圆柱形消化池模态分析简化计算
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摘要
为求解圆柱形消化池在有液状态下的自振频率,并找出不同储液量下消化池自振频率的变化规律,采用大型通用有限元软件ANSYS建立参数化的圆柱形消化池有限元模型,将池内液体在动力作用下产生的动液压力等效为与结构物具有相同加速度的附加质量,并通过对储液罐的对比计算证明此方法的正确性.结果表明,在有液体的状态下,液体的存在会使消化池自振频率降低,且在满池状态下,液体对低阶频率的影响大于对高阶频率的影响.因此,当圆柱形消化池储液量不超过池体容积的一半时,可近似按空池状态计算;当储液量超过池体容积的一半时,需考虑液体振动对消化池振动频率的影响.
In order to calculate the natural frequency of cylindrical sludge digester with liguid and to find out the regularity of natural frequency change with different heights of sewage,the finite element software ANSYS was applied to build the finite element model of a parameterized cylindrical sludge digester. The hydrodynamic pressure caused by the dynamic load of the liquid in sludge was equated with the added-mass that had the same acceleration as the structure. Compared with the result of a liquid storage tank,the method was proved to be correct. Numerical results show that the liquid in the digester decreases the natural frequency,and that when the digester is full of liquid,the effect on the low frequency is stronger than that on the high frequency. Therefore, if the sewage quantity is no more than half of the digester,the frequency can be calculated approximately in terms of an empty digester. If the sewage quantity is more than half of the digester,the effect of the liquid vibration on digester should be taken into consideration.
In order to calculate the natural frequency of cylindrical sludge digester with liguid and to find out the regularity of natural frequency change with different heights of sewage,the finite element software ANSYS was applied to build the finite element model of a parameterized cylindrical sludge digester. The hydrodynamic pressure caused by the dynamic load of the liquid in sludge was equated with the added-mass that had the same acceleration as the structure. Compared with the result of a liquid storage tank,the method was proved to be correct. Numerical results show that the liquid in the digester decreases the natural frequency,and that when the digester is full of liquid,the effect on the low frequency is stronger than that on the high frequency. Therefore, if the sewage quantity is no more than half of the digester,the frequency can be calculated approximately in terms of an empty digester. If the sewage quantity is more than half of the digester,the effect of the liquid vibration on digester should be taken into consideration.
引文
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[2]Cho K H,Kim M K.Seismic response of base-isolated liquid storage tanks considering fluid-structure-soil inter-action in time domain[J].Soil Dynamics and Earthquake Engineering,2004,24(11):839-852.
[3]白玉萍.无粘结预应力卵形消化池的结构分析与设计[D].天津:天津大学建筑工程学院,2005.Bai Yuping.Analysis and Design of An Unbonded Prestressed Egg-Shaped Digester[D].Tianjin:School of Civil Engineering,Tianjin University,2005(in Chinese).
[4]姜忻良,丁学成.桩土物理模型及结构-桩-土相互作用[J].振动工程学报,1993,6(2):143-152.Jiang Xinliang,Ding Xuecheng.The physical model of pile-soil and structure-pile-soil interaction system[J].Journal of Vibration Engineering,1993,6(2):143-152(in Chinese).
[5]Housner G W.The dynamic behavior of water tanks[J].Bulletin of the Seismological Society of America,1963,53(2):381-387.
[6]Fischer D.Dynamic fluid effects in liquid-filled flexible cylindrical tanks[J].Earthquake Engineering and Struc-tural Dynamics,1979,7(6):587-601.
[7]秦延龙.三万方浮顶油罐地震反映的模型试验与分析[G]//圆柱形储液罐抗震论文集.北京:地震出版社,1986:46-58.Qin Yanlong.The30.000.m3oil tank with floating top model test and analysis of seismic responds[G]//Earth-quake Resistance of Cylindrical Liquid Storage Tanks.Beijing,Seismological Press,1986:46-58(in Chinese).
[8]项忠权.储液罐梁式基本周期的近似计算[G]//立式储罐抗震.北京:地震出版社,1990:107-112.Xiang Zhongquan.The approximate calculation of liquid storage tank basic mode[G]//Earthquake Resistance of Vertical Storage Tank.Beijing,Seismological Press,1990:107-112(in Chinese).
[9]Hamdan F H.Seismic behaviour of cylindrical steel liquid storage tanks[J].Journal of Constructional Steel Research,2000,53(7):307-333.
[10]Kianoush M R,Chen J Z.Effect of vertical acceleration on response of concrete rectangular liquid storage tanks[J].Engineering Structures,2006,28(2):704-715.
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