Refined extraction of crack characteristics in large-scale concrete experiments based on digital image correlation

Abstract

The accurate extraction of the crack patterns and measurements of crack kinematics are essential for understanding the mechanical behaviour in experiments on structural concrete as well as in the validation and further development of sound mechanical models. This paper presents important refinements of the authors' recently published automatic crack detection and measurement procedure (ACDM) based on surface displacement measurements obtained with digital image correlation (DIC). The proposed refinements are crucial for reliably assessing the crack behaviour in large-scale experiments with complex crack patterns, since the original methods of ACDM may fail or result in biased measurements at locations with closely spaced cracks, crack intersections or cracks with high morphological curvature. The main refinements are (i) a Canny edge-based crack detector, which is applied on the DIC major principal strain field and (ii) enhancements in the crack kinematic measurement to assess the reliability of the results. The latter includes the automatic selection of optimum reference points used in the crack kinematic measurement to increase its reliability and remove uncertain results. The refined ACDM procedure is validated using several large-scale 2.0 × 2.0 m shear panel experiments with highly complex crack patterns. Compared to the original ACDM, significantly thinner cracks can be detected with a much higher reliability of crack locations and crack kinematic measurements, particularly close to crack intersections and at closely spaced cracks. Additionally, two approaches for the statistical consolidation of the large amount of gathered data into characteristic crack properties in large-scale homogeneous concrete element experiments are proposed and compared. The results show that the statistical consolidation of the ACDM data using a 95%-quantile match well with the direct extraction of the best-fit homogeneous crack properties from the fullfield DIC displacements. The consolidated data provides highly valuable insight into the mechanical behaviour, especially regarding crack phenomena.

Direction-dependent behaviour and size effect of steel fibre reinforced concrete based on the double punch test

“…The accuracy of this approximation was examined by investigating the full displacement and strain fields of the surfaces tracked with DIC. Using the open-source software ACDM [31,32], the cracks were detected, and the crack width was continuously computed based on the displacement and strain fields. The ACDM software allows multiple cracks to be detected and provides a much more precise measurement of the crack width since the inspection points are much closer to the crack.…”

Effective reinforcement ratio of RC beams: Validation of modelling assumptions with high‐resolution strain data

“…A DIC system provides full‐field information of the displacements over an area of interest (AOI). The strain data of a concrete specimen's surface can be used to assess the crack behaviour (location, width and slip of cracks), for example, by using the automated crack detection and measurement (ACDM) approach 30,31 . Moreover, concrete strains on the surface can be calculated from the measured displacements.…”

“…The strain data of a concrete specimen's surface can be used to assess the crack behaviour (location, width and slip of cracks), for example, by using the automated crack detection and measurement (ACDM) approach. 30,31 Moreover, concrete strains on the surface can be calculated from the measured displacements. To this end, a high-resolution system is needed to generate meaningful data.…”

Experimental Investigation of Mechanical Characterizations of a POM Fiber-Reinforced Mortar Material

“…Cementitious composites have been widely used in various engineering constructions. Although cementitious composites have excellent engineering properties, they exhibit adverse mechanical performances, such as brittleness, poor tensile resistance and cracking behaviors [1] due to their unequal strengths in tension and compression. These defects harm the durability and workability of engineering structures.…”