A simplified method to predict grounding damage of double bottom tankers

This paper presents a set of analytical expressions for the calculation of damage opening sizes in tanker groundings. The simplified formulas were given for the grounding force, longitudinal structural damage and the opening width in the inner and outer plating of a tanker's double bottom. The simplified formulas derived are based on a set of numerical simulations conducted with tankers of different dimensions- 120, 190 and 260 m in length. The simulations were performed for five penetration depths and for several rock/ground topologies.The formula for the horizontal grounding force was derived provided the grounding force is proportional to the contact area and the contact pressure. By use of regression analysis it was shown that the contact pressure for any combination of ship and rock size can be expressed with a single normalized polynomial. The actual contact pressure was found by scaling the normalized pressure with the structural resistance coefficient. Given the formulation for the normalized contact pressure, the actual contact force for a ship can be found as a product of average contact pressure and the contact area.The longitudinal length of the damage was evaluated based on the average contact force and the kinetic energy of the ship. The damage opening widths in the outer and inner bottom of the ship were derived separately for two ranges of relative rock sizes as they have strong influence on the deformation mode. The damage widths were given as a function of rock size, penetration depth and double bottom height. To improve the prediction of the onset of the inner bottom failure, a critical relative penetration depth as a function of the ratio of the rock size and the ship breadth was established.Comparison to the numerical simulations showed that the derived simplified approach describes the horizontal grounding force and the damage length well for the penetration depths above 0.5 m. For the range of specified relative rock sizes, the damage width in the inner and outer bottom deviates from numerical simulations approximately up to 25%, which was considered sufficient for the analyses where rapid damage assessment is needed. Comparison was also made to real accidental damage data and to the results of several simplified formulas.     

九段沙北侧输沙对长江口深水航道的影响

为了研究南汇边滩促淤圈围工程对长江口九段沙滩面输沙和南导堤越堤水沙运动带来的影响,在长江口整体潮 流河工模型上,采用定床输沙物理模型试验方法,研究了九段沙沿程滩面泥沙起动后的跨槽越堤输移,根据底沙在北槽的 分布分析了促淤圈围工程对北槽航道的影响。研究表明：无论有无圈围工程,九段沙的底沙均能够越堤进入长江口深水航 道,但促淤工程使九段沙头部进入北槽航道的泥沙略有减少,九段沙中部进入北槽航道的泥沙略有增加。     

抗水下爆炸载荷的新型船舶结构形式研究

以吸能原理为理论依据,提出船舶双层底的四种新型抗爆结构形式,建立传统形式和四种新型结构形式的有限元模型.利用MSC.Dytran软件进行数值仿真,获得在相同水下爆炸载荷下五种结构形式的吸能性能、内底板最大变形量、典型部位加速度,并分析比较了五种结构的抗爆性能,从中获得较优的结构形式.     

加肋轴对称组合壳稳定性的一个特殊问题——肋间壳板"诱导"失稳

文章对凹型加肋锥-环-柱结合壳稳定性进行了模型试验研究,观察到凹环壳段失稳的一个特殊现象.通过对这一特殊现象的深入分析,作者提出肋间壳板"诱导"失稳的概念,并对"诱导"失稳产生的条件及其特性进行了探索.     

上海片内非通航河道跨河桥梁梁底高程研究

上海地处太湖流域下游,地区河网密集,地势低洼,跨河桥梁数量众多。由于上海地区地势低洼,桥梁工程梁底高程控制往往与桥梁接坡之间存在较大的矛盾。通过综合分析片内非通航河道行洪安全、规划堤顶高程、作业船舶通行等方面的需求,根据河道等级提出桥梁梁底高程优化取值建议。以长宁区为例,分析该区桥梁梁底高程合理取值范围,为区域桥梁梁底高程控制提供一定参考。     

厦门某码头附近海底滑坡分析与治理

在沿海地区由于受到人类活动以及环境条件的改变、自然灾害等因素的影响，常会有诸如海岸崩塌、海工建筑物倒塌、护岸滑坡等地质灾害的发生。通过厦门某码头附近海底滑坡事故的经验，对该滑坡的内在原因、诱发原因、危害性和整治的必要性进行了分析和研究，并对其整治方案进行了探讨。     

平整度对水泥砼路面疲劳寿命的影响分析

通过现场试验,分析了在车板相互作用下水泥砼路面板底动应变与路面平整度、车速之间的关系.在此基础上,进一步分析了路面板底应力与疲劳寿命的关系,认为平整度是水泥砼路面疲劳破坏的重要影响因素之一,为水泥砼路面设计理论和方法提供依据.     

斜抛撑与水平撑在深基坑支护中控制变形的对比分析

在目前的实际工程应用中,深大基坑的开挖支护内支撑体系主要有水平撑和斜抛撑两种形式。为此,对支撑桩加承台的斜抛撑形式通过大型通用有限元软件ABAQUS对其在深大基坑中的应用进行模拟,并与水平撑在深大基坑中的数值模拟结果进行对比分析。通过比较两种不同的内支撑体系对开挖深大基坑的基坑外地表面土体沉降、基坑底部土体隆起及围护桩的水平位移不同变化情况,得出支撑桩加承台的斜抛撑支护体系在控制围护桩水平位移和基坑外地表面土体沉降的优点及控制效果。     

82000dwt散货船底部纵骨节点疲劳分析优化

自从散货船共同规范(2006)颁布后,极大地提高了船舶设计的安全度,对于船舶结构的疲劳计算如何在满足CSR疲劳寿命要求的前提下,有效可行的优化是讨论热点。通过对几种不同的散货船底部纵骨节点进行疲劳分析比较,证明了一些可行的优化方案,并提出了对于这些节点在简化计算法中可参照使用的系数。经节点优化及采用有限元直接计算证明,散货船底部纵骨取消背部肘板,仍能保证疲劳寿命,对船厂节约成本有重大意义。