STRESS CONCENTRATION FACTORS OF FRP-WRAPPED TUBULAR T-JOINTS OF JACKET TYPE OFFSHORE PLATFORMS UNDER BRACE AXIAL LOADING

Due to the cyclic nature of wave loading on offshore structures, care must be given to their fatigue resistance. Fatigue life of offshore jacket joints is calculated using aparameter called stress concentration factor (SCF). SCF can be computed in un-stiffened and stiffened joints. In unstiffened joints, many researchers did efforts since the 70s and their main objective was to derive parametric equations for SCF calculation. Ahmadi and Lotfollahi- Yaghin [1] have performed recent studies in this field.There are some metallic-based methods which are used for strengthening CHS joints in order to decrease the SCF. Lesani et al. [2] reviewed some of these strengtheningtechniques. There are also some non-metallic external reinforcement schemes such as FRP strengthening method. FRP wrapping method due to its convenience for handling and application, corrosion resistance, potentially high overall durability, light weight, superior strength-to-weight ratio and high specific performance attributes could be easier for application in areas in which using conventional materials may not be feasible due to durability, weight or lack of design flexibility constraints. Lesani et al. [2] reviewed the studies in which this non-metallic reinforcement technique is used. Lesani et al. [2-4] numerically and experimentally studied the performance ofthis technique on the static strength of steel tubular T and Y-joints. According to these studies, it would be necessary to investigate SCF improvement using the FRP wrapping technique. This paper is aimed to present the relevant findings of such investigations.