Analysis of a Monopile under Two-Way Cyclic Loading

2021 ◽  
Vol 12 (2) ◽  
pp. 0-0
Keyword(s):  
Cyclic Loading ◽  
Lateral Displacement ◽  
Slenderness Ratio ◽  
Large Diameter ◽  
Load Cycle ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Element Analysis ◽  
Load Amplitude ◽  
Dimensional Finite Element

A large diameter monopiles are commonly used as an offshore wind turbine (OWT) foundation to withstand lateral cyclic loads due to wind and wave action. In the present study, a two-dimensional finite element analysis was performed to evaluate the behavior of a monopile under two-way lateral cyclic loading. The centrifuge test carried out on a 0.7m diameter pile was being used to validate the constituent model. The parametric study was carried out on a monopile by varying the slenderness ratio (L/D = 4, 5, and 6) and load amplitudes (30%, 40%, and 50% of the ultimate pile capacity). From the load-displacement response of a monopile, it was observed that the measured accumulated displacement increases drastically for the first load cycle. For a given embedded length, the lateral displacement was observed to increase with an increase in load amplitude. For an embedded length of L/D = 4, the increase in load amplitude from 30% - 40% resulted in an increase in lateral displacement to 24%.

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.

Scour Effects on the Structural Integrity of Offshore Wind Turbine Monopiles

2021 ◽  
Author(s):  
George E. Varelis ◽  
Jun Ai ◽  
Prasad Kane ◽  
Hossam Ragheb ◽  
Elie Dib
Keyword(s):  
Structural Integrity ◽  
Large Diameter ◽  
Simulation Models ◽  
Offshore Wind ◽  
Mitigation Measures ◽  
Offshore Wind Turbine ◽  
Element Analysis ◽  
Gas Industry ◽  
Integrated Simulation ◽  
Life Predictions

Abstract Large diameter monopiles are widely used for the installation of offshore wind turbines in relatively shallow water depth applications. Monopiles are considered as a cost and time-efficient foundation solution, taking advantage of the experience gained from the Oil&Gas industry. Due to their relatively large diameter, monopiles are susceptible to scour effects that threaten their structural integrity and necessitate the application of high-cost mitigation measures. The mitigation measures are also associated with heavy environmental impact at the local subsea environment, as well as increased CO2 emissions for their application. The present work examines the effect of scour on the structural integrity of monopiles using integrated simulation models that combine advanced finite element analysis (FEA) and computational fluid dynamics (CFD) techniques. A typical monopile geometry and North Sea representative metocean data are used in a case study. In this example analysis emphasis is given on the structural integrity deterioration resulting from the scour development over time. Advanced techniques are employed to simulate the soil-pile interaction. Furthermore, fluid-structure interaction effects due to the water flow around the monopile are examined using CFD techniques. Finally, fatigue life predictions of sensitive areas are conducted based on the “S-N methodology” and are enhanced by employing crack-growth analyses based on linear elastic fracture mechanics principles.

Finite Element Analysis of Large Diameter Grouted Connections

2007 ◽  
Author(s):  
Lars P. Nielsen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbine ◽  
Large Diameter ◽  
Wind Farms ◽  
Element Model ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Joint Research ◽  
Element Analysis

When considering offshore monopile foundations designed for wind turbine support structures, a grouted connection between the monopile and an overlapping transition piece has become the de facto standard. These connections rely on axial loads being carried primarily by the bond between the steel and grout as shear. Given the critical nature of the grouted connection in a system with zero redundancy, the current design verification requirement is that a finite element analysis is performed to ascertain the viability of the connection with respect to combined axial and bending capacity whilst pure axial capacity is handled as a decoupled phenomenon using simple analytical formulas. The present paper addresses the practical modeling aspects of such a finite element model, covering subjects such as constitutive formulations for the grout, mesh density, and steel/grout interaction. The aim of the paper is to discuss different modeling approaches and, to the extent possible, provide basic guidelines for the minimum requirements valid for this type of analysis. This discussion is based on the accumulated experience gained though the independent verification of more than 10 currently operational offshore wind farms that have been certified by DNV, as well as the significant joint research and development with industry captured in the DNV Offshore Standard for Design of Offshore Wind Turbine Structures DNV-OS-J101. Moreover, general observations relating to the basic subjects such as overall geometric extent of the model, inclusion of secondary structures, detail simplification, boundary conditions, load application etc. are presented based on the authors more than 3 year involvement on the subject at DNV.

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

2019 ◽  
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 (OWT) requires the assessment of the long-term performance of the soil–structure-interaction (SSI) which is subjected to a large number of cyclic loadings. In terms of serviceability limit state (SLS), it has to be ensured that 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 criteria in terms of maximum allowable rotation during an extreme cyclic loading event. This reliability framework allows the quantification of uncertainties in soil properties, in 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 is employed for the design of a large diameter monopile supporting a 10 MW offshore wind turbine.

scholarly journals A Finite Element Study on Compressive Resistance Degradation of Square and Circular Steel Braces under Axial Cyclic Loading

2021 ◽  
Vol 11 (13) ◽  
pp. 6094
Author(s):  
Hubdar Hussain ◽  
Xiangyu Gao ◽  
Anqi Shi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cyclic Loading ◽  
Slenderness Ratio ◽  
Hysteretic Behavior ◽  
Element Analysis ◽  
Section Shape ◽  
Axial Cyclic Loading ◽  
Global Buckling ◽  
Parametric Studies

In this study, detailed finite element analysis was conducted to examine the seismic performance of square and circular hollow steel braces under axial cyclic loading. Finite element models of braces were constructed using ABAQUS finite element analysis (FEA) software and validated with experimental results from previous papers to expand the specimen’s matrix. The influences of cross-section shape, slenderness ratio, and width/diameter-to-thickness ratio on hysteretic behavior and compressive-tensile strength degradation were studied. Simulation results of parametric studies show that both square and circular hollow braces have a better cyclic performance with smaller slenderness and width/diameter-to-thickness ratios, and their compressive-tensile resistances ratio significantly decreases from cycle to cycle after the occurrence of the global buckling of braces.

Permanent accumulated rotation of offshore wind turbine monopile due to typhoon-induced cyclic loading

2021 ◽  
Vol 80 ◽  
pp. 103079
Author(s):  
Hongwang Ma ◽  
Zhiyue Lu ◽  
Yutao Li ◽  
Chen Chen ◽  
Jun Yang
Keyword(s):  
Cyclic Loading ◽  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine

scholarly journals Safety Evaluation of the Combined Load for Offshore Wind Turbine Suction Foundation Installed on Sandy Soil

2021 ◽  
Vol 33 (5) ◽  
pp. 195-202
Author(s):  
Jeong Seon Park
Keyword(s):  
Wind Turbine ◽  
Sandy Soil ◽  
Wind Waves ◽  
Safety Evaluation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Element Analysis ◽  
Combined Load ◽  
Combined Loads ◽  
Moment Load

Offshore wind turbine (OWT) receive a combined vertical-horizontal- moment load by wind, waves, and the structure’s own weight. In this study, the bearing capacity for the combined load of the suction foundation of OWT installed on the sandy soil was calculated by finite element analysis. In addition, the stress state of the soil around the suction foundation was analyzed in detail under the condition that a combined load was applied. Based on the results of the analyses, new equations are proposed to calculate the horizontal and moment bearing capacities as well as to define the capacity envelopes under general combined loads.

scholarly journals Analysis of Factors Affecting Bearing Capacity of Large Diameter Single Piles of Offshore Wind Power under Earthquake Loads

2019 ◽  
Vol 136 ◽  
pp. 04061
Author(s):  
Yazhou Li ◽  
Li Dong
Keyword(s):  
Wind Power ◽  
Influencing Factors ◽  
Pile Foundation ◽  
Large Diameter ◽  
Horizontal Displacement ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Single Pile ◽  
Horizontal Deformation ◽  
Offshore Wind Power

The offshore wind turbine single pile foundation structure is simple and easy to install, but in the earthquake environment, large horizontal displacement is easy to occur, which affects the safe operation of offshore wind turbines. For this reason, the bearing characteristics and influencing factors of large-diameter single-pile offshore wind power under earthquake load are analyzed. The Mohr-Coulomb model is used as the model. The ABAQUS is used to construct the large-scale single-pile finite element model of offshore wind power. Loads and analysis of bearing characteristics and influencing factors of large-diameter single-pile offshore wind power under seismic loading. It is found that the increase of pile foundation depth will significantly reduce the horizontal displacement at the top of single pile. After increasing to a certain extent, it has no significant effect on the development of horizontal deformation of large diameter single pile; with the increase of pile diameter and wall thickness, The deformation of large diameter single pile foundation is reduced, but the influence of the pile foundation thickness on the horizontal deformation of the large diame-ter single pile foundation is no longer significant.

Analysis of Working Condition and Load Direction for Tripod Substructure of Offshore Wind Turbine

2013 ◽  
Vol 454 ◽  
pp. 27-33
Author(s):  
Bin Wang ◽  
Ying Li ◽  
Na Lv ◽  
Bin Bin Zhu ◽  
Wei Li
Keyword(s):  
Dynamic Analysis ◽  
Wind Turbine ◽  
Working Condition ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Load Direction ◽  
Element Analysis ◽  
Static And Dynamic Analysis ◽  
The Finite Element Analysis ◽  
Control Load

The control working condition and the control load direction of the typical Tripod substructure for the offshore wind turbine are studied by the finite element analysis software SACS. The results show that the different control criterions are corresponding to the different control working conditions for the Tripod substructure of the offshore wind turbine, and the control load directions vary with the structure form and the marine environments. Therefore, the static and dynamic analysis of the offshore wind turbine substructure in the single or limited load directions cant reflect the static and dynamic characteristic of the structure sufficiently. The multidirectional static and dynamic analysis of the offshore wind turbine structure has to be carried out.

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