| dc.description.abstract | Non-linear finite element analyses (NLFEA) can be used to predict the physical behaviour of reinforced concrete (RC) structures. However, in order to obtain numerical results in compliance with the real physical behaviour of RC structures, an accurate solution strategy, with a low modelling uncertainty, is desired. The numerical solution strategy contains choices regarding kinematic compatibility, material models and force equilibrium.
In this Master's Thesis, a solution strategy has been developed for a general set of reinforced concrete beams with web openings. The selected solution strategy has been established based on careful investigations of the outcome from several NLFEAs, run in a FEA software called DIANA, version 10.2. The obtained numerical results were compared to experimental results from different benchmark analyses. Several concrete constitutive sub-models were investigated in detail in a sensitivity study. Furthermore, a range of varying mesh densities were tested with the aim of finding an optimal FE discretization for a general set of beams with openings.
The modelling uncertainty, quantified by a mean ratio of the experimental to predicted capacity, θ m=1.06, and a coefficient of variation, V θ =16.4%, was obtained in this study. The obtained values were based on eight different beams modelled with the selected solution strategy. Compared to the experimental results, this reflects a general underestimation of the capacity in the NLFEAs.
Significant sensitivities related to the material models are observed and discussed in this thesis. Consequently the selected solution strategy may not be able to obtain the realistic failure mode and failure load for all concrete beams with web openings. The solution strategy can be considered as an elementary procedure to evaluate the capacity for such beams, and may be improved by use of more detailed submodels for the dominant material behaviours of the failure modes. However, as the failure modes may be difficult to predict for beams with complex geometries, the NLFEAs should be accompanied by thorough postanalysis checks. These checks aim to detect possible spurious strengths, resulting in false capacity, as detected in some NLFEAs reported in this thesis. | |
