Title:
Bond Strength Variability in Pullout Specimens with Plain Reinforcement
Author(s):
Lisa R. Feldman and F. Michael Bartlett
Publication:
Structural Journal
Volume:
102
Issue:
6
Appears on pages(s):
860-867
Keywords:
bond; reinforcement; slip; stress
DOI:
10.14359/14794
Date:
11/1/2005
Abstract:
Bond strength results from 252 plain bar pullout specimens are presented. Parameters investigated include: concrete compressive strength, bar size, bar shape, concrete cover, and bar surface roughness. All load-slip curves displayed a characteristic shape: the maximum tensile load occurred at a very small slip (~0.01 mm) and the load then dropped asymptotically to a residual value as the slip increased to 10 mm. Empirical equations based on least-squares analysis are presented to predict maximum and residual average bond stresses. The load-slip curve can be represented with load as a linear function of the logarithm of slip. The average bond strength was 0.98 MPa for as-received bars, and increased by 124% to 2.2 MPa for bars sandblasted to simulate realistic surface roughness. Coefficients of variation were 8% for maximum average bond stress and 24% for residual average bond stress.