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Polymers 2015, 7(11), 2332-2343; doi:10.3390/polym7111517

Effect of Thermal Distress on Residual Behavior of CFRP-Strengthened Steel Beams Including Periodic Unbonded Zones

1
Department of Civil and Environmental Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
2
IHI Infrastructure Systems Co., Ltd., 3 Ohama Nishimachi, Sakai, Osaka 590-0977, Japan
3
Department of Civil Engineering, University of Colorado Denver, Denver, CO 80217, USA
4
Mitsubishi Plastics Infratec Co., Ltd., 1-2-2 Nihonbashihongokucho, Chuo-ku, Tokyo 103-0021, Japan
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Academic Editor: Raafat El-Hacha
Received: 29 June 2015 / Revised: 4 September 2015 / Accepted: 12 November 2015 / Published: 17 November 2015
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Abstract

This paper presents the residual behavior of wide-flange steel beams strengthened with high-modulus carbon fiber-reinforced polymer (CFRP) laminates subjected to thermal loading. Because the coefficients of thermal expansion of the steel and the CFRP are different, temperature-induced distress may take place along their interface. Periodic unbonded zones are considered to represent local interfacial damage. Five test categories are designed depending on the size of the unbonded zones from 10 to 50 mm, and corresponding beams are loaded until failure occurs after exposing to a cyclic temperature range of ΔT = 25 °C (−10 to 15 °C) up to 84 days. The composite action between the CFRP and the steel substrate is preserved until yielding of the beams happens, regardless of the thermal cycling and periodic unbonded zones. The initiation and progression of CFRP debonding become apparent as the beams are further loaded, particularly at geometric discontinuities in the vicinity of the unbonded zones along the interface. A simple analytical model is employed to predict the interfacial stress of the strengthened beams. A threshold temperature difference of ΔT = 30 °C is estimated for the initiation and progression of CFRP debonding. Multiple debonding-progression stages in conjunction with the extent of thermal distress appear to exist. It is recommended that high-modulus CFRP be restrictively used for strengthening steel members potentially exposed to a wide temperature variation range. View Full-Text
Keywords: carbon fiber-reinforced polymer; interfacial stress; steel; strengthening; thermal coefficient carbon fiber-reinforced polymer; interfacial stress; steel; strengthening; thermal coefficient
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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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MDPI and ACS Style

Yoshitake, I.; Tsuda, H.; Kim, Y.J.; Hisabe, N. Effect of Thermal Distress on Residual Behavior of CFRP-Strengthened Steel Beams Including Periodic Unbonded Zones. Polymers 2015, 7, 2332-2343.

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