Measurement of Slip Between Steel and Concrete Core

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Title: Measurement of Slip Between Steel and Concrete Core

Author(s): Brant J. Lahnert, Jules Houde, and Kurt H. Gerstle

Publication: Journal Proceedings

Volume: 83

Issue: 6

Appears on pages(s): 974-982

Keywords: bond (concrete to reinforcement); bonding; bond stress; slippage; finite element method; measurement; reinforced concrete.

Date: 11/1/1986

Abstract:
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.