Effect of grooves on the static strength of tubular T joints of offshore jacket structures

Abstract

The present research work deals with effect of grooves on static strength and stiffness of tubular T joints of offshore jacket structures. Tubular structures are commonly employed in offshore jacket platforms due to better mechanical properties and economic advantages. The tubular T model considered for this study has chord dimensions of 1000 mm length, diameter 102 mm and thickness 5 mm and brace dimensions of 388 mm length, diameter 55 mm and thickness 4 mm. Material used for present analysis is Steel with Young’s modulus of 210 GPa and the Poisson ratio of 0.3. Three-dimensional finite element analysis has been carried out to investigate the effect of grooves placed over thickened chord section on the static strength of tubular T joints subjected to axial compressive load. In the present study, unstiffened tubular T joint is analysed and compared with stiffened tubular T joints to observe the improvement in the static strength of the tubular T joints. The groove configurations considered are: 5 circumferential grooves at 16.5 mm spacing, 3 circumferential grooves at 16.5 mm spacing and 3 circumferential grooves at 33 mm spacing. The grooves were having the dimension of 1 × 1 mm, 2 × 2 mm were used for the analysis. The joint local stiffness of ungrooved tubular T joint is 116.43 N/mm. The grooved configuration increases the joint local stiffness by more than 250 percent.