A Retrofit Theory to Prevent Fatigue Crack Initiation in Aging Riveted Bridges Using Carbon Fiber-Reinforced Polymer Materials
1
Empa, Swiss Federal Laboratories for Materials Science and Technology, Structural Engineering Research Laboratory, Überlandstrasse 129, Dübendorf 8600, Switzerland
2
School of Civil Engineering, University of Tehran, Tehran 1417466191, Iran
*
Author to whom correspondence should be addressed.
Academic Editor: Russell E. Gorga
Polymers 2016, 8(8), 308; https://doi.org/10.3390/polym8080308
Received: 8 June 2016
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Revised: 25 July 2016
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Accepted: 11 August 2016
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Published: 18 August 2016
(This article belongs to the Special Issue Selected Papers from “SMAR 2015”)
Most research on fatigue strengthening of steel has focused on carbon fiber-reinforced polymer (CFRP) strengthening of steel members with existing cracks. However, in many practical cases, aging steel members do not yet have existing cracks but rather are nearing the end of their designed fatigue life. Therefore, there is a need to develop a “proactive” retrofit solution that can prevent fatigue crack initiation in aging bridge members. Such a proactive retrofit approach can be applied to bridge members that have been identified to be deficient, based on structural standards, to enhance their safety margins by extending the design service life. This paper explains a proactive retrofit design approach based on constant life diagram (CLD) methodology. The CLD approach is a method that can take into account the combined effect of alternating and mean stress magnitudes to predict the high-cycle fatigue life of a material. To validate the retrofit model, a series of new fatigue tests on steel I-beams retrofitted by the non-prestressed un-bonded CFRP plates have been conducted. Furthermore, this paper attempts to provide a better understanding of the behavior of un-bonded retrofit (UR) and bonded retrofit (BR) systems. Retrofitting the steel beams using the UR system took less than half of the time that was needed for strengthening with the BR system. The results show that the non-prestressed un-bonded ultra-high modulus (UHM) CFRP plates can be effective in preventing fatigue crack initiation in steel members.
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Keywords:
carbon fiber-reinforced polymer; bonded; unbonded; high-cycle fatigue life; prevention of crack initiation; rehabilitation; old steel members; riveted metallic bridges; constant life diagram; strengthening
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MDPI and ACS Style
Ghafoori, E.; Motavalli, M. A Retrofit Theory to Prevent Fatigue Crack Initiation in Aging Riveted Bridges Using Carbon Fiber-Reinforced Polymer Materials. Polymers 2016, 8, 308. https://doi.org/10.3390/polym8080308
AMA Style
Ghafoori E, Motavalli M. A Retrofit Theory to Prevent Fatigue Crack Initiation in Aging Riveted Bridges Using Carbon Fiber-Reinforced Polymer Materials. Polymers. 2016; 8(8):308. https://doi.org/10.3390/polym8080308
Chicago/Turabian StyleGhafoori, Elyas, and Masoud Motavalli. 2016. "A Retrofit Theory to Prevent Fatigue Crack Initiation in Aging Riveted Bridges Using Carbon Fiber-Reinforced Polymer Materials" Polymers 8, no. 8: 308. https://doi.org/10.3390/polym8080308
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