Elastic-plastic Stress Performance Study Of K-Eccentrically Braced Semi-Rigid Steel Frames

Eccentrically braced semi-rigid steel frame structure is a new type of structural system,which combines the advantages of two kinds of structures,which are eccentrically braced steel frame and semi-rigid steel frame.Steel frame with semi-rigid connections has good ductility,but the structural stiffness is small,eccentrically braced steel can provide a large lateral stiffness of steel frame structure,the combination of the two can make up for the shortcomings of both sides,so that their respective advantages to be fully exploited.Therefore,it is a kind of structural system with excellent seismic performance.But the theoretical and Experimental Research on this type of structure is relatively poor and there is no perfect design and analysis theory in engineering application in our country,therefore,the subject of this paper is focused on the study of the K-eccentrically braced semi-rigid steel frame,so as to enrich the theoretical basis of the structure in engineering application.In this paper,a finite element software SAP2000 is used to establish 10 K-eccentrically braced semi-rigid steel frame model with 12 layers,6 of them with the length of Energy dissipation beam is variable,4 with beam column joint initial rotational stiffness is variable,the modal analysis and the static nonlinear analysis of the 10 models are carried out to study the influence of the structure on the dynamic characteristics and the elastic-plastic behavior.The results show that with the increase of the length of Energy dissipation beam,structural period change,especially for the first three modes,an increase of up to 3.3%?6.3%,but has little effect on higher modes,the horizontal displacement of the structure vertex and the performance point increases,the base shear and the acceleration of the performance point decreases.the length of energy dissipation beam is longer,the lateral stiffness of structure is reduced;shorter,it is too rigid to yield.Therefore,it is suggested that the length of the energy dissipation beam should be between 1000mm and 1250mm,which can not only ensure the lateral stiffness of the structure,but also help the development of plastic hinge.When the initial rotational stiffness is less than5 ×105kN·m/rad,With the increase of stiffness,the lateral displacement of the structure vertex and the performance point decreases,the base shear and the acceleration of the performance point increases,and the number of the plastic hinge is increased.But when the initial rotational stiffness is greater than 5×105kN·m/rad,the increase of stiffness has little effect on the parameters of the structure.Therefore,this paper proposed the semi-rigid connection initial rotational stiffness value should be between 1 ×105kN·m/rad and 5 ×105kN·m/rad.The change of the energy dissipation beam length and the initial rotational stiffness has little influence on the mass participation coefficient of the structure in X and Y direction,which is negligible.