Optimized planning for weather-sensitive offshore construction operations - An application to float-over installation of super-heavy offshore topsides

Abstract

Float-over method offers an efficient, reliable, and practical installation scenario for large-scale offshore topsides. It is, however, highly sensitive to marine environmental conditions and necessitates comprehensive pre-planning. Conventional deterministic approaches methodologies exhibit shortcomings in achieving a cost-effective and time-efficient float-over design, thereby necessitating a comprehensive reconsideration. This study aims to develop a reliability-based methodology for float-over analysis of super-heavy offshore topsides. Incorporating diverse geometric and mechanical limit state functions, the permissible weather window is determined by use of Monte-Carlo Simulation. This methodology leverages the data set generated based on nonlinear coupled multi-body hydrodynamic simulation of the float-over operations. The presented idea provides a decision-making platform that integrates safety and efficiency considerations. The float-over design is optimized utilizing the developed approach and some recommendations are made to enhance applicable codes and guidelines. To reduce the computational expenses, the application of the importance sampling technique is subsequently proposed. Long-term planning of float-over installation is derived finally, optimizing operational time and cost while keeping risks as low as reasonably practical. In conclusion, it is crucial to establish a reliability-based framework for scheduling weather-sensitive offshore construction projects.