Research On How The Thickness Of Joint Zone Affects The Mechanical Performance Of Steel Joint

Steelwork has the advantages such as light in weight, good in ductility, flexible instructure, effective in energy saving, quick to be constructed and friendly towardsenvironment. Hence, it is widely used in today’s society. The joint of steelwork is the part thatbears the most complex stress, and also the part that ensures the regular function and excellentperformance of the whole unit. Therefore, the study of joint has become an important researchdirection of the current study as far as steelwork is concerned. In a joint, the flanges on bothsides of the pole connecting the beam and column and the web plate encircled by thehorizontal stiffening rib in the pole are called joint zone. At the effects of loading anddeformation, such zone simultaneously bears the forces from the beam and the column, whichhas the most complicated stress state, and exerts huge impact on the stress property of thejoint. The main purpose of this paper is to adopt the joint zone of the Normal BeamJoint(NBJ)and Reduced Beam Joint(RBJ), which is most widely used at the time, as theresearch object, and discuss how the thickness of the joint zone affects the overall stressproperty of the joint.This paper reviews the current research status on steelwork beam-column joint home andabroad, and introduces the large-scale finite element software ABAQUS and the finiteelement analysis method. Drawing on the relevant experience of literature, with reference tothe requirements of “Seismic Design of Buildings”(GB50011-2010) and “Design of SteelStructures”(GB50017-2003), the writer designs a finite element model of the specimen, andestablishes a gradient with the thickness of the joint zone as parameter:4mm,6mm,9mm,12mm,15mm,20mm. The model is built on ABAQUS software, the finite element modelingexperiment is conducted by low-cycle cyclic shift loading and the analytical results areobtained by the finite element method. According to the results of simulation experiments, thepaper studies how the thickness of the joint zone affects the overall stress property of the jointfrom multiple perspectives such as the development of stress concentration, the developmentof elastic deformation, the development of plastic deformation, the development of bearingcapacity, the formation of plastic hinges, the capacity of hysteretic behavior, ductility, seismicresistance and energy dissipation, and the regular pattern of damage deterioration, by Misesstress cloud, PEEQ cloud, hysteresis curves, skeleton curves, ductility factor, equivalentviscous damping factor he, equivalent stiffness factor K and equivalent stiffness degradationcoefficient factor Ψ.Following are the rules found through research: the thicker the joint zone is, the stressconcentration phenomenon is more difficult to form on the joint zone, and the flange sides atthe end of the beam connecting to the column is easier to be where the stress concentrationfirst occurs; the thicker the joint zone is,the longer the joint has to endure elastic stress, thegreater the elastic displacement is and the plastic deformation appears more late; the thicker the joint zone is, the joint zone is more unlikely to yield, and the flange sides at the end of thebeam connecting to the column is easier to be where the yielding first occurs; the thicker thejoint zone is, the greater the yield load of the joint is; as the thickness of the joint zonechanges from small to huge, there are three cases of the yielding part of the joint, theoccurring sequence of which are: the yielding of the joint zone only, the yielding of both thejoint zone and the flange sides at the end of the beam connecting to the column, and theyielding of the flange sides only; as the thickness of the joint zone changes from small to hugethere are three cases of the plastic hinge occurrence, which in sequence are: the joint zone, noplastic hinge occurs, and the end of the beam near the column; when plastic hinge is formed atthe joint zone, the thicker the joint zone is, the later the plastic hinge occurs; the thickness ofthe joint zone does not affect when the joint reaches its ultimate bearing capacity; the thickerthe joint zone is, the greater the bearing capacity of the joint is, but when the thickness of thejoint zone is big enough, the beam will has an overall buckling, limiting the development ofthe ultimate bearing capacity of the joint, the growth of which changes more slowly andbecomes more stable with the thickening of the joint zone; if the beam is not buckled, whenthe loading ends, the thicker the joint zone is, the greater the remaining bearing force of thejoint is, which could reach80%-90%of the ultimate bearing capacity, and the carryingcapacity loss is smaller. When the overall buckling of the beam occurs, the thicker the jointzone is, the smaller the remaining bearing force of the joint is, which could be less than30%-50%of the ultimate bearing capacity, and the carrying capacity loss is severer; the thinnerthe joint zone is, the more likely the column to partly buckle, and the sooner will the bucklingoccurs; the thicker the joint zone is, the more likely the beam to overall buckle, and the soonerwill the buckling occurs; the thicker the joint zone is, the better the hysteretic behavior of thejoint is; when the thickness of the joint zone is comparatively small, the joint has goodductility performance and seismic resistance and energy dissipation capacity, which declineswith the thickening of the joint zone and when has reached certain level, will remain steadyand do not change according to the change of the thickness of the joint zone; when thethickness of the joint zone is proper, it will have a better capacity of rigidity degenerationresistance. The phenomenon of rigidity degeneration is rather obvious whether the joint zoneis too thick or too thin; in the stage of elastic loading, the severity of the joint is a constant,and there is no phenomenon of rigidity degeneration or rigidity reinforcement; the thicker thejoint zone is, the bigger the initial stiffness of the joint is.