Numerical Study of Dynamic Response of Shallow Foundations to Vertical Loads Induced by Machines

Pourdeilami, Abbas | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41431 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadi, Mohammad Mehdi
  7. Abstract:
  8. The main purpose of designing machine foundation is to limit its motion to such an amount that not to prevent the perfect workability of machine, not to let the foundation strains exceed the elastic limit and also not to disturb the persons working around the machine. The key note in successfull design of machine foundation, is to precisely analyse the response of foundation to dynamic loads induced by machine operations.The numerical study of shallow foundations response to vertical harmonic loads induced by machinaries have been discussed in this investigation.To aim this purpose, FLACD3D has been utilized in order to 3 dimensionally analyse a continuum medium comprising soil-foundation or soil-foundation-rigid base under vertical sinusoidal loads.At first, results of an experimental test on soil-foundation-rigid base system are used to demonstrate the capability of the model for reliable analysis of shallow foundations under vertical harmonic loading. For this purpose, dynamic response such as displacement amplitude and resonance frequency of a square foundation on a soil layer underlain by a rigid base is compared with the experimental measurements.Finally, the verified model is used for parametric study. The parametric analysis includes evaluation the effect of dynamic amplitude loading, soil poisson ratio, foundation contact area, material damping, presence of rigid base underlain the soil, soil inhomogeneity and foundation weight on dynamic response of foundation, especially impedance functions. In addition, static stiffness of the foundation has been calculated for each section and its pertinent equation examined.The obtained results indicate that variation in amplitude of dynamic loading has no effect on impedance functions. Also, increase in contact area between foundation and soil leads to increase in real part(dynamic stifness) and imaginary part(damping) of impedance function. Existence of material damping will cause decrease in dynamic stiffness while increasing the dynamic damping. In general, the parametric study demonstrates that, presence of rigid base has a profound influence on impedance function so that it has no longer a smooth trend. In addition, taking into account the inhomogeneity of the soil can affect impedance function. Moreover, with increase in foudation weight the displacement amplitude and resonance frequency of the system will decrease and compared to halfspace soil theory we can say that the mentioned theory predicts the resonance frequency same as numerical analysis while understimate the displacement amplitude
  9. Keywords:
  10. Dynamic Response ; Numerical Modeling ; Shallow Footing ; Impedance Function ; Vertical Harmonic Load

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