Experimental study and numerical analysis of flexural behaviour of post-fire reinforced concrete beam

Abstract

A cycle of heating and cooling can cause gradual chemical changes in reinforced concrete after a fire and these can affect the strength of the concrete. The study aims to analyse the deflection and damage of post-fire concrete beams. The method of study used numerical and experimental analysis on reinforced concrete beam models 1250 mm in length, with a cross-section width of 100 mm and height of 200 mm. The combustion of the specimen was carried out in a brick furnace for a duration of 30 and 60 minutes with an average combustion temperature of 930 and 926 °C. The flexural strength test of the post-burn beam was carried out using a load cell and measured using LVDT at room temperature. The results showed that the deflection that occurred on reinforced concrete beams burned for 30 minutes (BN30) resulted in increased beam deflection by 7% compared to the unburned concrete beam model (BN). Similarly, the concrete beam model which was burned for 60 minutes (BN60) resulted in a 22% increase in beam deflection compared to the unburned concrete beam model. Also, there is a sloping pattern in the relationship curve between load and deflection with increasing duration of the combustion time. This condition is due to a 62% decrease in the load received by the beam when the beam burned for 30 minutes (BN30). Likewise, when the beam burned for 60 minutes (BN60), this caused a 72% decrease in load compared to the unburned concrete beam model. Thus, the duration of fire combustion in concrete beams significantly affects the strength of the reinforced concrete beam.