Experimental Research On Static Behavior Of New Type Concrete Filled Steel Tubular Composite Column Concrete Beam Joint

Concrete filled steel tubular(CFST)composite column is a new type of reinforced concrete structural member.It is made of concrete-filled steel tubular(CFST)encased with reinforced concrete.Because of its high bearing capacity,superior seismic performance,relatively simple construction,good fire,corrosion and rust resistance,it has been widely used in high-rise building structures.At present,there are three kinds of beam column joint connection methods in practical engineering,but the three methods all have the disadvantages of complex structure and low construction efficiency,which limit the popularization of CFST composite column structure.In order to realize the effective anchorage of the longitudinal reinforcement of the concrete beam and ensure the good static performance,a new type of concrete filled steel tubular composite column concrete beam joint is proposed in this paper.On this basis,three kinds of joint buckle anchorage structures are carried out,and its feasibility is verified by monotonic loading test.The main work and research results are as follows.1)Five groups of specimens of concrete filled steel tubular composite column concrete beam middle joint are tested and studied: the main research parameters include beam column joint form,stirrup ratio of joint area in core area and length of welded short reinforcement;monotonic static loading test is carried out for each group of specimens.The whole process and failure mode of cracking,deformation,yielding and failure of concrete-filled steel tubular(CFST)composite column concrete beam joints under monotonic loading are investigated.The results show that the longitudinal reinforcement of the new type of beam column joint is reliable,and the new type of concrete filled steel tubular composite column concrete beam intermediate joint is feasible under bending failure mode;2)On the basis of experimental study,the model of concrete-filled steel tubular composite column concrete beam joint is established by using nonlinear finite element software ABAQUS,and the numerical simulation analysis of monotonic loading is carried out.The results show that the finite element simulation results are in good agreement with the experimental results,and the finite element simulation analysis is feasible;3)Based on the feasibility of finite element simulation,the parametric analysis of CFST composite column-concrete beam intermediate joint is carried out with the help of finite element software.The main analysis parameters are: axial compression ratio,stirrup ratio of joint area,span height ratio,beam height ratio at both ends,concrete strength in steel tube,with or without floor and different reinforcement ratio of floor.Through a series of parametric analysis,the final conclusion is drawn,which provides a reference for the use of the actual project.The purpose of this paper is to put forward three kinds of structural forms of CFST composite column concrete beam joint,demonstrate its feasibility,and improve the theoretical system of CFST composite column concrete beam joint,which is of great significance to the design and application of engineering practice.