Effect of FRP Material Properties on Chord SCFs of an FRP-Strengthened Offshore Tubular T-Joint under Brace Axial Loading

The relative stress concentration factors (SCF) on the chord member of a tubular T-joint strengthened with FRP which is subjected to brace axial loading are studied. ABAQUS Finite Element software package is used to perform the numerical analyses. Prior to the main studies, the unstiffened joint was validated against the API and Lloyd’s Register equations together with the experimental data. Six different types of FRP materials such as Glass/Vinyl ester, Glass/Epoxy (Scotch ply 1002), S-Glass/Epoxy, Aramid/Epoxy (Kevlar 49/Epoxy), Carbon/Epoxy (T300-5208) and Carbon/Epoxy (AS/3501) are used as strengthening material in order to enhance the fatigue life of tubular T-joints through lowering the SCFs. Promising results derived from analyses which show that FRP strengthening method can be considered as an effective method for decreasing the SCF values at tubular T-joints. Results of the analyses for 6mm CFRP layup revealed that under the action of axial loading the FRP strengthening could decrease the SCFs up to 30% and 50% at crown and saddle points of the chord member.