Testing Techniques For Digital Speckle In Bridge Health Monitoring

Along with national economy fast developing, the highway bridge construction of our country has gotten the huge achievement in recent years. Highway nets extending in all directions of many province cities that take Higher- level highway as main skeleton have already formed preliminarily. Bridge is the important composition part of highway, many new established highway bridges are needed to pass through quality safely detection acceptance in every year. At the same time, the bridge that established and open to traffic, various factors can make bridge safe degree drop along with time passed. Many bridges have had huge safe hidden trouble and nearly have bridge collapse accident reported every year that causes significant economic loss. Therefore, how to adopt a kind of economic, efficient, fast detection methods to the structure of bridge healthy condition monitor and evaluate is an important problem of worth-whiles solicitude and research.Digital speckle correlation method is a nondestructive detection method that development gets up along with photoelectron information technology and digital image technology. It has been extensively used to accurately determine two-dimensional in-plane displacements and strains in both theoretic study and engineering measure. Many possible problems are reached in this paper when the digital speckle correlationmethod is used in the large construct safe detection.This paper is completed mainly with chapter four. The theory of digital speckle correlation is discussed and bilinear is used to raise the measure precision from pixel to inferior pixel in part one. In chapter two, one bridge experiment of displacements and strains in different time and different weather condition speckle image are rectified through the image rectify software programming of Visual C++. It discussed the feasibility of digital camera using in digital speckle correlation method. The different distances and different displacements condition through selecting the different sizes of particle experiments are researched and compared in chapter three. The speckle influence of particle size for measure precision is given. According to relative errors of experiments result, under given image collection system, in different image collection distance how to select reasonably size of particle to obtain measure purpose are given. A reliable experiment selection for the future application of DSCM measurement using in the large construct safe detection of speckle field making is provided. In chapter four, the content of thesis studied is used to get the elastic modulus of PMMA through the loading measurement of 3 point bending. The change of every mechanics performance is given by bridge structure loading experiment. It is not only verified the experiment regular that we get, but also offered a kind of new experiment method to explore through experiment to get stress-strain relation. Finally, the main achievements of this thesisare summed up and direction of further developing in this field ispointed out.It proves that the contents and the method of studying in this paper solved the problems in bridge structural healthy safe detection. It established theoretical basic and experiment foundation for bridge structure health monitoring.