Nonlinear Mooring Component for Shallow-Water Load Management
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Solution Overview
Problem
Conventional mooring systems for floating marine structures, such as offshore wind turbines, face challenges in shallow waters due to high background thrust loads and dynamic loads, leading to high stiffness and increased costs, with existing solutions like catenary chain systems experiencing undesirable stress-strain behavior and fatigue issues.
Innovation Solution
A mooring component with a compressive element that undergoes specific stages of compression in response to tensile stress, inducing extension and varying stiffness values, allowing for a non-linear stress-strain response to manage background and dynamic loads effectively, reducing fatigue and component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional catenary chain systems are used to provide restoring force, then the mooring system can handle background thrust loads, but the system becomes excessively stiff and components require larger sizes to protect against failure
Solution Approach 1:
The patent applies parameter changes by transitioning from a linear elastic stress-strain relationship to a non-linear stress-strain relationship with distinct stages. The first stage provides high stiffness to resist background thrust, while the second stage provides low stiffness to accommodate wave-induced motions, thereby reducing peak loads and component sizes without sacrificing strength capability
Solution Approach 2:
The invention introduces dynamic adaptability through a mooring system that automatically adjusts its stiffness characteristic based on the magnitude of applied loads. Under high background thrust conditions, the system operates in the first compression stage with high stiffness, but under dynamic wave loads, it transitions to the second stage with low stiffness, providing an adaptive response that optimizes performance across varying operational conditions
2Stability of the object's composition
If the mooring system stiffness is increased to resist high background thrust, then the structure remains in position, but variable loads from wave motion increase significantly
Solution Approach 1:
The patent resolves this contradiction by implementing a non-linear stress-strain curve with two distinct stages. The first stage provides high stiffness to maintain position stability under background thrust, while the second stage provides low stiffness to reduce variable loads during wave-induced platform motions, thereby achieving both position holding capability and load reduction
3Reliability
If larger mooring components are used to protect against failure under high loads, then system strength increases, but cost and installation complexity increase
Solution Approach 1:
The invention reduces component size requirements by changing the stress-strain parameter from linear to non-linear. The low stiffness second stage absorbs wave-induced motions and reduces peak loads, allowing the use of smaller, less expensive components that still provide adequate failure protection, thereby reducing installation complexity and cost
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The mooring component effectively manages high background and dynamic loads, reducing fatigue and the need for large, expensive components, while maintaining the structure's position and safety, thereby lowering costs and extending the operational lifetime.
Implementation Method 1
arranged such that a tensile stress experienced by the mooring component up to a first stress value of the tensile stress compresses the at least one compressive element in a first stage of compression by up to a first fraction of an uncompressed length of the at least one compressive element
Data Source
AI summary
A mooring component includes at least one compressive element arranged to undergo compression in response to a tensile stress experienced by the mooring component that induces an extension of the mooring component. A tensile stress experienced by the mooring component up to a first stress value compresses the compressive element in a first stage of compression with a first average stiffness value. A tensile stress experienced by the mooring component above the first stress value and up to a second stress value further compresses the compressive element in a second stage of compression with a second average stiffness value. A tensile stress experienced by the mooring component above the second stress value further compresses the compressive element in a third stage of compression with a third average stiffness value. The first and third stiffness values are greater than the second stiffness value.