Long anchorage resistance of reinforcement bars derived from local bond-slip relationships for good and poor bond conditions

The fib Model Code 2010 (MC2010) contains a semi-empirical formulation for the local bond-slip relationship for both pull-out and splitting failure modes (derived from short pull-out tests), as well as a semi-empirical formulation of the steel stress that can be activated in the reinforcement as a function of the anchorage length (anchorage resistance derived from a large database of lapped joint and anchorage tests). Considering equilibrium and compatibility conditions, the anchorage strength can be calculated on the basis of the local bond-slip relationship. Using this approach with the bond-slip relationship of MC2010, the obtained anchorage strengths are not consistent with the anchorage resistance according to the same code. Recent works have shown discrepancies between measured local bond-slip responses and the proposal of MC2010. Within this frame, this paper presents an experimental programme consisting of pull-out tests instrumented with detailed measurement systems (digital image correlation and fibre-optic measurements). The results show the effect of the evaluated parameters in the local bond-slip relationship along the bar. The different local bond-slip responses can be explained by the crack development in the surrounding concrete.