四边简支均匀受剪板如何模拟

想请教下四边简支均匀受剪板如何模拟，特别剪力如何加，如下图以及命令流，谢谢了.


finish
/clear
/prep7
et,1,63
r,1,0.003
mp,ex,1,2.1e11
mp,prxy,1,0.3
blc4,,,0.2,0.3
n=20
lesize,all,,,n
amesh,all
dk,1,ux,,,,uy
dk,2,uy
dl,all,,uz
nsel,s,loc,x,0
f,all,fy,1/(n+1)
nsel,s,loc,x,0.3
f,all,fy,-1/(n+1)
nsel,s,loc,y,0
f,all,fx,1/(n+1)
nsel,s,loc,y,0.3
f,all,fx,-1/(n+1)
allsel,all
finish
!求解
/solu
allsel,all
solve
finish

/solu
antype,buckle
bucopt,lanb,1
mxpand,1
solve
finish