Reinforced concrete infrastructure assets built during the last century are required to stay in-service beyond their intended design lives, which requires techniques that allow the effects of deterioration and overloading to be monitored to ensure these assets are still fit for purpose. One such indicator of distress in a reinforced concrete structure is crack movement; models have been proposed that allow the internal stresses within a structure to be estimated if crack width and slip can be measured. This paper introduces a technique that uses digital image correlation (DIC) to measure not only crack width but also crack slip. The effect of curvature on this measurement technique is discussed and a method for minimizing the errors due to curvature is presented. The technique is used to measure crack width and slip in reinforced concrete beams with both small crack slip and significant crack slip. The results suggest that the technique can be used to measure crack movement in beams once the effects of curvature are accounted for. Future research in this area will focus on development of this technique for use in the field.

A need exists for a non-contact two-dimensional strain measurement system,which could provide information for field monitoring and greatly enhance theaccuracy of structural models through the development of larger data sets for model calibration. This paper introduces a potential technique for measuring displacement with a high degree of accuracy, which is required for a two-dimensional strain sensor, using relatively inexpensive digital cameras using the digital image correlation technique and a software package called GeoPIV. The basics of the digital image correlation technique are presented. The paper focuses on the importance of image texture in achieving accurate displacement measurements. As an illustration of this, compression tests on textured and untextured concrete cylinders are presented. Using a full displacement field analysis region, it was found that the cylinders with artificially added texture produced more accurate results than those without. These results are discussed to highlight the impact of image texture on the digital image correlation technique.

A method for measuring longitudinal strains with the height at a section, and thus the curvature, using a technique based on digital image correlation (DIC), is presented. The background to this technique is introduced as well as previous work in this area. The accuracy of DIC under ideal conditions is established using artificially generated images that represent beams with various curvatures. The practical accuracy of DIC is established by comparing the strains measured using DIC to those predicted by elastic theory and measured using strain gauges for a steel beam. The correlation between these results is found to be excellent. DIC is then used to measure curvatures in RC beams and these results are compared with analytically predicted results with good agreement. The choice of an appropriate gauge length for RC is discussed and is shown to be one of the significant advantages of using DIC as opposed to strain gauges in both laboratory testing and field monitoring of bridge structures.