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Shi Chen,Wang Jialu,Yang Lingzhi,Bao Xingxian 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1
Thermoplastic Composite Pipes (TCPs) have potentials to be used as subsea pipelines. TCPs are superior in corrosion resistance, yet vulnerable to impact damages. In this study, a Bayesian Network (BN) model was developed taking the factors, such as water depth, weather condition, seabed stiffness, material aging, etc., as variables of the BN model to evaluate the probability of failure of TCP subsea pipelines when they were subjected to falling objects from passing vessels. Case study examples of an assumed TCP pipeline in shallow water area of Bohai sea of China were used to illustrate the topology structure of the BN model and the modeling procedures of the Conditional Probability Table (CPT) of the BN model variables. The case study examples illustrated that the BN model can predict the probability of failure of a TCP pipeline and diagnose the likely causes of the failure. Additionally, the BN model can be updated by taking into account new data such as aging of materials for the entire service life of the pipeline. The predicted failure probability of the assumed TCP pipeline was not benchmarked due to lack of observation data; however, the proposed BN model is a useful tool for the integrity management of TCP pipelines when widely installed in the future.
Shi Chen,Liu Yang,Wang Jialu,Chen Fabo,Liu Zhihui,Bao Xingxian 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1
Vortex-Induced Vibration (VIV) is a major contributor to the fatigue damage of marine risers which are often arranged in an array configuration. In addition to helical strakes and fairings, studies have been strived in searching for possible VIV suppression techniques. Inspired by giant Saguaro Cacti, flexible cylinders of different cactus-shaped cross sections were tested in a water tunnel facility, and test results showed that cactus-like body shapes reduced VIV responses of a cylinder at no cost of significant increase of drag. A series of experiments were conducted on a pair of two tandem-arranged flexible cylinders and an array of four cylinders in a square configuration to investigate the effects of wake on the dynamic responses of cylinders and the VIV mitigation effectiveness of the cactus-like body shape. Results showed that the cylinders in a square configuration, either at the upstream or downstream positions, might have larger dynamic responses than those of a single cylinder. The cactus-like body shape could mitigate VIV responses of cylinders at upstream positions in an array configuration; however, similar to helical strakes, the mitigation efficiency was reduced on downstream cylinders. Note that the cactus-like cross-sectional shape investigated was not optimized for VIV suppression. The present study indicates that the modification of the cross-sectional shape of a cylinder to a well-designed cactus-like shape may be used as an alternative technique to mitigate the VIV of marine risers.