Static Performance Of Fully-bolted Joints Between Concrete-filled Rectangular Steel Tubular Beam And Column

The joint play an important role in structures because it could transfer the loads between beams and columns.At the same time,increasing the assembly rate of joints can improve the assembly effect of the entire structural system.However,limitations still exist in the current code-recommended joints of square concrete-filled steel tube(CFST)columns.Specifically,only reinforced concrete beams and steel beams can be applied in these joints,and the joints are usually fabricated by welded connection or web-bolted and flange-welded connection,in which the assembly rate is relatively low.The ductility and bearing capacity of rectangular CFST beams are great,which is beneficial to the overall seismic performance of the structure.Meanwhile,the main components of the fully-bolted joints are processed in the factory firstly,and then connected by bolted at the construction site,which significantly improve the assembly rate of the structure.Therefore,to apply rectangular CFST beams to the frame structure and promote the application of fabricated buildings,fully-bolted joints between rectangular CFST beam and square CFST column are necessary to be studied.In this thesis,the static performance of three types of fully-bolted joints between rectangular CFST beam and column were studied experimentally and numerically,and the main contents are as following:(1)Three types of fully-bolted joints between rectangular CFST beam and square CFST column were proposed in the text.The new joints include angle connection joints,joints with intersecting parallels stiffeners,and joints with inner diaphragm.In particular,the CFST beams were connected to the columns using high-strength blind bolts to make construction easier.Then the appropriate boundary condition,loading scheme and measurement scheme were selected to provide preliminary preparations for the experiment.(2)Six full-scale assembled joints were loaded on the beam end under monotonic loading scheme.The test phenomena and failure modes of each test specimens were presented and analyzed.The influence of the connection form on the bearing capacity,deformation capacity,stiffness and stress distribution of the joints were studied.The results showed that the joint with inner diaphragm is more competitive than the other two because no rectangular hole is required on the columns.In addition,the use of the inner diaphragm at the position of the beam flange would result in clearer load transfer,higher bearing capacity,and larger initial rotational stiffness of the joints.(3)Finite element models were developed using ABAQUS to simulate the static performance of joints.After validated by experimental results,parameter analysis was conducted to investigate the influence of different parameters on the bearing capacity and stiffness of the joints.The analyzed parameters include the yield strength of steel,with or without concrete,the concrete compressive strength,the axial compression ratio,the steel tube thickness of beam,and the thickness of the end plate.According to the analytical results,suggestions were given to improve the efficiency of the joints.