臺灣博碩士論文加值系統

離岸風電之結構分析與設計過程中，各種載重情境下之載重組合繁多及分析時程長，使相關軟硬體與分析模式之選定顯得十分重要，尤其是邊界條件的設定方式。本研究以美國再生能源研究室(National Renewable Energy Laboratory, NREL)，所提出之5MW單樁式離岸風機為例，考量不同邊界條件於地震力下土壤與結構互制行為(Soil-Structure Interaction, SSI)，並比較結構振動模態與力量傳遞之反應。
本研究為研擬不同邊界條件的影響範疇，首先以蒐集之離岸風機數值，分析國際案例及方法，再透過臺灣西部海域之場址環境條件與地質報告，採用Mechanical APDL (ANSYS 2019 R3)有限元素軟體，進行三種邊界條件之單樁式離岸風機模擬分析：(1)基礎直接固接(Fixed-End)；(2)單點多自由度線性彈簧(Simplified Method)；(3)多點非線性土壤彈簧(Standard Method)等，將三種邊界條件之單樁式離岸風機進行模態分析與動力歷時分析，並基於地盤受震反力分析(Seismic Site Response Analysis, SSRA)結果輸入地震加速度歷時，探討單樁式離岸風機於三種不同邊界條件之力量傳遞機制、振動模態、長期性能和分析時間。
根據分析結果顯示，於模態分析中，考慮土壤彈簧邊界條件的模型頻率略低於固定式邊界模型，且依據國際設計規範對風力機振動頻率1P~3P區間的要求(即Soft-Stiff條件)，三種邊界條件模型均符合安全範圍。在動力歷時分析方面，本研究進行兩種模擬分析，分為僅考量地震載重與依據DNV規範建議作法之考量載重組合兩種分析情境，此外，還多考慮土壤阻尼之效應，以評估不同動力分析結果。在僅地震載重分析情形下，多點非線性土壤彈簧模型對結構之反應有較大之趨勢；而在載重組合分析情形下，則為基礎直接固接模型對結構反應有較大之趨勢。故在邊界條件之選擇對離岸風機結構動態行為和力量傳遞有顯著影響，本研究提供不同邊界條件下地震對單樁式離岸風機結構之寶貴數據和見解，冀望能為工程實務設計提供重要的參考依據。

In the structural analysis and design of offshore wind turbines, designers must consider numerous load combinations and extended analysis durations under various loading scenarios, making the selection of appropriate software, hardware, and analytical models critical, particularly in the setting of boundary conditions. This study utilizes the 5MW monopile offshore wind turbine proposed by the National Renewable Energy Laboratory (NREL) as a case study, considering soil-structure interaction (SSI) under seismic forces to compare structural vibration modes and force transmission responses under different boundary conditions.
To explore the scope of different boundary conditions, this study begins by collecting offshore wind turbine data, analyzing international cases and methodologies, and utilizing environmental and geological reports from the site conditions of Taiwan's western sea. The finite element software Mechanical APDL (ANSYS 2019 R3) is employed to conduct simulation analyses of three boundary condition models: (1) the monopile end is fixed at the mudline level, (2) the monopile end is restrained by a single 6DOF spring, (3) the SSI effect is considered by implementing a set of soil springs along the soil-to-monopile interfaces. Modal and dynamic time-history analyses are performed on the monopile offshore wind turbine models under these three boundary conditions. Based on the Seismic Site Response Analysis (SSRA) results, seismic acceleration time histories are input to investigate the force transmission mechanisms, vibration modes, long-term performance, and analysis duration of the monopile offshore wind turbine under these three different boundary conditions.
The analysis results show that in the modal analysis, models considering soil spring boundary conditions have slightly lower frequencies than fixed-end boundary models. According to international design standards for wind turbine vibration frequencies in the 1P~3P range (i.e., soft-stiff conditions), all three boundary condition models fall within the safe range. In the dynamic time-history analysis, two simulation scenarios are conducted: one considering only seismic loads and the other considering combined loads, with the results evaluated from the perspective of soil damping. Under the scenario considering only seismic loads, the multi-point nonlinear soil spring model exhibits a greater tendency for structural response; whereas, under the combined load scenario, the fixed-end model shows a greater tendency for structural response.
These results indicate that the choice of boundary conditions significantly affects the dynamic behavior and force transmission of offshore wind turbine structures. This study provides valuable data and insights into the impact of different boundary conditions on monopile offshore wind turbine structures under seismic conditions, aiming to offer important reference points for practical engineering design.

摘 要 i
ABSTRACT iii
誌 謝 v
目 錄 vii
表目錄 x
圖目錄 xi
第一章 緒論 1
1.1 研究動機與目的 1
1.2 研究方法 2
1.3 本文內容 2
第二章 文獻回顧 5
2.1 前言 5
2.2 離岸風機支撐結構設計標準 5
2.2.1 離岸風機結構檢核限度狀態 6
2.2.2 載重組合說明 7
2.3 離岸風機設計載重 8
2.3.1 風載重條件 8
2.3.2 海浪載重條件 11
2.3.3 海流載重條件 13
2.4 土壤與結構互制影響探討 14
2.4.1 線性土壤彈簧理論 15
2.4.2 非線性土壤彈簧理論 16
2.5 單樁式離岸風機地震分析文獻探討 23
2.6 能量介紹 28
第三章 分析方法 30
3.1 分析流程 30
3.2 有限元素理論 31
3.3 模型建立 32
3.3.1 風力機規格 33
3.3.2 單樁式支撐結構參數 34
3.3.3 單樁式離岸風機不同邊界條件設定 35
3.4 使用元素說明 42
3.4.1 質量元素MASS 21 42
3.4.2 梁元素BEAM 188 42
3.4.3 管元素PIPE 288 43
3.4.4 矩陣元素MATRIX 27 43
3.4.5 非線性彈簧元素COMBIN 39 44
3.5 土壤阻尼計算說明 45
3.6 考量土壤阻尼模型分析說明 46
3.7 能量計算方法說明 47
第四章 結構分析設定與結果探討 49
4.1 模態分析說明與結果檢核 49
4.1.1 模態分析說明 49
4.1.2 模態分析結果與檢核 50
4.2 結構動力歷時分析說明 51
4.2.1 設定說明 51
4.2.2 雷利阻尼(Rayleigh Damping)設定說明 51
4.2.3 本研究地震動力分析說明 52
4.3 僅考量地震載重之動力分析 52
4.3.1 地震地盤反應分析結果 53
4.3.2 不同邊界條件模型地震力施加條件與位置 55
4.3.3 考量土壤效應模型土壤阻尼施加條件與位置 57
4.3.4 結果探討 58
4.4 載重組合動力分析 85
4.4.1 環境載重說明 85
4.4.2 分析結果 88
第五章 結論與建議 95
5.1 結論 95
5.2 建議 97
參考文獻 98

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