Instabilidade lateral de vigas pré-moldadas sobre apoios elastoméricos considerando o efeito das imperfeições geométricas

Abstract

Using prestressed slender beams has become common in Civil Engineering, especially those designed to transpose long spans of bridges and viaduct. It is worrying behavior of these beams due to the lateral stability in the transitional phases and in service. The presence of geometric imperfections aggravates the situation of these beams. Two stages must be evaluated: lifting and when the beam is on provisional supports, i.e., when final connections are not yet executed. These beams, in most cases, are supported on elastomeric bearing pads that, due to its flexibility, provide additional degrees of freedom to the structure that can lead the beam to collapse. Considering the occurrence of collapse of beams in the pre-service phase already registered, this paper has as main objective to evaluate the behavior of concrete beams on elastomeric bearings and to analyze the influence of variables such as: initial imperfections, concrete resistance, with or not wind load and bearing compression stiffness. For the numerical analysis, ANSYS, based on the Finite Element Method, was used. The analyzes show that the influence of the strength of the concrete is significant in the lateral stability of the beam. The wind load represents a considerable increase for the loss of contact (lift off) between the beam and the bearing. The consideration of concrete physical nonlinear behavior shows that in some situations it is not possible to find a position of equilibrium in the numerical model. The roll stiffness of the bearing decreases as the skew angle increases. Finally, the combination of these factors can result in a critical stress situation on the beam, that it is not possible to have equilibrium, causing its toppling.