Return to index: [Subject] [Thread] [Date] [Author]

Re: CQC and SRSS

[Subject Prev][Subject Next][Thread Prev][Thread Next]
>I would like to ask the difference with CQC and SRSS. Does anyone know how
>they would differ in the results and when to use the CQC or SRSS
>computation. Just a question. Thanks !
The CQC method combines closely space modes on an absolute sum method 
using a weighting coefficient based on how nearly equal the frequencies 
are. SRSS can't account for closely spaced modes by itself. The CQC 
method degenerates to SRSS when no modes are closely spaced, so I use it 
in preference to SRSS. You can get about the same effect using a 
so-called 'cluster factor' with the SRSS combination. Modes with 
frequencies which differ by less than the factor are combined on an 
absolute sum basis and the results combined  with the remaining 
significant modes using SRSS. 

Straight SRSS assumes that modal maxima aren't simultaneous, which is 
likely for widely differing frequencies. Closely spaced modes tend to 
reach maxima simultaneously, so it's important to add the corresponding 
responses properly. 

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)