求助ansys前辈高手！！

我是学习ansys的新手！最近在模拟钢板混凝土的模型遇到一些问题希望大伙帮忙解决下！在ansys求解中出现下面的警告，该如何处理？
“the value of uz at 816 is 162426393.it is greater than the current limit of 1000000.this generally indicates rigid body motion as a result of an unconstrained model. verify that your model is properly constrained”
另外附上命令流：（模型是采用250*250*750的柱子）
asel,s,loc,y,0
asel,r,loc,z,0,250
asel,r,loc,x,0,250
da,all,,uy
p0=1600000
q0=p0/250/250
asel,s,loc,y,750
asel,r,loc,x,0,250
asel,r,loc,z,0,250
sfa,all,1，pres,q0
allsel,all
/solu
antype,0
nsubst,100
outres,all,all
antos,on
neqit,100
cnvtol,u,,0.02
solve