用梁格法建模，向下的均布荷载，但是模型出来的弯矩图是反的，不知道哪里出了问题？下面是命令流，求大神帮忙看看
/prep7
et,1,82
mp,ex,1,3.45e4
mp,prxy,1,0.2
mp,dens,1,2550 
!箱梁截面
K, ,0,1,0
K, ,0,1.4,0
K, ,2.45,1.4,0
K, ,2.45,0.4,0
K, ,0.3,1,0
K, ,2.45,0,0
K, ,3.35,1.4,0
K, ,3.35,0,0
K, ,2.59,0.28,0
K, ,2.59,1.1,0
K, ,2.69,1.2,0
K, ,3.11,1.2,0
K, ,3.21,1.1,0
K, ,3.21,0.28,0
K, ,3.11,0.18,0
K, ,2.69,0.18,0
K, ,3.35,0.32,0
K, ,5.87,1.4,0
K, ,5.87,1.26,0
K, ,4.55,1.26,0
K, ,3.35,1.08,0
K, ,5.87,0.12,0
K, ,5.87,0,0
a,1,2,3,4,5
a,9,10,11,12,13,14,15,16
a,3,7,8,6
asba,3,2
a,7,18,19,20,21 
a,8,17,22,23
agen,1,1,6, ,-2.9,-1.4 , , , ,1
aadd,all
asel,all
esize,1
amesh,all
secwrite,jm3,,,mesh
finish
/clear
/prep7
et,1,44
mp,ex,1,3.45e4
mp,prxy,1,0.2
mp,dens,1,2550 
sectype,1,beam,mesh
secread,jm3,,,mesh
secoffset,origin
*do,i,1,11,1
K,i,(i-1)*1
*enddo
K,100,0,1
*do,I,1,10,1
L,I,i+1
Latt,1, ,1, ,100,,1
Lsel,s,,,i
Lesize,I,,,10
Lmesh,i
Allsel,all
*enddo
/eshape,1
Eplot
Dk,1,ux
Dk,1,uy
Dk,1,uz
Dk,1,rotx
Dk,11,uy
Dk,11,uz
sfbeam,all,1,pres,100
/SOLU
Solve
Finish
/POST1
ETABLE,MI,SMISC,6
ETABLE,MJ,SMISC,12
Plls,MI,MJ,1,0