Influence des gaines sur la résistance des âmes de poutres en béton précontraint

Résumé

Les recommandations du CEB-1978 préconisent, dans le cas de la vérification de la résistance des âmes des poutres en béton précontraint à l'effort tranchant, la prise en compte de l'épaisseur effective de l'âme, déduite de la moitié de la somme des diamètres des gaines.

Dans le but de vérifier cette recommandation, on a essayé jusqu'à la rupture par écrasement des bielles, 14 poutres en béton armé dont les seuls paramètres variables étaient les diamètres et l'injection ou non des gaines.

Summary

CEB Recommendations preconize that in case of verification of the web strength of the prestressed concrete beams against the shear force, the effective web thickness (by deduction of the half sum of the ducts diameters) might be taken into account in the considered region b_wef=b_w−(1/2). Σ Ø).

With the purpose of verifying this recommendation, fourteen reinforced concrete beams were tested until the crushing of the concrete web, in the direction of the diagonal cracks.

The beams had the same geometrical characteristics and the same transversal and longitudinal reinforcement. The variable parameters were the diameters of the ducts and their injection, or not, with mortar.

We have concluded that in case the injection is reliable, a reduction of the value of the web thickness would not be necessary, and that in cases in which the full efficiency of the injection cannot be trusted, the reduction b_wef=b_w−0,38. Σ Ø is recommended.