Behavior of Unstiffened and Stiffened Steel Tubular T-Joints

Offshore towers standing in deep sea are susceptible to cyclic nature of wave forces. Fatigue failure initiates at the welded tubular joints of these structures where a very high stress gradient and localized stress concentration exist due to abrupt changes in the geometry. Stress concentration plays a vital role in the design of steel tubular joints, as it directly affects the fatigue life of the structures. This paper presents results of an experimental study on the behavior of an unstiffened and a stiffened steel tubular welded T-joint under axial brace loading. The effect of internal ring stiffeners has been studied theoretically and experimentally. In the experimental technique, the specimens were extensively strain-gaged and the stress distribution determined under static load. The analytical results have been obtained by finite element technique.