Research On Mechanical Behavior Of Concrete-Filled Square Steel Tubes With Inner I-Shaped CFRP Under Flexural Loading

Concrete-filled square steel tube column with inner I-shaped CFRP is a new type of composite structure that the I-shaped CFRP profile is placed in the concrete-filled steel tube.The formation of a new type of composite member in the CFRP material with concrete filled steel tube can make the component on the basis of maintaining good ductility to further raise the bearing capacity of components,so the new type composite component has higher bearing capacity and ductility.So far,the experimental and theoretical research on CFST has been relatively mature,but the research on this new type of member is not extensiveBased on the experimental study,the force performance of concrete filled square steel tube pure bending column with inner I-shaped CFRP under flexural Loading is studied by finite element simulation.With steel yield strength and steel content change parameter design 5 root specimens.The failure modes,the load-mid-span deflection curve,the curve of sine half-wave,the plane section assumes the verification curve,the neutral axis curve,the load-strain curve of steel tube and CFRP and effect of different parameters on the bearing capacity of the new type of concrete-filled steel tube of pure bending were observed and studied.A finite element analysis model is established and numerically calculated by using the finite element analysis software ABAQUS to select the constitutive relationship,boundary conditions and unit types of materials reasonably.On the basis of good agreement between the finite element calculation results and the test results,the mechanism of the specimen and the effect of different parameters on the mechanical performance of the specimen are further analyzed.,according to the experimental and finite element results and the existing calculation formulas,the formulas for calculating the bearing capacity of square concrete-filled steel tubular members with I-shaped CFRP are obtained by fitting the date.The results show that the whole specimen is bent and deformed in the middle section.The whole process of failure shows good ductility.The bending moment-curvature curve can be divided into three stages:elastic stage,elastoplastic stage and strengthening stage.The I-shaped CFRP profile in CFST can effectively improve the ultimate bearing capacity of specimens.With the increase of concrete strength,steel yield strength and steel ratio,the ultimate bearing capacity of the specimen increases,but they have little influence on the initial stiffness of the specimen The change of steel yield strength and steel ratio of a member has a significant impact on the ductility of the member,the initial flexural stiffness and the service flexural stiffness.With the increase of steel yield strength,the ductility and the flexural stiffness decreases.With the increase of steel ratio,the ductility increases and the bending stiffness decreases.The calculation formula of bearing capacity obtained by modifying the code of our country is clear in concept,simple in form,and the calculation result is close to the test result with little dispersion.It is suggested to use this formula to calculate the bearing capacity of this new type of concrete-filled steel tube pure bending member.