The primary objectives of this study are: (1) investigate the effects of vertical casting position on the bond performance of reinforcing steel, and (2) compare the results to the current ACI provisions for bond performance of top cast bars to determine whether improvements can be made to the current design criteria.

The vertical casting position of a steel reinforcing bar in a reinforced concrete structural member (such as a beam of column) greatly affects the bond performance between the two. Recent research contests the traditional definition and causes of the top bar effect, presenting evidence that the bond strength of reinforcement is more dependent on the amount of concrete above a bar than below. Further research is needed for a better understanding of this phenomenon and to ensure that the proper design considerations are implemented.