Publish and Present
“The piles are falling apart at the seams.” What the engineer-diver was seeing was a premature failure of the steel pipe piles’ vertical weld seam. The phenomenon is a result of an accelerated corrosion process between dissimilar metals that are exposed to seawater. In this instance, the weld material becomes anodic to the steel pipe material when submerged in the electrolytic seawater. In effect, the weld material filler metal is sacrificed to the benefit of the pipe pile steel.
Corrosion of steel in the marine environment is a well-known and well documented process; however it is generally thought of as affecting the entire structural element. What makes this particular mode of corrosion unique is that it aggressively attacks the weld material and can result in premature failure of the entire pile. When the piles become “unzipped” there is a significant effect on its load capacity.
This condition is a result of the piles’ original fabrication process and is becoming unmasked on a more frequent basis on waterfront structures. Understanding the fabrication process of vertically welded steel pipe piles provides insight not only into why the process occurs on existing structures but also how to reduce the risk of occurrence on new structures.
This paper will discuss the causes of this condition as well as the effect it has had on several waterfront structures in the northeast. It will also discuss the structural implications to the overall pile capacity as well as the repair efforts taken to mitigate these effects.