大型抽水蓄能电站地下厂房结构振动反应分析

Structural Vibration Response Analysis of Underground Powerhouse of a Large Pumped Storage Power Station

为了解一大型抽水蓄能电站地下厂房结构设计的合理性,通过建立地下厂房三维有限元模型对其厂房整体结构进行自振频率分析和共振复核。采用谐响应分析方法和时程分析方法,分别计算了厂房结构在机组振动荷载作用下、水轮机脉动压力作用下的振动反应,并依据相关规程提出振动控制标准。研究结果表明:厂房结构自振频率为23.736Hz,与尾水管低频涡带、额定转速频率、飞逸转速频率、叶片数频率、导叶后压力脉动频率保持有足够的错开度,基本不存在共振的危险性。振动荷载作用下,厂房机墩结构振幅相对较大,最大振幅发生在左侧定子基础板处,为0.064mm;最大径向动位移为0.011mm,位于上机架基础截面左侧上游基础板内侧;最大切向动位移为0.020mm,位于定子基础截面左侧上游基础板内侧,均满足设计规范控制要求;各部位径向与扭转动位移之和均小于规范规定的标准组合最大振幅值。厂房各部位最大均方根速度和均方根加速度分别为2.369mm·s^-1和0.124m·s^-2,均出现在左侧定子基础板处的竖向,且均小于允许值。厂房结构最大动拉应力出现在左侧上游侧定子基础板处竖向,最大值为1.09MPa,满足钢筋混凝土结构的动强度控制标准。在脉动水压力作用下,厂房各典型部位混凝土结构各方向的振动位移、速度和加速度均较小,满足相关规范要求;部分主要构件的均方根加速度稍微超出建筑结构安全控制标准(1.0m·s^-2),但不会引起结构的损坏(<10m·s^-2)。

In order to understand the rationality of the structure design of underground powerhouse of a large pumped storage power station, a three-dimensional finite element model of underground powerhouse was established to analyze the natural frequencies and check the resonance of the whole structure of the powerhouse. The harmonic response analysis method and the time history analysis method were used to calculate the vibration response of the powerhouse structure under the vibration load of the unit and the fluctuating pressure of the turbine, and the vibration control standard was put forward according to the relevant regulations. The results show that the natural frequency of the powerhouse structure is 23.736Hz, which keeps sufficient staggering degree with the draft tube low frequency vortex band, rated speed frequency, runaway speed frequency, blade number frequency and pressure pulsation frequency behind guide vane, and there is generally no risk of resonance. Under the action of vibration loads, the vibration amplitude of the powerhouse pier structure is relatively larger, and the maximum vibration amplitude occurs at the left stator foundation plate, which is 0.064mm. The maximum radial dynamic displacement is 0.011mm, which is located on the upper left side of the upper frame foundation section and on the inner side of the upper foundation plate. The maximum tangential dynamic displacement is 0.020mm, which is located in the inner side of the upper foundation plate on the left side of the stator foundation section, and meets the control requirements of design specifications. The sum of the radial and torsional dynamic displacements of each part is less than the maximum amplitude value of the standard combination specified in the code. The maximum root-mean-square velocity and root-mean-square acceleration of different parts of the powerhouse are 2.369mm·s^-1 and 0.124m·s^-2, respectively. They all appear in the vertical direction of the left stator foundation plate, and are less than the allowable value. The maximum dynamic tensile stress of the powerhouse structure appears at the vertical direction of stator foundation plate on the upper left side, and the maximum value is 1.09MPa, which meets the dynamic strength control standard of reinforced concrete structure. Under the impact of the pulsating water pressure, the vibration displacement, velocity and acceleration of concrete structures in all directions in typical parts of the powerhouse are small, which meets the requirements of relevant specifications. Though the root-mean-square acceleration of several main components slightly exceeds the safety control standard of building structures (1.0m·s^-2), it will not cause structural damage (<1.0m·s^-2).