M.Sc. Tezi Görüntüleme

Student: Korhan ÖZGAN
Supervisor: Prof. Dr. Ayşe DALOĞLU
Department: Civil Engineering
Institution: Graduate School of Natural and Applied Sciences
University: Karadeniz Technical University, Turkey
Title of the Thesis: Finite Element Analysis of Thick Plates Resting on Elastic Foundation Using Modified Vlasov Model and Determination of the Effective Depth of the Soil Stratum
Level: M.Sc.
Acceptance Date: 20/2/2007
Number of Pages: 136
Registration Number: di582

      The purpose of this study is to improve the plate-subsoil interaction models and to get more realistic results with taking into account the effect of the shear deformation through the plate thickness using thick plate theory and determining the effective depth of the soil stratum depending on dimension of the plate, type of the loading and properties of the subsoil. A four-noded, 12 degrees of freedom, and an eight-noded, 24 degrees of freedom, quadrilateral finite elements based on Mindlin plate theory that accounts for the effect of shear deformation are used for the purpose. Selective reduced integration technique is used in addition to full integration technique for both of the elements to avoid the shear locking problem, which is faced when Mindlin plate elements are used for the plates with small thicknesses. Furthermore an iterative method is suggested in order to determine the effective subsoil depth considering the stress distribution within the subsoil. After the details about Modified Vlasov model and Mindlin plate theory are given, the plate element stiffness matrices, the load vectors, the vertical deflection and the shear deformation element stiffness matrices of the foundation for each type of elements are presented in explicit forms using the finite element formulation. To demonstrate the performance of the elements used in this study, the plates without the elastic foundation are considered first and how the shear locking problem occurs and how it is prevented using selective reduced integration rule are explained. Then the effects of various parameters such as transverse shear strain, plate thickness, boundary conditions and changes in the modulus of elasticity of the subsoil from top to the bottom, on the behaviour of thick plates on elastic foundations are investigated. Finally the accuracy and efficiency of effective subsoil depth determined in this study are tested with various examples. It is concluded that generally the effect of the shear strain on the behaviour of the plate is always quite smaller for free plates compare to supported ones, and using a deeper depth of soil stratum doesn’t affect the results much but taking a shallow depth may result with an unrealistic solution if there is not a relatively rigid foundation at a certain depth. Keywords : Plates on elastic foundation, Modified Vlasov model, Finite element model, Thick plate theory, Shear locking problem