【作者】 李火坤；

【导师】 练继建；

【作者基本信息】 天津大学 ， 水利水电工程， 2008， 博士

【摘要】 随着水利水电工程高水头、大流量泄水建筑物的大量兴建及工程结构趋于轻型化,水流诱发振动问题会更加突出。研究水流诱发结构振动的机理,泄流结构耦合动力分析的模拟、预测分析方法,泄流结构优化设计方法和安全动态检测方法等,是泄流结构设计和安全运行的重要课题。本文主要开展以下三个方面的研究:(一)泄流结构耦合动力分析的模拟与预测方法研究。本文成功地实现了从传统的单一水动力效应分析方式到水动力-结构体系多效应耦合分析方式的跨越。(1)在前人研究水流脉动压力频谱相似律符合重力律的基础上,以弧形闸门为例,综合考虑整个闸门体系耦合作用及闸门的水动力特性,首次全面地用物理模型仿真模拟了水力系统-弧形闸门结构(系统)-支撑结构(闸墩、启闭杆)整个体系的耦联振动问题;并采用充分反映闸门薄板空间结构特点板壳单元模拟预测闸门空间体系结构的耦合动力特性。(2)提出了弧形闸门支臂在偏心荷载作用下的动力稳定性理论研究方法,研究了偏心动力荷载对弧形闸门支臂动力稳定性的影响。(3)综合物模、数模、动力稳定性分析的研究成果分析了闸门的动力安全性,提出了避免弧形闸门强烈振动的措施。(二)泄流结构耦合动力优化设计方法研究。本文提出基于耦合动力安全的泄流结构动力优化设计方法。(1)首次提出了考虑导墙结构耦合动力安全为控制指标的结构优化设计方法,提出了导墙断面结构优化数学模型;在考虑导墙结构耦合动力安全约束条件的基础上,同时考虑导墙结构的几何条件、静力强度和稳定性的约束,将静力分析、耦合动力分析与支持向量机技术相结合对导墙结构断面形式的优劣进行智能评估;采用遗传算法实数编码,利用随机方式产生初始导墙断面种群群体进行优化计算,在保证导墙结构满足静、动力安全的前提下,实现导墙断面型式的最优化。(2)首次提出了考虑弧形闸门支臂静、动力稳定性的弧形闸门优化设计方法,提出了弧形闸门主框架优化数学模型;在同时考虑闸门的几何约束、静力强度、刚度约束、静动力稳定性约束的基础上对弧形闸门主框架进行动力优化设计,在保证静动力安全的前提下节省了工程投资。(三)基于泄流激励的泄流结构动力检测与工作性态识别研究。针对原型动力试验激励难的问题,本文结合水工结构在工作状态下环境激励荷载的特点,直接根据水工结构在工作环境激励荷载作用下的动力响应识别结构的动力特性。(1)首次提出一种利用特征矩阵奇异熵对信号进行降噪、重构、定阶以及模态参数识别ERA方法,解决了定阶和降噪难的问题,揭示了结构在工作状态下的模态阶次及模态特性。(2)针对频域分解法中的奇异值曲线峰值(谱密度函数峰值)选取的主观性及其精度取决于计算功率谱密度函数时傅立叶变换精度的影响,根据泄流激励的特点,提出通过定义模态一致性函数的方法,比较准确地确定了奇异值曲线的峰值,解决所拾取峰值是结构真实模态频率还是噪声引起的虚假模态频率(如水流噪声模态频率)的问题,并同时确定该阶模态起主要作用的优势频域带宽,提高了阻尼比的计算精度。(3)首次对二滩拱坝、三峡溢流坝及其左导墙、李家峡双排机厂房进行了大规模全面的正常运行状态下(如汛期泄洪工作状态)的原型振动测试,并将本文提出的基于泄流激励的模态参数识别理论方法首次应用到上述大型水工结构的原型工作模态参数识别,对其正常运行工作性态进行了评估。更多还原

【Abstract】 With the large number of high-head and large discharge flood discharge structures construction and the trend of lightweight of flood discharge structures, the problem of flow-induced vibration will become prominent. It is an important subject for flood discharge structures design and safe operation to study on flow-induced vibration mechanism, simulation and prediction methods of coupled dynamic analysis of flood discharge structure, optimum design and safety dynamic detection methods of flood discharge structures. In the paper, the following three main areas are studed:Firstly, the study on simulation and prediction methods of coupled dynamics analysis of flood discharge structure. The paper has succeeded in achieving coupled dynamic analysis from traditional analysis mode with single hydrodynamic effect considered to coupled analysis mode with hydrodynamic-structure system coupled effect considered. (1) Based on the study on that the similarity law of fluctuating pressure spectrum agrees with the gravity law, taking radial gate as an example, the paper consider the effect of the system coupling of the whole gate and the hydrodynamic characteristic of gate. This whole coupling system vibration of hydraulic system—structure system of gate—prop system (pier, start and stop lever) is simulated using physical model for the first time, and then a 3D space FEM mathematical model using three-dimensional shell element is set up and its dynamic characteristic is analyzed. (2) The dynamic-stability analysis method of the radial gate arm under eccentric loading is produced, and the influences of the dynamic-stability of radial gate arm under eccentric loading are also studied. (3) Finally, associated with physical, numerical model and dynamic stability analysis, the dynamic safety of the gate was analyzed, and several suggestions and proposal that avoid adverse vibration are presented.Secondly, study on coupled dynamic optimization design methods of flood discharge structures. The paper produces the coupled dynamic optimization design methods of flood discharge structures. (1) Considering the coupled dynamic safety index of guide wall, the paper propose the guide wall structure optimization design method and put forward the section optimization mathematic model of guide wall. Based on the consideration of coupled dynamic safety constraint condition, the geometrical condition, static strength, stability constraint are also taken into account, and the static analysis, couple dynamic analysis and Support Vector Machine(SVM) technique are combined to evaluate the quality of guide wall section intelligently. Employing real encode of GA and generating initial population groups of guide wall sections randomly, the guide wall section is optimized on the condition of that the guide wall structure meet the specification of static and dynamic safety. (3) Considering the static restriction and the dynamic stability of the arms of radial gate, the paper propose the optimization design method and optimization mathematic model of main frame of radial gate. The main frame of radial gate is optimized on the basis of considering geometrical constraint condition, static strength, rigidity constraint, static and dynamic stability constraint. The result shows that the weight of the gate is lightened with the guarantee of the static and dynamic stability of the arms and saves the investment of the project.Thirdly, study on dynamic detection and working state characteristic identification of flood discharge structures under flood discharge excitation. Aimed at the difficult problem of exciting the prototype to test, combined with the ambient loading characteristic, the dynamic characteristic of hydraulic structure is directly identified according to the dynamic response of structure under ambient excitation in the paper. (1) We propose a method in the paper to denoise, reconstruct, determine the order and identify modal parameters based on singular entropy of eigenmatrix. It can be used to solve the problem of system eigenmatrix order determination, and to identify the modal order and the characteristics of structures under the working state. (2) The subjective selection and accuracy of singular value curve peak (spectral density function peak) depend on the accuracy of the calculation of power spectral density function in process of Fourier transform. In order to solve this problem, modal coherence function is put forward in the paper to identify the singular value curve peak accurately. This method solve the problem of modal frequency peaking which is likely to be false modal frequency caused by noise (such as flow frequency) or structural modal frequency, and identify the dominate frequency domain of one mode, improve the accuracy of damping ratio calculation. (3) A large-scale comprehensive prototype vibration tests against Ertan arch dam, Spillway dam and Left guide wall of Three Gorges, Powerhouse with a two-row placed unit of Lijiaxia hydropower station are primarily carried out during the working state (e.g. Flood spillway working state in flood season). And the modal parameter identification theory under flood discharge excitation proposed in the paper is primarily applied to the operational modal parameter identification of these large-scale prototype hydraulic structures, and the normal operational behaviors of these hydraulic structures are evaluated.更多还原