Experimental and numerical investigation of ultimate strength of ring-stiffened tubular T-joints under axial compression

The design procedure based on empirical equation for computing the chord strength of tubular joints in offshore structures has been established by various researchers and adopted by American Petroleum Institute and other organizations. Local stiffening of chord may be required to carry the loads from braces from various directions. One such method is to introduce internal circular rings at the brace-chord interface. In the present study experimental and numerical investigation on a ring-stiffened tubular joint have been carried out using 1:8 scale model of commonly adopted configuration used in the industry. Experiments have been conducted to measure the failure loads of stiffened and unstiffened tubular joints of (T-geometry) with plain and flanged ring-stiffeners fitted inside the chord. Models were fabricated using steel material and tests were conducted to measure the chord deformation using displacement transducers. First peak in load-displacement relationship has been used to determine the ultimate capacity. Numerical simulations have been carried out using ABAQUS software based on nonlinear stress-strain relationship of steel. The load-displacement characteristics for stiffened and unstiffened joints have been established. Results obtained from numerical simulation have been compared with that obtained from the experimental studies. Strength enhancement factors for stiffened joints have been calculated and compared with that of the unstiffened joints. The enhancement factors for plain and flanged internal ring-stiffener are noted to be 1.66 and 2.03 respectively.