The thermal incompatibility between fiber reinforced polymer (FRP) bars and concrete may cause splitting cracks within the concrete and, eventually, the deterioration of the bond between the FRP bar and the concrete. This paper presents a numerical study using ADINA finite elements software to investigate the thermal behavior of actual one-way concrete slabs reinforced with glass FRP (GFRP) bars varying the ratio of concrete cover thickness to FRP bar diameter (c/db) from 1.3 to 2.8. Slabs are submitted to temperature variations varied from −50 to 60 °C. The main results prove that first radial cracks occur in concrete, at the FRP bar – concrete interface, at thermal loads (ΔTcr) varied between 15 °C and 30 °C. While, the circumferential cracks appear within concrete, at FRP bar – concrete interface, at ΔTcr varied between −15 °C and −35 °C depending of the ratio c/db (1.3 to 2.8) and the tensile strength of concrete fct (1.9 to 2.9 MPa). These numerical thermal loading values are relatively in good agreement with those predicted from the analytical model. The numerical model shows that there is no failure of the concrete cover for low temperatures for slabs having c/db = 1.3 to 2.8 and fct = 1.9 to 2.9 MPa. Nevertheless, for high temperatures, the splitting failure of concrete cover is produced at thermal loads ΔTsp′ varied from 30 °C to 59 °C. While, for concrete situated between GFRP bars, the splitting failure occurred at thermal loads ΔTsp′ equal to 46 °C. Thermal stresses and strains, and also cracking thermal loads predicted from the numerical model are compared with those obtained from analytical models and experimental tests.
Reinforced concrete slabs subjected to thermal loads