Probabilistic demand models and fragility estimates for offshore wind turbine support structures

Mardfekri, Maryam; Gardoni, Paolo

doi:10.1016/j.engstruct.2013.03.016

Cited by 51 publications

(12 citation statements)

References 13 publications

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“…where M is the artificially large mass; m represents the mass of NREL 5MW wind turbine and is 697 460 kg; and, a(t) is the acceleration time history of the input ground motion. Referring to the literature [44,45], the large mass M is set as 7 × 10 9 , which is 10,000 times larger than the mass of NREL 5MW wind turbine.…”

Section: Earthquake Loadmentioning

confidence: 99%

Evaluation of an Uncoupled Method for Analyzing the Seismic Response of Wind Turbines Excited by Wind and Earthquake Loads

Wang

et al. 2020

Energies

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There is a significant interaction between wind and earthquakes for large-scaled wind turbines due to an aeroelastic effect. This study evaluates the accuracy of an uncoupled method extensively utilized to analyze the seismic response of wind turbines at the operational state. Initially, the oscillation of the blade for the National Renewable Energy Laboratory (NREL) 5 MW wind turbine excited by wind and wind-earthquake combination, respectively, is compared using the fully coupled method to verify the assumption in this uncoupled method. Subsequently, the influence of ground motions on the aerodynamic loadings of the rotor is discussed to evaluate the interaction between wind and earthquake loads. In addition, the accuracy of the uncoupled method is assessed by comparing the analysis results of the coupled and uncoupled methods, where different mean wind speed and equivalent aerodynamic damping ratio are considered. The results indicate that the oscillation velocity of blades and thrust on the rotor are significantly influenced by ground motions. Moreover, the amplitude of thrust variations caused by earthquakes increases monotonously with the oscillation velocity amplitude of blade-root. The errors between the two models are beyond the engineering margins for some earthquakes, such that it is difficult to optimize a consistent aerodynamic damping in the uncoupled model to accurately predict the seismic response of wind turbines.

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Section: Earthquake Loadmentioning

confidence: 99%

Evaluation of an Uncoupled Method for Analyzing the Seismic Response of Wind Turbines Excited by Wind and Earthquake Loads

Wang

et al. 2020

Energies

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“…A detailed 3D model of the entire soil-foundation-wind turbine system has been also developed by Mardfekri & Gardoni,108,109,132 who adopted nonlinear constitutional laws to represent both the soil behavior and the soil-pile dynamic interactions. Particularly, the Mohr-Coulomb plasticity model was utilized to define the nonlinear behavior of soil media, and an elastic-plastic Coulomb model along with advanced modeling techniques (i.e., use of 'contact pairs' provided by ABAQUS) was adopted to describe the nonlinear response of the soil-pile contact.…”

Section: Soil-structure Interaction Effects and Other Special Considementioning

confidence: 99%

Wind turbines and seismic hazard: a state-of-the-art review

2016

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Wind energy is a rapidly growing field of renewable energy and as such, intensive scientific and societal interest has been already attracted. Research on wind turbine structures has been mostly focused on the structural analysis, design and/or assessment of wind turbines mainly against normal (environmental) exposures while, so far, only marginal attention has been spent on considering extreme natural hazards that threat the reliability of the lifetime-oriented wind turbine's performance. Especially, recent installations of numerous wind turbines in earthquake prone areas worldwide (e.g., China, USA, India, Southern Europe and East Asia) highlight the necessity for thorough consideration of the seismic implications on these energy harnessing systems. Along these lines, this state-of-the-art paper presents a comparative survey of the published research relevant to the seismic analysis, design and assessment of wind turbines. Based on numerical simulation, either deterministic or probabilistic approaches are reviewed, since they have been adopted to investigate the sensitivity of wind turbines' structural capacity and reliability in earthquake-induced loading. The relevance of seismic hazard for wind turbines is further enlightened by available experimental studies, being also comprehensively reported through this paper. The main contribution of the study presented herein is to identify the key factors for wind turbines' seismic performance while important milestones for ongoing and future advancement are emphasized.

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“…Several studies [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] showed that structural reliability assessment is commonly applied to assess the safety level of OWT structures. Most reliability methods are established as time-invariant; however, in numerous instances, owing to the continuous degradation of the resistance of the structure through corrosion, fatigue, etc., or due to fluctuating loads in time, reliability models should be accounted for as time-variant [45,46].…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Structural Reliability Assessment Methods for Offshore Wind Turbine Jacket Support Structures

et al. 2020

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Offshore wind turbines (OWTs) are deployed in harsh environments often characterized by highly stochastic loads and resistance properties, thus necessitating the need for structural reliability assessment (SRA) to account for such uncertainties systematically. In this work, the SRA of an OWT jacket-type support structure is conducted, applying two stochastic methods to predict the safety level of the structure considering various design constraints. The first method refers to a commercial finite element analysis (FEA) package (DesignXplorer© from ANSYS) which employs direct simulations and the six sigma analysis function applying Latin hypercube sampling (LHS) to predict the probability of failure. The second method develops a non-intrusive formulation which maps the response of the structure through a finite number of simulations to develop a response surface, and then employs first-order reliability methods (FORM) to evaluate the reliability index and, subsequently, the probability of failure. In this analysis, five design constraints were considered: stress, fatigue, deformation, buckling, and vibration. The two methods were applied to a baseline 10-MW OWT jacket-type support structure to identify critical components. The results revealed that, for the inherent stochastic conditions, the structural components can safely withstand such conditions, as the reliability index values were found acceptable when compared with allowable values from design standards. The reliability assessment results revealed that the fatigue performance is the design-driving criterion for structural components of OWT support structures. While there was good agreement in the safety index values predicted by both methods, a limitation of the direct simulation method is in its requirement for a prohibitively large number of simulations to estimate the very low probabilities of failure in the deformation and buckling constraint cases. This limitation can be overcome through the non-intrusive formulation presented in this work.

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Probabilistic demand models and fragility estimates for offshore wind turbine support structures

Cited by 51 publications

References 13 publications

Evaluation of an Uncoupled Method for Analyzing the Seismic Response of Wind Turbines Excited by Wind and Earthquake Loads

Evaluation of an Uncoupled Method for Analyzing the Seismic Response of Wind Turbines Excited by Wind and Earthquake Loads

Wind turbines and seismic hazard: a state-of-the-art review

Comparative Study of Structural Reliability Assessment Methods for Offshore Wind Turbine Jacket Support Structures

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