Bond strength of confined normal strength concrete beam-column joints

Abstract

The article presents the results of a research study that was conducted at the American University of Beirut (AUB) on the effect of transverse reinforcement crossing the critical hooked bars region of normal strength concrete (NSC) beam-column joints on the bond strength and ductility of the mode of failure of the hooked bars. Nine full-scale beam-column joint specimens were tested. The specimen simulated the rigid connection of a cantilever vertical beam to a base column. The load was applied near the tip of the beam while the column was fixed to the strong floor. The tensile beam bars were anchored in the column using hooked-bar anchorages. In previous research, confinement to the joint was provided either by carbon fiber reinforced polymer (CFRP) sheets externally confining the joint or steel fibers incorporated in the concrete mix. Results revealed that the transverse reinforcement crossing the hooked bars region was effective in increasing the anchorage capacity and the ductility of the load-deflection history of the specimens. Correlation of the effects of the three different confinement modes is presented.

Keywords:

• Reinforced concrete
• bond (concrete to reinforcement)
• beam-column joints
• hooked-bar anchorages
• confinement
• transverse reinforcement
• fiber reinforced polymers
• steel fibers

Acknowledgments

The authors gratefully acknowledge Hussein Mallat Professor Hamad’s graduate student at AUB, who was working on his MS degree when he had to leave for the US for cancer treatment and was out of reach during the preparation of the article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The University Research Board at the American University of Beirut, Beirut, Lebanon.