三體船長期波浪負荷極值特性分析

CHARACTERISTIC LONG-TERM EXTREME VALUE ANALYSIS ON WAVE LOADS OF A TRIMARAN

本研究使用三維前進──振盪（3D Translating-pulsating）格林函數數學模型，配合三維小板法，使用HSC-3D程式進行船體在波浪中運動及波浪負荷之頻率域反應分析，將船體視為一平浮於水中之自由樑，計算三體船在斜浪規則波中，船體橫剖面及橫跨甲板縱剖面各處所承受之波浪負荷。非規則波譜則採用Bretschneider波譜進行三體船在船速30節，不同航向角下，非規則波中之整體波浪負荷分析，期盼能完整探討三體船在不同航向波浪中，船體橫剖面及橫跨甲板縱剖面各處所承受之波浪負荷特性；本研究根據勞氏驗船協會法規之建議，長期之波浪統計分佈取自北大西洋波浪頻度表，發展三體船之長期波浪負荷極值分析統計模式，分析三體船在二十年左右船齡之船體負荷極值特性，以與勞氏驗船協會法規之設計負荷進行比較與討論，提供船體負荷極值，藉以分析三體船結構強度，進行三體船結構之最佳輕量化，以達到增加結構安全及降低結構重量之目標。 Since the wave load characteristics of trimaran ships cannot be estimated from experiences with conventional mono-hull vessel and Catamaran, investigations on these hydrodynamic aspects of trimarans are urgently needed to exploit their potential. The global loads of a trimaran in oblique waves have been investigated by means of the 3D translating-pulsating source distribution panel method. The wave loads which including the shear forces, bending moments and torsional moments at different transverse sections of the trimaran ship hull and longitudinal section of connected deck had been predicted at various wave heading and frequencies. In this study, the characteristics of longitudinal and transverse sectional wave load responses of the trimaran ship in irregular waves are discussed. By using the Bretschneider spectrum and Long-term wave statistics, North Atlantic scatter diagram, the long-term extreme value analysis of motion and wave load responses of the trimaran has been carried out. The numerical results of long-term extreme loads are compared with the design loads of Lloyd's Register rules. This is a kernel technique for analyzing the ultimate structural strength of a trimaran.