Theoretical Analysis of Thermal Behavior of Overlapped GFRP Bars Embedded in Reinforced Concrete Beams

Fiber-reinforced polymer (FRP) bars are being increasingly used in civil engineering constructions due to their excellent properties in comparison with steel bars, especially in terms of corrosion resistance. Designers generally adopt over-reinforced sections to avoid a sudden failure mode of FRP bars. Therefore, the overlap of the bars is omnipresent. However, under large temperature increase, the overlap area may be regarded as a zone of radial stress concentration generated by a pressure caused by the thermal expansion of both bars. Several studies have been conducted on the thermal behavior of FRP bars-reinforced concrete elements, but none of these studies has taken into account the overlapping effect of bars under high temperature. The aim of this study is to develop numerical and analytical models to predict transverse thermal strains and stresses in FRP bars interaction zone by varying the ratio of concrete cover thickness to FRP bar diameter ( $$c/d_\mathrm{b})$$ from 1 to 3.2, and the temperature increases from 0 to $$+\,60\,^{\circ }\hbox {C}$$ for concrete beams reinforced with two overlapped glass FRP (GFRP) bars. The numerical model is developed using ADINA finite element software, and its results are compared with those obtained from the analytical model based on linear elasticity theory.