The current ASTM requirements for reinforcing bar geometry were established over 40 years ago and are now incorporated in four ASTM specifications covering reinforcing bars. The proposed research will apply the latest in analysis and testing techniques to evaluate currently used and potential new rib geometries, and to develop recommendations aimed at obtaining optimum reinforcing bar development characteristics. The program will include a basic study of the interactions at the steel-concrete interface, apply nonlinear finite element analyses to evaluate different rib geometries, test existing patterns and prototype bars, design and produce reinforcing bars with new patterns, and evaluate the bars in full-size structural members. Structural considerations will include the effects of the interactions of closely spaced reinforcement, the behavior of splices as well as straight development, cyclic loading, fatigue and fracture, and high strength concrete. In addition the effects of epoxy coating on bond strength and modifications to epoxy coatings, such as the addition of grit, will be considered.
