Experimental Study On Morphological Changes Of Steel Truss-concrete Composite Beam Based On Fixed-point Photography

Bridge for the regular safety inspection of low efficiency,poor accuracy and the lack of quantitative scientific basis,research is put forward using the fixed point photogrammetry method for bridge structure contour line,through the analysis of the superimposed differential morphology change of the structure of the bridge,for different periods in order to reach the purpose of bridge safety inspection or long-term monitoring.This article depends on the key project of natural science foundation of chongqing "bridge facial perception method and theory of safety evaluation research"(project number: cstc2012jjB0118),in the laboratory of prefabricated steel girder-concrete composite beams is carried out based on fixed-point photography loading test beam form change research,the main research work is as follows:First,based on fixed-point photography deformation measurement basic research idea is: the camera in a fixed position for bridge structure in the digital images of different time and analysed and calculated the separation bridge structure outside the contour line selection on behalf of the structure of the linear profile,and the initial condition of contour line fold,get in pixel structure deformation curve;Then according to the actual size and the relationship between the pixel structure deformation curve.The second,under laboratory conditions for a prefabricated steel girder-concrete composite beams with 0T – 60 Tthe classification of the static loading test.Test beam deformation respectively adopted traditional dial indicator displacement meter and photogrammetry and two plans are compared.The third,access to the test result is perspective projection image,image diagonal perturbation and distortion,direct contrast structure contour line can't get the right result,to solve the problem of the use of digital images of the tested beam correct perspective transformation,reshape the test beam structure is linear,and combined with capturing the image edge detection test girder bridge under the load condition but at the bottom of the steel plate,steel truss of the original line.The fourth,based on the original contour line and the initial condition of stacking faults in pixels were obtained for the unit test of the condition of load displacement curve of the beam,using the outside dimensions proposed a camera calibration model tocomplete the unit conversion of the pixels to the actual distance.Through image acquisition of forced deformation test results and the dial indicator comparing the measured results,proved this method within the error range,and it's feasible.The fifth,in view of the test beam under the condition of symmetrical loading appeared the phenomenon that the asymmetric deformation by using the finite element software ABAQUS to not have steel girder-concrete composite beams in the structure damage and the introduction of the fine finite element analysis,the calculation results and and structure based on fixed-point photography to get relatively close.