Seismic Performance of Axially Restrained Reinforced Concrete Frame Beams
Publication: Journal of Structural Engineering
Volume 145, Issue 5
Abstract
Reinforced concrete beams tend to elongate after flexural cracking and yielding; however, the elongation is restrained by the surrounding structural components in a RC moment frame. Experiments were conducted on seven -scale interior beam-column subassemblies to study the effects of axial restraint on the seismic performance of RC frame beams and beam-column joints without the presence of floor slabs. The test setup permitted applying axial restraint to beam ends and measuring the compressive axial force passively generated in the beams. Major test variables included beam flexural reinforcement ratio and axial restraining rigidity. Without axial restraint, the total beam elongation reached 3.75% of the beam height at 3% lateral drift. Under the considered levels of axial restraining rigidity, large compressive axial force developed in the beams, leading to an axial force ratio up to 0.25. The axial restraint increased both beam flexural stiffness and strength. Depending on the tensile reinforcement ratio, beam flexural capacity increased 40%–150% at 3% drift. Compared with the unrestrained specimens, the axially restrained specimens suffered greater damage in the beam plastic hinge regions and beam-column joints due to the dramatically increased shear demand, which can negatively impact the seismic performance of a RC frame.
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Acknowledgments
The authors are grateful for the financial supports received from the National Natural Science Foundation of China (No. 51808087) and Chongqing Science and Technology Commission (No. cstc2018jcyjAX0695). The opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the sponsors.
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Published In
Journal of Structural Engineering
Volume 145 • Issue 5 • May 2019
Copyright
©2019 American Society of Civil Engineers.
History
Received: Apr 29, 2018
Accepted: Oct 18, 2018
Published online: Feb 20, 2019
Published in print: May 1, 2019
Discussion open until: Jul 20, 2019
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