ASRANet Consultancy

SOFTWARE FOR SALE: RELIABILITY BASED ANALYSIS & DESIGN OF MONOPILE AND JACKET PILE FOUNDATIONS FOR WIND TURBINE STRUCTURES

This software which we have recently developed under the Scottish Enterprise SMART Initiative looks at a Reliability Based Analysis and Design of Monopiles and Jacket Pile Foundations for Wind Turbine Structures.

The software demonstrated here is developed for the purpose of using probabilistic design of offshore wind turbine structures, and will deal with the Ultimate Limit State, Fatigue Limit State and Serviceability Limit State.

All the above methods are then used to establish the safety level format for the structural reliability analysis and has been developed through Microsoft Excel, with the spreadhseets interlinked for automatic updates once specific data has been entered into the fields.
This software is now available for purchase and may be of interest to companies involved in offshore wind. A brief sheet with more detail of the software is given below



SUMMARY


The software demonstrated here is developed for the purpose of using probabilistic design of offshore wind turbine structures. The software will be able to deal with three different limit states:

- Ultimate Limit State - ULS

- Fatigue Limit State - FLS

- Serviceability Limit State - SLS

With the ULS method two conditions of soil loading is considered, Blum's Method and Reese & Matlock Method. The environmental load is calculated through the use of Linear Airy Wave Theory. The maximum bending moment in the pile structure is calculated and checked using an interaction equation proposed by DNV GL, thus establish safety level of the structure

For the FLS, the input will be the dynamic stress range (To be calculated by FE Analysis). Using the Miner - Palmgren rule the Fatigue Damage is calculated thus the fatigue life is evaluated.

In the case of SLS, three conditions are proposed. The structures natural frequency is matched against the frequency of wave, rotor and the blades. The natural frequency is calculated through a theoretical formulation, the frequency for the pile of a jacket structure is caluclated through a FE Analysis. The structures natural frequency is plotted against frequency ranges of wave, rotor and blades to ensure the resonance doesn't occur.

All the above methods are then used to establish the safety level format for the structral reliability analysis. In this case, these are known as g(.) functions which are the safety margins for resistance and load. The uncertanties of the design variables along with their distributions are then input into a reliability analysis program called CALREL. The output of any reliability programme is the sensitivity factor, partial safety factor, safety index and probability of failure. This probability of failure is then compared with the target reliability level proposed by DNV GL in the classification note 30.6: STRUCTURAL RELIABILITY ANALYSIS OF MARINE STRUCTURES. JULY 1992 [2]. The reliability method is the only methods that can take into account the uncertanties of the design variables, while the deterministic design procedure does not take this into account.

The software is being developed through Microsoft Excel, the spreadsheets are interlinked together for automatic update.

REFERENCES
[1]CALREL, Structural Reliability & Analysis Program, University of California, Berkely [2]DNV GL Classification Note Code 30.6, 1992

Research & Development

ASRANet specialises in R&D projects in the area of marine structures. The various areas are as follows:

  • Advanced Analysis using non-linear Finite Element Method
  • Structural Risk Analysis
  • Structural Reliability Analysis
  • Integration of Advanced Analysis and Reliability Analysis - Response Surface Methods
  • Fatigue and Fracture Analysis
  • Ultimate Strength of Ship and Offshore Structures
  • Reliability Analysis of Composite Structures with both FRP and Aluminium materials
  • Reliability Analysis of Subsea Structures
  • Reliability Based Design of Offshore Foundations for Wind Turbines

The R&D work carried out for companies like Atkins Global, Wood group PSN, Shell, GL SE, Lloyds Register, Subsea 7 and amongst others.