A critical appraisal of existing models for nonlinear finite element analysis of reinforced concrete response
Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: This study entails the appraisal of the constitutive models available for the non linear finite element analysis of reinforced concrete, using the DIANA finite element package and following generally accepted guidelines for non linear finite element analyses. The constitutive models considered are plasticity and total strain based (fixed and rotating crack) models. The appraisal consists of the analysis of various experiments performed on reinforced concrete beams that are governed by compressive, shear and tensile dominated failures. The investigation is not limited to the accuracy of the results obtained using these models but also of the consistency of the results obtained with regard to various mesh types and sizes, as well as a study of the individual influence of several material parameters. The intention of the study was to provide the reader with an indication of the performance capacity (accuracy and consistency) of the available constitutive models, where the notion of the use of the results obtained from non linear finite element analyses for design purposes is considered. The results obtained were varied. The models performed reasonably well in the compressive and tension dominated studies, with the importance of accurate material parameters being emphasized especially for the more advanced cementitious materials investigated. The total strain rotating crack model also showed a proclivity of simulating incorrect failure modes as well as exhibiting reluctance towards stress redistribution. All models used for the shear dominated study yielded mostly inaccurate and inconsistent results, but it was found that the four node quadrilateral element with selective reduced integration performed the best. The plasticity model did not capture shear failure well, and convergence was often not attained. The constant shear retention factor of the total strain fixed crack model was found to yield more detailed response curves for the smaller mesh sizes. The results of the tension dominated beams inspired more confidence in the models as quite accurate values were attained, especially by the plasticity model used. The ability of the available models to simulate realistic structural behaviour under various failure modes is very limited, as is evident from the results obtained. The development of a more advanced and robust model is required, which can provide consistently accurate results and failure modes, and even ‘anticipate’ potential failure modes not considered by the user.