Structural Efficiency of Internally Ring‐Stiffened Steel Tubular Joints

Abstract

Welded tubular structures are widely used for offshore platforms. In India, there are more than 120 offshore platforms in the Bombay High region, all of which are jacket‐type structures consisting of welded tubular members. The tubular joints of these structures are subjected to stress concentration, which because of the increased hot‐spot stresses reduces the fatigue life of the structure. Also, the ultimate strength of the tubular joints is very much reduced due to the local buckling effect of the tubular members. Based on the analytical and experimental studies conducted at the Structural Engineering Research Centre, at Madras, it is observed that these deficiencies of tubular joints can be reduced to a great extent by providing internal ring stiffeners in the chord members. Internal ring stiffeners are found to reduce stress concentration, increase fatigue life under cyclic loads, and also improve the ultimate strength of the joints. The results of investigations on internally ring‐stiffened steel tubular T and Y joints are presented in this paper.