Analysis Of The Causes Of Cracks In Wide Flange Prestressed Concrete Box-girder And Its Reinforcement Method

Prestressed concrete continuous box-girder bridges due to its many advantages arewidely used in bridges of domestic and abroad, however,with the sharp increase in the amountof traffic,the bridge-type appears more common diseases,especially crack problem is mostprominent. In this paper,basis on a wide-flange continuous prestressed concrete box-girder,wemake these jobs Including the structural calculation and analysis of its causes cracks,andmake the appropriate scheme of repair and reinforcement of cracks. The main contents are asfollows:(1)Calculation of the theoretical analysis of box-girder were studied,and the paper indetail discusses the mechanical properties and the analysis method of box-girder,and thenbending stress,shear lag effect,rigid torsion,distortion effects,calculation of temperatureeffects and shrinkage and creep effects of wide flange box-girder are theoretically analyzed.(2)By the shear-flexible beam grid method of large areas of Midas/Civil and consideringshear lag effect,we can make the bridge simulation analysis,calculated in accordance with theprinciples of class B prestressed.Respectively,from the dead load，live load,the temperatureeffect, shrinkage and creep effects and other aspects to analyze the control section of the stressresults,the results show that the stress of the main beam are in line with regulatoryrequirements.(3)Considering the old bridge correction factor,prestressed pipe is not full,the impactcaused by the sinking of reinforced floating mandrel and relaxation of the strand and otherfactors,the cross-section calculation carried out safely in accordance with the calculatedcorrection twenty percent reduction of its design strength of the strand.The results show that:at the edge of the main cross–section,it has the greatest tensile stress and maximum principaltensile stress and is seriously out of specification limits. Combined with the calculation resultswe can analyze the reasons for the cracks of top,bottom and webs.Finally,for the bottomtransverse cracks,the paper proposes two structural reinforcement program,and establishedprograms-structural reinforcement is calculated after analyzing external prestressingreinforcement method,the results show that the situation of the main stress after reinforcementhas been greatly improved,and the maximum principal tensile stress improved34.2percent，the curve of stress is more uniform,and meet the regulatory requirements.In this paper,we make these jobs—preliminary analysis of the causes of cracks in wideflange prestressed concrete continuous box-girder with a bias across and its reinforcement method,which has an great significance of practice reference for the maintenance andreinforcement of other same type of bridge.