Repairing and Preserving Bridge and Steel Structure Using an Innovative Crack Arrest Repair System

Abstract

Cracking in steel road or rail bridges is a major concern for continued safe operation of the bridge. Traditional crack arrest hole (CAH) or drill stops placed at the end of the detectable crack have been shown to be ineffective in stopping cracks. A method adapted from the aerospace industry, which utilizes a high interference fit bushing expanded into the CAH, has been tested in large A36 steel coupons under typical cyclic bridge loading. Expansion of the bushing into the hole yields the surrounding steel and induces a residual compressive stress around the hole to shield it from the cyclic load and prevent further crack growth. Not only did this method completely arrest the crack with a life improvement factor exceeding 60:1 over the conventional CAH but it also increased the load factor capability of the coupon by over 20%. This paper will describe the methodology, present the results of the test program and show how this innovative method dramatically increases the effectiveness of a typical CAH that could forestall major structural failure.