Study On Structural Performance And Design Method Of T-head Square-neck One-side Bolted Beam To SHS Column Joints

Bolting is one of the forms of structural steel connections and refers to the construction technique or process of connecting steel members by means of bolted fasteners.Compared to welding,bolting is not affected by the site environment,the construction schedule can be controlled,no specialist welding equipment and skilled workers are required and the technical requirements of the construction site are reduced.In addition,bolted joints allow for semi-rigid connections,increasing the deformation capacity of the joints and giving the structure better seismic performance.T-head square-neck one-side bolt(TSOB)is a novel fastener,which can be used for the connection of steel hollow section(SHS)members,with its simple construction,easy installation,no additional aids,can adapt to the rough installation manners in construction site,and has a large application potential.In steel structures,the frame system is the most common,where the beam-column joints are crucial and determine the overall safety of the structures.Although TSOBs offer many advantages in the fastener range,there are no structural tests and design standards for beam-column connections to study their structural performance and guide practical engineerings.Therefore,it is of great theoretical significance and engineering application to carry out research on the mechanical properties and design methods of TSOBs bolted beam to SHS column joints.This paper presents a systematic and complete study on the static and seismic performance of TSOBs bolted beam to SHS column joints using experimental,numerical and theoretical methods,with the following main findings and conclusions:(1)Static performance tests under monotonic load and seismic performance tests under low cyclic load were carried out on eight TSOBs bolted beam to SHS column joints and two conventional bolted joints to investigate the effects of the slotted bolt hole arrangements and two strengthening measures,namely endplate stiffeners and filled concrete in SHS columns,on the structural response of the joints.The failure modes,bending moment-rotation relationship,energy dissipation capacity,strain-rotation relationship at critical parts and yielding sequence of the joint components were investigated to reveal the working and failure mechanism of such joints.The results show that TSOBs bolted beam to SHS column joints have similar failure modes,initial stiffness,strength and stiffness degradations to conventional bolted joints,over 85%bearing capacity,130%seismic ductility and 150%energy dissipation capacity in full life cycle.(2)Double-channel component and H-steel component were proposed,and two strengthened joints with double-channel component and eight with H-steel component were tested under monotonic load and low cyclic load to investigate the effects of type,length and plate thickness of the strengthening components on the joint structural response.The results show that the TSOBs bolted beam to SHS column joints are converted from the semi-rigid partial strength connection to the semi-rigid full strength connection through setting strengthening components,with an increase in energy consumption of up to 102.3%and successful avoidance of bolt hole punching failure.It is recommended that TSOBs bolted beam to SHS column strengthening joints adopt extended H-steel components and that their crosssections should have sufficient bending and shear capacities to carry the bending moment and horizontal shear force in the panel zone.(3)The performance of TSOBs bolted beam to SHS column joints was further evaluated by ABAQUS finite element analysis software,including the establishment of Finite element models(FEMs)for such joints;Revealing the key structural response mechanisms of such connections using FEM analysis results;Parametric analysis of TSOBs bolted beam to SHS column joints,including bolt and bolt hole parameters specific to such connections,member parameters common to conventional bolted connections and relevant parameters for strengthening joints;The final evaluation of the TSOBs bolted beam to SHS column joints and the joint strengthening measures was completed by extensive numerical simulations.(4)The theoretical analysis models and calculation equations for predicting the initial rotational stiffness,bending bearing capacities and bending moment-rotation relationships under monotonic and cyclic loads of TSOBs bolted beam to SHS column joints are developed by applying the component analy sis method and the plastic hinge line theory of thin plates.