Abstract: The length-to-breadth ratio ( L/B) of a heavy icebreaker is generally between 4~5. The applicability of conventional calculation formulae for calculating wave loads on hull girder is limited. The characteristics of heavy icebreakers hull lines differ significantly from those of vessels designed for open waters. Numerical methods are consequently required to study the characteristics of wave loads on hull girder. A time-domain Rankine source method accounting for speed is employed to predict the wave loads on hull girder by using the hydrodynamic software WASIM. Both the long-term values of linear wave loads and the direct calculation results of nonlinear wave loads are obtained. Comparisons are then made among the long-term linear wave loads (after nonlinear correction), the directly calculated nonlinear wave loads and the standard values. The results show that the long-term linear vertical wave bending moment is approximately 1.4 times the standard linear value, and the long-term linear vertical wave shear force is 1.9 times that of the standard linear values, owing to the unique hull lines of heavy icebreakers. It is indicated that the standard formulae cannot provide a reasonable evaluation of the wave loads on the hull girder for these vessels. From a practical engineering design perspective, the long-term linear vertical wave loads (after non-linear correction) at a speed of 5 knots are adopted as the design wave loads of the hull girder for the evaluation of the overall strength of the hull structure. The non-linear effect of the sagging wave bending moment is significant, resulting in special consideration of the structural buckling of long superstructures during the check of the longitudinal strength of the hull under sagging condition.

Key words: heavy icebreaker, wave beam load, non-linear effect, linear value, non-linear correction coefficient

摘要： 重型破冰船的长宽比（L/B）一般为4~5,故常规的船体梁波浪载荷规范计算公式适用性受限,且重型破冰船的船体型线特征与开敞水域航行的船舶有显著不同,因此需利用数值方法研究其船体梁波浪载荷特性。该文基于有航速时域Rankine源法,采用水动力软件WASIM对其船体梁波浪载荷进行预报,得到了波浪载荷线性长期值和波浪载荷非线性直接计算值;随后,将波浪载荷线性长期值（非线性修正后）、波浪载荷非线性直接计算值,分别与规范值进行对比。结果表明：由于其船体型线特殊,垂向波浪载荷弯矩线性长期值约为规范线性值的1.4倍,垂向波浪剪力线性长期值约为规范线性值的1.9倍,规范公式无法对其船体梁波浪载荷进行合理的评估;基于工程设计的实际出发,建议取5kn航速下垂向波浪载荷线性长期值（非线性修正后）作为船体梁波浪设计载荷,用于船体结构总强度评估;中垂波浪弯矩载荷非线性效应显著,在对中垂状态下的船体进行总纵强度校核时,应特别关注长上层建筑的结构屈曲问题。

关键词: 重型破冰船, 船体梁波浪载荷, 非线性效应, 线性值, 非线性修正系数