Este trabalho apresenta um modelo mecânico para análise de vigas em concreto armado com base no método dos elementos finitos, considerando a não-linearidade física dos materiais em conjunto com mecanismos específicos de resistência ao cisalhamento do concreto armado, tais como a armadura transversal e o efeito de pino. Esses mecanismos são acoplados a um modelo de dano para o concreto com o objetivo de representar melhor as perdas de rigidez do material, bem como a resposta global das vigas. Foram apresentados exemplos numéricos para validação do modelo, verificando-se a importância dessas contribuições, principalmente em vigas hiperestáticas com elevada relação altura/comprimento.

This paper shows the development of a mechanical model to reinforced concrete analysis based on the finite element method, taking into account the non-linear material behavior with shear strength mechanisms, such as shear reinforcement and dowel action. These mechanisms are coupled to a damage model for concrete to better represent the material stiffness loss, as well as the global response of beams. Numerical examples are presented to validate the model, verifying the importance of these contributions, mainly for hyperstatic beams with high span-to-depth ratio.

Crack formation and growth in steel bridge structural elements may be due to loading oscillations. The welded elements are liable to internal discontinuities along welded joints and sensible to stress variations. The evaluation of the remaining life of a bridge is needed to make cost-effective decisions regarding inspection, repair, rehabilitation, and replacement. A steel beam model has been proposed to simulate crack openings due to cyclic loads. Two possible alternatives have been considered to model crack propagation, which the initial phase is based on the linear fracture mechanics. Then, the model is extended to take into account the elastoplastic fracture mechanic concepts. The natural frequency changes are directly related to moment of inertia variation and consequently to a reduction in the flexural stiffness of a steel beam. Thus, it is possible to adopt a nondestructive technique during steel bridge inspection to quantify the structure eigenvalue variation that will be used to localize the grown fracture. A damage detection algorithm is developed for the proposed model and the numerical results are compared with the solutions achieved by using another well know computer code.