三體船整體結構極值負荷反應分析

EXTREME WAVE LOADS ON THE GLOBAL STRUCTURAL RESPONSE ANALYSES OF A TRIMARAN

本研究重點在於針對高速三體船重要且具特色的波浪負荷進行分析，並找出三體船在 25 年航行年限中所發生的 極值負荷；以等效設計規則波概念，進行全船有限元素法分析，透過船體有限元素模型找出三體船在等效設計規則 波下之應力集中區域，在不影響航行安全情況下，達成三體船結構輕量化之設計需求，提昇國內在三體高速客輪之 結構直接計算分析之核心競爭力。三體船的優點在於比單船體具較細長的主船體，左右輔船體可增加船舶航行時的 穩度，此可有效降低阻力，提供較大的甲板空間提供載客和貨物，因要擁有高速的特性，其結構重量需特別注意， 若設計過於保守則會增加輕船重量，減少載重量，也不利於高速航行，反之設計的強度若不足，則會造成航行時安 全上的問題；三體船其特殊的外型，除了主船體擁有單體船的負荷特性，主船體與輔船體之間之橫跨甲板連結，也 擁有與雙體船相似的負荷特性。本研究藉由三維小板法對三體船在規則波中進行計算負荷、非規則波之短期與長期 所受到的負荷極值進行分析，再進行等效設計規則波擇定，據以進行水線下船殼之波浪動壓力與全船體在波浪中之 加速度變化產生之慣性力，將兩者結合後，使用船體有限元素模型進行分析三體船在長期極限負荷之縱向扭矩和垂 向波彎矩，及橫跨甲板之扳裂剪力、扳裂力矩和橫向扭矩發生的結構反應並藉以探討三體船在波浪中之整體結構反 應特性。

A structure of trimaran consists of single central-hull and two side hulls, with a cross deck connecting all of them. The advantages come that the trimaran offers a high travelling speed, relatively stable performances and more spacious place to load cargo or passenger. The structure of the trimaran is complex, the central-hull has mono-hull load characteristics, and the cross deck also has similar catamaran load characteristics. Based on the technique of equivalent regular design waves, called extreme wave loads, the ship inertial forces, hydrodynamic pressure distributions of Finite Element Method (FEM) model nodes have been calculated by the 3D panel method. The global structural response analyses of a trimaran in waves have been carried out by using the FEM analysis software, ANSYS, to get the structure responses and stress concentrations of the trimaran in waves. Based on the numerical study, the stress concentrations on the amidships which connect the bridge and the chorus deck have been occurred. The stress concentrations along the cross deck are found nearby the stern in the oblique wave conditions. The stress concentrations at transverse bulkhead are due to the bending moment when side hulls in wave crest or wave trough. The global structural response analyses of a trimaran in waves have been discussed.