Re: dynamic loading Factor

Isnt that a problem with the Macintosh version?

• Original message --------------

>
> On Apr 28, 2005, at 10:54 AM, Tony Paulin wrote:
>
> > Displacements are certainly
> > lower as a function of the square of the frequency but stresses,
> > because of
> > the small radius of curvature associated with higher modes continue to
> > add.
> > This has been a problem with the approach used in CAESAR since 1987,
> I'll defer to your judgment with CAESAR, but I've been doing dynamic
> analysis with ANSYS and COSMOS/M for about 25 years and I've never seen
> a problem diverge like that by increasing the number of modes. The mode
> coefficients all drop off at frequencies higher than the ZPA level. The
> accelerations remain constant at the ZPA and the modal mass drops off
> to zero, so the mode coefficients become vanishingly small. Stress
> certainly increases at with increasing number of modes considered at
> first, but after 4 or 5 modes it invariably (in my experience)
> converges as the mass participation gets up past 50%
>
> What radius of curvature are you referring to? If you plot out mode
> shapes it may appear that you get increasing curvature, but once you
> apply the mode coefficients to get actual displacements, the
> displacements and radii of curvature drop off. I will try your problem,
> though. What kind of impact load do you use? Seismic loading cuts out
> at 33 Hz, but actual impacts have frequency content all over the map. I
> can do either.
>
> Christopher Wright P.E. |"They couldn't hit an elephant at
> chrisw@skypoint.com | this distance" (last words of Gen.
> .......................................| John Sedgwick, Spotsylvania
> 1864)
> <a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> <a href="http://www.pipingoffice.us/">http://www.pipingoffice.us/</a>
> =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>

[Non-text portions of this message have been removed] Received on Thu Apr 28 12:46:00 2005