Comparaison des essais d'adhérence par flexion (beam test) et par traction (pull-out test)

Résumé

Dans trois laboratoires, autrichien, belge et français ont été exécutés des essais d'adhérence selon les deux types d'éprouvettes retenus par la RILEM: beam-test et pull-out-test. Les résultats regroupés de tous les essais ont montré que les deux méthodes conduisaient à des valeurs moyennes des glissements, du même ordre mais avec des dispersions importantes à l'intérieur des séries. Aucune relation certaine n'a pu être trouvée entre les rapports POT/BT et la surface relative des nervures ou le diamètre des barres.

Summary

In three different institutes 33 series of bonding tests (beam test and pull-out test) have been carried out independently in accordance with the Recommendations published in Materials and Structures No. 15 of May–June, 1970, regarding high bonding-strength bars having diameters varying from 8 to 30 mm.

The results obtained by the two types of tests have been interpreted in accordance with the Recommendations for the control and the agreement of high bonding strength (Section 1 of the Annexes to the CEB-FIP 1970 Practical Recommendations).

The relative surface of the ribs ranged from 0.011 to 0.125, with a mean value of 0.47 and thus covered the whole practical range.

The concrete's compression strength was within the normal scatter limits for all the series of tests.

The bonding stresses τ_m and τ_R, determined by the flexural bond test, fall within the whole range of the practical values. For a few bars having very low f_R values, the τ_m values do not come up to the imposed values. For others, showing high f_R values, the τ_m values can be as high as twice the imposed values.