环境激励下二滩拱坝拍振机理的研究
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摘要
在二滩拱坝泄洪振动时程曲线中,可以看到波形的包络线随时间增大或减小的现象,波形非常像振动中的"拍"现象。通过对原型观测数据的分析,研究二滩拱坝拍振机理。首先引入自然界中"拍"的概念,论述了初相差、频率比和振幅比对"拍"的影响以及多列波合成拍的特性;然后应用随机子空间方法(SSI)和频谱分析方法,对二滩拱坝的模态参数进行识别;最后结合实测拍振现象的自身特点,对泄洪激励下二滩拱坝拍振现象的机理进行研究。结果表明,拱坝工作频率相近的前两阶振型振动是形成拍振的主要原因,此外,一个频带在1.27～1.39Hz的振动分量也参与了拍的合成,初步认为这一分量是由坝段间接触非线性引起的。
On the vibration time history curve of Ertan arch dam under flood discharge excitation,the phenomenon that the wave envelope rises or reduces along with the time can be observed.The effects caused by initial phase difference,frequency ratio and amplitude ratio were discussed.The dominant frequency of measured data was collected and analyzed with the auto regressive model,and the first four vibration modes were obtained based on SSI.Considering the special features of beat vibrations,the beat vibration of Ertan arch dam under discharge flow was investigated.The result shows that the main cause forming beat vibration is the first two orders of vibration modes whose frequencies situate closely.In addition,a vibration component with the its frequency band at 1.27 ～1.39Hz also gives rise to forming "beat".The component is considered to be caused by nonlinear contact between dam sections.
On the vibration time history curve of Ertan arch dam under flood discharge excitation,the phenomenon that the wave envelope rises or reduces along with the time can be observed.The effects caused by initial phase difference,frequency ratio and amplitude ratio were discussed.The dominant frequency of measured data was collected and analyzed with the auto regressive model,and the first four vibration modes were obtained based on SSI.Considering the special features of beat vibrations,the beat vibration of Ertan arch dam under discharge flow was investigated.The result shows that the main cause forming beat vibration is the first two orders of vibration modes whose frequencies situate closely.In addition,a vibration component with the its frequency band at 1.27 ～1.39Hz also gives rise to forming "beat".The component is considered to be caused by nonlinear contact between dam sections.
引文
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[2]练继建,杨敏,李火坤,等.高坝泄流工程[M].北京:中国水利水电出版社,2008.
[3]应怀樵.波形和频谱分析与随机数据处理[M].北京:中国铁道出版社,2003.
[4]苏未安,陈秀洪.用旋转矢量法研究“拍”现象[J].江西理工大学学报,2009,30(1):60-63.
[5]周康魂.拍现象与外差变频的区别[J].大学物理,1983,5:1-4.
[6]Peeter B,De Roeck G.Stochastic subspace techniquesapplied to parameter identification of civil engineeringstructures[A].Proceeding of New Advances in ModalYunthesis of Large Structures:Nonlinear,Damped andNondeterministic Cases,Lyon,France,September,1995,151-162.
[7]Peeters B,De Roeck G.Reference-based stochastic subspaceidentification for output-only modal analysis[J].MechanicalSystem and Signal Processing,1999,13(6):855-878.
[8]Chen A l,Zhang L M.Study of stochastic subspace systemidentification method[J].Chinese Journal of Aeronautics,2001,14(4):222-228.
[9]刘昉,练继建,辜晋德.基于自回归模型的水流脉动压力频谱特征研究[J].水力学报,2009,40(11):1397-1402.
[10]胡广书.数字信号处理[M].北京:清华大学出版社,2003.
[11]李成业.基于HHT的二滩拱坝工作性态识别及其“拍振”机理研究[D].天津:天津大学,2010.
[12]晏启祥.有横缝高拱坝的非线性地震响应分析[D].成都:四川大学,2002.
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