我國預計於 2030 年前完成3,000 MW離岸風場設置，其中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，必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，工程實務最常採用之設計方法為p-y曲線法。但是，目前離岸風機基礎設計規範建議之p-y曲線分析法並無法考量局部淘刷所產生之淘刷坑幾何形狀，可能錯估大口徑單樁基礎受到淘刷後之受力變形反應與基礎勁度，影響離岸風機支撐結構整體反應分析結果。由於目前並無考量大口徑單樁基礎受淘刷時之受力變形反應工程分析建議方法，本研究結合現有文獻提出對大口徑單樁基礎之p-y曲線進行之樁徑影響對側向地盤反力係數之修正建議，以及考量單樁受淘刷時側向極限阻抗修正之建議，計算考量淘刷時之大口徑單樁受力變形反應與基礎勁度。
透過以Bladed軟體建立台電海氣象觀測塔於台灣西部海域彰濱風場環境條件下之整體振動反應分析模型，藉由模態分析評估淘刷對海氣象觀測塔支撐結構自然振動頻率之影響，結果顯示本研究建立之數值分析模型所得之模擬頻率值與實測自然振動頻率值相符。若採用耦合彈簧模型進行模擬整體支撐結構之動態行為時，p-y曲線初始斜率變化對支撐結構自然振動頻率之影響顯著。若採用均佈彈簧模型進行模擬整體支撐結構之動態行為時，支撐結構之自然振動頻率對p-y曲線初始斜率變化並不敏感。此外，淘刷對於某些特定模態會有顯著的影響，振動頻率衰減程度最大可達14%。本研究可提供以結構監測及分析偵測離岸風機基礎淘刷損傷之初步策略。
本研究同時透過Bladed軟體建立5MW參考風機於台灣西部海域彰濱風場環境條件下之整體振動反應分析模型，評估動態條件下基礎淘刷對離岸風機基礎作用力之影響，結果顯示以目前離岸風機設計規範所建議之p-y曲線計算大口徑單樁受力變形反應時，於淘刷深度大於一倍樁徑時將高估基礎變形量，但當淘刷深度小於一倍樁徑時卻可能低估基礎變形量。
由於目前之現有工程分析方法對於考量基礎淘刷下之基礎變形並無法有效合理計算，使得於淘刷深度較小時，低估樁身變形量及高估支撐結構自然振動頻率。雖然以均佈彈簧基礎模型進行整體動態反應分析，可獲得較合理之支撐結構自然振動頻率，但考量基礎淘刷作用下之動態基礎勁度及變形反應之統一分析方法仍亟待研究，因此進行大口徑單樁基礎仍建議設置防淘刷保護工。若考慮防淘刷保護工設置流程，大口徑單樁基礎之基礎勁度應可較設計值略高。

Severe foundation scour may occur around monopile foundations of offshore wind turbines due to currents and waves. The p–y curve method recommended in the current offshore foundation design codes does not account for the local scour around the pile foundation; it overestimates the lateral pile deformation and underestimates the foundation stiffness. This study presents a method to correct the initial modulus of subgrade reaction and modify the ultimate lateral resistance caused by the local scour. The natural frequency of the met mast structure is also determined by a numerical model and verified with the measured data in situ. A comprehensive parameter study is performed to analyze the effect of scour on the dynamic responses of the met mast. Furthermore, the scour exerted significant effects on certain modes of the vibration responses. The natural frequencies of the met mast structure can be reduced by approximately 14% due to scour, particularly in the horizontal bending modes. This study also provides a preliminary strategy for structural monitoring and analysis to detect scour damage on offshore wind turbines with monopile foundations. And the numerical model of the reference offshore wind turbine with monopile unprotected against scour at Chang-Bin offshore wind farm in Taiwan Strait is established. The results showed that when the p-y curve suggested by existing design regulation was used to calculate the load-deformation response, the foundation stiffness was underestimated where the scour depth was greater than the pile diameter, but the foundation stiffness was overestimated when the scour depth was less than the pile diameter.

1. Abdel-Rahman, K., & Achmus, M. (2005). Finite element modelling of horizontally loaded monopile foundations for offshore wind energy converters in Germany. Paper presented at the Proceedings of the international symposium on frontiers in offshore geotechnics, Perth.
2. Achmus, M., Kuo, Y.-S., & Abdel-Rahman, K. (2010). Numerical investigation of scour effect on lateral resistance of windfarm monopiles. Paper presented at the The Twentieth International Offshore and Polar Engineering Conference.
3. Achmus, M., Thieken, K., & Lemke, K. (2014). Evaluation of py approaches for large diameter monopiles in sand. Paper presented at the The Twenty-fourth International Ocean and Polar Engineering Conference.
4. Adhikari, S., & Bhattacharya, S. (2011). Vibrations of wind-turbines considering soil-structure interaction. Wind and Structures, 14(2), 85.
5. Adhikari, S., & Bhattacharya, S. (2012). Dynamic analysis of wind turbine towers on flexible foundations. Shock and Vibration, 19(1), 37-56.
6. APIRP2A-WSD. (1993). Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms – Working Stress Design. Washington (DC): American Petroleum Institute.
7. APIRP2A-WSD. (2007). Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms – Working Stress Design. Washington (DC): American Petroleum Institute.
8. APIRP2GEO. (2011). Geotechnical and Foundation Design Considerations: American Petroleum Institute.
9. Arany, L., Bhattacharya, S., Adhikari, S., Hogan, S., & Macdonald, J. (2015). An analytical model to predict the natural frequency of offshore wind turbines on three-spring flexible foundations using two different beam models. Soil dynamics and earthquake engineering, 74, 40-45.
10. Arany, L., Bhattacharya, S., Macdonald, J., & Hogan, S. (2017). Design of monopiles for offshore wind turbines in 10 steps. Soil dynamics and earthquake engineering, 92, 126-152.
11. Baguelin, F., Frank, R., & Said, Y. (1977). Theoretical study of lateral reaction mechanism of piles. Geotechnique, 27(3), 405-434.
12. Barltrop, N. D., Adams, A. J., & Hallam, M. (1991). Dynamics of fixed marine structures (Vol. 8): Butterworth-Heinemann Oxford.
13. Blanco, M. I. (2009). The economics of wind energy. Renewable and sustainable energy reviews, 13(6-7), 1372-1382.
14. Broms, B. B. (1964). Lateral resistance of piles in cohesionless soils. Journal of the Soil Mechanics and Foundations Division, 90(3), 123-158.
15. Brown, P., & Gibson, R. (1972). Surface settlement of a deep elastic stratum whose modulus increases linearly with depth. Canadian Geotechnical Journal, 9(4), 467-476.
16. Bush, E., & Manuel, L. (2009). The influence of foundation modeling assumptions on long-term load prediction for offshore wind turbines. Paper presented at the ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering.
17. Chang, Y. (1937). Discussion on Lateral Pile-Loading Tests by Feagin. Paper presented at the Transition of ASCE.
18. De Vries, W. (2011). Support structure concepts for deep water sites. EU Project UpWind, final report WP 4.2. the Netherlands: Delft University of Technology.
19. De Vries, W., & van der Tempel, J. (2007). Quick monopile design. Paper presented at the European Offshore Wind Conference, Berlin, Germany.
20. DNV-OS-J101. (2004). Design of Offshore Wind Turbine Structures: Det Norske Veritas AS.
21. DNV. (1992). Classification Notes No. 30.4 - Foundations. Oslo, Norway: Det Norske Veritas.
22. DNV/Risø. (2002). Guidelines for design of wind turbines, 2nd ed. Viby, Denmark: Jydsk Centraltrykkeri.
23. DNVGL-RP-C203. (2016a). Fatigue design of offshore steel structures: Det Norske Veritas Germanischer Lloyd.
24. DNVGL-ST-0126. (2016b). Support structures for wind turbines: Det Norske Veritas Germanischer Lloyd.
25. DNVGL-ST-0437. (2016c). Loads and site conditions for wind turbines: Det Norske Veritas Germanischer Lloyd.
26. DONGEnergy. (2013). Environmental Statement Volume 1 - Chapter 6: Project Description: DONG Energy Burbo Extension (UK) Ltd.
27. Douglas, D., & Davis, E. (1964). The movement of buried footings due to moment and horizontal load and the movement of anchor plates. Geotechnique, 14(2), 115-132.
28. DS449. (1983). Dansk Ingeniørforenings Norm for Pælefunderede Offshore Stålkonstruktioner (in Danish). Copenhagen, Denmark: Dansk Ingeniørforening, Teknisk Forlag, Normstyrelsens Publikationer.
29. Effiom, S. O., Nwankwojike, B., & Abam, F. (2016). Economic cost evaluation on the viability of offshore wind turbine farms in Nigeria. Energy Reports, 2, 48-53.
30. EWEA. (2011). Wind in our Sails - The coming of Europe's offshore wind energy industry: the European Wind Energy Association.
31. GL. (2005). Guideline for the certification of offshore wind turbines. Hamburg Germany: Germanischer Lloyd.
32. GLGarradHassan. (2013). Bladed user manual-version 4.5. Bristol, UK: Garrad Hassan and Partners Ltd.
33. Guo, W. D. (2008). Laterally loaded rigid piles in cohesionless soil. Canadian Geotechnical Journal, 45(5), 676-697.
34. GWEC. (2018). Global Wind Statistics 2017: Global Wind Energy Council
35. Hetenyi, M. (1946). Beams on elastic foundation. Ann Arbor: University of Michigan Press.
36. IEC61400-3. (2009). Wind Turbines—Part 3: Design Requirements for Offshore Wind Turbines: International Electrotechnical Commission.
37. Jonkman, J., & Musial, W. (2010). Offshore code comparison collaboration (OC3) for IEA task 23 offshore wind technology and deployment. Contract, 303, 275-3000.
38. Jung, S., Kim, S.-R., & Patil, A. (2015). Effect of monopile foundation modeling on the structural response of a 5-MW offshore wind turbine tower. Ocean Engineering, 109, 479-488.
39. Kühn, M., Cockerill, T., Harland, L., Harrison, R., Schöntag, C., Van Bussel, G., & Vugts, J. (1998). Opti-OWECS final report vol. 2: Methods assisting the design of offshore wind energy conversion systems. Delft University of Technology: Delft.
40. 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.
41. Kuo, Y.-S. (2008). On the behavior of large-diameter piles under cyclic lateral load: Eigenverl. IGBE.
42. Kuo, Y.-S., Achmus, M., & Abdel-Rahman, K. (2010). Investigation on the Requirements regarding the minimum embedded length of monopiles Deep Foundations and Geotechnical In Situ Testing (pp. 315-324).
43. Kuo, Y.-S., Achmus, M., & Abdel-Rahman, K. (2012). Minimum embedded length of cyclic horizontally loaded monopiles. Journal of Geotechnical and Geoenvironmental Engineering, 138(3), 357-363.
44. Lesny, K., & Wiemann, J. (2006). Finite-element-modelling of large diameter monopiles for offshore wind energy converters GeoCongress 2006: Geotechnical Engineering in the Information Technology Age (pp. 1-6).
45. Li, Y., Chen, X., Fan, S., Briaud, J.-L., & Chen, H.-C. (2009). Is scour important for pile foundation design in deepwater? Paper presented at the Offshore Technology Conference.
46. 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.
47. 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.
48. Lombardi, D., Bhattacharya, S., & Wood, D. M. (2013). Dynamic soil-structure interaction of monopile supported wind turbines in cohesive soil. Soil dynamics and earthquake engineering, 49, 165-180. doi:10.1016/j.soildyn.2013.01.015
49. Matutano, C., Negro, V., López-Gutiérrez, J.-S., & Esteban, M. D. (2013). Scour prediction and scour protections in offshore wind farms. Renewable energy, 57, 358-365.
50. Nielsen, A., & Hansen, E. (2007). Time-varying wave and current-induced scour around offshore wind turbines. Paper presented at the ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering.
51. Petersen, C. (2001). tahlbau - Grundlagen der Berechnung und baulichen Ausbildung von Stahlbauten.
52. Poulos, H. G. (1971). Behavior of laterally loaded piles: I-Single Piles. Journal of Soil Mechanics & Foundations Div.
53. Poulos, H. G., & Davis, E. H. (1980). Pile foundation analysis and design: Wiley.
54. Prendergast, L. J., & Gavin, K. (2016). A comparison of initial stiffness formulations for small-strain soil–pile dynamic Winkler modelling. Soil dynamics and earthquake engineering, 81, 27-41.
55. Qi, W., Gao, F., Randolph, M., & Lehane, B. (2016). Scour effects on p–y curves for shallowly embedded piles in sand. Geotechnique, 1-13.
56. Qi, W. G., & Gao, F. P. (2014). Physical modeling of local scour development around a large-diameter monopile in combined waves and current. Coastal Engineering, 83, 72-81.
57. Randolph, M. F. (1981). The response of flexible piles to lateral loading. Geotechnique, 31(2), 247-259.
58. 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.
59. Reese, L. C., Wang, S., Isenhower, W., & Arrellaga, J. (2004). Computer program Lpile plus version 5.0 technical manual. Ensoft, Austin, TX.
60. REN21. (2017). Renewables 2017 - Global Status Report: Renewable Energy Policy Network for the 21st Century.
61. Roulund, A., Sumer, B. M., Fredsøe, J., & Michelsen, J. (2005). Numerical and experimental investigation of flow and scour around a circular pile. Journal of Fluid Mechanics, 534, 351-401.
62. Sørensen, S. P. H. (2012). Soil-structure interaction for non-slender, large-diameter offshore monopiles. (Ph.D. Thesis), Aalborg University, Aalborg, Denmark.
63. Sørensen, S. P. H., Ibsen, L. B., & Augustesen, A. H. (2010). Effects of diameter on initial stiffness of py curves for large-diameter piles in sand. Paper presented at the The European Conference on Numerical Methods in Geotechnical Engineering, Trondheim, Norway.
64. Schauman, P. (2008). Einführung Offshore- Windenergieanlagen. Paper presented at the Fachveranstaltung im Haus der Technik, Essn, Germany.
65. Sumer, B. M., & Fredsøe, J. (2002). The mechanics of scour in the marine environment: World Scientific.
66. Titze, E. (1970). Über Den Seitlichen Bodenwiderstand Bei Pfahlgründungen. Bauingenieur-Praxis, 77.
67. van der Tempel, J., & Molenaar, D.-P. (2002). Wind turbine structural dynamics-a review of the principles for modern power generation, onshore and offshore. Wind Engineering, 26(4), 211-222.
68. van der Tempel, J., Zaaijer, M., & Subroto, H. (2004). The effects of Scour on the design of Offshore Wind Turbines. Paper presented at the Proceedings of MAREC.
69. Vesic, A. B. (1961). Bending of beams resting on isotropic elastic solid. Journal of the Engineering Mechanics Division, 87(2), 35-54.
70. Vugts, J. (2000). Considerations on the dynamics of support structures for an OWEC. Delft University of Technology, Faculty of Civil Engineering and Geoscience, Section Offshore Technology.
71. Wang, Y.-K., Chai, J.-F., Chang, Y.-W., Huang, T.-Y., & Kuo, Y.-S. (2016). Development of Seismic Demand for Chang-Bin Offshore Wind Farm in Taiwan Strait. Energies, 9(12), 1036.
72. Whitehouse, R. (1998). Scour at marine structures: A manual for practical applications: Thomas Telford.
73. Whitehouse, R., Sutherland, J., & O'Brien, D. (2006). Seabed scour assessment for offshore windfarm. Paper presented at the Proceedings of the 3rd International Conference on Scour and Erosion, Gouda, The Netherlands.
74. Williams, D. J. (1979). The behaviour of model piles in dense sand under vertical and horizontal loading. (PhD thesis), Cambridge University.
75. WindEurope. (2018). Offshore Wind in Europe - Key trends and statistics 2017: WindEurope.
76. Zaaijer, M. (2002). Design methods for offshore wind turbines at exposed sites (OWTES)—sensitivity analysis for foundations of offshore wind turbines. Delft, The Netherlands.
77. Zaaijer, M. (2006). Foundation modelling to assess dynamic behaviour of offshore wind turbines. Applied Ocean Research, 28(1), 45-57.
78. 王訓濤、周南山(1988)，「承受側向力之基樁與土壤之互制作用」，地工技術，第24期，第39-48頁。
79. 台灣電力股份有限公司(2015)，「離岸風力發電第一期計畫可行性研究」，作業計畫，台北。
80. 台灣電力股份有限公司(2017)，「離岸海氣象觀測塔監測資料庫建置與應用模組開發」，研究計畫，台北。
81. 莊明仁(2001)，「基樁承受側向荷重之反應分析」，博士論文，國立成功大學土木工程研究所，台南。
82. 許博凱(2015)，「基礎勁度對離岸風機支撐結構行為影響研究」，碩士論文，國立成功大學水利及海洋工程所，台南。
83. 郭玉樹、王昱凱、許博凱、曾韋禎(2014)，「離岸風機基礎設計與驗證考量」，地工技術，2014年12月號，第142期，第7-16頁。
84. 廖學瑞、丁金彪、林俶寬，(2014)，「離岸風力電場開發之海事工程施工船機與安裝技術初探」，中華技術，第103期，96~109頁。
85. 經濟部能源局(2018)，千架海陸風力機風力資訊整合平台網站(http://www.twtpo.org.tw/index.aspx)。