Study On The Relationship Between Deck Deformation And Structure Damage Of PMMA Model Bridge

This paper,relied on the text of Chongqing Natural Science Foundation of China:Bridge Safety Assessment Methods and Face Perception Theory(project number:cstc2012jjB0118)undertaken by Professor Zhixiang Zhou in Chongqing Jiaotong University,as well as on latest domestic and international researches,studies the relationship between deck form and structure damage of PMMA model bridge.The paper involves several subjects including bridge engineering,surveying engineering,reverse engineering,computer science etc.The main contents and conclusions of this paper are as follows:By investigating the status quo of bridges routine examination at home and abroad,the paper discusses a new concept of bridges routine examination which is based on the theory of "Bridge physiognomy".In this new concept,3D point cloud data of geometric coordinate of deck are obtained through the analysis of three dimensional measurement and then the point cloud data are relied to measure the safety of the bridge.In an example of a simply supported T-beam bridge,the author carried out load test twice,respectively on damaged bridge and undamaged condition.In both experiments,Leica Ms50 was used to obtain the point cloud of 3D geometric coordinate of deck,and dial indicator was used to obtain thedeflection of feature points in the bottom surface of T-beam.Then the author explores methods of point cloud data denoising,and compares all of point cloud in different load levels.Last,this paper compares those feature points measured by Leica Ms50 and dial indicator.The results show that the point cloud of deck measured by Leica Ms50 is able to reflect the real form of deck in different load levels turly,the measurement error of Leica Ms50 is less than 10%,the measurement accuracy fulfills the demand of engineering applications.Firstly,the finite element model of PMMA Simple T-beam bridge was established,then two different damages were set on the bridge:main girder cracking and bearing separation.Secondly,the deflection changes of feature cross-sectional are analyzed in the following three conditions:different degrees of cracking,different location of cracking and different number of cracks.Thirdly,the deflection changes of feature cross-sectional are analyzed in the following two conditions:different location of bearing separation and different number of bearing separation.According to correspondence between moment and curvature in material mechanics,the identification of damage in bridge structure us explored,and DamageIdentification Method Based on Curvature mutations is put forward.By using this method to analyze the curve of deflection curvature of feature cross-sectional,and then distinguishing the extent of damage,the location of damage and the number of damage of main beam in the following three conditions:different degrees of cracking,different location of cracking and different number of cracks.Finally,this method was applied to the point cloud data of deck to distinguish the damage of bridge structure.The location and extend of damage distinguished are close to the actual situation.