Research On The Cause Crack For Small Prestressed Concrete Box Girder

Prestressed concrete small box girder with light weight，torsional strength and othercharacteristics have been widely applied to the construction of the bridge. In small box girderconstruction process，Web cracks which in direction of prestressed pipe is very serious. Thispaper analyzed research on longitudinal cracks along the prestressed pipe of small box girderwebs.Detailed statistics for the small box girder webs cracks，including sproject length，width，depth，and specific location.In the Statistics on the appearance of cracks in the concrete boxgirder，around the actual measurement strength and depth of carbonation the small cracksarea，combined with a small box girder web cracks statistical results of a preliminary analysisof the causes of cracks in the web. Combining with prestressed concrete small box girdermodel，using midas2012to establish finite element model.For five continuous span small boxgirder，a comprehensive analysis of the stress field of the web in prestressed tension erectionstage to operation stage.Consider the overall construction process， web Tendons and the roofbeam negative moment Influence on web stress.And simulation box girder may occur creepand shrinkage， Supports settlement And temperature effects which Impact on the web andeven the causes of stress cracks in the longitudinal web.After the overall analysis of the small box girder structure， The use of largegeneral-purpose finite element program ANSYS solid model analysing Parameters which maybe affecting local small box girder webs. Analysis of prestressed pipe local deviations，webthickness variations and the impact of ordinary steel，to create a series of simulations wereperformed similar webs causes.Analysis of prestressed pipe local deviations in the web，Vertical stress have a great impact on the web，The results showed that: web prestressed localdeviations that would greatly affect the principal tensile stress, web offset partially prestressedpipe2cm, radial force generated when tensioned prestressed box girder webs that willproduce small vertical cracks. Radial force prestressed tension impact on the web stress field，Prestressed local small deviations that would have a significant impact on the web verticalstress， A direct result of the web of cracks along the prestressed pipe crackingWeb thicknesswould expedite cracks. Reducing the web thickness of2cm vertical cracks in the web willreduce cracking load, easy to produce longitudinal cracks. Marine concrete structures usingfast hydration, heat of hydration, improper mix of web longitudinal cracks were less affected. And use observations and results of this study, put forward reasonable proposals for asmall box girder longitudinal crack control measures.