The jacket structures are often employed in the range of shallow-moderate water depth. The bracing systems and jacket legs typically use the circular section in order to compromise the hydrodynamic resistance and high torsional rigidity However, under lateral impact, these tabular bracing members are susceptible to local denting due to ship collisions or through impact of falling objects and that can weaken overall performance of the entire platform. It is a great significance for forecasting dent depth of these members accurately. This paper investigates the use of adaptive meta-heuristics algorithm to provide an automatic detection of denting damage in an offshore structure. A model is developed combining with the percentage of the dent depth of damaged member diameter and is used to assess the performance of the method. It is demonstrated that the small changes in stiffness of individual damaged bracing members are detectable from measurements of global structural motion.

No abstract

No abstract

Offshore jacket platforms are widely used for oil and gas extraction as well as transportation in shallow to moderate water depth. Tubular cross‐sectional elements are used to construct offshore platforms. Tubular cross sections impart higher resistance against hydrodynamic forces and have high torsional rigidity. During operation, the members can be partially or fully damaged due to lateral impacts. The lateral impacts can be due to ship collisions or through the impact of falling objects. The impact forces can weaken some members that influence the overall performance of the platform. This demonstrates an urgent need to develop a framework that can accurately forecast dent depth as well as dent angle of the affected members. This study investigates the use of an adaptive metaheuristics algorithm to provide automatic detection of denting damage in an offshore structure. The damage information includes dent depth and the dent angle. A model is developed in combination with the percentage of the dent depth of the damaged member and is used to assess the performance of the method. It demonstrates that small changes in stiffness of individual damaged bracing members are detectable from measurements of global structural motion.

Steel jacket offshore platforms are typically employed for use in shallow to moderate water depths. During platform operations, there have been some historical accidents completely damaging the diagonal members of the bracing systems due to explosions, fire accidents and dropped objects. Different locations of damaged bracings demonstrate different levels of risk for safety and integrity of the structures. This research illustrates the effects of redundancy in the bracing systems for steel jacket offshore platforms. Assessments have been carried out using the nonlinear pushover analysis method and formations of nonlinear hinges of different members were noted. Redundancy in different positions has been considered to investigate the consequences. Reserve strength ratio (RSR) and damage strength ratio (DSR) of the global structure were also evaluated to understand the importance of different local members. From the collapse data of local failures, fragility curves for the global structures were estimated. The results demonstrated that the position of damage can be a great concern which affects the overall performance of the structures.