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- Numerical modeling of concrete beams under serviceability conditions with a discrete crack approach and noniterative solution-finding algorithmsPublication . Dias-da-Costa, Daniel; do Carmo, Ricardo N. F.; Graça-e-Costa, R.This paper describes the development and validation of a comprehensive numerical model enabling the simulation of reinforced concrete beams under serviceability conditions using a discrete crack approach. The highly nonlinear behavior introduced by the different material models and the many localized cracks propagating within the member pose a challenge to classic iterative solvers, which often fail to converge. This limitation is solved using a noniterative solution-finding algorithm to overcome critical bifurcation points. The finite element model was validated using experimental data on lightweight aggregate concrete beams under flexural loading. It was shown that the model properly simulates both the overall and localized features of the structural response, including curvature, crack openings, and crack patterns. The model was used to carry out a numerical study of the role of longitudinal reinforcement ratios and crack widths in reinforced concrete beams. It was observed that the total crack openings along a member seem to remain nearly independent of the tensile reinforcement for ratios >2.5% and the same level of strength.
- O reforço de vigas de betão armado com chapas metálicas coladas com resinaPublication . Alfaiate, J.; Graça-e-Costa, R.Neste trabalho efectua-se a simulação do reforço com chapas metálicas coladas com resinas epoxy, em vigas de betão armado. Cada viga é inicialmente carregada à flexão e submetida a um elevado nível de dano. Posteriormente, sob carga constante, as fendas são reparadas com resina epoxy e aplica-se o reforço, colando a chapa metálica na face traccionada da viga. Conclui-se o teste aumentando a carga até se obter a rotura da viga reforçada. O nível de dano pré-reforço é modelado recorrendo a uma abordagem discreta com fendas embebidas e a ligação betão-resina-chapa é modelada em modo II de fractura através de elementos de interface com espessura inicial nula. Os resultados numéricos são comparados com os resultados obtidos em vigas ensaiadas experimentalmente de acordo com os procedimentos referidos.