Flexural Behavior Of Elliptical FRP Tube Confined Steel Reinforced Concrete Beams

At present,the construction field in the world faces the durability problem of concrete structures due to steel corrosion.It is imperative to study alternative corrosion-resistant materials.The traditional reinforced concrete members are protected by concrete,having good fire resistance,good integrity.They can be taken locally,but the durability in the corrosive environment is not negligible.In recent years,Fiber reinforced polymer(FRP)is widely used in industrial and civil construction as a new type of composite material.It has the advantages of light weight,high strength and corrosion resistance,which can effectively solve the erosion of concrete structure's durability issues in the environment.In this paper,the FRP materials are complementary to the traditional concrete flexural members and combined research is carried out.The composite material(referred to as FRP)pipe is used to restrain the concrete,and the composite material pipe is used to replace the stirrups in the conventional scheme,and the cross-sectional shape is changed into an elliptical shape to form an elliptical composite pipe-constrained steel concrete beam.In order to study the bending resistance of elliptical composite pipe-constrained steel concrete beams,a total of 15 beam specimens were produced in this test for four-point bending test.The test variables include two different composite pipe thicknesses,two different steel profiles and three different sections.Among them,13 specimens were loaded monotonically,and 2 were cyclically loaded.The bending resistance of the specimen under different parameters was analyzed.The effects of tube thickness,steel content,section type and loading method on the bearing capacity and ductility of the specimen were studied.The results show that:(1)The load-displacement curve of FRP pipe-constrained steel concrete beam is roughly two-fold line;(2)under the same conditions,the bearing capacity of specimens with high steel content is significantly improved;(3)under the same conditions,complex The specimens with thick pipe thickness have correspondingly higher bearing capacity;(4)According to the shape of the deflection curve,the FRP pipe-constrained steel-concrete beam has good ductility,and the mid-span deflection is at least 1/10 of the span.All experiments were predicted by Teng et al's 2016 design model,and the theoretical load-deflection curve was obtained.The comparison with the test showed that the composite pipe(FRP pipe)restraint has a good improvement on the bending resistance of the steel reinforced concrete beam.