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Investigation of Dynamic Behavior of Nonlinear Plates Subjected to a Moving Mass

Enshaeian, Alireza | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49744 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Rahimzadeh Rofooei, Fayyaz; Nikkhoo, Ali
  7. Abstract:
  8. In this study, effect of a single concentrated moving mass on thin linear and nonlinear rectangular plates is investigated. The present research focuses on the dynamic behavior of thin plates traversed by a moving mass. Although vast amount of literature is available regarding the modeling of plates with geometric and material nonlinearity as well as evaluation of the inertial components of the external moving mass, but actually no one has addressed implementation of dynamic effects of moving mass for a nonlinear plate. Due to scientific significance of inertial effects in most cases, the external dynamic loading is considered as a moving mass. However, moving force loading is also taken into account for some selected cases. Obtained results from dynamic analyses on rectangular plates substantiate the importance of inertial effects as functions of weight and velocity of the moving mass. Moreover, complete formulation associated with the inertial terms of the moving mass is emphasized over a wide range of mass velocities and weights. In that regard, first the required dynamic analyses are performed on linear structural members. Then, the nonlinearity effects especially those associated with the geometrical nonlinearity are included in the governing dynamic differential equations. Also, material nonlinearity is considered in modeling of thin plates by applying appropriate plasticity and plastic flow rules. To begin with, only the first dominant mode shape of the plate is considered to model the plate behavior, but applying semi-analytic and also numeric methods revealed the need to include more number of mode shapes in the dynamic analyses. In this study both material and geometric nonlinearity effects are investigated. Regarding geometric nonlinearity, both analytic methods especially perturbation techniques based on single mode presentation of the plate member which leads to a single nonlinear differential equation and also semi-analytic methods based on participation of multi-modes, are utilized. For material nonlinearity, the finite element method is applied. The extent by which the inclusion of nonlinear effects may influence the dynamic responses of the plate is widely discussed. The obtained results show that including geometric nonlinearity for plate leads to smaller vibration amplitudes, especially for heavy inertial loads. On the contrary, material nonlinearity effect tends to increase the deformations. Also, it was observed that for fast moving inertial loads, the maximum dynamic deformations occur somewhere with notable distance from the plate’s center point. Moreover, the no separation assumption which is the basis for derivation of governing dynamic equations in this study, was verified by numeric examples
  9. Keywords:
  10. Finite Element Analysis ; Dynamic Amplification Factor ; Moving Mass Load ; Perturbation Method ; Dynamic Behavior ; Thin Plates

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