Performance of insulated FRP-strengthened concrete flexural members under fire conditions

Abstract

This paper presents the results of fire resistance tests on carbon fiber-reinforced polymer (CFRP) strengthened concrete flexural members, i.e., T-beams and slabs. The strengthened members were protected with fire insulation and tested under the combined effects of thermal and structural loading. The variables considered in the tests include the applied load level, extent of strengthening, and thickness of the fire insulation applied to the beams and slabs. Furthermore, a previously developed numerical model was validated against the data generated from the fire tests; subsequently, it was utilized to undertake a case study. Results from fire tests and numerical studies indicate that owing to the protection provided by the fire insulation, the insulated CFRP-strengthened beams and slabs can withstand four and three hours of standard fire exposure, respectively, under service load conditions. The insulation layer impedes the temperature rise in the member; therefore, the CFRP–concrete composite action remains active for a longer duration and the steel reinforcement temperature remains below 400°C, which in turn enhances the capacity of the beams and slabs.

Keywords

concrete beams / concrete slabs / carbon fiber-reinforced polymers / fire resistance / FRP strengthening / repair / retrofitting

References

[1] ACI 440.2R–17. Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures. Farmington Hills: American Concrete Institute, 2017

[2] ACI 216.1–14. Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies. Farmington Hills: American Concrete Institute, 2014

[3] IBC. International Building Code. Country Club Hills: International Code Council, 2015

[4] Naus D J. The effect of elevated temperature on concrete materials and structures—A literature review. Washington, D.C.: Report of Oak Ridge National Laboratory, U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research, 2006

[5] Kodur V K R, Dwaikat M M S, Dwaikat M B. High-temperature properties of concrete for fire resistance modeling of structures. ACI Materials Journal, 2008, 105(5): 517–527

[6] Phan L, Carino N. Review of mechanical properties of HSC at elevated temperature. Journal of Materials in Civil Engineering, 1998, 10(1): 58–65

[7] Kodur V K R. Spalling in high strength concrete exposed to fire—Concerns, causes, critical parameters and cures. In: Proceedings of the ASCE Structures Congress, Advanced Technology in Structural Engineering. Philadelphia: ASCE, 2000, 1–9

[8] Ali F A, O’Connor D, Abu-Tair A. Explosive spalling of high strength concrete columns in fire. Magazine of Concrete Research, 2001, 53(3): 197–204

[9] Kodur V R, Sultan M A. Structural behaviour of high strength concrete columns exposed to fire. In: Proceedings of International Symposium on High Performance and Reactive Powder Concrete. Sherbrooke: NRCC1998, 217–232

[10] Kodur V, Cheng F, Wang T, Sultan M. Effect of strength and fiber reinforcement on fire resistance of high-strength concrete columns. Journal of Structural Engineering, 2003, 129(2): 253–259

[11] Ali F, Nadjai A, Silcock G, Abu-Tair A. Outcomes of a major research on fire resistance of concrete columns. Fire Safety Journal, 2004, 39(6): 433–445

[12] Bilodeau A, Kodur V R, Hoff G C. Optimization of the type and amount of polypropylene fibers for preventing the spalling of lightweight concrete subjected to hydrocarbon fire. Cement and Concrete Composites, 2004, 26(2): 163–174

[13] Ali F, Nadjai A. Fire resistance of concrete columns containing polypropylene & steel fibers. ACI Special Publications, 2008, 255: 199–216

[14] Khaliq W, Kodur V. High temperature properties of fiber reinforced high strength concrete. ACI Special Publications, 2011, 279: 1–42

[15] Bhatt P P, Kodur V K R, Matsagar V. Numerical approach to evaluate elevated temperature behavior of steel fiber reinforced concrete columns. Indian Concrete Journal, 2019, 93(8): 8–15

[16] Deuring M. Fire Tests on Strengthened Reinforced Concrete Beams. Research Report No. 148’795. Dubendorf: Swiss Federal Laboratories for Materials Testing and Research, 1994

[17] Blontrock H, Taerwe L, Vandevelde P. Fire tests on concrete beams strengthened with fiber composite laminates. In: Konrad B, eds. Proceedings of the 3rd Ph.D. Symposium in Civil Engineering. Vienna: Institute of Structural Engineering, University of Agricultural Sciences, 2000, 151–161

[18] Williams B, Kodur V K R, Green M F, Bisby L A. Fire endurance of fiber-reinforced polymer strengthened concrete T-beams. ACI Structural Journal, 2008, 105(1): 60–67

[19] Gao W Y, Hu K X, Lu Z D. Fire resistance experiments of insulated CFRP strengthened reinforced concrete beams. Chinese Civil Engineering Journal, 2010, 43(3): 15–23 (in Chinese)

[20] Ahmed A, Kodur V. The experimental behavior of FRP-strengthened RC beams subjected to design fire exposure. Engineering Structures, 2011, 33(7): 2201–2211

[21] Firmo J P, Correia J R, França P. Fire behaviour of reinforced concrete beams strengthened with CFRP laminates: Protection systems with insulation of the anchorage zones. Composites. Part B, Engineering, 2012, 43(3): 1545–1556

[22] Yu B, Kodur V. Fire behavior of concrete T-beams strengthened with near-surface mounted FRP reinforcement. Engineering Structures, 2014, 80: 350–361

[23] Firmo J P, Correia J R. Fire behaviour of thermally insulated RC beams strengthened with EBR-CFRP strips: Experimental study. Composite Structures, 2015, 122: 144–154

[24] Dong K, Hu K, Gao W. Fire behavior of full-scale CFRP-strengthened RC beams protected with different insulation systems. Journal of Asian Architecture and Building Engineering, 2016, 15(3): 581–588

[25] Carlos T B, Rodrigues J P C, de Lima R C A, Dhima D. Experimental analysis on flexural behaviour of RC beams strengthened with CFRP laminates and under fire conditions. Composite Structures, 2018, 189: 516–528

[26] Blontrock H, Taerwe L, Vandevelde P. Fire testing of concrete slabs strengthened with fiber composite laminates. In: Burgoyne C J, eds. In: Proceedings of the 5th International Conference on Fiber-Reinforced Plastics for Reinforced Concrete Structures FRPRCS-5. Cambridge: Thomas Telford Publishing, 2001, 547–556

[27] Williams B, Bisby L, Kodur V, Green M, Chowdhury E. Fire insulation schemes for FRP-strengthened concrete slabs. Composites. Part A, Applied Science and Manufacturing, 2006, 37(8): 1151–1160

[28] López C, Firmo J P, Correia J R, Tiago C. Fire protection systems for reinforced concrete slabs strengthened with CFRP laminates. Construction & Building Materials, 2013, 47: 324–333

[29] ACI 318–14. Building Code Requirements for Reinforced Concrete and Commentary. Farmington Hills: American Concrete Institute, 2014

[30] ASTM D638. Standard Test Method for Tensile Properties of Plastics. West Conshohocken: American Society for Testing and Materials, 2014

[31] ASTM D4065. Standard Practice for Plastics: Dynamic Mechanical Properties: Determination and Report of Procedures. West Conshohocken: American Society for Testing and Materials, 2012

[32] ASTM E119. Standard Test Methods for Fire Tests of Building Construction and Materials. West Conshohocken: American Society for Testing and Materials, 2016

[33] Firmo J P, Arruda M R T, Correia J R. Contribution to the understanding of the mechanical behaviour of CFRP-strengthened RC beams subjected to fire: Experimental and numerical assessment. Composites. Part B, Engineering, 2014, 66: 15–24

[34] Kodur V K R, Ahmed A. Numerical model for tracing the response of FRP-strengthened RC beams exposed to fire. Journal of Composites for Construction, 2010, 14(6): 730–742

[35] Kodur V K R, Bhatt P P. A numerical approach for modeling response of fiber reinforced polymer strengthened concrete slabs exposed to fire. Composite Structures, 2018, 187: 226–240

[36] Eurocode-2 EN 1992–1-2. Design of Concrete Structures, Part 1–2: General Rules-Structural Fire Design. Brussels: European Committee for Standardization, 2004

[37] Kodur V K R, Bhatt P P, Naser M Z. High temperature properties of fiber reinforced polymers and fire insulation for fire resistance modeling of strengthened concrete structures. Composites. Part B, Engineering, 2019, 175: 107104

[38] Bisby L A, Green M F, Kodur V K R. Response to fire of concrete structures that incorporate FRP. Progress in Structural Engineering and Materials, 2005, 7(3): 136–149

[39] Dai J G, Gao W Y, Teng J G. Bond-slip model for FRP laminates externally bonded to concrete at elevated temperature. Journal of Composites for Construction, 2013, 17(2): 217–228

[40] Kodur V K R, Naser M Z. Structural Fire Engineering. New York: Mc Graw-Hill Professional, 2020

RIGHTS & PERMISSIONS

Higher Education Press