| Eccentrically braced steel frame(EBFs)are very commonly used in buildings from 30 to60-stories.The shear link is the main energy dissipating component in the EBFs.Because the shear link of the EBFs is integrated with the frame beam.When the shear link is damaged under a serious earthquake,the frame beam will also appear larger plastic deformation.For this reason,scholars improved the connection between the shear links and the frame beams,separated the shear links from the frame beams,and realized the replacement of the shear links.But the height of sections of the shear links are reduced by 1/3～1/2 relatively to the height of sections of frame beams,which will cause a larger gap between the floor and the shear links.The lateral stiffness of the EBFs with replaceable shear links will also be reduced by about 15% to 20%.The above two shortcomings can be avoided by changing the low-yield-point steel replaceable shear links.In this paper,the seismic performance of the K-shaped eccentrically braced steel frame with replaceable low-yield-point shear links is studied through experiments and numerical simulations.The traditional K-shaped EBFs is designed using YJK software,and on this basis,a replaceable low-yield-point shear links for EBFs is designed.The hysteretic experiments of traditional and replaceable low-yield-point shear links for EBFs are carried out,and ABAQUS finite element simulation are analyzed.Through variable parameter analysis,the factors affecting the seismic performance of the new eccentrically braced steel frames are studied.The main research contents and results are as follows:(1)Using YJK software,a 15-story K-shaped EBFs model was established according to the actual working conditions,and the horizontal seismic forces of the selected single steel frame under the action of small,medium and large earthquakes were obtained,and corresponding The interlayer displacement angle was compared with the specification limit,and the size of the traditional K-shaped eccentric braced test specimen was determined.(2)The end plates and bolts are designed on the basis of the traditional EBFs,and the cross-sectional dimension of each member is checked under certain load conditions,including the check calculation of strength and stability,to prove its practicality Reasonability at work.(3)The uniaxial tensile comparison test of LY160 low-yield-point steel and Q235 steel was carried out,and the yield and ultimate stress and strain performance indexes of the two were measured,and the differences in the properties of the two steels were compared.The following conclusions were drawn through the test: Compared with ordinary steel,low-yield-point steel has lower yield strength,and there is almost no obvious yield platform during the stretching process;its yield ratio is small,but the elongation is larger than that of Q235 steel;low-yield-point steel is very ductile Good and better plastic deformation abilitythan Q235 steel.(4)Low-cycle cyclic loading tests of the 1/2 scale model of the traditional K EBFs and the new K EBFs were carried out respectively.It also summarizes the similarities and differences of the performance,the turning ability of the shear links and the failure characteristics,and the problems and phenomena encountered in the experiment are summarized.The test results show that the traditional EBFs has a shuttle-shaped hysteresis curve,with better energy dissipation performance,greater initial rigidity and bearing capacity of the structure,and good ductility.At the end of the test,only the flange of the shear links appears larger.Deformation;although the hysteretic curve of the new EBFs has a certain degree of pinching,the hysteretic performance is also good,the ultimate bearing capacity and rigidity are not significantly reduced compared with the traditional EBFs,and the shear links can rotate Even better,at the end of the test,only large plastic deformations were found in the shear links section and its end plates,and other components such as beams,columns and braced were basically in good condition.(5)The traditional K-type EBFs and the new K-type EBFs models were established by ABAQUS finite element analysis software,and the stress distribution of the shear links of the two under horizontal earthquakes was analyzed by applying cyclic displacement loads.Conditions,energy dissipation capacity,stiffness,bearing capacity and ductility,shear plastic corner;later,by changing the yield strength of low-yield-point steel and the arrangement of stiffeners of shear links,the replaceable low-yield-point shear links was studied Factors affecting seismic performance.The following conclusions are drawn: Compared with the traditional EBFs,the stress generated on the shear links of the new EBFs is reduced,the hysteresis performance and equivalent damping coefficient,and the ductility and plastic rotation capacity of the shear links are reduced.There is a greater degree of improvement,but the stiffness and bearing capacity under the limit state are reduced to a certain extent.The new EBFs has better energy dissipation capacity,and can fully demonstrate the important role of the shear links as a structural "fuse" in the earthquake;secondly,it is found that when the yield strength of the shear links steel is within a certain range(100MPa～225MPa)gradually increases,the stress generated in the shear links gradually increases,the structural rigidity is not much different,the bearing capacity gradually increases,the ductility gradually decreases,the turning angle of the shear links gradually increases,and the hysteretic performance gradually improves;Different arrangements of stiffeners at the webs of shear links,under the same other conditions,when the two-sided small-spaced layout is adopted,it has better energy dissipation capacity than the single-sided small-spaced layout or the double-sided large-spaced layout.The structural rigidity and ductility are not much different from the other two arrangements,the load-bearing capacity has been improved to a certain extent,and the corner of the shear links has been slightly increased. |
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