对一根卷边槽钢梁在等间距集中力作用下进行特征值屈曲分析，根据屈曲系数算出的结果总是不能和理论解接近。不知为什么，请大家指正，谢谢！
fini
/cle
/filname,C0,1
/prep7
L=3.000
h=0.160
b=0.060
a=0.020
t=0.002
et,1,shell181
r,1,t
!材料的非线性定义（理想弹塑性）
MPTEMP,1,
MPDATA,EX,1,,206E9
MPDATA,PRXY,1,,0.3
TB,BISO,1,1,2,
TBDATA,,235E6,0,,,,
k,1
k,2,b
k,3,b,a
k,4,,h
k,5,b,h
k,6,b,(h-a)
l,1,2
l,2,3
l,1,4
l,4,5
l,5,6
k,7,,,L
l,1,7
lsel,,,,1,4,3
lesize,all,,,6
allsel
lesize,3,,,h/0.010
lsel,,,,2,5,3
lesize,all,,,a/0.010
allsel
esize,,150
adrag,all,,,,,,6
amesh,all
/view,1,1,1,1
/rep
SAVE
fini
/solu
nsel,s,loc,z
d,all,ux,,,,,uy
lsel,,loc,z,L
nsll,,1
dsym,symm,z
alls
*do,i,1,9
nsel,,loc,y,h
nsel,r,loc,x,b/2
nsel,r,loc,z,i*0.3
f,all,fy,1
F,ALL,MZ,-0.0567
*enddo
nsel,,loc,y,h
nsel,r,loc,x,b/2
nsel,r,loc,z,0
f,all,fy,1/2
F,ALL,MZ,-0.0567/2
nsel,,loc,y,h
nsel,r,loc,x,b/2
nsel,r,loc,z,L
f,all,fy,1/2
F,ALL,MZ,-0.0567/2
arclen,off
nlgeom,off
antype,0
nsubst,5
pstres,on
allsel
solve
fini
/solu
antype,buckle
bucopt,lanb,1
mxpand,1
solve
fini
/post1
set,list !屈曲系数是200.91N。
!根据材料力学可知最大弯矩发生在跨中，为15m*P，故临界弯矩Mcr=15*Pcr=3.01KN.m,但是理论解是1.835KN.m，实在是相差甚远啊！