Spalling of concrete cover of fiber-reinforced polymer reinforced concrete under thermal loads

A unite element method using a proposed mesoscopic thermoelastic damage model (MTED) is verified for simulating the cracking process of a concrete section reinforced with fibre-reinforced polymer (FRP) bars. The cracking was due to the significant difference in thermal expansion properties between the concrete and the FRP materials at elevated temperatures. The numerical study reveals that although a conventional elastic analytical method can provide good estimates of the critical temperature increment of concrete cover failure of a cylindrical concrete section that is reinforced with a single bar, it gives too conservative predictions for typical rectangular sections with multiple bars. The study also shows that the concrete cover and the horizontal bar spacing have more influence than the vertical bar spacing on the determination of the critical temperature increments. Horizontal lapping of bars significantly lowers the critical temperature increment.