plls察看弯矩图 加不加-1的问题

zp4655958

finish
/clear
/prep7
et,1,beam3
mp,ex,1,2.1e11
mp,prxy,1,0.3
r,1,0.007848,4.9087e-6,0.1
k,1
k,2,0,4
k,3,0,4
k,4,3,4
k,5,3,4
k,6,3,0
k,7,3,7
k,8,6,7
k,9,6,7
k,10,6,7
k,11,6,4
k,12,9,7
l,1,2
l,3,4
l,6,5
l,5,7
l,7,8
l,11,10
l,9,12
lesize,all,,,8
lmesh,all
dk,1,all
dk,6,all
dk,11,all
dk,12,ux,,,,uy
lsel,s,,,2
esll
sfbeam,all,1,pres,2000
lsel,s,,,5,7,2
esll
sfbeam,all,1,pres,3000
allsel
ksel,s,,,2,3
nslk,s
cp,next,rotz,all
cp,next,uy,all
ksel,s,,,4,5
nslk,s
cp,next,ux,all
cp,next,uy,all
ksel,s,,,8,10
nslk,s
cp,next,ux,all
cp,next,uy,all
allsel
finish
/solu
solve
finish
/post1
pldisp,1
etable,mi,smisc,6
etable,mj,smisc,12
plls,mi,mj,-1
etable,fxi,smisc,1
etable,fxj,smisc,7
plls,fxi,fxj
etable,fyi,smisc,2
etable,fyj,smisc,8
plls,fyi,fyj
etable,si,nmisc,1
etable,sj,nmisc,3
plls,si,sj
请教高手 PLLS查看弯矩图是何时要加'-1'？？？？网上有说法根据beam单元决定是否'-1',高手指点！~~