Fatigue resistance and repairs of riveted bridge members

In 1993, the dismantling of a ninety-one-year-old railway bridge presented an opportunity to perform tests on four of its cross girders. The goal of the tests was to determine the fatigue resistance of riveted mild steel details and the effectiveness of different repair techniques. On the basis of these fatigue tests, as well as earlier tests performed at ICOM, it was found that highly prestressed riveted details subjected to a small bearing force can be considered a detail category ECCS XO. However, when the level of prestress in the riveted detail is unknown and the detail is subjected to a large bearing force, it is more appropriate to use a detail category ECCS 71. Apart from a few exceptions, it was shown that the replacement of rivets with prestressed bolts can prevent further crack propagation of small cracks. However, this method acts only locally. A more efficient method to repair riveted elements is the bonding of pretensioned strips of carbon fibre reinforced plastic (CFRP) on the cracked element. The stiffness of the CFRP-strip and the application of a compressive stress at the crack tips causes the crack propagation to be reduced or, in some cases, stopped. Reasons for using the CRFP-laminates include their high fatigue resistance and high ultimate strength. The effectiveness of this technique is currently being verified by fatigue tests and crack propagation measurements on small scale specimens, and shows potential for use in practice.