ansys 命令流求教

小可做王新敏老师书中的ex9.9（振动台分析），但分析结果却不对，如绘制例题中振动台中心点的位移时，是一条倒直线，不是为何，请高手指教，谢谢！图片为分析 的位移曲线，明显有误。
finish$/clear$/prep7
width=1$length=2$high=-1$et,1,shell63$et,2,beam4
mp,ex,1,2e11$mp,prxy,1,0.3$mp,dens,1,7800
r,1,0.02$r,2,2e-4,2e-8,2e-8,0.01,0.02
rect,,length,,width
k,5,,,high$k,6,length,,high$k,7,length,width,high$k,8,,width,high
l,1,5$*rep,4,1,1
esize,0.1$amesh,all
type,2$real,2$lmesh,5,8

/solu$antype,trans
nsel,s,loc,z,high$d,all,all$alls
alphad,5
time,1$deltim,0.2,0.05,0.5
autots,on$kbc,0
sfa,1,,pres,10000
lswrite,1
time,2$lswrite,2
time,4$sfa,1,,pres,5000
kbc,1$lswrite,3
time,6$sfa,1,,pres,0
kbc,1$lswrite,4
lssolve,1,4
finish

/post26
nsol,2,146,u,z
/grid,1$plvar,2