Nonlinear Finite Element Analysis Of Concrete Structures And FEM Software Development

During the past half of century, through fruitful researches of scholars around the world, great achievements on the basic theory of concrete mechanics and concrete nonlinear analysis have been obtained. On the other hand, with increasing attentions paid to the safety, serviceability and durability of concrete structures, it is necessary to apply the nonlinear FEM to the analysis of large practical concrete structures. Conversely, if the sophisticated concrete constitutive model and the complicated finite element model are adopted in the analysis of real size concrete structures, great computation effort is scaled up, and this computational drawback prevents further application of this technology to large scale structure engineering.Considering the practical application of nonlinear FEM analysis technology to the concrete structures, this thesis devotes to develop an efficient and accurate nonlinear FEM methodology which can take into account all the factors related to the structure construction process, and which is capable of simulating the nonlinear response of large concrete structural system. Employing some effective FEM models involved with simple constitutive laws, taking account of the important factors in the structure analysis, and neglecting the secondary aspects, the concrete structure nonlinear FEM analysis technology can be widely applied to real size concrete structure system. Therefore, the following research works have been carried out in this master degree thesis.1. A 3D Degenerated Beam Element, adopting the uniaxial concrete constitutive laws, is developed in this thesis. This Degenerated Beam Element can not only accurately and effectively treat with the beams with all kinds of section configurations, but also expediently describe the nonlinear structural behaviors such as the crack and the crush of concrete and steel's plastic flow after the yielding stress.2. Based on the degenerated beam element, the important factors affecting the structural nonlinear behaviors are studied such as prestressing, 3D temperature field analysis, construction process analysis and the creep effect of concrete structures etc.3. A nonlinear FEM program is developed for analyzing real size concrete structures by nonlinear FEM technology. A great number of numerical examples are tested to demonstrate the accuracy and effectiveness of the FEM algorithmsdescribing the prestressing effect, the 3D temperature effect, and construction process analysis and the creep effect.4. A nonlinear FEM analysis software entitled "YANGHUA Bridge" is developed for the nonlinear FEM analysis of concrete structures.5. Employing the "YANGHUA Bridge" software, two concrete bridges are analyzed. The results demonstrate that this nonlinear FEM software can be widely applied to the FEM analysis of real concrete structures.