Research On The Cracks In O#Box Girder Of Prestressed Concrete Continuous Rigid Frame Bridge

On the basis of plentiful documents, we can ifnd that the most common problemsto continuous irgid frame birdge have been summairzed. Research shows that boxgirder blocks0#crack defect is one of long span continuous irgid frame Birdgescommon disease, and it is a very big problem of the birdge engineers, it is necessaryto do ifirther study.The paper research on the reasons of0#block cracks from vairous angles oftemperature, shrinkage, constraints by Finite element method. The analysis showedthat0#block will crack cause by thermal stress, shrink stress, shrink secondary stressand Temperature secondary stress due to the temperature, shrinkage, constraints ofbox girder.The paper using the method of finite element analysis to study the influence ofthe temperature field and0#block stress，the conclusions are following:①Thetemperature difference increases of roof will result in the maximum tensile stress of0#block roof，web and diaphragm increases. The maximum tensile stress of roofincrease is greater than the diaphragm, the addition of diaphragm is greater than web.②The temperature difference increases of web will result in the maximum tensilestress of0#block increases. The maximum tensile stress of web increase is greaterthan the roof，the roof increase is greater than backplane, the addition of backplane isgreater than diaphragm.The article research the influence of box beam size to0#block by finite elementmethod，the results are as follows:①it would not change the box beam stressdistirbution regulairty by increasing the thickness of roof, though the box beam stresslevel will increase a few?②the box girder tensile stress level will be raised byincreasing the box girder diaphragms thickness, and the maximum value of girderdiaphragms’ pirncipal stress will be raised，it must be carefully considered in birdgedesign.The article make a simulation analysis to the0#block strength’s forming processin the actual construction process by finite element method, and get the stress-strength relation in this process, the results are as follows:①The maximum tensilestress of roof chamfer area exceeds the tensile strength of concrete in the concretecuirng process.’The maximum tensile stress close to the concrete tensile strength atthe bottom of flange plate?②The maximum tensile stress of diaphragm hole exceeds the tensile strength of concrete in the concrete cuirng process. This conclusion is thesame as0#block cracking phenomenon in the actual project，it prove that0#blockcracking causes and mechanism of action is correct.the author determined method of0#piece of crack defect of finite elementthrough analysis the Vairous factors like blocks0#geometry size，the structuralcharacteirstics and construction constraints, and set models for calculation. In the First,this paper analyzes the box girder temperature field and geometry dimension ofblocks0#stress influence. The research got influence law of0#piece of roof，websinside and outside temperature changing in the stress changes; The influence law of0#piece of roof, hoirzontal clapboard thickness changes in the stress changes. Theauthors ifnd the relationship of stress and intensity through simulated blocks0#strength forming process，provides theory basis for the roof and a hoirzontal partitioncauses common cracks. At the same time, engineeirng example of crack disease alsoproved the reliability of the conclusion in this paper.This paper give some suggestions and measures about cracks of0#box girder toimprove box girder disease by summairzes drawn conclusion. Through the researchwork，the author got the box girder temperature ifeld and geometry size change onblocks0#general rules of the stress influence. The article study on the dynamicmaintenance process of0#box girder, this paper expounds the cracking mechanism ofbox girder, this paper discusses the factors on the influence law of the cracks of0#box girder.