Analysis Of Spatial Morphology And Mechanical Properties Of Bridges Based On 3D Point Cloud Data

Nowadays,with problems of traffic growth,load increment and bridges aging,many bridges in operation are facing defect problems,so it's necessary to conduct regular detection and evaluation.The testing method of manual observation relies on subjective experience of inspectors,and equipment like support is needed to help inspectors get close to the bridge;the use of contact methods is also limited when inspectors cannot get close to bridges.Comparing with manual observation methods and contact methods,common non-contact methods like total station has higher accuracy and wider applicability in bridge detection.However,these traditional methods are single-point measurement methods with low efficiency and heavy workload,and only evaluate global deformation with a few points' location change.Unlike these single-point measurement methods,the 3D laser scanning technique can get locations of points in a section instead of getting the location of one point.By using laser scanning technique in bridge detection,locations of points on the bridges' surface can be detected and composed of a point cloud model.In this way,global spatial change and local deformation can be detected.This thesis presents a method to analyze the bridge's spatial morphology and mechanical condition based on the bridge's point cloud data,and verifies the feasibility taking HeDong Bridge(long span continuous rigid frame bridge)as a research project.At first,two point cloud registration methods for unchanged points are proposed: a robust registration algorithm based on feature point clouds and a registration algorithm based on detection experience.These algorithms have higher reliability and efficiency than traditional ICP algorithm.Based on them,the spatial deformation is divided into three parts: structural level global rigid motion,element level global rigid motion and element level local deformation.The translation and rotation in the lateral,longitudinal and vertical direction of the bridge structure can be obtained from structural level global rigid motion,the translation and rotation of the element can be obtained from element level global rigid motion,similarly,bending and torsion of element can be obtained from the element level local deformation.Next,the thesis summaries possible reasons that induce spatial morphology changes,and analyzes spatial changes of each possible factor by finite element model.Finally,by updating model with influence matrix method,deriving backward factors that induce such spatial morphology changes.The proposed method is a non-contact measurement with high accuracy and efficiency.The change tendency is benefit to instant bridge operation condition and provides reliable monitoring information for bridge's safe operation and reinforcement measurements.