Experimental investigation on flexural performance of splicing glass fiber-reinforced polymer (GFRP)-Concrete-steel sandwich composite members

In practical engineering, fiber-reinforced polymer (FRP) tubes have limited lengths due to fabrication and transportation constraints. It is needed to develop reliable splices for FRP-concrete composite member. This paper focuses on the flexural performance of splicing glass fiber-reinforced polymer (GFRP)-concrete-steel sandwich composite members. Seven spliced sandwich composite specimens connected by steel bars and a continuous sandwich specimen were tested under three-point bending. The steel ratio of connecting rebar, steel tube diameter and GFRP tube thickness were all investigated. The results show that the GFRP tube has an apparent restraining effect on the concrete at around 55% of the ultimate load (Pu), and the spliced beams degrade at about 75% Pu. The splicing method based on connecting rebar satisfies the demand that the bearing capacity of a splicing member is greater than that of a continuous member, and the splicing specimens show sufficient ductile behavior with an average displacement ductility coefficient of 4.51. The connection steel ratio greatly affects the failure mode and the steel ratio 3.66% is suggested as the optimal value in the splicing joint of the sandwich composite members, for it ensures splicing strength and provides an ideal failure mode. The inner steel tube diameter affects the stress characteristic of section and improves bending stiffness, bearing capacity and ductility to a large extent.