摘要
水利工程弧形钢闸门,主要用于水库的控制泄洪,是保证大坝安全的最重要建筑物之一。工程实践证明,闸门在动水启闭过程及在某些局部开启运行时由于水流的作用,都有不同程度的振动。在一些特定条件下,某些闸门曾产生较强烈的振动,少数闸门曾产生共振和动力失稳现象。研究闸门流激振动机理,探讨闸门振动规律,给出控制判据,对指导钢结构闸门设计是具有非常重要的意义。目前,由于闸门的结构复杂,水流动力作用与闸门振动的关系尚未完全摸清,国内外对闸门振动的研究仍属初步阶段,现行规范采用动力系数法,暂规定同一动力系数取值范围,根据水流条件、闸门型式选取,近似考虑振动的影响。
本论文的主体是研究辽宁省石佛寺水库低水头水工弧形钢结构闸门流激振动问题,有部分内容从工程预报的需求,作了一定延拓,属学术讨论。论文综述了水工弧形钢闸门以往的研究工作,从振源,振动机制,数值模拟预报,物理模型预报,原型观测五个方面叙述了闸门流激振动研究历史与发展。论文结合石佛寺水库弧形钢闸门设计,探讨弧形钢闸门振动机理和特性,分别研究弧形钢闸门的自由振动与受迫振动,自激振动和参数共振,给出定量分析方法和结果,本文主要研究内容包括:
1,预报石佛寺弧形闸门在水流脉动荷载作用下的强迫振动特性(EIE)。选用的技术路线为:用只满足重力相似律的水力模型同步纪录闸门面板上若干个面脉动压力传感器上的水流脉动荷载,然后再用大型结构计算软件确定闸门的动力响应。面脉动压力传感器的承压面面积和结构动力计算时的闸门面板有限元分割相应。因此迫振预报包括两部分内容:一是面脉动压力测定,二是结构动力计算。
2,为了方便设计人员初步判断所设计的弧形闸门的动力特性,采用瑞利法,给出不同开度下弧门切向、径向、侧向三个自振频率的简单计算公式。利用这些公式,给出弧门设计的一个指标,如能满足这个指标,那么弧形闸门不会产生显著的强迫振动。
3,利用关于弧形闸门水力负阻尼和计及阻尼时压杆参数共振的已有研究成果,以及联合考虑水力负阻尼与参数共振,讨论了弧形闸门在三种典型工况下支臂动力失稳的可能性及防止动力失稳应采取的措施。
本文创新性的工作内容包括:
1、本文所采用的闸门流激振动预报方法是国内外第一次使用。这种预报方法的概念在半个世纪前已经提出。但本论文摒弃了传统的水流点脉动压力测量而代之以与结构有限元计算闸门面板单元分割一致的相似面积作为承压面,同步测量面脉动荷载,
A hydraulic tainter gate is mainly used for controlling flood and is one of the most important structures for dam safety. The engineering projects show that tainter gates have vibration of different degree caused by water flow action during gate operation in dynamic water or gate partial opening. In some specific conditions, some gates had stronger vibration, and few ones had resonance and hydraulic instability. It is of great signification for instructing tainter gate design to study mechanism of gate flow-induced vibration, discuss rule of gate vibration and give out controlling criteria. At present, as to gate complex structure, the relationship between water flow dynamic action and gate vibration has not been known clearly, it is still in primary stage for gate vibration study in the world. In China, the prevailing standard adopts dynamic coefficient method and defines dynamic coefficient by water flow condition and gate type. It is an approximate method for considering vibration effect.
The purpose of the paper is to study flow-induced vibration of low head hydraulic tainter gate of Shifoshi Reservoir, Liaoning Province. To meet the requirement of engineering forecast, some parts of the paper is extended, belonged to academic discussion. The paper summarizes the past research on hydraulic tainter gate, states the research history and development of gate flow-induced vibration from the aspects of vibration source, vibration mechanism, numerical simulation forecast, physical model forecast and prototype observation. Combining tainter gate design of Shifoshi Reservoir, the paper goes into the vibration mechanism and property of tainter gate, studies free vibration and forced vibration, self-induced vibration and paramgtric resonance respectively, and gives out quantitative analysis methods and results. The main research contents of the paper include:
1. To forecast the forced vibration property of tainter gate under the action of water flow pulsating loads. The selected technical route is: to record synchronously the water flow pulsating loads acted on facial pulsating pressure sensors (FPPS) on tainter gate face plate with a hydraulic model only meeting the law of gravity similitude, and then to determine gate dynamic response with structural analysis software. The pressure-bearing faces of FPPS correspond to the elements of gate face plate FEM structural dynamic calculation. Thus, forced vibration forecast includes face pulsating pressure measurement and structural
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