scholarly journals Updating Failure Probability of a Welded Joint in Offshore Wind Turbine Substructures

2016 ◽  
Author(s):  
Quang A. Mai ◽  
John D. Sørensen ◽  
Philippe Rigo
Keyword(s):  
Wind Turbine ◽  
Welded Joint ◽  
Limit State ◽  
Offshore Wind ◽  
Design Stage ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Material Strength ◽  
State Function ◽  
Inspection Planning

The operation and maintenance cost of offshore wind turbine substructures contributes significantly in the cost of a kWh. That cost may be lowered by application of reliability- and risk-based maintenance strategies and reliability updating based on inspections performed during the design lifetime. Updating the reliability of a welded joint can theoretically be done using Bayesian updating. However, for tubular joints in offshore wind turbine substructures when considering a two dimensional crack growth and a failure criterion combining brittle fracture and material strength, the updating is quite complex due to the wind turbine loading obtained during operation. This paper solves that updating problem by using the Failure Assessment Diagram as a limit state function. It is discussed how application of the updating procedure can be used for inspection planning for offshore wind turbine substructures, and thus also for reducing the required safety factors at the design stage.

scholarly journals Maintenance Grouping Optimization for Offshore Wind Turbine Considering Opportunities Based on Rolling Horizon Approach

2018 ◽  
Vol 25 (2) ◽  
pp. 123-131 ◽  
Author(s):  
Yang Lua ◽  
Liping Suna ◽  
Jichuan Kanga ◽  
Xinyue Zhang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Poor Performance ◽  
Offshore Wind ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Rolling Horizon ◽  
Imperfect Maintenance ◽  
Opportunistic Maintenance ◽  
Maintenance Schedule

Abstract In future, offshore wind turbines may be consider a crucial part in the supply of energy. Maintenance processes are directed to attain a safe and reliable operation of offshore machines and wind turbines. In this paper, an opportunistic maintenance strategy for offshore wind turbine is proposed, considering imperfect maintenance and the preventive maintenance durations. Reliability Centric Maintenance serves as a proactive tactic to operations and maintenance by inhibiting the possible reasons of poor performance and controlling failures. Other components can implement the opportunistic preventive maintenances if one component has reached its reliability threshold. According to the rolling horizon approach, it is of great importance to update the maintenance planning for the sake of the short-term information. By figuring out the best combination, the maintenance schedule in the mission time has been finally determined. Failure information are obtained from previous studies to accomplish the calculations. The outcomes indicate that the maintenance cost has been dramatically reduced through the application of opportunistic maintenance.

scholarly journals Reliability-Based Serviceability Limit State Design of a Jacket Substructure for an Offshore Wind Turbine

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2751 ◽  
Author(s):  
Jianhua Zhang ◽  
Won-Hee Kang ◽  
Ke Sun ◽  
Fushun Liu
Keyword(s):  
Correlation Analysis ◽  
Reliability Analysis ◽  
Limit State ◽  
Statistical Correlation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
State Function ◽  
Optimized Design ◽  
Foundation Design ◽  
Serviceability Limit State

The development of a structurally optimized foundation design has become one of the main research objectives for offshore wind turbines (OWTs). The design process should be carried out in a probabilistic way due to the uncertainties involved, such as using parametric uncertainties regarding material and geometric properties, and model uncertainties in resistance prediction models and regarding environmental loads. Traditional simple deterministic checking procedures do not guarantee an optimized design because the associated uncertainties are not fully considered. In this paper, a reliability analysis framework is proposed to support the optimized design of jacket foundations for OWTs. The reliability analysis mainly considers the serviceability limit state of the structure according to the requirements of the code. The framework consists of two parts: (i) an important parameter identification procedure based on statistical correlation analysis and (ii) a finite element-simulation-based reliability estimation procedure. The procedure is demonstrated through a jacket structure design of a 3 MW OWT. The analysis results show that the statistical correlation analysis can help to identify the parameters necessary for the overall structural performance. The Latin hypercube sampling and the Monte Carlo simulation using FE models effectively and efficiently evaluate the reliability of the structure while not relying on a surrogate limit state function. A comparison between the proposed framework and the deterministic design shows that the framework can help to achieve a better result closer to the target reliability level.

scholarly journals Reliability analysis of offshore wind turbine foundations under lateral cyclic loading

2020 ◽  
Vol 5 (4) ◽  
pp. 1521-1535
Author(s):  
Gianluca Zorzi ◽  
Amol Mankar ◽  
Joey Velarde ◽  
John D. Sørensen ◽  
Patrick Arnold ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Wind Turbine ◽  
Limit State ◽  
Large Diameter ◽  
Probabilistic Approach ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Foundation Design

Abstract. The design of foundations for offshore wind turbines (OWTs) requires the assessment of long-term performance of the soil–structure interaction (SSI), which is subjected to many cyclic loadings. In terms of serviceability limit state (SLS), it has to be ensured that the load on the foundation does not exceed the operational tolerance prescribed by the wind turbine manufacturer throughout its lifetime. This work aims at developing a probabilistic approach along with a reliability framework with emphasis on verifying the SLS criterion in terms of maximum allowable rotation during an extreme cyclic loading event. This reliability framework allows the quantification of uncertainties in soil properties and the constitutive soil model for cyclic loadings and extreme environmental conditions and verifies that the foundation design meets a specific target reliability level. A 3D finite-element (FE) model is used to predict the long-term response of the SSI, accounting for the accumulation of permanent cyclic strain experienced by the soil. The proposed framework was employed for the design of a large-diameter monopile supporting a 10 MW offshore wind turbine.

Coupled Numerical Analysis of a Concept TLB Type Floating Offshore Wind Turbine

2019 ◽  
Author(s):  
Iman Ramzanpoor ◽  
Martin Nuernberg ◽  
Longbin Tao
Keyword(s):  
Wind Turbine ◽  
Renewable Energy Sources ◽  
Second Order ◽  
Offshore Wind ◽  
Design Stage ◽  
Offshore Wind Turbine ◽  
Clear Understanding ◽  
Mooring System ◽  
Floating Platform ◽  
Floating Offshore Wind Turbine

Abstract The main drivers for the continued decarbonisation of the global energy market are renewable energy sources. Moreover, the leading technological solutions to achieve this are offshore wind turbines. As installed capacity has been increasing rapidly and shallow water near shore sites are exhausted, projects will need to be developed further from shore and often in deeper waters, which will pose greater technical challenges and constrain efforts to reduce costs. Current floating platform solutions such as the spar and semi-submersible rely on large amounts of ballast and complex structural designs with active stabilisation systems for stability of the floating offshore wind turbine platform (FOWT). The primary focus of this study is to present a design concept and mooring arrangement for an alternative floating platform solution that places emphasis on the mooring system to achieve stability for a FOWT. The tension leg buoy (TLB) is designed to support future 10MW offshore wind turbine generators. This paper presents the numerical methodology used for a coupled hydro-elastic analysis of the floater and mooring system under combined wind, wave and current effects. A concept TLB design is presented and its platform motion and mooring line tension characteristics are analysed for a three-hour time domain simulation representing operating and survival conditions in the northern North Sea with water depths of 110 metres. The importance of wave drift forces and the other non-linear excitation forces in the concept design stage are evaluated by comparing the motion and tension responses of three different numerical simulation cases with increasing numerical complexity. The preliminary TLB system design demonstrated satisfactory motion response for the operation of a FOWT and survival in a 100-year storm condition. The results show that accounting for second-order effect is vital in terms of having a clear understanding of the full behaviour of the system and the detailed response characteristics in operational and survival conditions. Extreme loads are significantly reduced when accounting for the second-order effects. This can be a key aspect to not overdesign the system and consequently achieve significant cost savings.

Probabilistic Analysis of the Fatigue Life of Offshore Wind Turbine Structures

2020 ◽  
Author(s):  
Abraham Nispel ◽  
Stephen Ekwaro-Osire ◽  
João Paolo Dias
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Structural Reliability ◽  
Research Question ◽  
Limit State ◽  
Fatigue Loading ◽  
Offshore Wind ◽  
Design Parameters ◽  
Offshore Wind Turbine ◽  
Loading Conditions

Abstract The structural response of the main components of offshore wind turbines (OWTs) is considerably sensitive to amplification as their excitation frequencies approach the natural frequency of the structure. Furthermore, uncertainties present in the loading conditions, soil and structural properties highly influence the dynamic response of the OWT. In most cases, the cost of the structure reaches around 30% of the entire OWT because conservative design approaches are employed to ensure its reliability. As a result, this study aims to address the following research question: can the structural reliability of OWT under fatigue loading conditions be predicted more consistently? The specific aims are to (1) establish the design parameters that most impact the fatigue life, (2) determine the probability distributions of the design parameters, and (3) predict the structural reliability. An analytical model to determine the fatigue life of the structure under 15 different loading conditions and two different locations were developed. Global sensitivity analysis was used to establish the more important design parameters. Also, a systematic uncertainty quantification (UQ) scheme was employed to model the uncertainties of model input parameters based on their available information. Finally, the framework used reliability analysis to consistently determine the system probability of failure of the structure based on the fatigue limit state design criterion. The results show high sensitivity for parameters usually considered as deterministic values in design standards. Additionally, it is shown that applying systematic UQ produces a better approximation of the fatigue life under uncertainty and more accurate estimations of the structural reliability. Consequently, more reliable and robust structural designs may be achieved without the need for overestimating the offshore wind turbine response.

Design of Mooring Lines of Floating Offshore Wind Turbine in Jeju Offshore Area

2014 ◽  
Author(s):  
Hyungjun Kim ◽  
Joonmo Choung ◽  
Gi-Young Jeon
Keyword(s):  
Wind Turbine ◽  
Limit State ◽  
Design Procedure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Ultimate Limit State ◽  
Mooring Lines ◽  
Offshore Area ◽  
Floating Offshore Wind Turbine ◽  
Wind Turbine System

This paper presents a mooring design procedure of a floating offshore wind turbine. The offshore environment data of Jeju south sea collected from Korea Hydrographic and Oceanographic Administration (KHOA) are used as environmental conditions for hydrodynamic analysis. A semi-submersible floating wind turbine system is considered based on Offshore Code Comparison Collaborative Continuation (OC4) DeepCWind platform and the National Renewable Energy Laboratory (NREL) 5MW class wind turbine. Catenary mooring with studless chain is chosen as the mooring system. Important design decisions such as how large the nominal sizes are, how long the mooring lines are, how far the anchor points are located, are demonstrated in detail. Considering ultimate limit state and fatigue limit state based on 100-year return period and 50 year design life, respectively, long-term predictions of breaking strength and fatigue are performed.

Predictive information and maintenance optimization based on decision theory: a case study considering a welded joint in an offshore wind turbine support structure

2021 ◽  
pp. 147592172098183
Author(s):  
Muhammad Farhan ◽  
Ronald Schneider ◽  
Sebastian Thöns
Keyword(s):  
Service Life ◽  
Wind Turbine ◽  
Value Of Information ◽  
Welded Joint ◽  
Offshore Wind ◽  
Inspection Time ◽  
Offshore Wind Turbine ◽  
Maintenance Optimization ◽  
Predictive Information ◽  
Repair Method

Predictive information and maintenance optimization for deteriorating structures is concerned with scheduling (a) the collection of information by inspection and monitoring and (b) maintenance actions such as repair, replacement, and retrofitting based on updated predictions of the future condition of the structural system. In this article, we consider the problem of jointly identifying—at the beginning of the service life—the optimal inspection time and repair strategy for a generic welded joint in a generic offshore wind turbine structure subject to fatigue. The optimization is performed based on different types of decision analyses including value of information analyses to quantify the expected service life cost encompassing inspection, repair, and fatigue damage for all relevant combinations of inspection time, repair method, and repair time. Based on the analysis of the expected service life cost, the optimal inspection time, repair method, and repair time are identified. Possible repair methods for a welded joint in an offshore environment include welding and grinding, for which detailed models are formulated and utilized to update the joint’s fatigue performance. The decision analyses reveal that an inspection should be scheduled approximately at mid-service life of the welded joint. A repair should be performed in the same year after an indication and measurement of a fatigue crack given an optimal inspection scheduling. This article concludes with a discussion on the results obtained from the decision and value of information analyses.

scholarly journals Ultimate Limit State Risk Assessment of Penta Pod Suction Bucket Support Structures for Offshore Wind Turbine due to Scour

2021 ◽  
Vol 33 (6) ◽  
pp. 374-382
Author(s):  
Young Jin Kim ◽  
Ngo Duc Vu ◽  
Dong Hyawn Kim
Keyword(s):  
Risk Assessment ◽  
Wind Turbine ◽  
Limit State ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Ultimate Limit State ◽  
Support Structures ◽  
Significant Wave ◽  
Scour Hazard ◽  
Ultimate Limit

The scour risk assessment was conducted for ultimate limit state of newly developed penta pod suction bucket support structures for a 5.5 MW offshore wind turbine. The hazard was found by using an empirical formula for scour depth suitable for considering marine environmental conditions such as significant wave height, significant wave period, and current velocity. The scour fragility curve was calculated by using allowable bearing capacity criteria of suction foundation. The scour risk was assessed by combining the scour hazard and the scour fragility.

Reliability of Offshore Wind Turbine Support Structures Subjected to Extreme Wave-Induced Loads and Defects

2016 ◽  
Author(s):  
Baran Yeter ◽  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Service Life ◽  
Wind Turbine ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Limit State ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Cycle Fatigue ◽  
Support Structures ◽  
Support Structure

The probability of existence of defects, fatigue damage and crack growth in the offshore wind turbine support structures subjected to extreme waves and wind-induced loads is very high and may occur at a faster rate in a low cycle fatigue regime and crack growth, leading to a dramatic reduction in the service life of structures. It is therefore vital to assess the safety and reliability of offshore wind turbine support structures at sea. The aim of the present study is to carry out a low cycle fatigue and crack growth reliability analysis of an offshore wind turbine support structure during the service life. The analysis includes different loading scenarios and accounts for the uncertainties related to the structural geometrical characteristics, the size of the manufacturing and during the service life defects, crack growth, material properties, and model assumed in the numerical analyses. The probability of failure is defined as a serial system of two probabilistic events described by two limit state functions. The first one is related to a crack initiation based on the local strain approach and the second one on the crack growth applying the fracture mechanic approach. The first and second order reliability methods are used to estimate the reliability index and the effect of low cycle fatigue and crack growth on the reliability estimate of the offshore wind turbine support structure. The sensitivity analysis is performed in order to determine the degree of the significance of the random variables and several conclusions are derived.

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