Research On The Mechanical Characteristics At Continuous Bridge Deck's Position Of Simply Supported Steel-concrete Composite Girder

The continuous girder bridge can meet the requirements of driving continuity and smoothness which are not available in the simply supported girder bridge,and at the same time reduce the setting of the expansion joint.The bridge deck continuous structure of simply supported girder is widely used.Some scholars have carried out research on the mechanical behavior of bridge deck at simply supported girder bridge with continuous bridge deck and the disposal methods after cracks appeared,but the research has not systematically studied the bridge deck located in mid-fulcrum of steel-concrete composite girder on the structural level.which still has a need for in-depth and systematic research.This paper will combine the specific design consulting project of Bridge Branch of China Merchants Chongqing Communications Technology Research and Design Institute to study the structural requirements and force characteristics of bridge deck located in midfulcrum of steel-concrete composite girder,which could provide the necessary data support for designers in the future design process.The relevant contents and conclusions are as follows:(1)This paper will make a simulation of the mid-fulcrum structural form,including the joint height and width,and so on that make the impact on the mechanical behavior of the mid-fulcrum structure.Firstly,this paper establishes the single girder model and grillage model by using Midas/civil.This paper establishes the composite beam model by Ansys on the basis of overall calculation results of Midas/civil,and then built into 16 calculation models with the different thicknesses and widths of the mid-fulcrum,and finally analyzed the effect of load combination on the mechanical performance of the mid-fulcrum bridge deck.The results show that the thicker the concrete in the mid-fulcrum is,the better crack resistance is,and the width has little effect on the structure.(2)This paper study the bearing problem of the main girder with simple support bridge continuous construction.Different bearing forms have different stiffness.Aiming at the different construction forms shape of the plate rubber bearing,this paper studies its influence on the mid-fulcrum.The content consists of three parts.Firstly,this paper contrasts the rubber bearing and the original rigid bearing.Secondly,the different rubber bearings are compared.Finally,this chapter researches the influence of the vehicle load on the displacement of two continuous along-bridge bearings is studied.The results show that the stress difference between the simulated rubber bearing and the original rigid bearing becomes smaller and smaller with the increase of the thickness,and there is almost no difference at 270mm;the calculation results of the six different shapes of the bearing differ very little.(3)According to the calculation results in the previous section,the fourth chapter will continue to optimize and improve the mid-fulcrum structure.From the conclusion of Chapter two,we can firstly thicken the concrete at the mid-fulcrum section to see how much the result of the thickening is improved,and then adjust the composite beam I-beam,increase or decrease the thickness of the upper and lower flange plates of the I-beam and the thickness of the web,and finally change the I-beam to the variable height beam.The trend indicates that as the thickness of the mid-fulcrum concrete increases after optimization,the completion state bridge and combined stress values continue to decrease,which is beneficial to the structure.When the web height ranges from 1m to 1.4m,the difference is not much different from 1.2m.The difference between the completion state and the most unfavorable frequency combined stress values of the contour web and variable height web is also small.