The Research Of Eccentrically Brace For Vertical Irregular Buildings Steel Frame Structure System Seismic Performance

Affected by the offset of their rigidity and mass centers under earthquake action,vertical irregular structures are very easy to produce torsion effect which can cause internal force or deformation of some components to be too large and lead to early collapse of structures.In order to explore the response pattern of vertical irregular steel frame structure under earthquake action,and to explore whether adding eccentric braces can better reduce the seismic response of vertical irregular steel frame structure than adding central braces,and which kind of arrangement of eccentric braces is more reasonable,the seismic performance of L-type vertical irregular steel frame structure,L-type vertical irregular steel frame structure with D-type eccentric bracing or single oblique bar central bracing under the same arrangement are analyzed and compared.Several L-type vertical irregular steel frame structures with different inlet storey heights are constructed and D-type eccentric bracing is added to explore the influence of inlet storey height and eccentric bracing arrangement on torsional performance of vertical irregular structure.Specific analysis and comparison results are as follows:1.Through modal analysis,it is found that adding D-type eccentric braces can greatly improve the overall stiffness and torsion resistance of L-type vertical irregular steel frame structure,and the effect of eccentric braces is better than that of central braces.2.Through response spectrum analysis,time history analysis and base shear analysis,it is found that eccentric bracing can better reduce floor displacement response of vertical irregular steel frame structures under frequent and rare occurred earthquakes than central bracing;the base shear of the structure all conform to the standard requirements.3.Through Pushover analysis,it is found that the weak floor of L-type vertical irregular steel frame structure is located below the elevation receding floor and on the other side of the receding part.Eccentric bracing can better improve the ability of vertical irregular steel frame structure to resist deformation under rare earthquakes than central bracing.It avoids the the whole structure collapse too early because of the large deformation of some components.4.Through the analysis of eccentric torsion effect,it is found that the torsion resistance of part of L-type vertical irregular steel frame structure below the elevation receding floor is weak;the higher the height of vertical irregular structure,the smaller the torsion effect of the substructure and the larger the torsion effect of the superstructure.The height of the receding layer should be as high as possible to improve the torsion resistance of the vertical irregular structure.Different arrangements of the same kind of eccentric bracing have different effects on the torsion resistance of the superstructure and substructure,and the V-shaped arrangement has the best effect.