Influence Of Ambient Temperature On Deformation Monitoring Of Daning River Bridge

This paper relies on the project of National Natural Science Foundation of China(NSFC)" Research on the Method of Obtaining the Bridge Deformation and Deucing the Structural State Based on the Differential Analysis of Image Contour"(51778094)and the project of NSFC Youth Science Foundation,chaired by our group professor," Bridge Safety Monitoring and Early Warning Theory Based on Surface Morphology"(5170082159).The mobile three-dimensional laser scanning technology and fixed-point photogrammetry method are applied to the deformation monitoring of the Daning River Bridge.Considering the seasonal variation of environmental temperature,we obtain the deformation state of the bridge structure under the effect of temperature variation.The research contents are as follows:(1)In view of the disadvantage of traditional level measurement depending on manual work,complicated repeated operation and discrete measurement,the mobile three-dimensional laser scanning system is used to monitor the deformation of the bridge deck of the Daning River Bridge in several periods and obtain the point cloud data of the structure;the bridge deck is reconstructed by NURBS surface fitting algorithm;and the holographic deformation chromatogram of the bridge deck is obtained by deviation of the monitoring results in each period.(2)In view of the limitation of traditional leveling to the facade measurement of bridge structure,the non-metric camera is applied to the fixed-point photogrammetry of the main arch structure of the Daning River Bridge.The high-definition image sequence of the structure is obtained by taking photos of the facade of the bridge structure at fixed position.The panorama of the main arch structure is obtained by splicing the image sequence based on SIFT image mosaic algorithm.Using Canny edge detection-operator to extract edge profile of main arch structure in panoramic images.(3)We established the finite element model of the structure of Daning River Bridge,then obtained the deflection data of theoretical calculation.The deflection data obtained from precise level measurement are extracted from the monitoring data of the bridge in the early stage.The comparative analysis of theoretical deflection data,pre-measured deflection data,three-dimensional laser scanning deflection data and fixed-point photogrammetry deflection data verifies the applicability of the two methods for deformation monitoring of long-span bridges.(4)The structural safety status of the Daning River Bridge was evaluated by using the deformation data obtained from three-dimensional laser scanning technology and fixed-point photogrammetry.(5)In view of the large amount of holographic deformation data obtained by three-dimensional laser scanning and fixed-point photogrammetry,a linear superposition effect separation algorithm is proposed.The measured deflection data are selected to separate the temperature effects,and the applicability of the separation algorithm is verified.