Effect of Elevated Temperatures on the Mechanical Properties and Relaxation of CFRP Strands
Publication: Journal of Composites for Construction
Volume 25, Issue 3
Abstract
Although prestressing carbon fiber–reinforced polymer (CFRP) strands outperform steel strands on different levels, such as strength and durability, their performance under elevated temperatures remains a susceptible design issue that requires careful evaluation. Moderate increase in the temperature of prestressing CFRP strands takes place during construction due to concrete curing. CFRP strands can also experience increase in temperature if the CFRP-prestressed structural element is subjected to fire during service. This paper addresses the effect of increasing the temperature on the strength of prestressing CFRP strands as well as the level of prestressing force. Two sets of CFRP strand specimens with two different diameters were prepared and evaluated for strength degradation triggered by the increase in temperature to 350°C (662°F). Two more sets of prestressed CFRP strands were evaluated for prestress loss due to increase in temperature to 204°C (400°F). The prestress loss due to temperature increase was verified by constructing and monitoring half-scale decked bulb T-beams prestressed with CFRP strands. Test results showed that tensile strength of CFRP specimens decreased with the increase in temperature. In addition, first heating cycle of prestressed CFRP strands led to a slight permanent strand relaxation and a corresponding prestress loss. Subsequent cycles of heating and cooling did not seem to generate additional relaxation of the strands as long as the temperature of the first cycle was not exceeded. Furthermore, CFRP specimens subjected to heating and cooling cycles showed no reduction in the strength when tested at ambient conditions afterwards.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The research investigation is funded by Michigan Department of Transportation (MDOT, Award No. OR15-541). The support from MDOT is greatly appreciated. In addition, the authors would like to acknowledge the hard work of the graduate research assistants at the Center for Innovative Materials Research (CIMR): Ezekiel Ababio, Peter Kornyoh and David Amegadoe. The authors also acknowledge the hard work of Lab Engineer, Marc Kasabasic.
References
ACI (American Concrete Institute). 2015. Guide for the design and construction of structural concrete reinforced with (FRP) bars. ACI 440.1R-15. Farmington Hills, MI: ACI.
Adelzadeh, M., H. Hajiloo, and M. F. Green. 2014. “Numerical study of FRP reinforced concrete slabs at elevated temperature.” Polymers 6 (2): 408–422. https://doi.org/10.3390/polym6020408.
ASTM. 2012. Standard test method for transition temperatures and enthalpies of fusion and crystallization of polymers by differential scanning calorimetry. ASTM D3418-12. West Conshohocken, PA: ASTM.
ASTM. 2016. Standard test method for tensile properties of fiber reinforced polymer matrix composite bars. ASTM D7205/D7205M-06. West Conshohocken, PA: ASTM.
ASTM. 2018. Standard test method for assignment of the glass transition temperature by dynamic mechanical analysis. ASTM E1640-18. West Conshohocken, PA: ASTM
Barr, P. J., J. F. Stanton, and M. O. Eberhard. 2005. “Effects of temperature variations on precast, prestressed concrete bridge girders.” J. Bridge Eng. 10 (2): 186–194. https://doi.org/10.1061/(ASCE)1084-0702(2005)10:2(186).
Benmokrane, B., A. H. Ali, H. M. Mohamed, M. Robert, and A. ElSafty. 2016. “Durability performance and service life of CFCC tendons exposed to elevated temperature and alkaline environment.” J. Compos. Constr. 20 (1): 04015043. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000606.
Blontrock, H., L. Taerwe, and S. Matthys. 1999. “Properties of fiber reinforced plastics at elevated temperatures with regard to fire resistance of reinforced concrete members.” ACI Spec. Publ. 188: 43–54.
Bryan, P. E., and M. F. Green. 1996. “Low temperature behaviour of CFRP prestressed concrete beams.” Can. J. Civ. Eng. 23 (2): 464–470. https://doi.org/10.1139/l96-050.
El-Hacha, R., R. G. Wight, and M. F. Green. 2004. “Prestressed carbon fiber reinforced polymer sheets for strengthening concrete beams at room and low temperatures.” J. Compos. Constr. 8 (1): 3–13. https://doi.org/10.1061/(ASCE)1090-0268(2004)8:1(3).
ElSafty, A., S. Rizkalla, M. Pour-Ghaz, H. M. Mohamed, A. H. Ali, and O. Khalaf. 2019. Degradation mechanisms and service life estimation of fiber reinforced polymer (FRP) concrete reinforcements. Rep. No. BDV34 TWO 977-05. Jacksonville, FL: Univ. of North Florida.
Enomoto, T., T. Harada, K. Ushijima, and M. Khin. 2009. “Long term relaxation characteristics of CFRP cables.” In Proc., 4th Int. Conf. on Construction Materials, 1205–1210. Japan: Japan Concrete Institute.
Grace, N., M. Bebawy, M. Kasabasic, E. Al-Hassan, A. Acharya, K. Abdo, and M. Mohamed. 2019. Evaluating long term capacity & ductility of carbon fiber reinforced polymer prestressing & post tensioning strands subject to long term losses, creep, and environmental factors, and development of CFRP prestressing specifications for the design of highway bridges. Rep. No. SPR-1690. Southfield, MI: Center for Innovative Material Research.
JSCE (Japan Society of Civil Engineers). 1995. Test method for long-term relaxation of continuous fiber reinforcing materials. JSCE-E 534-1995. Tokyo: JSCE.
Khalafalla, O., M. Pour-Ghaz, A. ElSafty, and S. Rizkalla. 2019. “Durability of CFRP strands used for prestressing of concrete structural members.” Constr. Build. Mater. 228: 116756. https://doi.org/10.1016/j.conbuildmat.2019.116756.
Kumahara, S., Y. Masuda, and Y. Tanano. 1993. “Tensile strength of continuous fiber reinforcing bar under high temperature.” In Fiber-Reinforced Plastic Reinforcement For Concrete Structures, edited by C. W. Dolan, S. H. Rizkalla, and A. Nanni, 731–742. Detroit: American Concrete Institute.
Kumar, B. G., R. P. Singh, and T. Nakamura. 2002. “Degradation of carbon fiber-reinforced epoxy composites by ultraviolet radiation and condensation.” J. Compos. Mater. 36 (24): 2713–2733. https://doi.org/10.1177/002199802761675511.
Lie, T. T. 1992. Structural fire protection, manuals and reports on engineering practice, No. 78. New York: ASCE.
Maraveas, C., K. Miamis, and A. A. Vrakas. 2012. “Fiber-Reinforced polymer-strengthened/reinforced concrete structures exposed to fire: A review.” Struct. Eng. Int. 22 (4): 500–513. https://doi.org/10.2749/101686612X13363929517613.
Robert, M., and B. Benmokrane. 2010. “Behavior of GFRP reinforcing bars subjected to extreme temperatures.” J. Compos. Constr. 14 (4): 353–360. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000092.
Saadatmanesh, H., and F. E. Tannous. 1999. “Relaxation, creep and fatigue behavior of carbon fiber reinforced plastic tendons.” ACI Mater. J. 96 (2): 143–153.
Sasaki, I., and I. Nishizaki. 2012. “Tensile load relaxation of FRP cable system during long-term exposure tests.” In Proc., 6th Int. Conf. on FRP Composites in Civil Engineering, 1–8. Rome, Italy: CICE.
Swenson, T., and C. French. 2015. Effect of temperature on prestressed concrete bridge girder strand stress during fabrication. MNDOT Rep. MN/RC 2015-50. Minneapolis: Dept. of Civil, Environmental, and Geo- Engineering, Univ. of Minnesota.
Information & Authors
Information
Published In
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Sep 11, 2020
Accepted: Feb 25, 2021
Published online: Apr 7, 2021
Published in print: Jun 1, 2021
Discussion open until: Sep 7, 2021
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.