我國目前建置離岸風場大部分座落於西部海域。由於季節性颱風引致之山區河道土砂向海域沖積，以及海流作用影響，西部海域基礎淘刷嚴重，因此離岸風機基礎設計時，須將基礎淘刷納入考量。目前進行離岸風機大口徑單樁基礎設計時，工程實務上最常採用之設計方法為p-y曲線法。但目前離岸風機基礎設計規範建議之p-y曲線分析法，並未明確考量局部淘刷坑之幾何形狀與土體再分佈效應，可能導致淘刷後單樁基礎之受力變形反應與基礎勁度評估產生偏差，進而影響離岸風機支撐結構整體動態反應分析之可靠度。鑒於目前尚缺乏針對大口徑單樁受淘刷時之受力變形反應之工程分析建議，本研究綜整既有文獻中對大口徑單樁 p–y 曲線之樁徑效應修正方法，以及考量淘刷時側向極限阻抗調整之建議[Kallehave et al. (2012); Lin & Wu (2019)]，據以建立考量淘刷影響之大口徑單樁側向受力變形反應與基礎勁度評估程序。
本研究利用 Bladed 軟體建立 NREL 5 MW 參考風機於北海環境條件下，透過模態分析評估淘刷對支撐結構自然振動頻率之影響，隨淘刷深度逐漸擴大，自然振動頻率將衰減；將環境外力對風機各位置之疲勞損傷輸出，並估算結構物壽命，以比較不同基礎模型對疲勞損傷之影響。
本研究建立基於Bladed輸出之疲勞損傷計算流程，並比較不同淘刷深度下運轉與怠速狀態之疲勞分析差異。結果顯示淘刷深度加深會降低基礎勁度與自然振動頻率、放大動態反應，使累積疲勞損傷增加並縮短壽命；且運轉狀態下之疲勞損傷普遍高於怠速狀態，顯示風機在運轉期間疲勞累積效應更為顯著，降低結構預期壽命。

Taiwan’s offshore wind farms are transitioning from construction to long-term operation and maintenance (O&M), where fatigue-based residual-life estimation becomes essential for controlling inspection and repair costs. Along the west coast of Taiwan, where seasonal typhoons, riverine sediment discharge, and marine currents can aggravate seabed mobility and cause severe foundation scour. In current engineering practice, large-diameter monopile foundations are commonly designed using the p-y curve method. However, guideline-recommended p-y formulations do not explicitly incorporate local scour-hole geometry or scour induced soil redistribution, which may bias post-scour lateral load-deflection behavior and the resulting foundation stiffness, and thus affect the reliability of integrated dynamic response analyses.
To address the lack of practical engineering guidance for large-diameter monopiles subjected to scour, this study synthesizes published recommendations on (i) diameter-dependent modifications to p-y curves for large-diameter piles and (ii) adjustments to lateral ultimate soil resistance under scour conditions, following the approaches proposed by Kallehave et al. (2012) and Lin & Wu (2019). Based on these considerations, a procedure is developed to evaluate the lateral behavior and equivalent foundation stiffness of scour-affected large-diameter monopiles.
Furthermore, a system-level numerical model of the NREL 5-MW reference wind turbine is established in DNV Bladed under representative North Sea environmental conditions. Modal analyses are conducted to quantify the influence of increasing scour depth on the natural frequencies of the support structure, and fatigue-related outputs under environmental loading are extracted to estimate structural lifetime and to compare fatigue damage among different foundation/scour models. The results indicate that increasing scour depth reduces the equivalent foundation stiffness and decreases the natural frequencies, leading to amplified dynamic responses and higher fatigue damage accumulation, thereby shortening the predicted service life. In addition, fatigue damage under operating (power-producing) conditions is consistently higher than that under idling conditions, highlighting that fatigue accumulation during normal operation plays a dominant role in reducing the expected lifetime of the support structure.

1. Aasen, S., Page, A. M., Skjolden Skau, K., & Nygaard, T. A. (2017). “Effect of foundation modelling on the fatigue lifetime of a monopile-based offshore wind turbine,” Wind Energy Science, 2(2), 361-376.
2. Achmus, M., Abdel-Rahman, K., & Kuo, Y.-S. (2008). “Design of monopile foundations for offshore wind energy converters,” Proceedings of the Goetechnics inMaritimeEngineering,” Proc. of 11thBaltic Sea Geotechnical Conference, 463- 470.
3. Achmus, M., Kuo, Y. S., & Abdel-Rahman, K. (2009). “Behavior of monopile foundations under cyclic lateral load,” Computers and Geotechnics, 36(5), 725-735.
4. API RP 2A-WSD, (2007). Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Working Stress Design, American Petroleum Institute.
5. API RP 2A-WSD (2010). Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Working Stress Design, American Petroleum Institute.
6. APIRP2GEO. (2011). Geotechnical and Foundation Design Considerations: American Petroleum Institute.
7. Beuckelaers, W. (2015). “Fatigue life calculation of monopiles for offshore wind turbines using a kinematic hardening soil model,” EYGEC, 2015:26-9.
8. Bhattacharya, S. (2019). Design of foundations for offshore wind turbines.
9. Carswell, W., Johansson, J., Løvholt, F., Arwade, S. R., Madshus, C., DeGroot, D. J., & Myers, A. T. (2015). “Foundation damping and the dynamics of offshore wind turbine monopiles,” Renewable energy, 80, 724-736.
10. Chen, C., & Duffour, P. (2018). “Modelling damping sources in monopile‐supported offshore wind turbines,” Wind Energy, 21(11), 1121-1140.
11. Chopra, A.-K. (2017). Dynamics of Structures, 5th Edition, University of California at Berkeley.
12. DNV (2002). “Risø National Laboratory,” Guidelines for design of wind turbines.
13. DNV-OS-J101. (2004). Design of Offshore Wind Turbine Structures: Det Norske Veritas AS.
14. DNVGL-RP-0286 (2019). Coupled analysis of floating wind turbines: Det Norske Veritas.
15. DNVGL-RP-C203. (2014). Fatigue Design of Offshore Steel Structures: Det Norske Veritas AS.
16. DNVGL-ST-0126. (2016b). Support structures for wind turbines: Det Norske Veritas Germanischer Lloyd.
17. DNVGL-ST-0437. (2016a). Loads and site conditions for wind turbines: Det Norske Veritas Germanischer Lloyd.
18. DNV-OS-J101. (2004). Design of Offshore Wind Turbine Structures: Det Norske Veritas AS.
19. EAU. (2012). Empfehlungen des Arbeitsausschusses Ufereinfassungen, Häfen und WasserstraBen. Ernst & Sohn Verlag.
20. Guan, D. W., Xie, Y. X., Chiew, Y. M., Ding, F., Ferradosa, T. F., & Hong, J. (2024). Estimation of local scour around monopile foundations for offshore structures using machine learning models. Ocean Engineering, 296,116951.
21. Jonkman, J., & Musial, W. (2010). “IEA wind task 23 offshore wind technology and deployment,” National Renewable Energy.
22. Kallehave, D., Thilsted, C. L., & Liingaard, M. (2012). Modification of the API py formulation of initial stiffness of sand. Paper presented at the Offshore Site Investigation and Geotechnics: Integrated Technologies-Present and Future.
23. Lin, C. (2017). The loss of pile axial capacities due to scour: vertical stress distribution. In Proc., Int. Conf. on Transportation Infrastructure and Materials (ICTIM 2017). Lancaster, PA: DEStech Transactions on Materials Science and Engineering.
24. Lin, C., & Jiang, W. (2019). Evaluation of vertical effective stress and pile tension capacity in sands considering scour-hole dimensions. Computers and Geotechnics, 105, 94-98.
25. Lin, C., & Wu, R. (2019). Evaluation of vertical effective stress and pile lateral capacities considering scour-hole dimensions. Canadian Geotechnical Journal, 56(1), 135-143.
26. Lin, C., Bennett, C., Han, J., & Parsons, R. L. (2010). Scour effects on the response of laterally loaded piles considering stress history of sand. Computers and Geotechnics, 37(7), 1008-1014.
27. Lin, C., Han, J., Bennett, C., & Parsons, R. L. (2014). Analysis of laterally loaded piles in sand considering scour hole dimensions. Journal of Geotechnical and Geoenvironmental Engineering, 140(6), 04014024.
28. Lin, Y., & Lin, C. (2019). Effects of scour-hole dimensions on lateral behavior of piles in sands. Computers and Geotechnics, 111, 30-41.
29. Lpile (2022). Technical Manual v2022.
30. Ma, H., & Chen, C. (2021). Scour protection assessment of monopile foundation design for offshore wind turbines. Ocean Engineering, 231, 109083.
31. Matsuishi, M., and Endo, T. (1968). “Fatigue of metals subject to varying stress,” in: Proc. Kyushu Branch of Japan Society of Mechanical Engineers, Fukuoka (1968) 37-40.
32. Murchison, J. M., & O'Neill, M. W. (1984). “Evaluation of py relationships in cohesionless soils,” Analysis and design of pile foundations ASCE, 174-191.
33. Pierson, Jr., W. J., & Moskowitz, L. (1964). “A proposed spectral form for fully developed wind seas based on the similarity theory of SA Kitaigorodskii,” Journal of geophysical research, 69(24), 5181-5190.
34. Reese, L. C., Cox, W. R., & Koop, F. D. (1974). Analysis of laterally loaded piles in sand. Offshore Technology in Civil Engineering Hall of Fame Papers from the Early Years, 95-105.
35. Rezaei, R., Fromme, P., & Duffour, P., “Fatigue life sensitivity of monopile-supported offshore wind turbines to damping,” Renewable Energy, 123, 450-459(2018).
36. Seed, HB., Wong, RT., Idriss, I., Tokimatsu, K., “Moduli and damping factors for dynamic analyses of cohesionless soils,” J Geotechn Eng 1986;112:1016–32 (1986).
37. Sørensen, S. P. H. (2012). Soil-structure interaction for nonslender, large-diameter offshore monopiles.
38. Sørensen, S. P. H., Ibsen, L. B., & Frigaard, P. (2010). Experimental evaluation of backfill in scour holes around offshore monopiles. Frontiers in Offshore Geotechnics II. London: Taylor & Francis Group, 635 640.
39. Sørensen, S. P. H., Ibsen, L. B., & Frigaard, P. (2012, June). Relative Density of Backfilled Soil Material around Monopiles for Offshore Wind Turbines. In ISOPE International Ocean and Polar Engineering Conference (pp. ISOPE-I). ISOPE.
40. Topham, E., Gonzalez, E., McMillan, D., & João, E. (2019). “Challenges of decommissioning offshore wind farms: Overview of the European experience,” In Journal of Physics: Conference Series 1222(1), 12-35. IOP Publishing.
41. Vesic, A. B. (1961). “Bending of beams resting on isotropic elastic solid,” Journal of the Engineering Mechanics Division, 87(2), 35-54.
42. Vught JH.(2000). Ph.D thesis, “Considerations on the dynamics of support structures for an offshore wind energy converter,” Delft University of Technology, The Netherlands.
43. Wind Europe(2021), “Offshore wind in Europe. Key trends and statistics 2020,” tech. rep.
44. Winkler E. (1867). “Die lehre von elasticzitat and festigkeit (on elasticity and fixity),” Prague, 182.
45. 杜冠廷 (2022)，「砂土阻尼給定對大口徑單樁基礎離岸風機動態反應影響分析」，碩士論文，國立成功大學水利及海洋工程學系，台南市。
46. 陳威廷 (2021)，「埋置於砂土層中之大口徑單樁基礎反覆加-卸載基礎勁度」，碩士論文，國立成功大學水利及海洋工程學系，台南市。
47. 黃昱睿(2018)，「大口徑單樁基礎側向穩定性分析」，碩士論文，國立成功大學水利及海洋工程系，台南市。
48. 曾韋禎(2018)，「淘刷對離岸風機大口徑單樁基礎整體結構動態反應之影響」，博士論文，國立成功大學土木工程系，台南市。