Ultimate Hull Girder Strength under Longitudinal Bending

1.研究了在推力作用下加筋板中加强筋的最佳建模方法。研究发现，无论用解析法还是有限元法分析连续加筋板的破坏行为时，加筋腹板应采用板模型，而加筋翼缘应采用梁柱模型，以有效地获得准确的结果.为了研究船底结构的破坏特性和强度，提出了一种简单而有效的方法，可以模拟加筋板在侧压和推力载荷联合作用下的破坏特性。通过与有限元分析结果的比较，验证了该方法的合理性。将该方法应用于计算机程序中，模拟了受纵向弯曲的船体梁的渐进屈曲行为。研究结果表明，船底侧压力和舷侧外板侧压力对船体外板抗侧力的影响是显著的， ...更多信息 船体梁极限强度较小.采用弹塑性大挠度有限元分析方法，模拟和研究了某型船的连续倒塌行为。在此基础上，建立了一个简单的动力学模型来模拟舱底圈的倒塌行为。将该模型应用到计算机程序中，模拟了受纵向弯曲的船体梁的连续倒塌行为。计算结果表明，在考虑撑环屈曲影响的情况下，两种结构的船体梁极限强度基本相同，但超过船体梁极限强度的承载力略有不同.本文提出了一种新的方法来考虑剪切力产生的横截面翘曲对连续倒塌行为和极限船体梁强度的影响。结果表明，当翘曲产生的正应力在船体梁弯曲的受压侧变为压应力时，船体梁的极限强度最大降低15%.提出了一种新的理想结构单元法（ISUM）单元，可以对受纵向弯曲的船体梁进行倒塌分析。在本研究项目中，尚未进行倒塌分析。然而，这种新的单元与梁-柱单元相结合，并在压缩加筋板的崩溃行为准确地模拟。将这些单元应用于船体梁的倒塌分析仍是未来的任务.分析了各种设计因素对船体梁极限强度的敏感性。利用这些敏感性，对四艘现有船舶进行了可靠性分析。得出的结论是，这些船只是足够安全的，不会发生船体梁断裂。建议根据设计阶段的不同，采用不同的方法对船体梁极限强度进行评估。在详细分析中，推荐了采用精确推导出加筋板单元平均应力-平均应变关系的Smith方法作为船体梁极限强度的最佳计算方法。少

1. The best modelling method of stiffener in the stiffened plating under thrust was investigated. It was found that the stiffener web should be modelled by a plate whereas stiffener flange should be modelled by a beam-column to obtain accurate results efficiently when the collapse behaviour of cotinuous stiffened plating is analysed either by the analytical method or the FEM.2. To investigate the collapse behaviour and strength of bottom structure, a simple but effective method was developed which enables to simulate the collapse behaviour of stiffened plating subjected to combined lateral pressure and thrust loads. The rationality of this method was confirmed by comparing the calculated results by this method with those by the FEM analysis. This method was implemented into the computer code to simulate progressive collpse behaviour of a ship hull girder subjected to longitudinal bending. It was confirmed that the influence of lateral pressure on ship bottom and side shell plating on t … More he ultimate hull girder strength is rather small.3. Performing a series of elastoplastic large deflection analysis by the FEM, progressive collapse behaviour of a bilge circle was simulated and investigated. On the basis of the calculated results, a simple dynamical model was developed to simulate collapse behaviour of bilge circle. This model was implemented into the computer code to simulate progressive collapse behaviour of a ship hull girder subjected to longitudinal bending. It was confirmed that the ultimate hull girder strength is almost the same but the capacity beyond the ultimate hull girder strength is a little different when the buckling effect of a bolge circle is accounted.4. New method was developed to account for the influence of warping of the cross-section produced by shear force on the progressive collapse behaviour and the ultimate hull girder strength. It was found that the ultimate hull girder strength is reduced by 15% at maximum when the normal stress by warping becomes compressive at the compression side of the hull girder bending.5. The plate ISUM (Idealised Structural Unit Method) element was newly developed which enables to perform collapse analysis of a ship hull girder subjected to longitudinal bending. In this research project, collapse analysis was not yet performed. However, this new element was combined with beam-column elements and the collapse behaviour of a stiffened plate in compression was accurately simulated. The application of this elements to hull girder collapse analysis remains as a future task.6. Sensitivities of various design factors on the ultimate hull girder strength were evaluated. Using these sensitivities, reliability analysis was performed on four existing vessels. It was concluded that these vessels are safe enough against breaking of their hull girder.7. It can be recommended that different method should be applied according to the stage of design to evaluate the ultimate hull girder strength. For the detailed analysis, the Smith's method using accuately derived average stress-average strain relationships of stiffened plate element was recommended as the best method to evaluate ultimate hull girder strength of a ship hull girder. Less