一个屈曲分析的问题，请大家赐教

最近在做一个 单榀脚手架的 特征值屈曲分析，下面是我的命令流
/filname,ctube-beam
/title,bucking
/prep7
et,1,beam189
mp,ex,1,2.0e11
mp,nuxy,1,0.3
mp,dens,1,7800
k,1,0,0,0
k,2,0.758,0,0
k,3,0,0.8725,0
k,4,0.758,0.8725,0
k,5,0.094,0.940,0
k,6,0.664,0.940,0
k,7,0,1.348,0
k,8,0.094,1.348,0
k,9,0.664,1.348,0
k,10,0.758,1.348,0
k,11,0.094,1.380,0
k,12,0.664,1.380,0
k,13,0.379,1.665,0
k,14,0,1.699,0
k,15,0.758,1.699,0
k,16,0,1.750,0
k,17,0.758,1.750,0
sectype,1,beam,ctube
secoffset,cent
secdata,0.0185,0.021,8
lstr,1,3
lstr,3,7
lstr,7,14
lstr,14,16
lstr,2,4
lstr,4,10
lstr,10,15
lstr,15,17
lstr,14,15
sectype,2,beam,ctube
secoffset,cent
secdata,0.0113,0.013,8
lstr,5,8
lstr,8,11
lstr,6,9
lstr,9,12
lstr,7,8
lstr,9,10
k,18,0.379,1.380,0
k,19,0.379,1.699,0
larc,11,13,18,0.285
larc,13,12,18,0.285
ltan,-12,4,-0.337,1,0
ltan,-10,3,0.337,1,0
lsel,s,,,1,9,1
latt,1,,1,,,,1
lesize,all,0.005
lmesh,all
lsel,all
lsel,s,,,10,19,1
latt,1,,1,,,,2
lesize,all,0.005
lmesh,all
lsel,all
dk,1,all,0
dk,2,all,0
fk,16,fy,-1
fk,17,fy,-1
cp,n,all,13,19 （这条命令流错了，就是13，19耦合，请高手教教我怎么样写才是正确的）
finish
/solu
antype,0
eqslv,spar
pstres,on
solve
finish
/solu
antype,1
bucopt,lanb,1,0,0
mxpand,1,0,0,1,0.001
solve
finish
最后得出这个单榀的脚手架的临界失稳荷载失14374N
老师说我的这个 荷载太小了，我做了很多很多遍了，还是这个结果。
请高手帮帮我，我的分析错了吗？命令流正确吗？谢谢！