Study On Seismic Behavior Of New K-Eccentrically Braced Steel Frames With Shear Yielding Links

Eccentrically braced frame(EBF)dissipates seismic energy through the link inelastic deformation when subjects to rare earthquakes,while the non-energy-dissipating members,such as beams,columns and braces,are basically in an elastic range,which is requires that the non-energy-dissipating members are sufficient to carry the internal force values generated by the link yielding(the strain hardening may also be considered.).However,the section coordination of the link and the beam leads to overdesigned structures and overall cost-increasing for the EBF,then,the EBFs are hard to be adopted in actual engineering projects.To give full play to the excellent seismic performance of the EBFs,this paper presents two shearing yielding variable I-section links design idea based on the direct weakening the I-section(web area)of link.Then the seismic performance of EBF with weakening the I-section links(referred to as the new EBFs)was investigatived.The following conclusions can be drawn within the scope of the study:1)Based on the principle of consistent stress ratios,three ten-story EBF buildings were designed as prototype structures,including two new EBFs proposed in this paper and a traditional EBF.Then the steel consumption,natural vibration frequency characteristics,and inter-storey drift angle under the frequent earthquakes were compared.The results show that the two new EBFs proposed in this paper reduce the steel consumption and improve the economic efficiency on the premise that inter-storey drift angle and natural vibration frequency characteristics are similar to those of traditional EBF.2)Three one-bay and one-story scaled models were designed and quasi-static cyclic tests were performed respectively.The failure mode,hysteresis property,initial stiffness,ductility,energy dissipation capacity,link rotation and strain response of the members were studies.The test results showed that,inelastic deformation of the three models were basically limited to the links and the inelastic deformation developed sufficiently,moreover,the non-energy-dissipation segments were basically in the elastic range;The traditional EBF elastic stiffness,yield load,ultimate load,equivalent viscous damping coefficient and energy dissipation capacity were slightly greater than the two new EBFs,but ductility and link rotation capacity were less than the latter models.And the difference in seismic performance between the two new EBFs was small.3)Nonlinear 3D finite element models were developed using ABAQUS 6.14 and the responses,including the failure models,hysteresis curve,load-carrying capacity and initial stiffness were compared with the tests.In general,the analysis results obtained by the numerical simulation were in good agreement with the experimental responses,which was helpful for the future research on the seismic performance of the EBFs.4)Finite element analysis parametric studies were performed to investigate the influences of different link lengths on seismic behaviours of the EBFs including the new EBFs and the traditional EBF.The effects of the variation of the link lengths on the load bearing capacity,stiffness,yield displacement and energy dissipating capacity of the EBFs were analyzed.Finally,based on the results of the finite element analysis,design recommendations for the link length were given for engineering design and application.