Bridge Safety Dangers - Fatigue Cracks, Brittle Failures and Grit Blasting

Abstract

Fatigue failures in bridges have been extensively studied for decades, and experimental data was applied to create fatigue curves to be used for bridge designs, however, new research questions the validity of these curves with respect to safe bridge design. Specifically, grit blasting for coating adherence creates surface damage in the form of sharp indentations and peaks over entire steel surfaces. These imperfections act as stress raisers that accelerate bridge failures by reducing the number of cycles to failure and the stresses required to cause failure. Strong differences of opinion exist with respect to this complex issue. This author believes that there is a significant threat to bridge safety, while other authors believe that there is no safety threat at all. The goal of this article is to effectively refute opinions which claim that bridge safety is adequate. To do so, a thorough review of earlier publications is combined with new developments on grit blasting fatigue. Bridge safety is questionable since bridge design requirements in the form of fatigue curves are questionable. There is limited information, one way or the other, to prove the full extent of grit blasting effects on steel bridge fatigue failures, and this paper fosters an understanding of this dangerous threat. Available results clearly prove that bridge fatigue properties are reduced by grit blasting, which in turn reduces the safety of design practices for bridges. An open and unknown question exists, what is the complete extent of grit blasting effects on large structures? That is, bridge failure mechanisms are not fully understood, there are uncertain risks with respect to bridge fatigue damages, and a paramount risk concerns grit blasting. Unknown grit blasting safety effects cannot be dismissed. Moreover, evolving facts prove that the inherent dangers in bridge design practices must be addressed and resolved. Specifically, bridge design curves account for repeated loads on bridges caused by traffic, and further research is mandatory to ensure the validity of these curves, which are shown to be inadequate by this innovative research. A resistance to new ideas serves as an unacceptable reason to curtail technology that will improve bridge safety.