Abstract: The bi-moment is a key factor in calculating the warping normal stress induced by restrained torsion in container ships. At present, bi-moment evaluation is mainly carried out using the transfer matrix method or one-dimensional finite element methods based on thin-walled structural mechanics, which involves relatively complex computational procedures. In this study, the CCS software for combined bending moment and longitudinal strength assessment of large-opening ships was employed to calculate the bi-moment for twelve container ships. The longitudinal distributions of torque and bi-moment were systematically analyzed for single-island and double-island configurations. Distinct bi-moment distribution characteristics were identified between the two ship types, revealing that the superstructure (i.e., island layout, referred to as "island" hereafter) significantly influences the bi-moment distribution. With torque and the bending-torsion characteristic coefficient selected as governing parameters, regression analyses were conducted to establish longitudinal bi-moment distribution formulas for single-island and double-island container ships, yielding two sets of concise regression formulas. These formulas can be applied to the global bending-torsion strength assessment and the torsional ultimate strength evaluation incorporating warping stress in the preliminary design stage of container ships.

Key words: container ship, bi-moment, torque, strength assessment

摘要： 双力矩是计算集装箱船约束扭转的翘曲正应力的重要一环,目前双力矩的计算主要采用薄壁结构力学的迁移矩阵或一维有限元方法,过程较复杂。该文应用中国船级社大开口船弯扭组合总纵强度校核软件,进行了12艘集装箱船的双力矩计算,总结了单岛船和双岛船的扭矩、双力矩沿船长的分布规律,发现这种船型的双力矩分布规律有一定的区别,其中上层建筑岛式布置对双力矩分布的影响较大。文章选取扭矩和弯曲扭转特性系数作为关键参数,分别对单岛船和双岛船开展双力矩沿船长分布的公式回归,获得了2套形式简明的回归公式,可应用于集装箱船初步设计阶段的弯扭组合总纵强度评估,以及计入翘曲应力的扭转极限强度评估。

关键词: 集装箱船, 双力矩, 扭矩, 强度评估