Analysis On Mechanical Properties Of Beam-Column Joints Of Concrete Filled Square Steel Tubular Column With Inner CFRP Circular Tube

Concrete filled square steel tubular with inner CFRP(carbon fiber reinforced plastic) circular tube is a new type of composite structure. It can not only effectively improve the ductility and deformation capacity, but also solve the shortage of the square steel tube constraints on the corner concrete. In recent years, the researchers conducted their study on the mechanical properties of components of concrete filled square steel tubular with inner CFRP circular tube more and column-beam joints less which focused on middle column joints. Therefore, it is very necessary to carry out the research of edge column and corner column joints of concrete filled square steel tubular with inner CFRP circular tube.By using ABAQUS finite element software, middle column joints were built and the results of hysteresis curve, skeleton curve, stiffness degradation and energy dissipation capacity were contrasted with reference, which can show that the finite element modeling method is reasonable and reliable. Based on this, edge column and corner column joints were built and the influence of CFRP setting to the mechanical properties of the joints was analyzed. By changing steel strength, concrete strength, axial compression ratio, steel ratio and other parameters, the influence to mechanical properties of the joints mainly from the skeleton curve, ductility, stiffness and strength degradation and energy dissipation capacity was analyzed.Results showed that:(1) the destruction of joints caused by the plastic hinge of the beam-end joint domain conforms to the "strong column weak beam" principle in project;(2) compared with ordinary joints, joints with inner CFRP circular tube can extend the flexible working period of concrete to a certain extent and improve the stability of the whole structure;(3) with the increase of the steel strength, the ultimate bearing capacity could be significantly improved, stiffness and strength degradation would be delayed;(4) with the increase of the steel ratio, the ultimate bearing capacity could be significantly improved, energy dissipation capacity could be improved, and ductility could be poor;(5) with the increase of the concrete strength and CFRP circular tube diameter, there is no change of the skeleton curve and the ultimate bearing capacity;(6) with the increase of the axial compression ratio, the ultimate bearing capacity could be significantly reduced, stiffness and strength degradation would be obvious;(7) with the increase of the outer stiffening ring width, the ultimate bearing capacity could be significantly improved, stiffness and strength degradation would be obvious, and ductility could be poor, there would be a tendency of brittle fracture. Therefore, in the design, the ductility and bearing capacity of the structure should be considered, and the maximum of the one party would not be pursued.