Investigation of Bond In Beam and Pull-Out Specimens with High-Yield -Strength Deformed Bars

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Title: Investigation of Bond In Beam and Pull-Out Specimens with High-Yield -Strength Deformed Bars

Author(s): Robert G. Mathey and David Watstein

Publication: Journal Proceedings

Volume: 57

Issue: 3

Appears on pages(s): 1071-1090

Keywords: none

Date: 3/1/1961

Abstract:
Bond strengths were determined in 18 beam and 18 pull-out specimens with deformed reinforcing bars having a nominal yield strength of 100,000 psi. The lengths of embedment ranged from 7 to 17 in. for $4 bars and from 7 to 34 in. for 18 bars. The bond strength was found to decrease with increases in the length of embedment for a bar of a given size. The bond also decreased with an increase in the bar diameter for a given length-diameter ratio. Bond failures were obtained in all beams containing $8 bars with $4 bars, both tensile and bond failures were observed. The ultimate bonds stressed in the pull -out specimens agreed in general with the values obtained in beams with $4 bars. However, for $8 bars the bond strengths in pull-outs were significantly greater than the values obtained with beams. It was found advisable to use either a loaded-end slip of 0.01 in. or a free-end slip of 0.002 in. to define critical bond stresses, depending on which of these slips developed first. Bond stresses corresponding to these values of slip were sufficiently low to insure that under-reinforced beams designed on the basis of these criteria would fail by yielding of reinforcement.