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中文核心期刊

黏弹性层状周期板动力计算的近似理论与解答

APPROXIMATE THEORY AND ANALYTICAL SOLUTION FOR DYNAMIC CALCULATION OF VISCOELASTIC LAYERED PERIODIC PLATE

  • 摘要: 由于周期性隔振结构动力计算中较少考虑轨道交通载荷及材料黏弹性,因此,本文以黏弹性层状周期板为研究对象,提出了垂向移动简谐载荷下,可以考虑材料黏弹性及板内横向剪切变形的黏弹性层状周期板动力计算近似理论并给出解析解答.设板中性面的横向剪切变形为横截面的整体剪切变形,利用Reissner-Mindlin假设及提出的剪切变形补充计算条件,得到了中性面法线转角与中性面剪应力的关系.基于平衡方程和应力连续条件,建立了黏弹性层状周期板振动控制方程,推导了对边简支对边自由条件下,板垂向位移的简化Fourier级数形式解.与经典层合板模型和有限元计算结果进行了比较,验证了本文解答的有效性.结果表明:(1)黏弹性层状周期板可以显著降低单一材料板在自振频率处的振动响应,但会引起局部低频频段的振动放大;(2)板的垂向位移随着载荷速度的增大而增大,当载荷速度超过300 km/h后,其对板振动响应的影响减弱;(3)黏弹性层剪切模量存在最佳设计值,可使结构的隔振性能最佳;(4)黏弹性层的阻尼特性在低频范围内对结构振动影响较小;(5)可在满足工程实际的情况下适当增加板长,以提高结构的隔振性能.

     

    Abstract: Rail transit loading and viscoelastic of material are mostly ignored in the previous dynamic calculations of the periodic vibration isolation structures. Approximate theory and analytical solution for viscoelastic layered periodic plate subjected to vertical moving harmonic loading is established, and the viscoelastic of material and the transverse shear deformation are considered. In this theory, Reissner-Mindlin assumption and additional equation of shear deformation are introduced, and the relation between the normal rotation and the shear stress of neutral plane is obtained on the assumption that the transverse shear deformation of the plate's neutral plane is the overall shear deformation of the cross section. Vibration governing equation of viscoelastic layered periodic plate is proposed according to equilibrium equations and stress continuity conditions, and vertical displacement in Fourier series is derived as well. The model is validated by the good agreement with solution of the classical laminate model and the finite element method (FEM).The results show that:(1) Vibration response at the natural frequency of plate can be significantly reduced by substituting viscoelastic layered periodic plate for homogeneous one, but vibration amplification in local low frequency band is aroused as well. (2) The vertical displacement of the plate increases with the increment of the loading velocity, and increase trend slows down once velocity above 300 km/h. (3) Shear modulus of viscoelastic layer can be designed to achieve the optimal vibration isolation characteristic. (4) Vibration response is not susceptible to damping characteristic in low frequency band. (5) It's appropriate to increase the plate length, within the engineering requirement, to improve the vibration isolation performance.

     

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