The Study Of Bridge Dynamic Deformation Monitoring Based On Digital Photogrammetry

The bridge is affected by the dynamic load of vehicles and other external forces in the process of its use,resulting in instantaneous and large dynamic deformation.It destroys the stability of the bridge structure,which collapse accidents at last,to the safety of people's lives and property caused huge losses.Therefore,it is of great significance to monitor the dynamic deformation of the bridge.The existing photogrammetric dynamic deformation monitoring system of the supervisor's research group uses the time baseline parallax method as the solution model to carry out the engineering dynamic deformation monitoring and has achieved good results.However,when monitoring the dynamic deformation of the bridge,there is a lack of systematic research on the dynamic deformation monitoring of the bridge when the plane of the bridge is not perpendicular to the optical axis of the camera.Therefore,this paper is based on the photogrammetric dynamic deformation monitoring system.The time baseline parallax method based on the coordinate change of optical axis and control plane is emphatically studied,and the pixel-real displacement space transformation expression of deformation point is derived.This method can obtain the deformation value of the deformation point when the bridge plane is not perpendicular to the camera's optical axis,or even at a small acute Angle,while keeping the optical axis perpendicular to the control plane.In order to verify the feasibility of this method,this paper first carried out several verification tests in the school.Then,the deformation monitoring experiment of Fenghuangshan Road bridge and the dynamic deformation monitoring experiment of viaduct are carried out,and the deformation analysis and fitting prediction of the bridge are carried out,and the following main conclusions are obtained.(1)The theoretical basis of dynamic deformation monitoring and data processing by non-measurement digital cameras was studied.The deformation experiments at different photographic distances were used to analyze the measurement errors of cameras and the evolution law of measurement errors with the change of photographic distances.(2)The mathematical model of time baseline parallax method based on the cooperative change of optical axis and control plane was established.It is found through experiments that In the vertical direction the average error of the deformation value calculated by this method is 0.79mm,the relative error is 0.42%,and the maximum error is 1.28mm.In the horizontal direction,the average error is 1.06mm,the relative error is 0.57%,and the maximum error is 2.85mm.The influence of the tilt Angle on the vertical and horizontal values is also analyzed.(3)The dynamic deformation monitoring experiment of Fenghuangshan Road bridge and the R1 viaduct was carried out.The experimentl verification the feasibility of the time baseline parallax method based on the coordinated changes of the optical axis and the control plane to monitor the dynamic deformation of the bridge when the plane is not perpendicular to the optical axis of the camera or even at a small acute Angle.This study expands the application scope of the photogrammetric dynamic deformation monitoring system developed.The basic theory of time baseline parallax method is further enriched.It provides a whole set of reference experiment and calculation process for the deformation monitoring application in the non-vertical state of the optical axis of the camera and the bridge.