A holistic strategy for rehabilitation of fatigue-cracks in steel bridges: evaluation of fatigue cracks in the field and laboratory testing
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Nationwide, a significant amount of bridges within the National Bridge inventory (NBI) have been found to develop fatigue cracks. Typically section(s) in and surrounding welded connection details are particularly prone to the development of fatigue cracks as a result of the significant stress concentration. Existing flaws and/or discontinuities caused by notches, corners, welding toes etc., under the presence of tensile stresses will encourage the initiation and propagation of these cracks. Fatigue cracks found in bridge members can become potential areas of concern for bridge owners, as if not mitigated, continued cyclically applied loading to the bridge encourages the propagation of these cracks at these connection details. Ultimately, these cracks can lead to the possible gross deformation, loss of function or serviceability, or complete separation of the component known as fracture. Although fatigue inherently does not always lead to fracture of a structural component, it must be considered as potential consequence of the development of fatigue cracks if not diminished. As a result of this propagating issue, a holistic approach to the rehabilitation of cracks found in these steel bridge members has been deployed. This approach emphasizes the use of composite materials in addition to a carbon nanotube (CNT)-based sensing layer in order to create a structural patch to be applied over a fatigue crack. This patch not only rehabilitates damaged sections but also continuously monitors its progress through use of the CNT sensing layer. If employed properly, this new technique of utilizing a composite patch over the fatigue crack will inevitably decrease the overall stress concentration exhibited around the crack/crack mouth, which ultimately prolongs the general fatigue life of the structural member.