad,these all make the construction quality is difficult to guarantee.Based on these phenomena,there is a new type of hybrid girder bridge which converts the single steel box into the separated steel box.In this way,the welding work in the box is greatly reduced,the construction is easier,and the construction quality is improved.At present,there are few researches and engineering examples for the new hybrid continuous girder bridge,and there is no relevant field measured stress data.In this paper,the joint's mechanical behavior and reliability of single concrete box-multi steel box hybrid girder bridge is studied with the background of the Jinxi Bridge and Changqiao Bridge as follows:Firstly,using the finite element software Midas Civil to establish the whole bridge model of the two hybrid girder bridges,analyze the internal force state at each construction stages and the operation stage.Then,confirming the internal force state of the key construction stage and the most unfavorable loading condition.Secondly,using ABAQUS to establish the local fine model of the steel-concrete joint section.The internal force of the steel-concrete joint in the whole model of Jinxi Bridge at the key construction stage and the most unfavorable loading condition is taken as the load acting on the ABAQUS model.Calculating the stress characteristic of the steel-concrete joint at the key construction stage,the finished stage and the most unfavorable loading condition.Thirdly,installing strain sensors in the construction process of Jinxi Bridge.Processing and analyzing the strain data measured by strain sensors at each construction stages and the finished stage.Getting the stress distribution data of the corresponding measured section,and comparing with the corresponding data of ABAQUS steel-concrete joint section model of Jinxi Bridge.Verifying and improving the ABAQUS model of the steel-concrete joint by the result of contrasts.Fourthly,establishing the local fine ABAQUS model of the steel-concrete joint section of Changqiao Bridge based on Jinxi Bridge.Comparing and analyzing the mechanical behavior of the steel-concrete joint section model of the two bridges at the finished stage and the most unfavorable loading condition.The results show:(1)The main area of longitudinal stress concentration is near the bearing plate.(2)The shear lag effect of the concrete box girder transition section and the steel box girder transition section decreases as moving away from the steel-concrete joint.(3)In the steel box girder of single concrete box-multi steel box hybrid girder bridges,the vicinity of mid webs is the main area of stress concentrations while it is the vicinity of side webs in the single concrete box-single steel box hybrid girder bridges,and the stress concentration degree of the latter is higher(4)Except the conclusion 3,the stress distributions of the two bridges are same roughly.(5)The finite element calculation results are consistent with the measured stress data.It is reliable.