Research On Mechanical Properties Of Steel Beam To Concrete-filled Steel Tubular Column Bolted Joint With External Diaphragms

At present,the external diaphragm connection is the most common connection way in steel beam to concrete-filled steel tubular column joint,which is general boltwelding connection.However,welding on site in engineering construction comes with problems such as poor welding condition and heavy welding work in the joints.And the unreasonable shape of external diaphragm will lead to stress concentration at joint column wall and beam end and then easily lead to brittle fracture failure.It has been a consensus in architectural engineering to minimize welding work on site after severe fracture failure was found in the beam-column welding connections in the Northridge earthquake and the Kobe earthquake.A guiding construction thought of “welding in factory,bolted on site” has been formed,which is an advanced manufacturing concept and also conforms to the sustainable development trend of “prefabrication” and “disassembly”.External diaphragm connection is a conventional and widely used connection mode,the next phase of research should focus on adopting bolt connection.This paper proposes a new type of steel beam to concrete filled steel tubular column prefabricated bolted joint with external diaphragms which are welded with concrete-filled steel tubular column and bolted with flanges of steel beam.And the finite element simulation analysis and experimental study on the new type of joint are carried out.The main research content is as follows:(1)Referring to domestic and foreign literature,this paper classifies and induces the related research of conventional concrete-filled steel tubular joints and fabricated concrete-filled steel tubular joints.This paper sums up the shortcomings of traditional welding joints and fabricated joints,and expounds the significance of this research.(2)The model of conventional steel beam to concrete-filled steel tubular column space joint with external diaphragms and the model of beam to concrete-filled steel tubular column bolted joint with external diaphragms are established through the finite element analysis software ABAQUS.Through the numerical simulation analysis of two kinds of joints with external diaphragm,ensuring the reasonable shape of external diaphragm,optimizing the joint structure and analyzing the influence of the thickness and width of external diaphragm on the mechanical property of joint.After determining the reasonable shape of external diaphragm,the influence of the factors such as diameter to thickness ratio of steel pipe,axial compression ratio,cross-section size of steel beam and bolt hole spacing on the mechanical property of joint is further analyzed,and the reasonable joint parameters are determined.(3)Experimental study on five steel beam to concrete-filled steel tubular column prefabricated bolted joints are carried out.Through the monotonic loading of two joints,the strength of the external diaphragm,the ductility and bearing capacity of the joints are analyzed.Test phenomena and the hysteretic curve of joint is obtained by the pseudo-static of three joints,the ductility,energy-dissipating capacity,the strength degradation and the rigidity degeneration of the joint is analyzed.Anti-seismic performance of the joint is evaluated by above-mentioned seismic evaluation method.The finite element numerical analysis model is established on the basis of the test of steel beam to concrete-filled steel tubular column bolted connection joint with external diaphragm.Research shows that bearing capacity and anti-seismic performance of the joints is well,the experimental results and the numerical simulation results were compared.