Reinforcement Anchorage and Bond – Slip Laws for UHPC Structures

Presented by Stavroula J. Pantazopoulou, York University, Canada; Konstantinos Tsiotsias, York University; and Katerina D. Papoulia, University of Waterloo Recent developments in the field of construction materials such as ultra-high-performance fiber-reinforced cementitious composites (UHPFRCC, or UHPC) present new opportunities for the research and design of reinforced concrete (RC) structures. The introduction of fiber reinforcement directly affects bond behavior, which is the mechanism responsible for the composite action of steel and concrete. Bond occurs at the interface between the reinforcing bars and the cover concrete and enables force transfer between the two media. In the absence of confinement, bond failure occurs by cover splitting and debonding, but under high confinement these modes are suppressed leading to increased bond and anchorage strain capacity. In Ultra-high-performance concrete distributed fibers act as a mechanism of internal confinement, and it is therefore anticipated that bond strength of reinforcement in this type of a matrix would be superior to that in plain concrete. The objective of the paper is to present results from reinforcement anchorage tests in three different Ultra High-Performance Concrete Matrices and one ECC matrix demonstrating the enhanced anchorage capacity of short bar anchorages due to the internal confinement of the matrix as well as the derived design requirements for anchoring reinforcement in UHPC structures. Apart from presenting the results of several experiments conducted on different specimen forms and setups to study anchorage behavior and the estimated bond-slip laws, results from detailed nonlinear finite element analysis will also be presented to illustrate the effect of the intrinsic confinement on anchorages on the macroscopic behavior (strength and deformation capacity) of UHPC structural members under load.