[Beowulf] removing tiles around heavy racks?

[Jim Lux]

At 09:53 AM 1/3/2006, Mark Hahn wrote:
> > I've not studied the physics of it, but I can't see where the
> > surrounding tiles would have an effect.  You obviously don't want to
>
>sorry!  I should have explicitly said I'm worried about stability,
>not pure downward load-bearing-ness.  I mean, the floor is level,
>but not microscopically, and if someone leans on a rack, I'd like
>not to have the whole machineroom suddenly shear ;)
>
> > remove the tiles the rack is sitting on.  And those tiles should be
> > supported by a metal grid.  As far as I know, the metal grid and the
>
>presumably the grid (stringers) do most of the lateral stabilization,
>but they're not all that hefty themselves.  obviously with all/most
>tiles in place, the mesh is MUCH stiffer.

Hmm.. a box with 4 sides isn't particularly stable for shear loads.  What's 
resisting the shear loads is probably the bracketry that holds the 
stringers to the uprights (gussets?) or, if there is diagonal bracing in 
the grid.

But.. I wouldn't go off the mfrs spec sheets, per se.  Ask them for the 
engineering drawings and calculations, and YOU can evaluate how much margin 
there is.  Whoever installed the floor should have done these calculations 
to get the building permit.

As far as leaning on a rack and causing a shear failure:
1) I doubt the tiles provide much resisting force for this.  So, it's 
entirely the grid.
2) Is your installation rated for seismic loads? and if so, how big?  0.3g 
tells you that you can push 3000 N on a rack weighing 1000 kg without it 
failing, no?


>but I guess that's the real point: it's a question of how much lateral
>thrust might possibly be encountered, and how well, say, a tile-less
>mesh of stringers+feet would handle it.
>
>thanks, mark hahn.
>
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James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875