Title:
Fire Tests of Hybrid and Carbon Fiber-Reinforced Polymer Bar Reinforced Concrete Beams
Author(s):
Muhammad Masood Rafi and Ali Nadjai
Publication:
Materials Journal
Volume:
108
Issue:
3
Appears on pages(s):
252-260
Keywords:
beams; deflection; failure; fiber-reinforced polymer; fire; hybrid bars; stiffness; temperature
DOI:
10.14359/51682490
Date:
5/1/2011
Abstract:
Fiber-reinforced polymer (FRP) bars are made of innovative materials and the establishment of the fire resistance of FRP reinforced concrete (RC) is necessary for their widespread application. Experimental behaviors of carbon FRP (CFRP) and hybrid (steel-CFRP) bar RC beams at elevated temperatures were investigated in this study. Data are presented from fire tests of six simply supported beams that were fabricated using normalweight concrete. The effect of varying concrete cover and reinforcing bar arrangement was studied. The beams were tested in a floor furnace and carried a service load of 40% of their ambient temperature load capacity. Nonlinear temperature distribution across the cross section was found. This caused additional beam curvature and stress that is known as eigen-stress. At temperatures beyond the glass transition temperature of the polymer resin, the FRP bars debonded from the concrete and behaved as tie rods if anchored at the ends. Consequently, the FRP RC beam resists thermomechanical loads by arch action. On the other hand, the thermal behaviors of hybrid beams were a combination of arch and beam action. Failure of a beam was typically initiated by reinforcing bar slip due to anchorage failure. All six beams failed in flexure, which was also the intended failure mode at ambient temperature. Hybrid bar reinforced beams were more ductile compared to FRP RC beams. The CFRP bar reinforced beams showed better strength and stiffness characteristics compared to the hybrid beams.