Experimental Behavior and Design of Exterior Reinforced Concrete Beam-Column Joints Strengthened with Embedded Bars
Publication: Journal of Composites for Construction
Volume 22, Issue 6
Abstract
Shear-deficient RC beam-column joints (BCJs) represent one of the main factors behind the seismic damage suffered by existing concrete infrastructure, as well as the associated loss of life. This study presents a novel technique for strengthening shear-deficient RC BCJs. The technique involves embedding carbon fiber–reinforced polymer (CFRP) or steel bars into epoxy-filled holes drilled within the joint core. Six exterior RC BCJs were constructed and tested under displacement-controlled cyclic loading. Five specimens, of which four were strengthened with embedded bars, were designed with shear-deficient joints according to the pre-1980s building codes. The remaining specimen was adequately designed according to the current standard. The test parameters are the type (steel or CFRP) and number (four or eight bars) of embedded bars. The unstrengthened control specimen experienced joint shear failure in the form of cross-diagonal cracks. The strengthened specimens, namely those strengthened with embedded steel bars, exhibited less brittle failure when damage occurred in the beam region at the early stages of loading, suggesting the outset of a beam hinge mechanism. Additionally, the strengthened specimens exhibited enhancements in joint shear strength, ductility, dissipated energy, and stiffness of 6%–21%, 6%–93%, 10%–54%, and 2%–35%, respectively, compared with the control specimen. This paper also presents a mechanics-based design model for RC BCJs strengthened with embedded bars. The proposed model covers all possible failure modes including yielding of the existing steel reinforcement, concrete crushing, and debonding of the embedded bars. The accuracy of the proposed model was checked against the test results. The model gave good predictions with an average predicted-to-experimental ratio of 1.05 and a standard deviation of 0.04.
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Acknowledgments
The first author highly appreciates the financial support provided by the Directorate General of Higher Education, Ministry of Research and Higher Education of Indonesia through Grant No. 323/E4.4/K/2012. The authors gratefully acknowledge the support provided by the technical staff of the Structures Laboratory at the University of Birmingham.
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Published In
Journal of Composites for Construction
Volume 22 • Issue 6 • December 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Jan 18, 2018
Accepted: May 16, 2018
Published online: Aug 28, 2018
Published in print: Dec 1, 2018
Discussion open until: Jan 28, 2019
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