Fiber-Element Modeling for Seismic Performance of Square RC Bridge Columns Retrofitted with NSM BFRP Bars and/or BFRP Sheet Confinement
Publication: Journal of Composites for Construction
Volume 20, Issue 4
Abstract
This paper presents an analysis of the seismic performance of square RC bridge columns retrofitted with near-surface-mounted (NSM) basalt fiber-reinforced polymer (BFRP) bars and/or BFRP sheet confinement based on fiber element modeling. An axial stress versus loaded-end displacement model of NSM FRP bars, including both elastic elongation and bond-slip effects, is proposed to account for the significant slippage of FRP bars in the plastic hinge region of strengthened columns. The simplified FRP bar model is then converted into the equivalent stress–strain relationship for easy implementation in fiber-based analysis. Moment-curvature analysis is performed based on the proposed FRP bar model, and the analytical moment versus fixed-end rotation relationship of a strengthened column is calculated and assigned to the rotational spring in the fiber element model. The proposed method avoids the nested iterations in sectional analysis that require force equilibrium and deformation compatibility. Comparisons between the numerical simulations and experimental results indicate that the proposed method is appropriate for predicting pushover curves and the hysteretic response of strengthened columns. Furthermore, the mechanism of the hybrid effect of combining NSM FRP bars with externally bonded FRP sheets can be interpreted after the analytical study; that is, confining the column with FRP sheets improves the bond conditions for NSM FRP bars, while the bond-slip effect mitigates the premature fracturing of the FRP bars, leading to more effective utilization of the NSM reinforcement and a more ductile column behavior.
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Acknowledgments
The authors would like to acknowledge financial support from the National Basic Research Program of China (973 Program) (No. 2012CB026200), the National Science Foundation of China (Nos. 51178099 and 51525801), the National High Technology Research and Development Program of China (Grant No. 2012AA03A204), and the Priority Academic Program Development of Jiangsu High Education Institutions (PAPD). The authors also wish to thank D. A. Bournas for providing the details of the experimental data necessary to validate the proposed model.
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Published In
Journal of Composites for Construction
Volume 20 • Issue 4 • August 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Apr 17, 2015
Accepted: Sep 28, 2015
Published online: Jan 5, 2016
Discussion open until: Jun 5, 2016
Published in print: Aug 1, 2016
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