Experimental Study On Bending-Torsion Mechanical Behavior Of Square Concrete Filled CFRP-Steel Tube

As a new type of composite structure,concrete filled CFRP-steel tube has the advantages of high bearing capacity,good plasticity and toughness,good corrosion resistance and good economic benefits.However,the domestic and foreign scholars have little research on its theory,only from the single stress and less composite stress to carry out experimental research and theoretical research.In this paper,the static performance of square concrete filled CFRP-steel tube is mainly studied.Although the situation of both bending and torsion of Square concrete filled CFRP-steel tube s rare in practical engineering,the research on the bending and torsion performance of Square concrete filled CFRP-steel tube is helpful to the understanding of the performance of compression,bending,torsion and shear members,so it is necessary to study it.In this paper,based on the experimental study,a total of 9 square-section concrete filled CFRP-steel tube specimens are studied.With the aid of the finite element analysis,there are 9square-section concrete filled CFRP-steel tube specimens under the same conditions as the test.Its purpose is to verify the accuracy of the finite element simulation and analyze the main parameters on the basis of the simulation.The main research results are as follows:?1?Square concrete filled CFRP-steel tube shows good ductility under the condition of bending and torsion,the steel tube and CFRP work well together,and the transverse and longitudinal CFRP can improve the torsional capacity to a certain extent.?2?Through the comparison between the finite element and the test,the accuracy of the finite element simulation is verified from the macro curve torque angle curve,the micro curve shear stress-strain curve and the deformation mode of the specimen.?3?Based on the verification of the finite element model,the five parameters of concrete strength grade f_cu,steel yield strength f_y,bending moment ratio m,transverse CFRP layers m_tand longitudinal CFRP layers m_l are simulated and analyzed.The finite element simulation results show that with the increase of concrete strength grade,steel yield strength,transverse CFRP layers and longitudinal CFRP layers,the ultimate bearing capacity of the members is improved.Among them,the yield strength of steel and concrete strength grade are the most significant,and the horizontal and vertical CFRP layers have no significant effect on its bearing capacity;With the increase of the moment ratio,the ultimate bearing capacity of the member decreases;the above five factors have no significant effect on the stiffness of the member in the early elastic stage.