Research On Hysteretic Behavior Of Replaceable Links For D-Type Eccentrically Braced Steel Frames

Eccentrically braced steel frame has a good capacity to resist lateral displacement,is very suitable for buildings in high-intensity earthquake regions.As one of the most commonly used structure,in the traditional D-type eccentrically braced steel frame(hereinafter referred to as the traditional system),the link as a part of the beam,is the main dissipative member of structure.In the earthquake,because of repeated deformation and local buckling,the link occurs failure,so that the post-disaster restoration work has become more difficult.In addition,the link of the traditional system is directly connected to column.Because of bending moment and shear force,the beam-column joints are more easily to damage.For the above shortcomings,the paper proposed a new type of eccentrically braced steel frame which the replaceable shear link was connected to the floor beam by end-plate(hereinafter referred to as the new system).The new system can separate the link from the beam.Under sever earthquakes,the plastic deformation focused on the link beam primarily,so we can check and replace the damaged link beam quickly;it also keeps plastic hinge away to avoid brittle fracture at the beam-column joints.This paper established the finite element model of 1 span 2 layers,the new system's hysteretic behaviors have been analysed,main contents and results are as follows:Firstly,this paper analysed seismic performance of the new system and the traditional system of eccentrically braced steel frame.I compared the two systems in force and bearing capacity of displacement process by one-way loading.To analyse whether it is feasible to replace for the replaceable shear link and the difference of energy dissipation between the new and traditional system by cycle loading.The results showed: the replacement of the replaceable shear link was feasible;the energy dissipation of the new system was superior to the traditional system,but its ultimate bearing capacity and initial stiffness were lower than the traditional system.In addition,in this paper,the replaceable link of the shear link and the shear-bending link were analyzed under cyclic loading by changing the parameter,which were the length of link,the length between the brace and column,the distance of stiffening ribs of link totally 18 specimens of 3 series.The results showed that: the length of the link was smaller,for the shear link and the shear-bending link,the energy dissipation,bearing capacity,ductility,stiffness and the plastic rotation angle were better.The length between the brace and column was smaller,for the shear link,the energy dissipation,bearing capacity,stiffness and the plastic rotation angle were were improved,only ductility improved marginally;for the shear-bending link,the energy dissipation,bearing capacity,ductility,stiffness and the plastic rotation angle were improved a lot.Changing the distance of stiffening ribs of link,for the shear link and the shear-bending link,there is no significant effect on the hysteretic properties of two structures.Finally,the new replaceable system with composite slab was analysed in this paper to research its hysteretic behavior and the development of cracks under cyclic loadings.The results show that: Under cyclic loading,the concrete floor above left end-plate cracked first,continued to load,carried out longitudinal cracks,and formed a cracking band.Continued to load,along the right side of the floor formed a longitudinal cracking band.So we can determine the cracking floor area,and use self-compacting,flowability of cement-based composite materials concrete to repair.For the shear link,after setting up the composite slab,its bearing capacity and initial stiffness were improved,and energy dissipation capacity,ductility and plastic rotation capacity had small decline;for the shear-bending link,after setting up the composite slab,energy dissipation capacity was little decreased,bearing capacity and initial stiffness has greatly improved,but ductility and plastic rotation capacity decreased a lot.It found that after setting the composite slab,shearing new system still had a good hysteretic behavior.But the ductilitys and the plastic rotation angle of shear-bending new system decreased obviously.