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空间框架式机墩具有结构简单、施工方便、利于机组安装和检修等优点,因而在中、小水电站得到普遍采用。对该结构的动力特性研究就更具有工程实际意义。该项试验研究是陕西省新庄水电站“机墩原型动力分析与试验研究”的组成部分。模型是原型的三分之一,模型Ⅰ采取机墩顶部自由方案,模型Ⅱ是机墩顶部加有电站厂房主梁的约束方案(实际上还有厂房楼板及风道壁的约束),这部分约束对机墩动力特性的影响目前均被许多设计和工程单位所忽略。通过对模型Ⅰ、Ⅱ的振动计算与动力试验,本文经过分析比较。得出忽略机墩顶部约束对机墩动力特性判据的定量差异。理论与试验结果均证明:机墩顶部约束不能忽略。众所周知,在水力发电工程中,如果对机墩结构各阶共振区判断错误,则将给水电站的安全运行带来不可设想的后果。模型试验是采用共振峰值法测试了机墩结构的前四阶自振频率,又分别进行了垂直水流脉动压力,水平离心惯性力、两相和三相短路电磁冲击扭矩作用时机墩结构的动力响应试验、得出了各种干挠力作用下机墩结构各测点的位移历程响应及其位移最大值。每阶段振动试验前,均对所用测振仪和传感器进行了系统配套标定,试验时仍按原仪器的配套编号测振,因此,振动试验数据是可信的。本文振动计算,是按空间有限元法进行,分别以空间梁单元和三维块体单元对机墩模型Ⅰ、Ⅱ的前十阶自振频率和动力响应均作了电算,采用SAP-5动力程序,在7760电子计算机(三机部六三一所)进行,并对计算成果作了分析讨论。本文的试验,计算成果与分析讨论,可供水力发电工程的设计与施工单位参考。
The space-frame machine piers have the advantages of simple structure, convenient construction, favorable installation and maintenance of the units, etc., and are therefore widely used in medium and small hydropower stations. The dynamic characteristics of the structure of the more practical engineering significance. This experimental study is an integral part of the “prototype analysis and experimental study of pier” at Xinzhuang Hydropower Station in Shaanxi Province. The model is one-third of the prototype. Model I adopts the free-top plan of machine piers. Model II is the restraint plan (in fact, the constraints of plant floor and duct walls) at the top of machine piers plus the power plant girder. This part The impact of the constraints on the dynamic characteristics of the pier is currently overlooked by many design and engineering units. Through the model I, II vibration calculation and dynamic test, this paper through analysis and comparison. The quantitative difference of the criterion of dynamic characteristics of pier is neglected. Both theory and test results prove that the top constraint of pier can not be neglected. As we all know, in the hydropower project, if the machine pier structure at all levels of resonance to determine the error, it will give the safe operation of hydropower stations with unintended consequences. In the model test, the first four natural frequencies of the pier structure were tested by the resonance peak method. The dynamic response of the pier structure with vertical flow pulsating pressure, horizontal centrifugal inertial force, two-phase and three-phase short-circuit electromagnetic impact torque The displacement history response and the maximum displacement of each measuring point under the influence of various dry and bending forces are obtained. Vibration test before each stage, are used on the vibrometer and sensor system calibration, the test is still based on the number of the original instrument vibration test, therefore, the vibration test data is credible. The vibration calculation in this paper is based on the spatial finite element method. Calculating the first ten natural frequencies and dynamic responses of the pier models I and II with space beam elements and three-dimensional block elements, respectively, using SAP-5 power Program, in the 7760 computer (three three six one three), and calculated the results were analyzed and discussed. This paper’s experiments, calculation results and analysis of discussion, for hydraulic power engineering design and construction unit reference.