Image analysis for crack observation of a cylinder RC structure cyclic test

The development of concrete surface cracks in an RC experiment is commonly observed and recorded by suspending a test at a few selected steps and sending inspectors to mark pen strokes on visible cracks. This work is labor intensive with a certain level of risk. An image analysis method was proposed to observe thin cracks of cylinder concrete surfaces, which has been implemented into a public software tool named ImPro Stereo. However, this method has never been verified by comparing image analysis results and labor pen marked cracks as it requires surface painting that may increase eye observation difficulty. This work compared the crack observation results observed by the image analysis method and labor pen marked cracks. The crack locations, widths, and lengths are compared. The limitations of both methods are discussed. A few strain concentration lines (probably cracks) that appeared in the very early stage of the test and observed by the image analysis method, before the labor pen marking was started, is presented and discussed in this paper.