Fatigue Behavior of Internally Ring-Stiffened Welded Steel Tubular Joints

Abstract

The use of internal ring stiffeners in offshore steel jacket platforms is a subject of controversy because of their peculiar failure pattern, observed in several tests in the early 1980s. It is estimated that at least 2,000 internally ring-stiffened steel tubular joints are in service in the North Sea. Despite the fact that internal ring stiffeners have been introduced in many offshore platforms, none of the design codes provide quantitative design guidance. Therefore, to create an extensive database on internally ring-stiffened steel tubular joints, experimental investigations were conducted at the Structural Engineering Research Centre, in Chennai, India, on the fatigue behavior of internally ring-stiffened steel tubular joints. Various loading conditions, joint geometries, and environments were considered. In this paper, the experimental results are compared with API and DEn design curves and the results are discussed.