Title: Measurement of Slip Between Steel and Concrete Core
Author(s): Brant J. Lahnert, Jules Houde, and Kurt H. Gerstle
Publication: Journal Proceedings
Appears on pages(s): 974-982
Keywords: bond (concrete to reinforcement); bonding; bond stress; slippage; finite element method; measurement; reinforced concrete.
An experimental method to determine the relative slip between concrete and reinforcing steel, first developed by Nies, is demonstrated and applied. This method uses magnetoresistors embedded in the concrete, which are capable of converting the flux density change of a coil embedded in the reinforcing bar to a voltage change. This method was applied to the determination of the local bond slip in pullout and tension specimens. Additionally, electric bonded strain gages embedded in the bar were used to measure the bar force and through it the bond stress. With these data, local bond stress-slip relations could be obtained. In both pullout and tension tests, non-unique and stress-slip curves were obtained, whose shape and values varied with the location of the gage point along the bar. A possible explanation of this is the variable confining pressure; it appears that the confining pressure will have to be considered as a variable to obtain rational bond stress-slip relations.