To: "SEAOC Newsletter" <seaint(--nospam--at)seaint.org>
Subject: Re: CQC and SRSS
From: Christopher Wright <chrisw(--nospam--at)skypoint.com>
Date: Thu, 27 May 99 09:14:28 -0500
>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
Christopher Wright P.E. |"They couldn't hit an elephant from
chrisw(--nospam--at)skypoint.com | this distance" (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)