Modelling the bond between concrete and reinforcing steel in a fire

A non-linear procedure is presented for modelling the bond characteristic between concrete and reinforcing steel for reinforced concrete structures in a fire. The accuracy and reliability of the model are demonstrated by the analysis of one pull-out test and one beam test at ambient temperature and four full-scale beams tested under two fire conditions. The model is clearly capable of predicting the response of reinforced concrete members and structures in a fire with acceptable accuracy. The bond-link element has been found to have good computational stability and efficiency for 3D analysis of reinforced concrete structures in fires. It is shown that the bond condition between the concrete and reinforcing steel bar has an important influence on the fire resistance of reinforced concrete structures, especially when the temperature of the reinforcing steel bar is high (more than 500 °C). Hence, the current assumption of a perfect bond condition for analysis of reinforced concrete structures under fire conditions is unconservative.