Comparative analysis of the numerical simulative methods of concrete plastic deformation

The purpose of the work is to analyse the advantages and weaknesses of existing methods to determine creep deformation, videlicet the CEB 90 Model and the method of a viscoelastic material (Harutyunyan's Model). Also it is to compare the analytical solutions with experimental data, to identify its main merits and demerits. To investigate a stress - strain state of a bridge design scheme, taking into account the elastic properties of concrete, using different constraint equations for external environment, rheological properties of concrete and specific creep. To achieve the goals, the authors used the following methodology. To analyze a stress - strain state of a design scheme a finite element method was used. In the PC "Lira-CAD" the bridge design scheme was divided into third-dimensional isoparametric finite elements with linear (for armature) and nonlinear (for concrete) deformation laws. Non-linear calculation of a design scheme was implemented using a system "Engineer nonlinearity". Creep deformation was calculated on the 7th, 15th, 20th, 30th, 50th and 100th days after loading. The least quantity of iterations was 300. In the light of the results the authors plotted a diagram of a deflection development as time goes on, using different concrete creep theories. Solving the problems the following results were obtained: based on the viscoelastic material model a process of reinforced concrete deformation was investigated. It is shown that during the calculation of structures (taking into account the appearance of plastic deformations of concrete) creep effect is of paramount importance in its stress - strain state. The scientific novelty of the work: the equations to determinate a creep function of concrete were adduced; the comparative analysis of the elastic recovery deformation models was carried out; it was made a theoretical investigation of stress - strain state of a reinforced concrete bridge based on the viscoelastic material model using different creep theories. The practical significance of the work: it was made comparative graphs of obtained time laws of creep compliance with experimental data, which permit to consider a precision degree of the given theories.