Study On Seismic Behavior Of Double Knee Braced Steel Frame Structure

The knee braced structure is a new type of steel structure support system.Because of its own advantages,it can make up for the deficiencies of the center support and eccentric support,so it is widely recognized by the industry.Relevant research shows that the double knee braced structure has better performance than the single knee braced structure.For buildings that are located in high-intensity areas and require high safety factors,or structures that require seismic strengthening,the double knee braced structure is more secure and reliable.At present,the domestic research on the form of double knee braced is relatively scarce,so it is of great significance to study the seismic performance of this structure form.This paper uses SAP2000 software to establish a three-dimensional calculation model of a 12-story steel frame.Firstly,four common double knee braced are added to the steel frame model,and modal analysis,response spectrum analysis and time history analysis are performed.The effects of the four common double knee braced on the seismic performance of the steel frame are studied and analyzed.The support structure with the best comprehensive performance was selected from the four schemes.Then based on the optimal steel frame in the form of a double knee braced structure,the elevation and plane layout positions were changed respectively.The elastoplastic time-history analysis of rare earthquakes is carried out,and the influence of different double knee braced placement locations on the seismic performance of the structure is analyzed.Finally,the values of the eccentricity and the high-span ratio of the double knee braced are changed respectively.The elastoplastic time-history analysis of rare earthquakes is carried out,and the influence of the changes of the parameters on the seismic performance of the double knee braced steel frame is studied.The results show that:The addition a double knee braced structure can greatly improve the lateral rigidity and energy dissipation performance of a pure steel frame.This structure is a form of support structure with excellent seismic performance.From the analysis of seismic performance,economic cost and the difficulty of construction,it is concluded that the comprehensive performance of the inverted V-shaped double knee braced structure is the best.For the elevation layout of the double knee braced steel frame,adopting a symmetrical,continuous,uniform and staggered arrangement of the entire elevation layout can improve the structure’s lateral rigidity.For the planer layout of the double knee braced steel frame,the stiffness of the structure increases first and then decreases with the arrangement of the double knee brace from the outside to the inside.At the same time,the torsional period ratio of the structure increases sequentially from the outside to the inside with the arrangement of the double knee braced.Under the premise of satisfying the torsional effect of the structure,it can be considered to be arranged inside the structure.A reasonable internal arrangement can further improve the rigidity of the structure.The eccentricity parameter has a certain influence on the double knee braced steel frame.Within a reasonable range of eccentricity,the smaller the value of eccentricity is,the more favorable the seismic performance of the structure is.For a steel frame using a double knee braced structure,this article suggests that an eccentricity of 0.10 times can be given priority consideration.High-span ratio parameters have a greater impact on the steel frame supported by double knee braced.As the high-span ratio decreases,the stiffness of the structure gradually increases,while the energy consumption performance gradually decreases.In actual engineering,on the premise of ensuring that the non-energy-consuming components of the structure have sufficient bearing capacity,this article proposes that a high-span ratio of 0.3 times can be given priority consideration.The conclusions obtained through research and analysis in this article have certain reference value for designers who use the double knee braced structure.