【作者】 何力；

【导师】 程远胜；

【作者基本信息】 华中科技大学 ， 船舶与海洋结构物设计制造， 2011， 博士

【摘要】 ‘结构动力优化设计是当前工程结构设计研究领域中的前沿性课题之一,是诸多学科相互交叉、有机结合的产物,开展对它的研究具有着重要的理论意义与实用价值。对船舶板架结构进行动力优化设计,可以改善结构和相关设备在外载荷作用下的动态特性,减小结构振动,降低结构上的动位移与动应力,避免结构产生失效破坏,确保它们能够安全可靠地工作。本文以船舶板架结构为研究对象,考虑多种优化约束条件和实际工程需要,对其进行了动力特性优化与动力响应优化。另外,针对在船舶结构上应用越来越广泛的金属夹层结构,提出了一种新的强度分析理论研究方法,在此基础上,对波纹夹层板架结构进行了有效的动力优化设计。主要研究工作包括：(1)在船舶板架结构动力特性优化中,提出了将板架结构布局参数转化成子结构的长度参数的结构布局转化新方法,该方法具有较好的通用性,可以有效地计算结构固有频率对相关结构布局参数的灵敏度,并在优化迭代过程中引入了结构重分析算法以降低灵敏度分析的计算量。通过应用改进的共轭梯度优化算法,在板架结构动力优化中直接求出了满足相应约束条件的离散最优解。(2)提出了一种基于板架动力刚度法与离散方案库的船舶板架结构减振优化设计方法。通过将板架动力刚度法与等效静力算法相融合,能够快速计算出带有机械隔振装置的板架结构在动载荷作用下的动应力分布。建立了满足构件剖面尺寸搭配关系要求的构件尺寸离散方案库,可以在优化中直接得到满足实际工程需要的结构参数离散值。(3)针对金属夹层结构,提出了一种基于整体位移场与局部位移场叠加的夹层板结构理论分析新方法,可以在考虑结构几何特征的前提下以较高的精度和计算效率对夹层板结构的强度、总体稳定性与自由振动特性进行计算分析。计算实例表明：本文方法能够对结构的应力分布作出有效预测,避免了繁琐的有限元建模与分析,大大提高了运算效率,为对结构进行动力优化设计打下了良好基础。(4)对波纹夹层板架结构的强度、总体稳定性与自由振动特性进行了分析研究,另外,使用序列二次规划算法对波纹夹层板架结构进行了动力特性优化设计。在对波纹夹层板架结构的力学特性分析中,通过对比验证了夹层板架结构形式相对于传统板架结构的优势,还讨论了相关参数对波纹夹层板架结构力学特性的影响。本文在提出新的灵敏度分析方法的基础上,对船舶板架结构进行了快速有效的动力优化设计。针对金属波纹夹层结构,本文也对其进行了相应理论分析与动力优化设计。本文的工作为结构动力优化设计提供了新的研究思路和途径,对今后的理论研究和工程设计具有一定的参考价值。更多还原

【Abstract】 Structural dynamic optimization is an advanced subject in the field of engineering structure design at present, concerned with many different subjects. The dynamic optimization researches have important theoretical significance and practical value. The vibration of marine structures could be reduced by optimizing the dynamic characteristics of these structures. And the dynamic displacement and stress can also be decreased. Dynamic optimum design of structures is an effective method to improve the dynamic capability and ensure it working safety and reliably.This study investigates the dynamic characteristics and response optimization of ship grillage under several constraints considering practical engineering requirements. Besides, according to the metal sandwich structures which have been widely used in marine engineering, a new theoretical method has been proposed in the thesis. Based on this method, an effective dynamic optimum design of corrugated-core grillages has been carried out. The main works presented in the thesis are as follows:(1) In the dynamic characteristics optimization of ship grillage, a novel method is proposed to ingeniously transform the structural layout parameters into substructure length parameters, while the sensitivity of natural frequency to structural layout parameters can be obtained through the sensitivity of element stiffness matrix and mass matrix with respect to length parameters. Besides, the structural reanalysis algorithm is introduced into the process of optimization iteration to reduce the calculation burden. By using this new frequency analysis method and the improved conjugate gradient method, the discrete optimal solutions which satisfy the constraint conditions could be obtained easily.(2) A structural dynamic optimization method which based on the grillage dynamic stiffness (GDS) algorithm and discrete scheme database has been presented. And the equivalent static load method together with the GDS algorithm is further used to obtain dynamic displacement and stress distributions of the grillage system with isolators. With the help of which, good calculation accuracy and higher calculation efficiency are reached compared with the traditional FEM method. A scheme database which consists of all possible T-shape girder design schemes satisfying section design requirements is built and further used to get an optimal grillage design scheme meeting the practical engineering requirements.(3) Aiming at the metal sandwich structures, this thesis presents a novel semi-analytical method based on the superposition of the global displacement field and local displacement field. The discrete geometric nature of the sandwich structures has been taken into account and the bending, global buckling, and free vibration characteristics have been calculated quickly and efficiently. Results from the proposed method agree well with those from detailed finite element analysis and the structural stress fluctuation can be captured with sufficient accuracy. This method lays a good foundation for the dynamic optimization of metal sandwich structures and can be extended to sandwich structures with other kind of cores.(4) The bending, global buckling, and free vibration properties of corrugated-core grillage are analyzed and the structural dynamic characteristics have been optimized using the sequential quadratic programming algorithm. The advantage of the sandwich structures contrasted with the solid plates has been validated by the comparison of the mechanical characteristics of these structures. The effects of some geometrical parameters of the corrugated-core grillage on the mechanical properties are also discussed in the analysis.In this thesis, some novel theoretical methods are proposed and the dynamic optimization of ship grillage structures is carried out efficiently by utilizing these methods. These methods and research findings can be employed to supply new ideas and approaches for improvement of structural dynamic optimization and have reference value for the further research and engineering design.更多还原