摘要
随着海运事业的不断发展、港口功能的日益增强,起重船成为中国船舶市场发展的热点。特别是中大型起重船舶的需求量更是日益增涨。市场的需要和利益的驱使,使用旧船型改装成为新船型也成为一种趋势。
作为工程船舶的起重船有着特殊的作业方式,所以在船体结构和所受载荷方面更为复杂。对于这种复杂的结构形式和载荷分布,传统的结构强度计算方法的弊端已经显现出来。随着计算机硬件技术的发展,使得将整船划分为有限元来进行分析成为可能,船体结构强度分析有了革命性的突破。世界各国的船级社都在不断寻求更科学可靠的设计方法,因此船舶结构强度有限元直接计算方法成为当今船舶设计业的领头羊。有限元直接计算方法是通过有限元软件对整船建立有限元模型。为了真实的表达构件的受力状况,分别以杆、板、壳和梁等单元来模拟不同受力状态的构件。并通过有限元软件分析求解,得到各个构件的实际变形和应力结果。
本文利用有限元软件MSC.Patran和MSC.Nastran对某驳船改装成500t浮吊的改装方案进行研究和优化。吊机吊重采用独立建模计算方法,计算机座处支座反力,再使用多点约束的方法加载到船体甲板相应位置。舷外水压力采用等效设计波的概念处理波浪中垂和波浪中拱工况。调整船体平均吃水来调整船体平衡。并使用“惯性释放”功能使船体模型处于“完全自由”状态。
对于衡量船体结构的安全性而言,对甲板、底板进行屈曲强度分析是十分必要且必须的。按照《钢质内河船船体结构直接计算指南》对该起重船的甲板、底板进行屈曲强度分析,并对强度不足构件进行加强。在船体板格屈曲强度校核方面,CCS中国船级社以Patran为平台开发了板格屈曲强度计算插件。本文利用该插件对船体部分板格再次进行屈曲强度校核,并对两次校核的不同计算结果进行了对比分析。
由于改装船方案直接影响到整个工程的成本和施工方案,所以对船体结构优化也是非常必要的。基于原船体部分不进行大的改动的前提下,本文对新增构件板厚进行了优化。并使整个设计方案更加经济和可行。
With the continuous development of shipping, ports functions of the growing, Floating crane become one focus of China shipbuilding, especially the demand for medium and large tonnage floating crane. Markets driven by the needs and interests have leaded the way to a new trend, the use of the old ship conversions.
As floating cranes are intended for special operations, its hull structure, due to specific loads, are more complicated. For such a complex structure and load distributions, traditional structural strength calculation method has given the way to a new once. With the development of computer hardware and software technology, it's now possible to make a model of whole ship and apply the finite element analysis on such model. Strength analyses of the hull structure have a revolutionary breakthrough. Classification societies around the world are constantly looking for a more scientific and reliable method of design. The direct calculating method of ship structural strength becomes necessary in today's shipbuilding industry. Entire hull finite element model rests on the FEM software. In order to express their real components of the inter-force conditions, respectively, bar, plate, beam, shell, and other units to simulate the different components of the state by force. And calculate through finite element analysis software, among all components of the actual results of the stress deformation.
In this examination, advantage of finite element software MSC.Patran and MSC.Nastran has been taken on the study, and optimization for conversion program of a 500t floating crane barge. The crane hoists have independent models, computer support anti-Block Office, and then use Multi-Point Constraint to load the deck corresponding to the location of the hull. Outboard water pressure equivalent to the concept design waves in the sag and hog conditions. Adjust the average draft of the hull to balance of the hull. The use of "Inertia Relief feature, the structure of the hull can be in a "completely free" status.
On the study of the hull structure security, buckling strength analysis of deck and floor are essential and necessary. In accordance with the FEM model, analyze the buckling intensity of the floating crane's deck and floor and strengthen the weak parts. In the frame of the hull plating buckling strength aspects of verification, CCS (China Classification Society) developed the grid plate buckling strength calculation plug-in based on Patran. In this examination, we use this plug-in for partial plates buckling strength checking of the hull and verification of the two different calculation results were analyzed.
As the ship conversion programs have a direct impact on the entire project cost and construction program, the structural optimization of the hull is very necessary. Based on the inconvertibility of the original parts of the hull, added component thickness have been optimized. It makes the whole design more economic and feasible.
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