Shear Performance of Steel Beams with Bonded GFRP Stiffeners: Weathering and Cyclic Load Effects
Publication: Journal of Composites for Construction
Volume 26, Issue 6
Abstract
Strengthening-by-stiffening (SBS) is a technique for enhancing the shear performance of buckling-prone webs of steel beams by bonding glass fiber–reinforced polymer (GFRP) stiffeners. This paper focuses on changes in load capacity, ductility, and mode of failure of SBS under cyclic loading and after exposure to weathering conditions for 1 year. First, weathering effects on mechanical properties of the adhesive used in bonding the GFRP stiffeners are presented. The ductility of the epoxy was significantly reduced; however, the ultimate stress increased by about 68% over the ultimate stress of the nonweathered coupons. Furthermore, weathering led to the formation of a thin film of rust that propagated around the edges of the bonding adhesive for the full-scale beams. Consequently, the ultimate load capacity of the weathered beam dropped about 11% after 1 year of environmental exposure. Cyclic loading, however, resulted in negligible change in the ultimate load capacity. For all tested beams, the ductile adhesive used in bonding the GFRP stiffeners prevented a sudden drop in load capacity due to debonding of the GFRP stiffener in all tests.
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Acknowledgments
This research is sponsored in part by the National Science Foundation (CMMI# 1030575). The donation of materials by Fyfe Co., LLC, and Bedford Reinforced Plastics, Inc. in addition to support from Strongwell Corporation are greatly appreciated. Additional support from the Department of Civil and Environmental Engineering at Louisiana State University is also acknowledged. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.
Notation
The following symbols are used in this paper:
- Aw
- area of steel web;
- a
- web panel width;
- cps
- centipoise (viscosity of adhesive);
- CV
- coefficient of variation;
- Cv
- steel web shear strength coefficient;
- elastic modulus of the reference adhesive;
- elastic modulus of the weathered adhesive;
- EIGFRP
- flexural rigidity of the GFRP stiffener;
- EIsteel
- flexural rigidity of the steel stiffener;
- EFFT
- total fracture toughness;
- Es
- elastic modulus of steel;
- rupture stress of the reference adhesive;
- rupture stress of the weathered adhesive;
- Fu
- ultimate stress of steel;
- Fy
- yield stress of steel;
- Fyw
- yield stress of steel web;
- h
- web panel height;
- Pin
- inelastic load limit;
- PR
- approximated nominal vertical load;
- Pul
- ultimate load;
- tw
- web plate thickness;
- Vn
- nominal shear capacity;
- VR
- approximated nominal shear capacity;
- ɛx
- uniaxial strain of adhesive;
- rupture strain of reference adhesive;
- rupture strain of weathered adhesive;
- Δin
- displacement inelastic load limit;
- Δul
- displacement at ultimate load ;
- μ
- mean value;
- σ
- standard deviation;
- ϕ
- resistance factor;
- −−,anal.
- analytical results;
- −−,exp.
- experimental results; and
- −−,FEM
- finite-element model results.
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Published In
Journal of Composites for Construction
Volume 26 • Issue 6 • December 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Feb 2, 2022
Accepted: Aug 17, 2022
Published online: Oct 11, 2022
Published in print: Dec 1, 2022
Discussion open until: Mar 11, 2023
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