Local strain monitoring study of offshore platform T shaped tubular joint using fiber bragg grating sensors

Complex stress monitoring test of big scale offshore platform T-shape tubular joint is designed and accomplished. To assist this study, a finite element model of the T-shape tubular joint is established to predict the complex strain distribution in the hot spot of the joint. Installation principle and scheme of FBG sensors are proposed. The right angle FBG strain rosette is developed to measure the principle strain, along with the strain distribution of the hot point, in comparison with results from strain gauges. The results show that FBG rosette can monitor the principle strain precisely, and single FBG sensor is acceptable for the hot point strain monitoring. A method is proposed to correct the FBG sensor measurement for its relatively long sensing gauge. Further experimental results show that a single FBG sensor with data correction can monitor the hot spot strain of the model. Static test using FBG sensors and strain gauges were designed and conducted, respectively. Results show that FBG sensors can precisely measure the axial force, the hot spot strain, and the local strain of the tubular joint model.