Study On Seismic Performance Of Improved Y-type Eccentrically Braced Steel Frame

In the Y-type eccentrically braced steel frame structure,the rational link can yield priority under earthquake and dissipate seismic energy through the inelastic shear deformation.Therefore,the integrity of the link is an important guarantee for the overall performance of the structure.However,many experiments have shown that the weld between the link and the frame beam and between the link and the brace is prone to brittle failure prematurely before the link dissipating seismic energy fully.It causes the brace to lose its function and cause the structure to be damaged ahead of schedule.After the Northridge earthquake and the Kobe earthquake in Japan,some scholars put forward the improved form of joints for the brittle failure of joint weld.There are two common forms of improvement: strengthening and weakening.In order to improve the seismic performance of the traditional Y-type eccentrically braced steel frame,the joint improvement measures are combined with the Y-type eccentrically braced steel frame in this paper.4 forms of Y-type eccentrically braced steel frame are put forward,namely,cover-plate reinforcement,rib reinforcement,dog-bone type reduced beam section,circle type reduced beam section.The finite element software ABAQUS is used to model the traditional and improved Y-type eccentrically braced steel frame in full scale,and the load-displacement hysteretic curve,stress contours,cracking index,skeleton curve,stiffness degradation,displacement ductility,energy dissipation coefficient,are compared and analyzed.The results show that the 4 improved Y-type eccentrically braced steel frame can effectively improve the stress distribution of the structure,reduce the stress and cracking index at the connection,make the failure position of the structure far away from the weld,reduce the possibility of brittle failure,and improve the ductility and energy dissipation capacity of the structure.Based on the above research,a new improved Y-type eccentrically braced steel frame is put forward,and its structural performance is analyzed under monotonic and cyclic loading.The analysis results show that the comprehensive effect of the new improvement measure is better than the previous 4 forms.After that,the variable parameter analysis of the improved Y-type eccentrically braced steel frame structure is carried out,and the influence of the thickness of the cover-plate,the length of the cover-plate,the length of the link,the size of theopening and the strength of the steel on the seismic performance of the structure is studied.Three dimensional model of the traditional Y-type eccentrically braced steel frame and the improved Y-type eccentrically braced steel frame is carried out.Two single span three floors of Y-type eccentrically braced steel frame are designed,and the seismic performance of the eccentric braces under horizontal monotonic and cyclic loading is compared and analyzed.The simulation result show that the new improved form is still applicable in the space frame.It can effectively improve the structure stress distribution,protect the weak region of the structure,improve the seismic performance of ductility,energy dissipation coefficient and so on.