Study On The Seismic Performance Of Eccentrically Braced Steel Frame With Replaceable Links And Floors

In the traditional eccentrically braced steel frame structure,for the link of energy dissipation and the frame beam are designed as a whole,the link of energy dissipation and the frame beam have the same section size,which is bad for playing the seismic energy dissipation capacity of the link of the energy dissipation sufficiently and cost too much;Because the link of energy dissipation accumulate the plastic deformation of under seismic load,the level of the destruction cannot be evaluated and the repair and replacement of the frame beam is relatively difficult and costly after the link is broken.In this paper,four 1/4 scale frame models were tested under cyclic loading to analyze the seismic performance,failure mode and the effect of replacing links on the overall performance of the structure and to verify the replaceability of energy dissipation links.In addition,a finite element model of 22 eccentrically braced steel frames with replaceable links and floors is established.The mechanical properties of the overall steel frames,such as bearing capacity,stiffness and ductility,as well as the seismic properties such as energy dissipation coefficient,stiffness degradation and plastic rotation angle were studied.The floor slab effect was considered and the influences of the parameters such as length,section size and stiffener spacing of the link on the mechanical properties such as bearing capacity,stiffness,ductility,and energy dissipation were analyzed.Compared with the tests results,the reliability of the numerical simulation was verified.The following conclusions are obtained:(1)Compared with eccentrically braced steel frame with replaceable links,the bearing capacity of eccentrically braced steel frame with replaceable links and floors is greatly improved,with the yield load increased by 25.1% and the ultimate load increased by 11.8%;However,the composite floor has no obvious influence on the shear energy dissipation capacity of the link,and the structure still has good ductility and energy dissipation performance.(2)The eccentrically braced steel frame with replaceable links and floors has good hysteretic performance,the link of energy dissipation,as the first energy dissipation element,dissipates energy through shear deformation,which concentrates the inelastic deformation of the structure on the link of energy dissipation,thus protecting the safety of other components and improving the seismic performance of the structure.(3)The length,section size and stiffener spacing of the link of energy dissipation have great influence on the mechanical properties of the structure,the bearing capacity of the structure increases with the decrease of the link length,the increase of the sectional size and the decrease of stiffener spacing.When the length and the stiffener spacing of the energy dissipation link that are 1.1-1.4 times Mp/Vp and 0.54-0.76 times ho respectively,the smaller the sectional size,the larger the energy dissipation coefficient of the structure,the greater the stiffness degradation range,and the better the energy dissipation performance.(4)The failure mode of eccentrically braced steel frame with replaceable links and floors is basically the same: when the loading displacement reaches the elastic-plastic story displacement h/50,the web of the link of energy dissipation has sheared and consumed energy,and cracks has appeared in the at the junction of the link of energy dissipation and frame beam;When the displacement reaches the ultimate displacement,the buckling deformation occurs in some areas of the flange of the link.The outer shell and the inner core tube of the bucklingrestrained brace have relative displacement,while the frame is still in an elastic state;Through cracks has appeared in the composite floor slab at upper part of the link,and the number of cracks gradually increases,while the rest of the composite floor has no obvious phenomenon.It is appropriate to make slit for the composite floor to reduce the plastic damage of the junction of the link and frame beam in the practical engineering.(5)After replacing the link of energy dissipation,the structure still has good bearing capacity,ductility and energy dissipation capacity,and it only takes 90-120 minutes to replace the link,which is relatively short,indicating that the he link of energy dissipation has good replaceability.