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Measurements in civil engineering load tests usually require considerable time and complex procedures. Therefore, measurements are usually constrained by the number of sensors resulting in a restricted monitored area. Image processing analysis is an alternative way that enables the measurement of the complete area of interest with a simple and effective setup. In this article photo sequences taken during load displacement tests were captured by a digital camera and processed with image correlation algorithms. Three different image processing algorithms were used with real images taken from tests using specimens of PVC and Plexiglas. The data obtained from the image processing algorithms were also compared with the data from physical sensors. A complete displacement and strain map were obtained. Results show that the accuracy of the measurements obtained by photogrammetry is equivalent to that from the physical sensors but with much less equipment and fewer setup requirements.C 2015 Computer-Aided Civil and Infrastructure Engineering.

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The traditional methodology used for displacement measurements in civil engineering load tests requires a considerable amount of equipment and a very complex installation procedure. In this paper, the authors used real images taken during a load test in order to measure by image processing techniques the displacement observed on the beam under stress. The main advantage of digital image processing is the calculation of the whole displacement field without physical contact, using a simple low cost camera. This way, a complete displacement map is obtained resulting on a more complete and more accurate analysis than on the traditional approach where only a few displacement points are measured. Two photo sequences were taken during the load tests on a concrete beam and on a Plexiglass bar. The images were subjected to three different algorithms: simple and efficient search (SES), adaptive rood pattern search (ARPS) and the rood pattern particle swarm optimization (RP-PSO). The data obtained from these algorithms was compared with the data from LVDT sensors. As we show, the image processing measurements have an accuracy at least equivalent to the LVDT sensors but with much less equipment and setup requirements.

Abstract. The measurement of deformations, displacements, strain fields and surface defects in many material tests in Civil Engineering is a very important issue. However, these measurements require complex and expensive equipment and the calibration process is difficult and time consuming. Image processing could be a major improvement, because a simple camera makes the data acquisition and the analysis of the entire area of the material under study without requiring any other equipment like in the traditional method. Digital image correlation (DIC) is a method that examines consecutive images, taken during the deformation period, and detects the movements based on a mathematical correlation algorithm. In this paper, block-matching algorithms are used in order to compare the results from image processing and the data obtained with linear voltage displacement transducer (LVDT) sensors during laboratorial load tests of T-beams.