ansys计算斜拉索各阶模态，有几个模态异常，求高手帮帮忙

命令流如下，第15阶和第26阶模态的形态有问题
finish
/clear
/prep7
pi=3.1415926
d=0.069
ea=0.00372
ei=2.20e-6
ee=1.95e11
force=2700e3
istrain=force/ea/ee
et,1,beam3
et,2,combin14,,,2
r,1,ea,ei,d,0,istrain,0,
r,2,5e6,0
mp,ex,1,1.95e11
mp,prxy,1,0
mp,dens,1,7.85e3
*do,i,0,36,1
x=i
y=-5.3e-5*x*(36-x)
k,i+1,x,y
*end do
*do,i,1,36,1
    l,i,i+1
*end do
k,38,2,-3
l,3,38
lsel,all
lsel,u,,,37
latt,1,1,1
lsel,s,,,37
latt,,2,2
ksel,all
dk,1,ux,,,,uy
dk,37,ux,,,,uy
dk,38,all
esize,0.01
lsel,all
lmesh,all

finish
!*
/sol
antype,0
acel,0,10,0,
pstres,on
solve
finish
!*
/SOL
antype,2
modopt,subsp,30
pstres,on
solve
finish
!*
/post1
set,list
finish

额，具体情况是查看模态时，其他各阶都是正弦波，但是15和26不是