How does the reaction-force RPSD (POST26) relate to the 1-sigma reaction force (POST1)?


The reaction force RPSD is the response, in force^2/Hz units, over the frequency range, so if you integrate and take the square root, you should get the same as 1-sigma reactions. Attached is an example:


finish
/clear

/prep7
/view,,1,2,3
/eshape,1
et,1,188
sectype,1,beam,csolid
secdata,1
mp,ex,1,2e5
mp,nuxy,1,0.3
mp,dens,1,8e-9

k,1
k,2,,25
l,1,2
esize,1
lmesh,all
d,1,all
dmprat,0.02
finish

/solu
antype,modal
modopt,lanb,12
mxpand,,,,yes
solve
finish

/solu
antype,spect
spopt,psd,,yes
psdunit,1,disp
psdfreq,1,,1,1e5
psdval,1, 1, 1
d,1,ux,1
pfact,1
psdcom
solve
finish

/post26
store,psd,10
rforce,2,1,f,x
rpsd,3,2
int1,4,3,1
vget,fpsd,4
*get,flast,parm,fpsd,dim,1
finish

/post1
set,3,1
*get,frms_post1,node,1,rf,fx
frms_post26 = sqrt(fpsd(flast))





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