New shape function solutions for fracture mechanics analysis of offshore wind turbine monopile foundations

Mehmanparast, Ali; Braithwaite, Jarryd; Shafiee, Mahmood

doi:10.1016/j.oceaneng.2018.04.073

Cited by 17 publications

(13 citation statements)

References 23 publications

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“…where a is the crack length, N is the number of cycles, ∆K is the SIF range, and C and m are material constants. State-of-the-art numerical and experimental research on bilinear crack-growth law phenomena can be found in [70][71][72][73][74][75][76][77][78][79]. The safety margin for fatigue reliability analysis based on LEFM (Linear Elastic Fracture Mechanics) is given by:…”

Section: Probabilistic Fatigue and Fracture Mechanics Approachesmentioning

confidence: 99%

A Systematic Review of Structural Reliability Methods for Deformation and Fatigue Analysis of Offshore Jacket Structures

Shittu

Kolios

Mehmanparast

2020

Metals

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This paper presents the state of the art in Structural Reliability Analysis (SRA) methods with a view of identifying key applications of each method and its proposed variations, qualifying characteristics, advantages, and limitations. Due to the increasing complexity and scale of modern offshore jacket structures, it becomes increasingly necessary to propose an accurate and efficient approach for the assessment of uncertainties in their material properties, geometric dimensions, and operating environments. SRA, as a form of uncertainty analysis, has been demonstrated to be a useful tool in the design of structures because it can directly quantify how uncertainty about input parameters can affect structural performance. Herein, attention was focused specifically on the probabilistic fracture mechanics approach because this accounts accurately for fatigue reliability mostly encountered as being dominant in the design of such structures. The well-established analytical/approximate methods such as the First- and Second-Order Reliability Methods (FORM/SORM) are widely used as they offer a good balance between accuracy and efficiency for realistic problems. They are, however, inaccurate in cases of highly non-linear systems. As a result, they have been modified using methods such as conjugate search direction approach, saddle point approximation, subset simulation, evidence theory, etc. in order to improve accuracy. Initially, direct simulations methods such as the Monte Carlo Simulation Method (MCS) with its various variance reduction techniques such as the Importance Sampling (IS), Latin Hypercube Sampling (LHS), etc. are ideal for structures having non-linear limit states but perform poorly for problems that calculate very low probabilities of failure. Overall, each method has its own merits and limitation, with FORM/SORM being the most commonly used, but recently, simulation methods have increasingly been used due to continuous advances in computation powers. Other relevant methods include the Response Surface Methods (RSM) and the Surrogate Models/Meta-models (SM/MM), which are advanced approximation methods and are ideal for structures with implicit limit state functions and high-reliability indices. Combinations of advanced approximation methods and reliability analysis methods are also found in literature as they can be suitable for complex, highly non-linear problems.

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Section: Probabilistic Fatigue and Fracture Mechanics Approachesmentioning

confidence: 99%

A Systematic Review of Structural Reliability Methods for Deformation and Fatigue Analysis of Offshore Jacket Structures

Shittu

Kolios

Mehmanparast

2020

Metals

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“…Foundation structure acts as a life‐limiting component for an OWT as it is subjected to a spectrum of structural loads, such as weight of the rotor and nacelle assembly, bending load from wind, wave currents, and vibrations due to rotor blades. Most of the installed OWTs consist of monopile foundations which are built by stacking 3 to 7 m diameter cylindrical sections of 30 to 125 mm thickness and can cost up to 35% of the total set‐up cost of an OWT 25–27 . Besides, the circumferential weldments joining the thick monopile sections lead to material property variations at the WM‐HAZ‐BM interface, which turns into a favorable site for fatigue crack initiation.…”

Section: Introductionmentioning

confidence: 99%

On the performance of monopile weldments under service loading conditions and fatigue damage prediction

Biswal

Mamun

Mehmanparast

2021

Fatigue Fract Eng Mat Struct

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Thick weldments used in offshore structures frequently act as fatigue crack initiation sites due to stress concentration at weld toe as well as weld residual stress fields. This paper investigates the cyclic deformation behavior of S355 G10+M steel, which is predominantly used in offshore wind applications. Owing to the vast size difference of monopile structure and weld cross-section, a global-local finite element (FE) method was used, and the weld geometry was adopted from circumferential weld joints used in offshore wind turbine monopile foundations. Realistic service loads collected using supervisory control and data acquisition (SCADA) and wave buoy techniques were used in the FE model. A nonlinear isotropic-kinematic hardening model was calibrated using the strain controlled cyclic deformation results obtained from base metal (BM) as well as cross-weld specimen tests. The tests revealed that the S355 G10 +M BM and weld metal (WM) undergo continuous cyclic stress relaxation.Fatigue damage over a period of 20 years of operation was predicted using the local stress at the root of the weldments as the life limiting criterion. This study helps in quantifying the level of conservatism in the current monopile design approaches and has implications towards making wind energy more economic.

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“…To model the floating structural support system failure, Bocher et al 17 proposed the application of fracture mechanics with a modified shape function for failure criteria prediction. This approach was applied to a monopile structure, and it captures the stress intensity factors and their dependence characteristic reliably.…”

Section: Introductionmentioning

confidence: 99%

Dynamic failure analysis of renewable energy systems in the remote offshore environments

Nitonye

Adumene

Sigalo

et al. 2020

Quality & Reliability Eng

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For effective integrity management of marine renewable energy systems in the dynamic and uncertain ocean environments, understanding the failure dynamics is crucial. The cost of investment in marine/offshore renewable energy infrastructures and the associated cost due to failure and loss of energy production necessitate a predictive monitoring methodology that is dynamic and adaptive. This paper presents an integrated multi‐state pure‐birth‐pure‐death Markovian‐net profit value model for the offshore turbine subsystem failure analysis and its cost‐based consequences. The integrated model captures the offshore turbine subsystem's dynamic failure states and its economic implications due to the cost of energy loss and downtime for the period under consideration. The model applies a phase‐type exponential distribution to describe the monotonic state of failure. The methodology is demonstrated with an offshore wind turbine gearbox, and it captures the dynamic state of the system and its failure mechanisms. The cumulative effect of the subelements deterioration decreases the gearbox performance by over 35% within the first 2 years of operation.

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New shape function solutions for fracture mechanics analysis of offshore wind turbine monopile foundations

Cited by 17 publications

References 23 publications

A Systematic Review of Structural Reliability Methods for Deformation and Fatigue Analysis of Offshore Jacket Structures

A Systematic Review of Structural Reliability Methods for Deformation and Fatigue Analysis of Offshore Jacket Structures

On the performance of monopile weldments under service loading conditions and fatigue damage prediction

Dynamic failure analysis of renewable energy systems in the remote offshore environments

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