Title: Measurement of the Distribution of Tensile and Bond Stresses Along Reinforcing Bars
Author(s): R. M. Mains
Publication: Journal Proceedings
Appears on pages(s): 225-252
Keywords: no keywords
Tensile and bond stresses were measured along reinforcing bars by a new technique which does not disturb bond stresses. Curves for representative beam and pull-out specimens show tensile force distribution, bond stress distribution, applied moment versus measured bar tension, comparison of beam and pull-out tensile force distribution, and applied load versus slip of the bar. Building code requirements imply that bond stress in a beam is a direct function of shear, and that longitudinal distribution of bond stress in a pull-out specimen is uniform. These tests show that these are oversimplifica-tions of the problem, which has been understood (but without experimental proof) for some years. Comparison of ordinarily calculated bond with measured local maximum values shows the calculated values to be frequently less than one-half the values measured in these tests. The effect of standard hooks on the behavior of plain and deformed bars is shown for the particular speci-mensused. Evidence is presented that cracks in beams decisively affect the magnitude and distribution of tensile and bond stresses-probably one of the more sig-nificant results of these tests. Tensile forces in reinforcing bars in beams as ordinarily calculated and as measured in these tests are compared. Calculated values are usually lower than measured values for loads near the ultimate when shear as well as moment acts on the beam.