Lateral buckling of precast reinforced concrete girders
Özet
The development of high-strength materials and new construction techniques enable engineers to design longer and deeper precast concrete bridge girders. The increase in the slenderness ratios of these girders causes the lateral stability to be a cause of concern in the design and during construction of bridges. This paper presents a study pertaining to the lateral torsional buckling of precast reinforced concrete beams with initial geometric imperfections. An analytical formula accounting for the material nonlinearities and non-homogenous nature of reinforced concrete and the contribution of longitudinal reinforcements is proposed to estimate the lateral torsional buckling moments of reinforced concrete beams with initial geometric imperfections. In the present study, standard AASHTO I-girders are analyzed using the proposed formula to determine the critical unbraced lengths and the maximum design spans of the girders. Considering the PCI girder sweep tolerances, this study determines the critical unbraced lengths, at which the lateral torsional buckling moment of the girders becomes equal to the ultimate flexural moment capacity, to prevent lateral instability of the girders. Furthermore, for the maximum design span lengths given by the PCI Bridge Design Manual, the critical initial sweeps are determined to ascertain that the girders are stable until they reach the ultimate flexural capacity. The results of the analyses are used for evaluating the girder sweep tolerances and the maximum span lengths of the PCI Manual.
