Experimental Study On Hysteretic Behavior Of Circular Concrete Filled CFRP-steel Tubes Under Bending And Shearing

Concrete filled CFRP-steel tube is a new composite structure in which concrete is poured inside the steel tube and CFRP is adhered to the outer surface of the steel tube.It combines the advantages of CFRP,steel tube and concrete.It is a high-performance composite structure with better bearing capacity and durability than CFST and better capacity and ductility than concrete filled CFRP tube.With the continuous deepening of research on this kind of combined structure and the continuous advancement of science and technology,all experts and scholars have repeatedly overcome various static performance problems,but their researchs on hysteretic performance are still not comprehensive.In order to enrich the research direction,this paper analyzes the bending-shear hysteresis behavior of circular concrete-filled CFRP-steel tube from experimental research and ABAQUS finite element simulation.Firstly,the shear span ratio and the number of transverse CFRP layers are taken as the main research parameters.A total of 9 specimens are designed and tested.Secondly,the ABAQUS finite element model is established based on the experimental research.The test curve is compared with the simulated curve to verify The correctness of the model;finally,under the premise of the correct model,the parameters of the test piece are analyzed.Research indicates:（1）The V-△hysteresis curves of each test pieces are“anti-S shape”,the shape of curves is not full and slippage is significant;The change of the shear force direction has little effect on the strength and rigidity of the test piece;Under the same level of load,the strength of the test piece decreases with the increase of the number of turns.（2）The shape of the V-△skeleton curve is roughly the same,and the curve is symmetric with respect to the origin;The initial stage of loading is in the elastic stage,at which time the specimen is stiff,and when the displacement reaches△_y,the specimen enters the stiffness degradation.The shear span ratio and the transverse CFRP layer have little effect on the strength and stiffness of the test piece;The shear span ratio increases,the shear capacity of the test piece decreases;The transverse CFRP layer increases,the shear capacity of the test piece increases slightly.（3）The range of shear strain in theτ-γcurve increases as the test progresses.（4）The longitudinal strain and transverse strain of the steel tube and CFRP of each test piece are positive,which means being pulled;The value of the 45°strain alternates with positive and negative,which means being pulled and pressed alternately.（5）ABAQUS can be used to simulate the V-△hysteresis curve and deformation mode of circular concrete filled CFRP-steel tube.（6）The results of parameter analysis show that the increase of f_cu or f_y can improve the shearing capacity of members significantly,and the increase of transverse CFRP layer or longitudinal CFRP layer makes the shearing capacity improved slightly.