Investigation of viscoelastic quadrilateral plate structures using finite elements method

Structural materials generally exhibits three types of behaviour which is called elastic, plastic and viscoelastic. The stress under the limit of proportionality of materials behaves elastic thus this approach is simple and effective. However, taking into consideration of the behaviour of plastic and viscoelastic materials get importance with increase of structural uses and service status. In this context, determining beavioral model which is nearest to the material's actual behaviour is necessary to determine structural element or the whole structure's behavior. Structural materials such as concrete, wood, and steel in high temperatures exhibit viscoelastic behavior is a fact known. In this study, creep behaviour of a viscoelastic thin square plate examined by using finite element and classical methods and their comparision is outlined below. In chapter one, material behaviour under stationary load effects is adverted shortly, the definition of viscoelasticity is outlined briefly and the importance of consideration of actual behaviour of the material is emphasized. The phases of viscoelastic behavior is explained at basic information about viscoelasticity given in second chapter. Furthermore, some illustrative information is pointed out about rheological models used in this study determined in this section. In section three, the general formulation of finite element method is obtained and the phases of solution is presented for thin square plate problem with a four noded finite element. In fourth section, the method, which is improved for viscoelastic thin square plate problemis obtained by using relaxation functions on the basis of Kelvin chain model. The square plate examples, which are improved under the different boundary and load conditions are solved by the programs made using MATLAB commercial language. These programs are presented in appendix. In the last section, the results obtained are discussed and interpreted. Keywords: Viscoelasticity, finite elements method, thin square plate, rheological models, relaxation functions