Videogrammetric Technique-based Monitoring Of Structural Vibration

Dynamic displacement and frequency are the basic parameters in analyzing the dynamic characteristics of engineering structures, of great value in structure testing and analysis, also the difficulty of structure detection and the research hotspot in engineering communities. They are important monitoring parameters to ensure safety in construction and operation. For large structures in civil engineering, it is hard to find fixed reference point for their displacement detection. All kinds of traditional methods about displacement detection of dynamic objects have their limitations, even though displacement is the most direct and valuable information. Therefore, it is favorable and necessary to develop a remote non-contact monitoring system which can record data automatically and process the data in real-time. This thesis presents a videogrammetry method for civil engineering structures, to collect videos and convert them to images and to use digital speckle correlation to get displacement information for dynamic frequency of structure. This paper investigates this method by theoretical and experimental studies.Videogrammetric technique is an important non-contact method which bases on photogrammetry to get space information using video-photos. It regards images as the carrier and means to detect or transfer the information. The image-based measurement technique can bring us the actual information of the examined object after analyzing the images. The development of the digital image technologies accelerate the development of the technology on obtaining and processing space information automatic, real-time, intelligentization. It attracts research interest to apply these high technologies in civil engineering to provide structure testing and monitoring with data flow of real-time dynamic space information, and thus to realize intelligentization in structural diagnoses and evaluations. Deformation measurement of bridges is an important content of health monitoring. Large deformation of long-span bridges demands measurement technology with large range, and it is difficult to measure this with general methods. Videogrammetry technology can be used to automatically measure the large deformation of long-span bridges with low cost.This paper developed the digital image processing technology to inspect the dynamic displacement of engineering structures. We conducted the experimental study on one- and two-dimensional vibration monitoring, and theoretical study on three-dimensional vibration monitoring. We collect videos on target points of monitored structures in the laboratory, then convert them to a series of digital image frames using a digital video editing software, calibrate the pixel-distance sensitivity from some image frames by Matlab programs, drag a window on the image frame as a speckle and another bigger window which contains the speckle as the searching area, locate the speckle in the images frame by frame by the program itself to get the coordinate data of dynamic aim point, and finally obtain the curve of the target point. In this way, we can carry out the continuous monitoring and modal analysis of dynamic displacement. We have proved this method is a simple and effective measurement method by theoretical and experimental studies.This paper discusses the application of videogrammetric technique for large civil engineering structural vibration monitoring, provides theoretical and experimental research foundation, and has a positive impetus for application of this technique in the engineering.