How does the reactionforce RPSD (POST26) relate to the 1sigma 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 1sigma 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,1,8e9 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)) 

