Optimization of Stiffening Rings' Position in Welded Tubular X-Joint

Abstract

Summary Experimental results are presented to show that the position of the stiffening rings in welded tubular X-joints has a great impact on the value of the stress concentration factor (SCF) at the hot spot as well as its location. Preliminary guidelines for an optimal ring position are proposed. proposed. Introduction In offshore structures, such as semisubmersible drilling vessels and fixed platforms, tubular members comprise the main load-carrying components. The platforms, tubular members comprise the main load-carrying components. The design of joints between these tubular members is complicated because the radial flexibility of the tube walls leads to significant stress concentrations. Since many of these structures are subjected to alternating loads, the presence of stress concentrations can lead to an early fatigue failure. Ring stiffeners often are used as a means of reducing the SCF and thus increasing the fatigue life. This has been confirmed by the results of Maeda et al. and Matoba et al. The effect of the position of ring stiffeners on the maximum SCF value and, hence, the fatigue life is, to my knowledge, not available in the open literature. This paper represents a preliminary study of the effect of positioning of both internal and external ring stiffeners on the value and positioning of both internal and external ring stiffeners on the value and the location of the maximum SCF. It should be recognized that this paper is not intended to give a generalized recommendation for the optimal ring position but rather to alert designers and fabricators to the danger of position but rather to alert designers and fabricators to the danger of unoptimized position. Poor positioning of the rings can result in very little improvement in the state of stress as well as the expense and drawbacks associated with welding. Experimental Details The experiments were conducted on welded tubular X-joints with an angle of intersection equal to 900 (this joint also is classified as double-T joint). JPT p. 328