Modelling glass fibre-reinforced polymer reinforced geopolymer concrete columns

Glass fibre-reinforced polymer (GFRP) bar and stirrup reinforced geopolymer concrete (GPC) is increasingly recognised as a potential replacement to the conventional steel-reinforced ordinary Portland cement (OPC) concrete due to its superior durability. This paper proposed an analytical model to predict the load-displacement relationship of the concentrically and eccentrically loaded GFRP-GPC columns. The cross-section was divided into a number of strips and a strain gradient was assigned to determine the stresses in the cover, core and reinforcement. The theoretical predictions were then validated using experimental results from previous studies on the behaviour of GFRP-GPC, GFRP-OPC concrete and steel-GFRP concrete systems. It was found that the predicted peaks load, displacements at peak load and ductility indices were generally in close agreement with the experimental results of the GFRP-GPC columns. However, the model had a tendency to over-predict the stiffness of GFRP-OPC concrete and steel-OPC concrete columns in the elastic range. Overall, the proposed analytical model is suitable for GFRP-GPC systems and could facilitate the widespread use of this composite material.