Bridges, Tunnels and other Transportation Structures
Digital Image Correlation (DIC) has been used in the past to examine flaws in structural components such as fatigue cracks. Previous research using DIC has focused on simple test setups; C(T) and SE(B) specimens are commonly adopted for these tests. Studies have shown that up to 90% fatigue cracks on highway steel bridges are due to distortion induced fatigue at the cross-frame connections [Connor and Fischer 2005]. These tensile specimens are generally tested in Mode I fatigue loading, whereas distortion induced fatigue is a combination of Modes II and III. This study will explore the applicability and challenges of using DIC for detecting fatigue cracks being loaded in Mode II and III. To obtain realistic distortion induced fatigue crack growth, measurements will be taken at the cross-frame connections of a half-scale steel bridge. This allows for a more complex test geometry to be considered, leading to a better understanding of the role that test setup complexity plays in DIC measurements. This study will also determine the effect of surface conditions on DIC measurements. Variable amplitude loading will also be investigated to determine the applicability of DIC for finding fatigue cracks in bridge components subjected to a range of ambient traffic loads.