Bond strength of hot-dip galvanized hooked bars in normal strength concrete structures

In 2001, a multi-phase research program was started at the American University of Beirut (AUB) to evaluate experimentally the effect of hot dip galvanizing on bond strength of reinforcement in concrete structures. In the first two phases, 24 full-scale beam specimens were tested in positive bending to evaluate the effect of galvanizing on bond strength of tension lap splices in normal and high strength concrete specimens. The variables were bar size, concrete strength, the amount of transverse reinforcement confining the splice region, and whether the bars were galvanized or not. Test results indicated that galvanizing had a negligible effect on bond strength of reinforcement in normal strength concrete. However, galvanizing caused an average of 20% decrease in bond strength of reinforcement in high strength concrete regardless of the amount of transverse reinforcement confining the splice region.This paper reports on a third phase of the AUB program, designed to evaluate the effect of galvanizing on anchorage performance of hooked bars in normal strength concrete structures. Up to date there has been no research work done in this area. Twelve specimens were tested. The specimen simulated the rigid connection of two cantilever beams to a column. The variables were bar size, the confinement mode of the beam bars anchored in the column, and whether the bars were galvanized or not. The effect of galvanizing was evaluated by comparing the performance of galvanized bars with black bars based on the mode of failure, ultimate load, and the general load–deflection behavior. Test results indicated that effect of galvanizing on the bond strength of hooked bars in normal strength concrete was not significant.