DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADS
DESING OF WIND TURBINE MONOPILES FOR LATERAL LOADSDESIGN OF WIND TURBINE MONOPILES FORLATERAL LOADSRobert B. GilbertThe University of Texas at AustinShin-Tower WangEnsoft Inc.Asitha SenanayakeThe University of Texas at AustinErica RendonEnsoft Inc.September 18th 2015
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSDISCLAIMERThis final report has been reviewed by the BSEE and approved for publication. Approval does not signifythat the contents necessarily reflect the views and policies of the BSEE, nor does mention of the tradenames or commercial products constitute endorsement or recommendation for use.ACKNOWLEDGEMENTThis study was funded by the Bureau of Safety and Environmental Enforcement (BSEE), U.S. Departmentof the Interior, Washington, D.C., under Contract E13PC00017.Page 1 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSTable of ContentsDisclaimer. 1Acknowledgement . 1List of Tables . 4List of Figures . 5Executive Summary. 11123Introduction . 131.1The p-y Method. 141.2Matlock (1970) p-y Curves . 151.3API RP 2GEO (2011) p-y Curves . 171.4Jeanjean (2009) p-y Curves . 18Database of Laterally Loaded Pile Tests. 212.1Format of Database . 212.2Summary of Database . 212.3Print Instructions. 22Laboratory Tests in Clay . 233.1Model Monopiles . 233.2T-Bar Penetrometer . 243.3Test Beds . 263.3.1Normally to Moderately Overconsolidated Kaolinite Clay Bed . 273.3.2Heavily Overconsolidated Kaolinite Clay Test Bed. 293.3.3Heavily Overconsolidated Kaolinite Clay Bed with a Stiff Crust. 323.3.4Heavily Overconsolidated Gulf of Mexico Clay Bed . 343.3.5Normally consolidated Gulf of Mexico Clay Bed. 373.4Tests in Normally Consolidated to Moderately Overconsolidated Kaolinite Clay . 403.4.1Monotonic/Static Lateral Load Tests . 403.4.2Cyclic Lateral Load Tests . 453.5Tests in Heavily Overconsolidated Kaolinite Clay . 573.5.1Monotonic/Static Lateral Load Tests . 573.5.2Cyclic Lateral Load Tests . 583.6Tests in Heavily Overconsolidated Kaolinite Clay Bed with a Stiff Crust . 613.6.1Monotonic/Static Lateraly Load Tests . 613.6.2Cyclic Load Tests . 61Page 2 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADS3.73.7.1Monotonic/Static Lateral Load Tests . 623.7.2Cyclic Lateral Load Tests . 633.845Tests in Normally Consolidated Gulf of Mexico Clay . 62Tests in Heavily Overconsolidated Gulf of Mexico Clay . 643.8.1Monotonic/Static Lateral Load Tests . 643.8.2Cyclic Lateral Load Tests . 65Numerical Modeling. 674.12-D Finite Element Modeling in Clay. 674.23-D Finite Element Modeling in Clay. 714.33-D Finite Element Modeling in Sand . 73Discussion. 795.1Lateral Capacity of Piles . 795.1.1Modification to Matlock (1970) p-y Curves . 795.1.2Effect of Gap Forming behind Pile . 885.2Effect of Pile Diameter . 905.2.1Laboratory Test Results. 905.2.23-D Numerical Modelling in Clay. 935.3Effect of Cyclic Loading . 995.3.1Reduction in Stiffness. 995.3.2Ultimate Pile Capacity after Cyclic Loading. 1066Conclusions and Recommendations . 1077References . 109A.Appendix – Database of Lateral Load Tests . 111B.Appendix – Summary of Model Tests . 119Page 3 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSLIST OF TABLESTable 1.1: API “soft clay” normalized p-y curve for static loading (API RP 2GEO, 2011) . 17Table 1.2: API “soft clay” normalized p-y curves for cyclic loading (API RP 2GEO, 2011) . 18Table 3.1: Summary of previous laboratory testing programs on model piles in clay under lateral loading. 24Table 4.1: Young’s modulus changing with depth . 75Table A.1: Contents of Pile Test Database . 112Table B.1: Summary of preliminary tests done in normally to moderately overconsolidated kaolin claybed . 120Table B.2: Summary of additional tests done in the normally to moderately overconsolidated kaolin claybed, with a load eccentricity of 5D . 121Table B.3: Summary of tests done in normally to moderately overconsolidated kaolin clay bed, with theload applied at the mudline . 122Table B.4: Summary of all tests done in the overconsolidated kaolin clay bed . 123Table B.5: Summary of tests done in normally to moderately overconsolidated kaolin clay bed withdirect lateral soil pressure measurements . 124Table B.6: Summary of tests done in the overconsolidated kaolin clay bed with a stiff top crust . 125Table B.7: Summary of tests done in overconsolidated Gulf of Mexico clay bed . 125Table B.8: Summary of tests done in normally consolidated Gulf of Mexico clay bed . 125Page 4 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSLIST OF FIGURESFigure 1.1: Schematic diagram of a monopile for offshore wind turbine . 13Figure 1.2: Tip and side resistance mobilized in a laterally loaded rigid pile . 14Figure 1.3: Schematic showing p-y model used for analysis of laterally loaded piles (Ref: LPILE TechnicalManual) . 15Figure 1.4: The complete set of normalized p-y curves proposed by Matlock (1970) . 16Figure 1.5: Comparison of API recommended normalized p-y curve for “soft clay” with the Matlock(1970) p-y model for static loading . 18Figure 1.6: Comparison of p-y curves (Jeanjean, 2009) . 19Figure 1.7: Variation of Np versus normalized depth proposed by Jeanjean (2009) . 20Figure 3.1: Schematic diagram of model piles, D 1-in, 2-in, 3-in, 4-in (Senanayake et al., 2015) . 23Figure 3.2: T-bar penetrometer . 25Figure 3.3: T-bar setup with rod, weights, and load cell attached . 25Figure 3.4: Loads acting on T-bar and the rod . 26Figure 3.5: T-bar test results, normally to moderately overconsolidated kaolin clay bed, D 2-in pilelocation . 28Figure 3.6: T-bar test results, normally to moderately overconsolidated kaolin clay bed, D 3-in and D 4in pile locations . 28Figure 3.7: T-bar test results in normally consolidated soil bed from El-Sherbiny (2005) . 29Figure 3.8: Variation of water content and unit weight with depth in the normally to moderatelyoverconsolidated soil bed . 29Figure 3.9: 100-gallon Rubbermaid stock tank which contained the soil bed with the heavilyoverconsolidated kaolinite clay (1-inch diameter pile installed is also shown) . 30Figure 3.10: Plan dimensions of the tank containing the heavily overconsolidated kaolinite clay bed . 31Figure 3.11: Variation of water content and unit weight with depth in the heavily overconsolidatedkaolinite clay bed (Su 10-psf) . 31Figure 3.12: T-bar test results, heavily overconsolidated kaolinite bed (tested on August 4th 2014) . 32Figure 3.13: Heavily overconsolidated kaolinite clay bed with a stiff crust with 2-inch diameter pileinstalled and ready to be tested . 32Figure 3.14: T-bar test results, heavily overconsolidated kaolinite clayl bed with stiff crust, approximately30-minutes of setup time (tested on December 08th 2014) . 33Figure 3.15: T-bar test results, heavily overconsolidated kaolinite clay bed with stiff crust, approximately4-days of setup time (tested on December 12th 2014) . 34Figure 3.16: Plan dimensions of the tank containing heavily overconsolidated kaolinite clay bed with stiffcrust . 34Figure 3.17: Heavily overconsolidated Gulf of Mexico clay bed with a 2-inch diameter pile installed andready to be tested . 35Figure 3.18: T-bar test results, overconsolidated Gulf of Mexico clay bed, approximately 30-minutes ofsetup time (tested on December 16th 2014). 36Figure 3.19: T-bar test results, overconsolidated Gulf of Mexico clay bed, approximately 48-hours ofsetup time (tested on December 18th 2014). 36Figure 3.20: T-bar test results, overconsolidated Gulf of Mexico clay bed, approximately 4-weeks ofsetup time (test results from January 13th 2014). 37Figure 3.21: Design undrained shear strength versus depth in the Gulf of Mexico (Cheon, 2010) . 38Page 5 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSFigure 3.22: Variation of the undrained shear strength . 38Figure 3.23: Normally consolidated GoM clay bed with 1-inch diameter pile installed and ready to betested . 39Figure 3.24: T-bar test results, normally consolidated GoM clay test bed, 10-days after preparation(tested on April 10th 2015) . 39Figure 3.25: Plan dimensions of the tank containing normally consolidated GoM clay bed . 40Figure 3.26: Monotonic load test: diameter 2-inches, embedment 8D, load eccentricity 5D, targetlateral displacement D . 41Figure 3.27: Monotonic load test: diameter 3-inches, embedment 8D, load eccentricity 5D, targetlateral displacement D . 41Figure 3.28: Monotonic load test: diameter 4-inches, embedment 8D, load eccentricity 5D, targetlateral displacement D . 42Figure 3.29: 4-in diameter model pile with tactile pressure sensor installed . 43Figure 3.30: Monotonic load tests, D 4-inches, embedment 8D, load eccentricity 5D, target lateraldisplacement D, normally to moderately overconsolidated kaolin clay . 44Figure 3.31: Static load tests, D 4-inches, embedment 8D, load eccentricity 5D, target lateraldisplacement D, normally to moderately overconsolidated kaolin clay . 44Figure 3.32: Static load test with pressure sensor, D 4-inches, embedment 8D, load eccentricity 5D,target lateral displacement 1-in, normally to moderately overconsolidated kaolin clay . 45Figure 3.33: Cyclic Load Test Results: Diameter 2”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 0.5 . 46Figure 3.34: Cyclic Load Test Results: Diameter 2”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 1.0 . 46Figure 3.35: Cyclic Load Test Results: Diameter 2”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 2.0 . 47Figure 3.36: Cyclic Load Test Results: Diameter 3”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 0.5 . 47Figure 3.37: Cyclic Load Test Results: Diameter 3”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 1.0 . 48Figure 3.38: Cyclic Load Test Results: Diameter 3”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 2.0 . 48Figure 3.39: Cyclic Load Test Results: Diameter 4”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 0.5 . 49Figure 3.40: Cyclic Load Test Results: Diameter 4”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 1.0 . 49Figure 3.41: Cyclic Load Test Results: Diameter 4”, Embedment 8D, Load Eccentricity 5D, Target TiltAngle 2.0 . 50Figure 3.42: Disturbed Soil around 2” Diameter Monopile after Cyclic Tests . 50Figure 3.43: Disturbed Soil around 3” Diameter Monopile after Cyclic Tests . 51Figure 3.44: Disturbed Soil around 4” Diameter Pile after Cyclic Load Tests Lateral Load Tests to Failure. 51Figure 3.45: Cyclic load test results, 2-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 0.5 , normally to lightly overconsolidated soil bed . 52Figure 3.46: Cyclic load test results, 2-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 1.0 , normally to lightly overconsolidated soil bed . 53Page 6 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSFigure 3.47: Cyclic load test results, 2-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 2.0 , normally to lightly overconsolidated soil bed . 53Figure 3.48: Cyclic load test results, 3-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 0.5 , normally to lightly overconsolidated soil bed . 54Figure 3.49: Cyclic load test results, 3-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 1.0 , normally to lightly overconsolidated soil bed . 54Figure 3.50: Cyclic load test results, 3-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 1.0 , normally to lightly overconsolidated soil bed . 55Figure 3.51: Cyclic load test results, 4-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 0.5 , normally to lightly overconsolidated soil bed . 55Figure 3.52: Cyclic load test results, 4-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 1.0 , normally to lightly overconsolidated soil bed . 56Figure 3.53: Cyclic load test results, 4-inch diameter, embedment 8D, load eccentricity 5D, target tiltangle 2.0 , normally to lightly overconsolidated soil bed . 56Figure 3.54: Monotonic load test: diameter 1-inch, embedment 8D, load eccentricity 5D, targetlateral displacement 2D . 57Figure 3.55: Monotonic load test: diameter 2-inches, embedment 8D, load eccentricity 5D, targetlateral displacement 2D . 58Figure 3.56: Cyclic load test results, diameter 1-inch, embedment 8D, load eccentricity 5D, target tiltangle 0.5 , overconsolidated soil bed . 59Figure 3.57: Cyclic Load test results, diameter 2-inches, embedment 8D, load eccentricity 5D, targettilt angle 0.5 , overconsolidated soil bed. 59Figure 3.58: 1-inch diameter monopile during cyclic test, overconsolidated soil bed . 60Figure 3.59: 2-inch diameter monopile during cyclic test, overconsolidated soil bed . 60Figure 3.60: Static load tests, overconsolidated kaolin clay with stiff top crust, D 2-inches, embedment 8D, load eccentricity 5D, target lateral displacement D . 61Figure 3.61: Static load tests, normally consolidated GoM clay, D 1-inch, embedment 8D, loadeccentricity 5D . 62Figure 3.62: Normally consolidated GoM clay bed with 2-inch diameter pile installed and ready to betested . 63Figure 3.63: Static load test, normally consolidated GoM clay, D 2-inches, embedment 8D, loadeccentricity 5D . 63Figure 3.64: Cyclic load test, normally consolidated GoM clay, D 2-inches, embedment 8D, loadeccentricity 5D, 0.5-deg tilt . 64Figure 3.65: Static load tests, overconsolidated Gulf of Mexico clay, D 2-inches, embedment 8D, loadeccentricity 5D, target lateral displacement D . 65Figure 3.66: Cyclic load test results, diameter 2-inch, embedment 8D, load eccentricity 5D, target tiltangle 0.5 , overconsolidated Gulf of Mexico clay bed (Test 1, 1 hour after installation, 1/12/2015) . 66Figure 3.67: Cyclic load test results, diameter 2-inch, embedment 8D, load eccentricity 5D, target tiltangle 0.5 , overconsolidated Gulf of Mexico clay bed (Test 2, 1-day after installation, 1/13/205) . 66Figure 4.1: 2D FE Model . 68Figure 4.2: Effect of A/B on normalized ‘p-y’ Curves (Pult 9SuB, A Width of Mesh, B Pile Diameter,Su 1440psf) . 69Figure 4.3: Contour and Vector Plots from ABAQUS (Width of Mesh 3 Times the Pile Diameter of 1 foot). 69Page 7 of 125
DESIGN OF WIND TURBINE MONOPILES FOR LATERAL LOADSFigure 4.4: Comparison of p-y curves (A/B 15) . 70Figure 4.5: Comparison of Normalized p-y Curves (A/B 15) . 70Figure 4.6: Pile model in ABAQUS . 72Figure 4.7: Load versus displacement at the pile head from ABAQUS models compared with LPILE results. 76Figure 4.8: Normalized load versus normalized displacement, ABAQUS model results . 76Figure 4.9: P-y curves at a depth of one pile diameter, comparison of ABAQUS results with API model. 77Figure 4.10: Normalized p-y curves at a depth of one pile diameter . 77Figure 4.11: P-y curves at a depth of two pile diameters, comparison of ABAQUS results with API model. 78Figure 4.12: P-y curves at a depth of three pile diameters, comparison of ABAQUS results with API model. 78Figure 5.1: Comparison of monotonic lateral load test results with LPILE analyses, normally consolidatedto moderately overconsolidated kaolinite, D 4-inches (no gap formed) . 80Figure 5.2: Calculation of p-multipliers to convert Matlock (1970) to approximate Jeanjean (2009) inLPILE, based on the idealized undrained shear strength profile and D 4-in . 80Figure 5.3: Comparison of test results with available p-y models using LPILE, heavily overconsolidatedkaolinite (Su 10-psf), D 1-inch (no gap formed) . 81Figure 5.4: Comparison of test results with available p-y models using LPI
Table 1.1: API soft clay _ normalized p-y curve for static loading (API RP 2GEO, 2011). 17 Table 1.2: API soft clay _ normalized p-y curves for cyclic loading (API RP 2GEO, 2011) . 18 Table 3.1: Summary of previous laboratory test
2. Brief Wind Turbine Description The wind turbine under study belongs to an onshore wind park located in Poland. It has a power of 2300 kW and a diameter of 101 m. Figure 1 shows its major components. A summary of the wind turbine technical specifications is Fig. 1. Main components of the wind turbine [16]. given in Table I. The wind farm .
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Jan 31, 2013 · blades. Horizontal-axis wind turbine was developed a high wind speed location. A hybrid composite structure using glass and carbon fiber was created a light-weight design Structural analysis for wind turbine blades is investigated with the aim of improving their design, minimizing weight. The wind turbine blade was modelled by using Catia.
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ZF Wind Power 26 Design of wind turbine gearboxes with respect to noise 11/12/2012 [1] Dr. Benoit Petitjean, Dr. Roger Drobietz, Dr. Kevin Kinzie, Wind Turbine Blade Noise Mitigation Technologies, in Fourth International Meeting on Wind Turbine Noise,Rome
Wind energy is generated by a wind turbine which converts the kinetic energy of wind into electrical energy. The system mainly depends on speed of the wind to enhance the performance the turbine in mounted on a tall tower. Wind energy conversion system has a wind turbine, permanent magnet synchronous generator and AC-AC converter. As wind .
Figure 1 structure of a typical wind energy conversion system 2.1 Vertical axis wind turbine The axis of rotation for this type of turbine is vertical. It is the oldest reported wind turbine. The modern vertical axis wind turbine design was devised in 1920s by a French electrical engineer G.J.M. Darrieus. It is normally built with two or three .
[3] Palmer, W. K. G., A new explanation for wind turbine whoosh – wind shear. Third International Meeting on Wind Turbine Noise, proceedings. Aalborg, 2009 [4] Boorsma, K. & Shepers, J.G. Enhanced wind turbine noise prediction tool SILANT. Fourth International Meeting on Wind Turbine Noise, proceedings. Rome, 2011
