Full-Scale Damage Detection of Railroad Crossties Using Digital Image Correlation

Abstract

Railroads experience different track failure mechanisms, which may cause problems ranging from service interruptions to derailments. With reference to the crossties-ballast system, one of the most acknowledged high-risk scenarios is the center binding condition, a situation in which the support of the ballast under the crossties is initially concentrated at the rail-seat rather than uniformly distributed. As a result, a firm support of the ballast is only provided at the center of the crosstie, while it cantilevers over its two ends. For this reason, novel track inspection technologies for detecting crossties’ vertical deflection and displacement are continuously sought. In recent years, three-dimensional (3D) Digital Image Correlation (DIC) systems have proven to be an effective technique for extracting structural deformations and geometry profiles of large-sized civil structures. In this study, the feasibility of a novel railroad tracks examination system is proposed for crossties-ballast conditions assessment. It consists of four pairs of cameras installed on the underside of a rail car to detect the induced displacements. To validate the performance of the proposed system, different center binding conditions were simulated on a full-scale railroad mock-test. Experimental results showed that the 3D-DIC system was able to measure the relative tie deflections with a resolution of approximately 10⁻⁴ m, well below the deflections that these crossties experience in operation.