Testing Research On The Relationship Between The Geometric Shape And Structural State Of The Concrete Box Girder Roof

This paper is based on the Chongqing natural foundation:Bridge safety assessment methods and face perception theory(project number: cstc2012jjB0118).In order to conquer this issue,the author consulted lots of reference and performed an experiment with a box girder model in the laboratory to explore the relationship between load、 deformation and damage.Bridge,engineering,close-range photogrammetry,computer technology,reverse engineering and many other disciplines are Involved in.In this paper,the main work and conclusions are as follows:Five static load condition were loaded on the deck of the box girder in order to research the relationship between load,deformation and damage.Displacement and crack width were measured with traditional method.Lots of local and global pictures have been shot with a high quality digital camera when load was ready.Pictures with cracks have been shot when the test was over.3D model with crack message have been reconstructed.There are two type of cracks in the load condition two and four when loaded on the top of the roof.One is around the load point and another is lengthways.The type of Roof bottom is diverging from load point.The relationship between load and displacement have been analyzed with the method of close range photogrammetry.Curvature of a hook face can be a principle for damage detection,but the original curvature is very obvious unless we subtract the point cloud after loading from the point cloud before loading.Geomagic studio and CATIA are both used for curvature analysis.It prove that this method can be used when the load is more than half of ultimate load to find the position of cracks.The formula for damage factor calculation have been deduced based on the principle of energy equivalence and the tensile damage factor of C50 concrete have been calculated with it.A finite element model have been built with ABAQUS to simulate load case 2 and load case 4.Tensile damage can be a criterion for crack location detection and it proves that the analysis results is similar to the actual cracks.