Bond Behavior of High Performance Reinforcing Bars for Concrete Structures

Abstract

Bond between the concrete and the reinforcing steel is a major factor affecting the performance of reinforced concrete structures. Advances in material science led to the production of High Performance Steel that has enhanced corrosion resistance and higher strength compared to conventional Grade 60 steel. Such material can lead to more economical design reducing the material requirements for a particular project and expanding its life span.

The objective of this research is to study the bond behavior of High Performance reinforcing bars for concrete structures and to evaluate the effect of different parameters believed to affect the bond characteristics. Twenty-two large scale reinforced concrete splice beams were constructed using No.8 and No.11 reinforcing bars, having different cross-sections with varying concrete compressive strengths and development lengths. The beams were tested using four point bending setup to provide a constant moment region over the splice zone. Test results indicate that stresses up 90 ksi can be achieved in the No.8 bars and up to 70 ksi in the No.11 bars without confinement; however, it is recommended to use transverse reinforcement to confine the High Performance bars in order to ensure ductility. These stresses can be evaluated at failure using a simple proposed equation. Test results were used to extend the current ACI Committee 408 equations to better predict the stresses in the High Performance Steel.