The Stress Performance Analysis Of Node Knee Brace Portal Frame Structure

Light portal frame is usually composed of thin-walled members,in the design according to the size of the internal force calculation of the section,this section of the design of the variable cross-section to avoid the waste of material.But the light portal frame structure shows its superiority in economy at the same time,in the extreme loads also exposed the shortcomings of redundant safety.In practical engineering,by increasing section to enhance its safety degree of redundancy is not realistic Therefore,This paper studies a kind of local area,strengthen the local members of the portal frame,to enhance the safety of redundant method---Add a node knee braceIn order to achieve the purpose of research,this paper through the finite element analysis program ANSYS established a variety of different parameters of the model group,to get the node-knee brace portal frame structure by the force performance and through the parametric analysis of the design suggestions are proposed.Through the portal frame in different stress analysis stage,this paper found that:1.Vertical ultimate bearing capacity of structure under vertical loads,node knee brace can effectively improve the portal rigid frame structure,improve the structure of vertical stiffness and to make the structure of the stress distribution more uniform beam column node field protection,increase the ductility of the structure;2.Structure under horizontal loads,node knee brace can improve the portal type rigid frame structure of the horizontal ultimate bearing capacity and improve the lateral stiffness of the structure,but due to portal just frame structure under horizontal load column easy to occur failure and then lose steady collapse,node knee brace can improve this kind of failure mode.3.Under low cycle repeated load,node knee brace can effectively enhance the portal rigid frame energy dissipation capacity,reduce the structural stiffness degradation,the corner support portal rigid frame than ordinary portal rigid frame,anti-seismic capability significantly enhanced.4.The node knee brace setting height on the structure performance influence is obvious,corner brace height is larger,structural stiffness is bigger,structural ultimate bearing capacity is higher,stress distribution is more uniform,structural seismic energy dissipation capacity is enhanced.The proposal does not affect the use of architectural features,node knee braces height should be as large as possible.5.The node knee brace setting angle on the limit load of structure effect is obvious,corner brace setting angle is 30 degree and limit bearing capacity increase rate is low;corner brace setting angle of 45 degrees,and the ultimate bearing capacity,ductility and seismic energy dissipation capacity has improved significantly;node knee brace setting angle of 60 degrees and final failure of the structure position often appear first in the steel column and corner brace are connected near,does not meet the seismic requirements for "strong column and weak beam";corner brace setting angle of about 45 degrees.6.When node knee brace and the cross section of the steel column stiffness ratio in the range of 0.01-0.07,by adjusting the corner braces section height change of section stiffness on the strnctural mechanical properties improve obviously.When the section stiffness ratio in the 0.07-0.25 range,by adjusting the corner braces section height change of section stiffness on the structure by the force performance less improvement.Proposed in the design of corner brace,should try to adjust the comer brace section height to make it and the cross section of the column stiffness ratio in the range of 0.01-0.07.7.By adjusting the node knee brace flange width to change its stiffness is obvious influence on the structural behavior.Node knee brace flange width is large,vertical structure stiffness,ultimate bearing capacity is high,the stress distribution is more uniform,it is recommended in the design of corner brace can be increased as much as possible the flange width.8.Through the adjustment of corner brace flange thickness change the section stiffness on the mechanical properties of the structure are affected is not obvious,the proposed design node knee brace flange thickness reference specif-ications generous than you can.