Experimental study and modelling of flexural behaviour of continuous fibre-reinforced lightweight aggregate concrete one-way slab at ambient and elevated temperatures

An experimental study on the flexural behaviour of six fibre-reinforced lightweight aggregate concrete (FRLWAC) one-way slab strips under ambient and elevated temperatures is presented in this paper. Two slabs, one simply-supported and one continuous, were loaded to failure at ambient temperature as references for the fire tests, while another simply-supported and three continuous slabs with varying degrees of design moment redistribution were loaded and exposed to elevated temperatures until failure. The ambient tests showed that the steel fibre addition prevents premature flexural-compression failure commonly observed in lightweight aggregate concrete structures. The rotations of FRLWAC plastic hinges were concentrated in a single crack under ambient temperature and a few cracks under fire exposure. The fire tests revealed significant moment redistribution towards the hogging moment area in the continuous slabs due to restrained thermal-induced deflection. Furthermore, the reinforcement configuration that catered for moment redistribution towards the hogging area was found to enhance the fire resistance of continuous FRLWAC slabs. A fibre-reinforced concrete (FRC) plastic hinge model, based on the rigid-body rotation concept, was proposed and validated. This model predicts the moment-rotation behaviour of FRC hinges at ambient temperature and the fire resistance of FRLWAC one-way slabs with good accuracy.