Parametric Study of FRP Strengthening on Stress Concentration Factors in an Offshore Tubular T-Joint Subjected to In-Plane and Out-of-Plane Bending Moments

This paper describes numerical investigations conducted on a tubular T-joint strengthened by FRP composites under in-plane bending (IPB) and out-of-plane bending (OPB) moments. The FRP materials were applied as a protective layer on the T-joint, and the analyzed models were eventually validated against the results obtained from an experimental study. The effectiveness of using FRP materials on enhancing the fatigue life of a tubular T-joint was investigated through computing the relative SCFs of 150 finite element models using ABAQUS software package. Analyses have been performed to investigate different FRP parameters such as fiber orientation, FRP thickness, wrapping length and FRP material properties of the wrapped joint. Effectiveness of these FRP parameters on SCF reduction along with the most efficient lay-ups against both IPB and OPB moments were reported. According to the results of this study, further reduction in SCFs was observed when the joint was confined with stiffer FRPs. SCF reduction of around 15% was observed for only a 1 mm thick CFRP layup. Moreover, using a thicker FRP layup tends to increase its effectiveness significantly. However, it was observed that increasing the FRP wrapping length has negligible effect on SCF values, and has to be chosen so as to cover all the chord surface area influenced by the brace loading in order to balance the state of stresses and deformations.