Direct Tension Pullout Bond Test: Experimental Results
Publication: Journal of Structural Engineering
Volume 136, Issue 6
Abstract
Results from 50 bond tests conducted using the so-called direct tension pullout specimen type are presented. Anchorages of steel bars with machined deformations were tested so as to enable a targeted study of the effect of rib height and related rib area on bond behavior; tests were conducted with or without the combined presence of external confinement over the embedded length. The novel specimen form presented in the paper was designed to simulate the state of stress arising in usual bar anchorages in the tension zones of flexural members (where both cover concrete and bar are stressed in tension). This development was motivated by the need to eliminate spurious influences of the test setup on specimen behavior, which are known to interfere with bond mechanics in conventional bond tests leading to unconservative estimates of bond strength and misleading interpretations as to the true parametric dependencies of the bond problem. Additional parameters studied in the experimental program were the development length, the cover thickness, the effect of confinement, and the tensile strength of concrete. Data reduction (local bond strength and slip estimates) was possible by fitting the exact solution of the differential equations describing the state of stress along the anchorage to the test measurements, while accounting for important phenomena such as yield penetration or debonding, and bond plastification. Next, the obtained values for local bond strength were used for calibration of the frictional analog for bond strength (a Mohr-Coulomb failure criterion). Milestone values for bond and slip were estimated with reference to the code limit-state model for bond.
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Acknowledgments
Funding for this investigation was provided by the Hellenic General Secretariat for Research and Technology, through the research program PENED’01. Tests were conducted in the Laboratory of Reinforced Concrete, Department of Civil Engineering, Democritus University, Greece. FRP materials were generously donated by MAC BETON HELLAS S.A.
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© 2010 ASCE.
History
Received: Jan 12, 2009
Accepted: Nov 16, 2009
Published online: Nov 21, 2009
Published in print: Jun 2010
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