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

doi:10.1007/s11709-021-0714-z

Front. Struct. Civ. Eng.

2021, Vol. 15

Issue (1) : 177-193 https://doi.org/10.1007/s11709-021-0714-z

RESEARCH ARTICLE

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

Pratik P. BHATT¹, Venkatesh K. R. KODUR¹(

), Anuj M. SHAKYA², Tarek ALKHRDAJI²

¹. Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI 48823, USA
². Structural Technologies A Structural Group Company, Columbia, MD 21046, USA

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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

Corresponding Author(s): Venkatesh K. R. KODUR

Just Accepted Date: 05 February 2021 Online First Date: 17 March 2021 Issue Date: 12 April 2021

Cite this article:

Pratik P. BHATT,Venkatesh K. R. KODUR,Anuj M. SHAKYA, et al. Performance of insulated FRP-strengthened concrete flexural members under fire conditions[J]. Front. Struct. Civ. Eng., 2021, 15(1): 177-193.

URL:

https://academic.hep.com.cn/fsce/EN/10.1007/s11709-021-0714-z
https://academic.hep.com.cn/fsce/EN/Y2021/V15/I1/177

Fig.1 Test specimen’s geometry: (a) elevation of T-beam; (b) cross-section of T-beam; (c) elevation of slab; (d) cross-section of the slab (all dimensions are in mm).

Tab.1 Details of strengthening and insulation system and summary of results

Fig.2 Thermocouple and strain gauge position in cross-section of tested specimens: (a) T-beam; (b) slab.

Fig.3 Fire test setup at the Michigan State University.

Fig.4 Temperature change measured at different locations at the mid-section of TB1 and TB2: (a) insulation–FRP and FRP–concrete interfaces; (b) bottom steel rebars and mid-depth of the concrete.

Fig.5 Variation in mid-span deflection with time in TB1 and TB2.

Fig.6 Temperature change measured at different locations at mid-section of S1 and S2: (a) insulation–FRP and FRP–concrete interfaces and mid-depth of concrete; (b) bottom steel rebars and top surface of the concrete.

Fig.7 Mid-span deflection of S1 and S2 during fire exposure.

Fig.8 Segmental and elemental discretization of the analyzed beam. (a) Segmental discretization of beam length; (b) elemental discretization of beam cross-section.

Fig.9 Measured and predicted time-temperature progression for beams: (a) TB1 and (b) TB2.

Fig.10 Measured and predicted time-temperature progression for slabs: (a) S1 and (b) S2.

Fig.11 Measured and predicted structural response comparison in beams and slabs: (a) TB1 and TB2 (b) S1 and S2.

Fig.12 Normalized strength contribution CFRP and steel rebars toward moment capacity of strengthened flexural members as predicted by the model: (a) TB1 and TB2 (b) S1 and S2.

Fig.13 Predicted moment capacity degradation in strengthened flexural members: (a) TB1 and TB2 (b) S1 and S2.

Tab.2 Summary of the parameter analyzed in the case study

Tab.3 Summary of results obtained in the case study

Fig.14 Design fire scenarios considered in the case study.

Fig.15 Fire response of beams analyzed in the case study: (a) corner rebar temperatures; (b) degradation of moment capacity; (c) deflections.

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