A re-evaluation of test data on bond in R/C by means of FEM modeling

The role of various parameters governing bond behavior is investigated in this paper taking advantage of a simple but efficient finite-element model, whose fundamental aspects are briefly recalled. Several well-documented test results on bond are examined in order to clarify the relevance of some aspects of bond phenomenological behavior, and to study a few bond situations where testing has been scarce in the past, as in the case of push-in tests. Parametric studies are performed as well, with reference to the loading mode (pull-out and push-in), to bar elastic and strain-hardening moduli, to steel yield strength and to bar lateral contraction/expansion, both in the elastic and in the plastic domain. Beside contributing to a better understanding of the role of the above-mentioned parameters, the paper confirms at the same time the uniqueness of the local bond stress-slip law, and the necessity of introducing a corrective factor, in order to take care of the damage to bond caused by the cone-shaped microcracks radiating from the bar close to the transverse cracks in tension ties and to the flexural cracks in R/C beams subjected to bending.