Study On The Influence Of Secondary Stress On The Seismic Performance Of Lattice Steel Columns

Lattice steel members have the characteristics of high bearing capacity,good stability,economical material and convenient construction.They are widely used in single-story industrial plant columns,tower supports,pier and foundation pit support.In particular,the economy of lattice lacing members is gradually better than that of lattice batten members with the increase of end pressure and calculation length.However,in the current steel structure design,to simplify calculations,the welded connection nodes between all lacing bars and limbs of the lattice lacing bar components are usually simplified as hinges,without considering the influence of lacing secondary stress.This article conducts finite element analysis on double-limb lattice steel columns with lacing bar connections,considering parameters such as lacing bar type,node eccentricity,lacing bar angle,and welding form,The effects of low-cycle reciprocating loads under different axial compression ratios on the seismic performance of steel columns were analyzed separately.The effect of different parameters on the secondary stress of lacing bars of double-limb lattice steel columns and their regularity are analyzed,and the change law of secondary stress of lacing bars on the seismic performance of double-limb lattice steel columns are obtained.The results are as follows :(1)The finite element analysis of the monoclinal double-limb lattice steel column without horizontal batten shows that with the increase of batten angle and stiffness,the influence of secondary stress increases,the seismic bearing capacity of steel column decreases by 40.05 % and the ductility decreases by 18.66 %.The eccentricity of the joint causes the secondary stress to increase by 11.59 %.The secondary stress caused by the eccentricity of the joint reduces the bearing capacity of the lattice column by 2.81 % and the ductility by 3.25 %.The batten stress caused by joint eccentricity is relatively small,but the joint eccentricity also weakens the seismic performance of steel columns.With the increase of axial compression ratio,the bearing capacity of steel column decreases rapidly after reaching the limit,the stiffness degradation is more obvious,and the ductility decreases.(2)Through the finite element simulation of the monoclinic double-limb lattice steel column with transverse lace strips,it is shown that the seismic performance of the monoclinic double-limb lattice steel column with transverse lace strips is consistent with the change trend of the seismic performance of the monoclinic double-limb lattice steel column without transverse lace strips,but the influence of the secondary stress of the lace strips on the seismic performance is greater than that of the monoclinic double-limb lattice steel column without transverse lace strips.Among them,the change of the angle has the greatest influence on the seismic performance,and the bearing capacity of the steel column with a large lace angle can be considered to be reduced by 36 %.(3)The seismic performance of double-inclined double-limb latticed steel columns without transverse lacing bars and double-inclined double-limb latticed steel columns with transverse lacing bars is consistent with that of single-inclined double-limb latticed steel columns without transverse lacing bars.Under the action of secondary stress,the energy dissipation capacity of the double-oblique latticed steel column with transverse strips increased by 6 % compared with the double-oblique latticed steel column without transverse strips.(4)While comparing how each model’s lacing bar stress affects the seismic performance of lattice steel columns,it is discovered that the lacing bar stress brought on by a change in joint stiffness has very little of an impact.The seismic performance of the single inclined double limb lattice column is significantly impacted by the lacing bar stress brought on by the eccentricity of the joint,whereas the seismic performance of the double inclined double limb lattice column is not much affected.The seismic performance of the lattice column is significantly impacted by the secondary stress brought on by a change in the angle of the lacing bar,but only marginally by the secondary stress brought on by a change in the angle of the lacing bar.