保证桥的边界条件不变，但是每次的结果都是应力会发生较大变化，附上静力分析和显示分析的命令流，希望大神们能帮忙解答！

！静力分析

allsel,all
/SOL
antype,0
allsel,all
acel,,,9.8 
time,20 
nsub,100,200,50
outres,all,all 
nlgeom,on  
sstif,on
alls
solve  

！动力分析

!定义重力加速度!
*DIM,time,array,20,1,1,,,
*DIM,GZ,array,20,1,1,,,
*set,TIME(1,1,1),0
*set,TIME(2,1,1),1
*set,TIME(3,1,1),2
*set,TIME(4,1,1),3
*set,TIME(5,1,1),4
*set,TIME(6,1,1),5
*set,TIME(7,1,1),6
*set,TIME(8,1,1),7
*set,TIME(9,1,1),8
*set,TIME(10,1,1),9
*set,TIME(11,1,1),10
*set,TIME(12,1,1),11
*set,TIME(13,1,1),12
*set,TIME(14,1,1),13
*set,TIME(15,1,1),14
*set,TIME(16,1,1),15
*set,TIME(17,1,1),16
*set,TIME(18,1,1),17
*set,TIME(19,1,1),18
*set,TIME(20,1,1),19
*set,GZ(1,1,1),9.8
*set,GZ(2,1,1),9.8
*set,GZ(3,1,1),9.8
*set,GZ(4,1,1),9.8
*set,GZ(5,1,1),9.8
*set,GZ(6,1,1),9.8
*set,GZ(7,1,1),9.8
*set,GZ(8,1,1),9.8
*set,GZ(9,1,1),9.8
*set,GZ(10,1,1),9.8
*set,GZ(11,1,1),9.8
*set,GZ(12,1,1),9.8
*set,GZ(13,1,1),9.8
*set,GZ(14,1,1),9.8
*set,GZ(15,1,1),9.8
*set,GZ(16,1,1),9.8
*set,GZ(17,1,1),9.8
*set,GZ(18,1,1),9.8
*set,GZ(19,1,1),9.8
*set,GZ(20,1,1),9.8
edload,add,ACLZ,0,suoyou,TIME,GZ,0,,,,,
allsel,all
rexport,dyna,disp,node,last,last,'Mode55555','rst',''
ALLSEL,ALL 
EDCGEN,ASTS,weigan,qiaomian,0,0,0,0,0,,,,,0,300,0,0
edsp,off,'','',1
allsel,all 
save
FINISH  !Close Preprocessor
/SOLU  
!初始条件
eddrelax,ansys,300,0.001,0.995,,0,0,0.04
EDVEL,VELO,STIFFHOPPER,,-5,0
allsel,all 
TIME,0.04,  !Time at end of load step
edopt,add,blank,both 
EDRST,20   !Results output interval
EDHTIME,1  !Time-history output interval
ALLSEL,ALL 
EDOUT,RCFORC
EDOUT,NCFORC
EDOUT,MATSUM
EDDUMP,1
ALLSEL,ALL 
/status,solu
solve    
FINISH