Effective arrangement of transverse strucrtural members of car carriers in preventing excessive racking deformation

滚转船的横舱壁设置了宽大的开口，以保持甲板上的良好通道，在最近的设计中进一步追求消除舷梁干舷甲板上部的横舱壁。由于其横截面是非常弱的加强，他们经常表现出显著的剪切变形所谓的机架由于不对称载荷相对于船体梁的中心线。我们首先考虑横向部分舱壁和强腹板框架的影响，它们与主船体梁的相对刚度以无量纲形式定义。利用这些相对刚度，我们提出了一个简单的公式来预测在安装舱壁或强腹板框架的部分的货架变形。预测结果与数值计算结果吻合较好。然后分别考虑横向框架的弯曲刚度和壳板厚度的影响。然后通过数值计算考察了舱壁/强腹板框架和横向框架/壳板的联合效应。结果表明，在某些情况下，复合作用可使货架变形减小10- 20%。最后对两种实际的汽车运输车进行了案例分析，这两种汽车运输车具有本质上不同的结构配置；一个有部分舱壁，另一个有坚固的网架。所提出的简单方法计算的船壳变形与复杂三维船体梁的分析结果基本一致。

Wide openings have been arranged in the transverse bulkheads of roll on/roll off ships in order to keep good behicles access on decks, which is further pursued in recent design by eliminating the transverse bulkheads in the upper part of the freeboard deck of a hull girder. Since its transverse sections are very weakly stiffened, they often exhibit significant shearing deformation so-called racking due to asymmetric loads with respect to the center line of the hull girder.We first consider the effects of transverse partial bulkheads and strong web frames, whose relative rigidities to the main hull girder are defined in a non-dimensional form. Using these relative rigidities, we propose a simple formula to predict the racking deformation at the sections where the bulkheads or strong web frames are installed. The predicted values are found to be in good agreement with the numerical calculations.Considerations are then made for the effects of the flexural rigidities of the transverse frames and the thickness of the shell platings, respectively. Then the combined effects of the bulkheads/strong web frames and transverse frames/shell platings are examined by numerical calculations. It is found that in some cases the combined effects may reduce the racking deformation 10-20 percents.Finally case studies are made for two actual car carriers, which have essentially different structural configurations; the one has partial bulkheads and the other has strong web frames. The racking deformation estimated by the proposed simple method is in conformity with the results ob<ained by the complex three-dimensional hull girder analysis.