Fire behaviour of GFRP-reinforced concrete slab strips. Effect of straight and 90° bent tension lap splices

Fire Behavior of GFRP-Reinforced Concrete Structural Members: A State-of-the-Art Review

“…Section Experimental assessment of fire resistance of GFRP-RC flexural members) have shown that, even with relatively low concrete covers (e.g. 2 times the bar diameter) these members are not necessarily more prone to cracking and spalling than those reinforced with steel bars Sadek et al 2005;Bellakehal et al 2014;Rosa et al 2022c) (with transverse CTE values much closer to concrete).…”

“…Recent studies have shown that GFRP-RC slabs (Weber 2008;Nigro et al 2011bNigro et al , 2012aHajiloo et al 2017Rosa et al 2020Rosa et al , 2022c and beams (Abbasi and Hogg 2006;Rafi et al 2011;McIntyre 2019) can withstand from 60 min to well over 180 min of fire exposure with significantly thinner concrete covers than those recommended in design standard CAN/CSA S806 (CSA 2017), provided that: (i) the concrete cover thickness is suitable to delay the temperature increase of the reinforcement; (ii) continuous reinforcing bars are used between supports (i.e. lap splicing is not executed in spans susceptible to direct thermal exposure), and (iii) the reinforcing bars are well-anchored in cool zones of the structure to prevent them from reaching the resin's Tg, thus avoiding premature debonding failures.…”

“…According to the literature Nigro et al 2011a;Rosa et al 2020Rosa et al , 2022c, the thermal behavior of GFRP-reinforced concrete members during fire can be regarded similar to that of conventional steelreinforced members, due to the low contribution of the GFRP reinforcement to the heat transfer in the member Nigro et al 2011a). On the contrary, the temperature variation of the concrete cross-section is predominantly affected by the composition of the concrete mix, the moisture content, the aggregate type, and the heating conditions (Abbasi and Hogg 2006); these parameters affect the thermal and mechanical properties of concrete, as well as its propensity for heat-induced explosive concrete spalling (Kodur 2014).…”

“…Aiello et al (1999) suggests that the occurrence of splitting cracks at elevated temperature depends on (i) the type of FRP reinforcement and concrete, (ii) the confining action provided by the transverse reinforcement and (iii) the geometry of the cross-section, including the spacing between reinforcing bars, as demonstrated by (Gentry and Husain 1999). Additionally, the moisture content in concrete also affects cracking and spalling (Sadek et al 2005;McIntyre 2019;Rosa et al 2020Rosa et al , 2022c.…”

“…The acute reduction of the bond strength and stiffness of GFRP bars near their Tg is particularly worrying during a fire event, posing serious risks in zones where the load bearing capacity of the members relies on anchorage of the reinforcement, as is the case of anchorage zones and lap splices (see Section Lap splices) -detailing of anchorage zones ought to be a primary concern in the fire-safe design of GFRP-RC members. Hajiloo et al (2017 and Rosa et al (2020Rosa et al ( , 2022c comprehensively investigated the relationships between the thermomechanical behavior of GFRP-reinforced slabs exposed to fire and the progressive degradation of both bond and tensile properties of the reinforcing bars with temperature. In these studies, the temperature of the reinforcement was duly monitored along the fire exposed span of the slabs as well as within the cooler GFRP bar anchorage zones (Figure 9), thus allowing the bond strength (Figure 10a) and tensile strength retentions of the reinforcing bars (Figure 10b), which had been previously determined from tensile and pull-out tests performed on identical bars, to be better understood during fire exposure.…”