﻿ 斜浪条件下大型集装箱船扭矩特征及结构强度研究
 舰船科学技术  2019, Vol. 41 Issue (8): 23-27 PDF

1. 江苏科技大学，江苏 镇江 212003;
2. 中国船舶重工集团有限公司，北京 100097;
3. 中国船级社上海规范研究所，上海 200135

Research on torque characteristics and structural strength of large container under oblique wave condition
DING Shi-feng1, ZHOU Li1, YU Hao2, ZHOU Ya-jun3
1. Jiangsu University of Science and Technology, Zhenjiang 212003, China;
2. China Shipbuilding Industry Corporation, Beijing 100097, China;
3. Shanghai Rules and Research Institute, China Classification Society, Shanghai 200135, China
Abstract: It is important to study on torque load characteristics and structural responses under oblique waves as the development of large container. This paper built up wet surface model and mass model based on a large container, and studied on how to determine the design wave parameters according to the torque response function and dominant load parameters. And we analyzed the relationship between the exceeding probability level and calculated torque. This paper worked on the torque’s differences and its reason among dynamic load approach (DLA), American Bureau of Shipping (ABS) container rule and " Common Structural Rules for Bulk Carriers and Oil Tankers (HCSR)” considering the typical oblique wave parameters and exceeding probability level. This paper also gave some proposals on how to calculate and applicate the torque load for container ships. On this foundation, we chosen three wave conditions (45°, 60° and 75°) for further case study, and identified the key structural positions under oblique waves by calculating the stress distribution. In conclusion, the study of this paper is a good reference for structural design of large container, such as the torsional strength calculation of hull girder, the design of hatch corner and the strength evaluation of torsional box.
Key words: container     dynamic load approach (DLA)     torque     oblique wave     structural strength     stress analysis     ship rule
0 引　言

1 水动力分析 1.1 水动力模型

 图 1 集装箱船水动力模型 Fig. 1 Hydrodynamic model of container ship
 ${l_{beam}} = \sqrt {12} \cdot {r_{roll - gyr}}\text{。}$ (1)

1.2 扭矩传递函数

 图 2 扭矩载荷传递函数（5/20 L位置） Fig. 2 Torque load transfer function（5/20 L position）

1.3 主要载荷控制参数

 $\lambda = \frac{{2{\text{π}}g}}{{\omega _a^2}}\text{，}$ (2)

 ${\alpha _w} = \frac{L}{A}\text{。}$ (3)

2 扭矩载荷特征分析 2.1 设计波参数对扭矩的影响

 图 3 斜浪工况下扭矩沿船长的分布曲线 Fig. 3 Distribution of Ttorque along ship length under oblique wave

2.2 扭矩极值与超越概率的关系

 图 4 不同超越概率水平的扭矩极值曲线 Fig. 4 Torque extremum curves with different probability levels

2.3 与规范扭矩的对比分析

 $\begin{array}{l} {M_t} = {k_s}kL{B^2}d\left[ {{{\left( {{C_w} - 0.5} \right)}^2} + 0.1} \right]\\ \;\;\;\;\;\;\;\;\; \times \left[ {0.13 - \left( {e/D} \right){{\left( {{c_0}/d} \right)}^{0.5}}} \right] \end{array}$ (4)

 ${M_t}\! =\!\! {f_\beta }\left( {0.4{f_{t1}}{C_W}\!\!\sqrt {\frac{L}{{{T_{LC}}}}} {B^2}D{C_b} \!+\! 0.22{f_{t2}}{C_W}L{B^2}{C_b}} \right)\text{。}\!\!$ (5)

 图 5 规范扭矩和DLA计算扭矩对比 Fig. 5 Comparison of torque calculated by ship rule and DLA

ABS规定该扭矩用于计算局部结构强度，扭矩曲线可近似为分段直线，在3/20 L～11/20 L处扭矩计算值最大，且最大值的作用范围大于DLA计算值，与超越概率10–4的DLA扭矩计算值大致相当，这也验证了“局部强度采用10–4超越概率水平”的观点。

HSCR规定该扭矩用于船体梁强度计算，规范扭矩曲线由多段曲线组合而成，曲线形状与DLA计算扭矩曲线相似，在船尾方向7/20 L ～8/20 L位置处出现扭矩最大值，该值较超越概率10–8的DLA扭矩计算值低30%左右，约与超越概率10–6.5的DLA扭矩计算值相当。

 图 6 规范扭矩和不同浪向角DLA扭矩比较 Fig. 6 Comparison of torque under different wave directions

ABS扭矩计算值约和45°浪向角时的DLA扭矩计算值相当，但曲线形状相反；HCSR扭矩计算值约和75°浪向角时的DLA扭矩计算值相当，曲线形状相似。

DLA扭矩计算值与船舶规范存在差异，可能的原因是：1）船型的差别，本文以集装箱船为研究对象，HSCR是散货船和油船规范，计算结果仅可作为借鉴；2）设计波和装载情况的差异，本文DLA计算考虑最恶劣斜浪和装载的组合，而ABS是综合多种因素的统计回归值；3）概率水平上的差异，本文DLA计算的超越概率水平分别为10–2，10–4和10–8，而规范中总强度主要考虑20年或25年一遇的概率水平、局部强度考虑10–4概率水平。

DLA计算扭矩最大值及作用范围与船舶规范要求存在一定差异，因此，对于大型集装箱船，在规范载荷的基础上，通过水动力分析直接预报扭矩值，具有必要性。

3 整船结构强度分析

 图 7 斜浪工况下集装箱船应力云图 Fig. 7 Stress of container ship under oblique wave condition

4 结　语

1）斜浪设计波参数是扭矩载荷的关键要素，本文集装箱船水动力分析算例中，最恶劣斜浪对应的设计波参数为浪向角为60°或120°，设计波长为125.8 m（1/3 L～1/4 L），最大扭矩出现在船中偏后的7/20 L截面处；

2）超越概率水平体现了不同的结构校核安全水平，对应10–2，10–4和10–8超越概率，沿船长分布的扭矩载荷包络值曲线形状相似，计算值呈比例关系（约为1.93倍），开展总强度、局部强度和疲劳强度分析时，需根据不同的校核目标选择相应的超越概率；

3）ABS规范与超越概率为10–4的DLA的扭矩最大值相当，但分布趋势有所差异，HCSR规范与DLA的扭矩分布趋势相当，但最大值仅相当于超越概率为10–6.5的DLA扭矩计算值，建议集装箱船结构设计时，除满足规范要求，还应开展恶劣斜浪工况下的扭矩载荷直接计算；

4）集装箱船整船结构强度直接计算结果表明，斜浪设计波参数对集装箱整船结构应力分布具有重要影响，特别是顶边舱、舱口角隅和机舱前后端等位置，集装箱船结构设计时需引起重视。

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