Ultimate Hull Girder Strength under Longitudinal Bending

1. 推导了考虑板与加劲板相互作用的连续加筋板在双轴推力作用下的局部屈曲强度计算公式。推导了连续加筋板在推力作用下的极限强度计算公式。阐明了横向推力和侧向压力对加筋和不加筋连续板屈曲强度和极限强度的影响，推导了屈曲强度和极限强度的计算公式。并将其应用于基于Smith方法的渐进式倒塌分析方法中。当局部板伴有饿马型初始挠曲时，挠曲和塑性变形集中在板的某一部分，而在板的其余部分发生弹性卸载。提出了一种理想结构单元法（ISUM）的板单元，可以准确地模拟这种行为。并将该单元与可模拟双轴弯扭屈曲行为的薄壁梁柱单元结合，应用于连续加筋板在双轴推力作用下的破坏分析。结果表明，该单元对船体梁在纵向弯曲作用下的倒塌分析是有效的。制作了1/10钢板焊接载体模型，并对其进行了下垂状态下的坍塌试验。结果发现，甲板和侧壳板上部的屈曲坍塌成为船体大梁整体坍塌的触发因素。对180块不同板宽高比、板厚、加筋类型和加筋尺寸组合的加筋板进行了基准计算。考虑了有和无焊接残余应力两种情况。采用了10种不同的方法。得出的结论是，计算结果会发生散射，这取决于各个计算方法中的条件和假设。在4艘现有舰船和1/3比例焊接钢护卫舰模型上进行基准计算，采用8种不同的方法评估最终纵向强度。结果表明，该计算方法能较好地模拟钢筋结构在局部挠曲、塑性变形及加劲肋脱扣等情况下的实际破坏行为。采用精确推导的加筋板单元平均应力-平均应变关系的史密斯法是评估船体梁纵向极限强度的最佳方法。少

1. Analytical formulation is derived to evaluate local buckling strength of continuous stiffened plate subjected to bi-axial thrust considering the interactions between panel and stiffener. Analytical formulation is also derived to evaluate the ultimate strength of continuous stiffened plate under thrust.2. The influences of transverse thrust and lateral pressure on buckling strength and ultimate strength of continuous plate with and without stiffeners are clarified, and the formulas to evaluate buckling/ultimate strength are derived. These are implemented into the method of progressive collapse analysis based on the Smith's method.3. In case of local panel accompanied by initial deflection of a hungry-horse mode, deflection and plastic deformation are localised at a certain part of the plate while elastic unloading takes place in the remaining part of the plate. A plate element of the Idealized Structural Unit Method (ISUM) is developed which can simulate such behavior accurately.4. T … More his ISUM element is combined with a thin-walled beam-column element which can simulate bi-axial flexural-torsional buckling behaviour, and is applied for the collapse analysis of a continuous stiffened plate subjected to bi-axial thrust. It is demonstrated that this element shall be effective for the collapse analysis of a hull girder under loingitudinal bending.5. 1/10-th welded steel scale models of a Chip Carrier are fabricated and the collapse tests are conducted on these models under the sagging condition. It is found that the buckling collapse of the deck and the upper part of the side shell plating become the trigger of the overall collapse of the hull girder.6. Benchmark calculation is performed on 180 stiffened plates with different combination of panel aspect ratio, panel thickness, type of stiffener and size of stiffeners. Two cases are considered with and without welding residual stress. 10 different methods are applied. It has been concluded that scatter takes place in the calculated results depending on the conditions and assumptions in the individual calculation methods.7. Benchmark calculation is performed on 4 existing vessels and a 1/3-scale welded steel frigate model to evaluate ultimate longitudinal strength applying 8 different methods. It has been concluded that the calculation method which can simulate the actual collapse behavior accompanied by localisation of deflection and plastic deformation as well as tripping of stiffeners.8. The Smith's method using accuately derived average stress-average strain relationships of stiffened plate element is recommended as the best method to evaluate ultimate longitudinal strength of a ship hull girder. Less