Influência do posicionamento e do uso de equipamentos auxiliares no içamento de vigas pré-moldadas

Abstract

The lateral instability of precast beams during transitory phases is a worrying phenomenon, considering the occurrence of accidents reported in the technical literature. During the transitory phase of lifting, the configuration adopted for the coupling between the crane cables and the structural element influences the safety of this procedure, and the definition of auxiliary equipment for handling must be judicious. The objective of this research is to numerically analyze, through simulations carried out in ANSYS software, the behavior of precast beams in relation to lateral stability, considering the influence of the type and positioning of auxiliary lifting equipment. Four situations were studied for the lifting arrangement: a handle at each end of the beam (without rigid bar), consideration of the rigid bar (yoke) for lifting above the upper face of the beam, two handles positioned transversely on the upper table (without rigid bar ) and use of a metal rod placed below the upper table of the beam (rod lifting). These possibilities of linking the lifting equipment are considered for three beams, one of which is symmetrical transversely and longitudinally, another with asymmetry in the cross section (parapet) and the other with a longitudinally variable cross section. The results show that the worst case is the lifting by a handle without the use of a rigid bar, as it presented the highest values of equilibrium angle and when compared to the use of a rigid bar, as already defended in the literature, smaller values were observed. values for balance angle, confirming that lifting farther from the beam's center of gravity is safer. On the other hand, it was concluded that even with the lifting close to the center of gravity, the use of two handles positioned transversely on the beam table presents the best results among all the modeling carried out. It was also seen that the lifting by rods presented results for and against safety and that the rod length is inversely proportional to the angle result, with the most favorable position being the ones farthest from the center of gravity. Finally, it was seen that in both cases, the configuration of the lifting equipment is crucial for the safety of the lifting, since situations of stability and instability were identified through comparison with the numerical or analytical crack angle of the structures.