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Polymers 2018, 10(3), 264; https://doi.org/10.3390/polym10030264

Prestressed Unbonded Reinforcement System with Multiple CFRP Plates for Fatigue Strengthening of Steel Members

1
Swiss Federal Laboratories for Materials Science and Technology (Empa), Überlandstrasse 129, 8600 Dübendorf, Switzerland, and Resilient Steel Structures Laboratory (RESSLab), Swiss Federal Institute of Technology Lausanne (EPFL), Station 18, 1015 Lausanne, Switzerland
2
Swiss Federal Laboratories for Materials Science and Technology (Empa), Überlandstrasse 129, 8600 Dübendorf, Switzerland
3
Swiss Federal Laboratories for Materials Science and Technology (Empa), Überlandstrasse 129, 8600 Dübendorf, Switzerland, and Department of Civil Engineering, Monash University, Melbourne, VIC 3800, Australia
4
Resilient Steel Structures Laboratory (RESSLab), Swiss Federal Institute of Technology Lausanne (EPFL), Station 18, 1015 Lausanne, Switzerland
5
Department of Civil Engineering, Monash University, Melbourne, VIC 3800, Australia
This paper is an extended version of the paper presented in SMAR 2017 conference, 13–15 September 2017, Zurich, Switzerland.
*
Author to whom correspondence should be addressed.
Received: 31 January 2018 / Revised: 28 February 2018 / Accepted: 2 March 2018 / Published: 4 March 2018
(This article belongs to the Special Issue Selected Papers from "SMAR 2017")
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Abstract

Carbon fiber reinforced polymer (CFRP) composites have exhibited a great potential for strengthening of steel structures. In the current study, an innovative prestressed unbonded reinforcement (PUR) system is introduced for fatigue strengthening of existing steel members. The system relies on a pair of mechanical clamps; each holds multiple CFRP plates and anchors their prestressing forces to the steel substrate via friction. A finite element model was established to optimize the design of the required mechanical components of the system. A set of static and fatigue tests was conducted on the developed mechanical clamps as the key elements of the proposed PUR system. The performance of the PUR system was then evaluated using a set of fatigue tests on two precracked steel plate specimens, one without any strengthening system and the other one strengthened with the proposed PUR system. In the latter specimen, the CFRP plates were prestressed up to about 800 MPa (approximately 30% of the CFRP tensile strength), which resulted in a complete fatigue crack arrest in the precracked steel plate. Furthermore, neither slippage of the mechanical clamps nor any prestress loss in the CFRP plates was observed after 7.5 million fatigue cycles. Based on the promising experimental results, obtained from the sets of fatigue tests performed in the current study, it can be concluded that the proposed PUR system can be considered as an efficient alternative to the conventional bonded reinforcement solutions for fatigue strengthening of damaged steel members. View Full-Text
Keywords: steel structures; fatigue crack; fatigue strengthening; carbon fiber reinforced polymer; prestressed unbonded reinforcement; mechanical clamp; finite element simulation steel structures; fatigue crack; fatigue strengthening; carbon fiber reinforced polymer; prestressed unbonded reinforcement; mechanical clamp; finite element simulation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Hosseini, A.; Ghafoori, E.; Motavalli, M.; Nussbaumer, A.; Zhao, X.-L.; Koller, R. Prestressed Unbonded Reinforcement System with Multiple CFRP Plates for Fatigue Strengthening of Steel Members. Polymers 2018, 10, 264.

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