﻿ 船体梁在循环载荷下的极限强度研究
 舰船科学技术  2019, Vol. 41 Issue (4): 44-48, 75 PDF

1. 武汉船舶职业技术学院 船舶与海洋工程学院，湖北 武汉 430050;
2. 武汉理工大学 交通学院，湖北 武汉 430063

Research on the ultimate strength of hull girder under cyclic bending loads
YU Ji1, YANG Ping2
1. School of Ship and Ocean, Wuhan Institute of Shipbuilding Technology, Wuhan 430050, China;
2. School of Transportation, Wuhan University of Technology, Wuhan 430063, China
Abstract: After imposing the longitudinal ultimate strength, the capacity of ship will be changed due to obviously nonlinear deformation. At present, the residual capacity of ship is very concerned in the study of hull girder strength. And the residual strength will be changed strongly under cyclic loading. In this paper, the nonlinear FEM calculations under cyclic loading of box beams and some real ships have been carried out by Abaqus respectively, to obtain moment - curvature curves, and based on the analysis of the incremental plastic method and the progressive collapse method, a calculation program have been developed, it can analysis the residual carrying capacity of hull girder under cyclic bending loads, then compare it to the FEM calculations' results.
Key words: cyclic bending     the progressive collapse method     residual strength
0 引　言

2014年4月，国际船级社协会颁布的协调版共同规范中，除了极限强度校核的要求之外，还增加了剩余强度校核，指出船舶在遭受高于极限强度的载荷后，仍然具有一定程度的承载能力，即所谓的后剩余承载能力。目前已有不少关于单板、加筋板、箱形梁等结构的研究成果发表。如Paik[1]采用半解析法预测船体板格在受外力屈曲后的剩余极限强度。Yao[2]运用有限元方法分析了矩形板在轴向面内压力作用下的后极限强度承载能力以及变形行为。Fujikubo[3]等运用水弹塑性分析方法研究箱型梁的剩余承载能力。目前比较有效的方法有试验法、非线性有限元法、逐步崩溃法等，这些方法都能够得到完整的应力-变形曲线，由此来分析结构承载能力的变化。

1 循环载荷下加筋板的后极限承载能力分析

Rahman[7]运用梁理论，将船体梁离散成若干加筋板单元，并运用逐步崩溃法来进行极限强度分析。在他的计算单元中，采用的是分段函数来表达平均应力应变关系，认为单元受压时，会经历稳定阶段，非卸载阶段和卸载3个阶段，如图1所示。

 图 1 Rahman梁理论的应力应变关系 Fig. 1 Stress-strain relationship in Rahman beam theory

 $\sigma = \left\{ {\begin{array}{*{20}{c}} {E{\varepsilon _x}\text{，} \quad \quad {\rm if}\;0 < {\varepsilon _x} \leqslant {\varepsilon _y}}\text{，} \\ {{\sigma _y}\text{，}\quad \quad \;\quad {\rm if}\;{\varepsilon _y} < {\varepsilon _x}} \text{。} \end{array}} \right.$ (1)

 $\sigma = E\varepsilon \text{。}$ (2)

 图 2 递增塑性法流程图 Fig. 2 Flow chart of incremental plastic method
2 循环弯矩作用下船体梁的后极限承载能力分析

2.1 箱型梁模型计算及讨论 2.1.1 单向循环载荷

 图 3 箱型梁结构试验模型 Fig. 3 Test model of box girder structure

2.1.2 双向循环载荷

 图 4 黄震球模型A单向循环加载 Fig. 4 One-way cyclic loading of huang’s model A

 图 5 黄震球模型C单向循环加载 Fig. 5 One-way cyclic loading of huang’s model C
2.2 某内河集散货船

 图 8 108 m集散货船横剖面结构图 Fig. 8 Cross section of 108 m distributed cargo ship

2.3 Dow's 1/3 Test Hull

 图 11 中剖面结构图 Fig. 11 Cross section of 108 m dow’s 1/3 test hull

 图 12 Dow's 1/3 Test Hull单向循环加载 Fig. 12 One-way cyclic loading of dow’s 1/3 test hull

 图 13 Dow's 1/3 Test Hull双向循环加载 Fig. 13 Two-way cyclic loading of dow’s 1/3 test hull

本文计算的意义为，目前对于循环载荷下的船体梁极限强度的研究还在初级阶段，特别有效地模拟船体梁循环载荷下的力学行为的方法不多，本文提出了一种简单的计算方法来得到循环载荷下的力学曲线，并采用了非线性有限元进行对比，虽还有许多问题，但也希望能抛砖引玉，使其更加完善。

3 结　语

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