Abstract
Abstract. This paper deals with the determination of crack widths of concrete beams during load tests from monocular image sequences. The procedure starts in a reference image of the probe with suitable surface texture under zero load, where a large number of points is defined by an interest operator. Then a triangulated irregular network is established to connect the points. Image sequences are recorded during load tests with the load increasing continuously or stepwise, or at intermittently changing load. The vertices of the triangles are tracked through the consecutive images of the sequence with sub-pixel accuracy by least squares matching. All triangles are then analyzed for changes by principal strain calculation. For each triangle showing significant strain, a crack width is computed by a thorough geometric analysis of the relative movement of the vertices.
Highlights
For the examination of the behavior of concrete structures, civil engineers conduct load tests on concrete beams
Several publications deal with photogrammetry in civil engineering material testing. (Whiteman et al, 2002) and (Fraser and Riedel, 2000) measured vertical displacements of targets placed on a line on the specimens surface with multi-ocular camera systems
(Dare et al, 2002) computed polygons along the crack using the fly-fisher algorithm and the route-finder algorithm. They presented a method for crack width measurement based on the analysis of profiles perpendicular to the polygons. (Hampel and Maas, 2003) and (Benning et al, 2004) used multi-ocular camera systems for displacement measurement in image sequences of planar plates with a grid of targets
Summary
For the examination of the behavior of concrete structures, civil engineers conduct load tests on concrete beams. (Dare et al, 2002) computed polygons along the crack using the fly-fisher algorithm and the route-finder algorithm They presented a method for crack width measurement based on the analysis of profiles perpendicular to the polygons. (Hampel and Maas, 2003) and (Benning et al, 2004) used multi-ocular camera systems for displacement measurement in image sequences of planar plates with a grid of targets. (Barazzetti and Scaioni, 2010) presented three image-based methods for displacement measurement in civil engineering material testing. They applied the Wallis filter on natural texture for contrast enhancement. Comparisons between other sensors were done by (Schacht, 2014)
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