Lateral instability of precast beams considering the effects of geometric imperfections and prestress efect at lifting

Abstract

ABSTRACT: The study of the instability of precast concrete beams has deserved more attention due to broad applications in large projects and concerning accidents with beam rupture by lateral instability. The geometry of the beam influences directly in instability problem, due to long and slender structural elements. In this context, this research analyzes the structural behavior of beams during the lifting phase by steel cables, taking into account the initial lateral eccentricity and positioning of the suspension cables, considering the length of the balances and the positioning deviations of the handles in the cross-section. These results are analyzed by theoretical models available in the technical literature to verify the safety conditions and by the numerical model developed in the Ansys program. The analyzes compare safety factor, roll angle, strain and the effect of prestress in precast beams during lifting. The studies shows that lifting conditions are safer when the handling is performed with balances and with handles in the opposite direction to the curvature, but care must be taken in prestressed beams, especially in relation to critical strains. The effect of lateral instability proved to be as undesirable as the positioning deviations of the handles in the direction of curvature, for the cases analysed.