Heat Transfer Analysis of Reinforced Concrete Beams Reinforced with GFRP Bars

Abstract

Corrosion of steel reinforcement has been identified as a key factor of deterioration and structural deficiency (Masoudi et al., 2011) in reinforced concrete (RC) structural members. The corrosion state of current RC bridges and high-rise buildings has been a source of concern to designers and engineers. In addition, such structures have been invulnerable to harsh environmental exposures, with little or no maintenance. Furthermore, such structures are experiencing larger amount of loads than their original capacities due to the increase number of users over the years (Bisby, 2003). Several different solutions were proposed to retrofit deteriorated structural members (Masoudi et al., 2011; Hawelih et al., 2011; AlTamimi et al., 2011) by replacing cracked concrete, using epoxy injected supplements, and FRP externally bonded systems. The use of embedded FRP bar reinforcement seems to be a promising solution (Masoudi et al., 2011; Bisby, 2003; Abbasi & Hogg, 2005; Abbasi & Hogg, 2006; Qu et al., 2009; Aiello & Ombres, 2002) to strengthen structural RC members in flexure and shear. Compared to the conventional reinforcing steel bars, the FRP bars seem to have a high strength to weight ratio, moderate modulus of elasticity and resistance to chemical and electrical corrosion. Although FRP materials were shown to have a brittle failure, due to their natural composition, still if designed properly they can show considerable amount of ductility (Rasheed et al, 2010; De Lorenzis & Teng, 2007). One of the draw backs of using FRP embedded bars is their low glass temperature and tendency to change state; from solid to liquid at elevated temperatures. Hence, the performance of FRP reinforced structural members under elevated temperatures draws many doubts and concerns and warrants further investigation. Few experimental tests have been conducted in the previous years on the fire performance of RC beams reinforced with FRP bars due to the high costs of such tests, tremendous amount of preparation, and shortage of specialized facilities (Franssen et al., 2009). Sadek et al. (Sadek et al., 2006) conducted a full scale experimental program on the fire resistance of RC beams reinforced with steel and Glass Fibre Reinforced Polymer (GFRP) bars. The test matrix composed of different reinforcing rebars used along with different concrete compressive strengths. The testing took place in a special testing facility and the beams were loaded statically at 60% of their ultimate load capacity during the course of the fire test. The tests followed the ASTM E119 (ASTM E119, 2002) standard and fire curve.