【作者】 张志民；

【导师】 戴仰山；

【作者基本信息】 哈尔滨工程大学 ， 船舶与海洋结构物设计制造， 2001， 博士

【摘要】 船首底部砰击是船舶在严重海况中航行时经常发生的一种物理现象。砰击发生瞬间，会在底部区域产生巨大的砰击压力，从而威肋底板的强度。本文的主要内容就是在考虑各种不确定性因素影响的情况下，用概率分析的方法较为合理地计算作用在底板上的砰击压力和底板极限承载能力，并用可靠性方法合理评定底板的安全性。为此，本文主要在下面几个方面进行了探索： 首先，建立了底板砰击极值压力的长期预报方法，通过分析海况、航速、航向角、装载状态等不同的影响，合理简化了长期预报的计算过程。使得该方法易于在实际工程计算中得以实现。 其次，依据极限状态的定义，给出了适用于有限元计算的底板失效模式。并采用该失效模式对大量计算模型进行了计算和分析，找到了底板几何尺寸和材料机械性能对底板极限承载能力的影响规律。在此基础上，对由传统极限分析方法得到的底板极限承载能力上限解的计算公式进行了合理的修正。得到了形式简单，结果较为准确的新公式。 再次，以五艘散货船为例，对中国、美国、挪威和英国的船舶设计与建造规范的有关规定进行了计算、比较和分析，指出了其中存在的问题和产生这些问题的原因。并采用可靠性分析的方法研究了实船和四国规范对应的船首底板的可靠性指标，以此为依据，给出目标可靠性指标的确定方法。 在上述工作的基础上，对我国建造规范中原有的砰击压力名义值和底板承载能力名义值的计算公式进行了修正，并参照选定的目标可靠性指标求出了安全系数，给出了更为科学合理的船首底部砰击强度定值评定公式。更多还原

【Abstract】 Bow bottom slamming of ship is one of the physical phenomena,which often appears during heavy sea conditions. At this instant,bottom plates experience large slamming pressure,which can damage bottom plates. The major content of this thesis is to calculate slamming pressures and ultimate bearing capacities more rationally by probabilistic analysis method,and to estimate the safety by reliability analysis method. For this reason,the following problems are researched emphatically:Firstly,the long-term prediction method for calculating the extreme values of slamming pressure is founded. The effects of sea conditions,ship speeds,traveling directions,loading conditions on the results of long-term prediction are studied. On this basis,the computing process is simplified rationally,so as to this method can be used in practical engineering computations.Secondly,the failure mode of bottom plates for finite element calculation is put forward based on the definition of ultimate states. Calculating and analyzing many calculation modes,the effects of plates’ sizes and material mechanical properties on ultimate bearing capacity are discovered. On this basis,the upper-limit solution calculation formula of ultimate bearing capacity gotten by limit analysis theory is modified. The new handy and more accurate formula is established.Thirdly,we calculate basing on the concerned contents of shipping design and building rules of China,America,Norway and Britain respectively,then compare and analyze,in which five bulk cargo ships are taken as examples. Through this,the existing problems and the reasons of those are pointed out. The reliability analysis methods areadopted to calculate the reliability specifications of the practical ships and the reliability specifications that correspond with the rules of the four countries. On the basis of this work,the methods of identifying the target reliability specification are gotten.Based on the above work,the calculation formulae of nominal slamming pressure and the bearing capability of the bottom plates in the rules are modified,and the safety coefficients are evaluated referring to the target reliability specification,then the more reasonable formula of assessing the slamming strength of bottom of the bow is given.更多还原