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Mechanical Room Explosion Resistant Construction

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I?m working on the design of a mechanical room housing refrigeration
equipment.  It must be designed for explosions per FM 1-44.  The room is
located adjacent to the warehouse.  It shares a common wall with the
warehouse and has 3 independent walls.  The wall farthest from the
warehouse is the explosion relief wall.  It is constructed from metal wall
panels and will have a release pressure of 20 psf. The other 3 walls have
to be explosion resistant per FM.  The design pressure is 70 psf.  I am
using concrete wall panels since I have tilt-up elsewhere on the project. 
The party wall with the warehouse will be concrete as will the two walls
that are perpendicular to the warehouse endwall.  This makes a 3 sided
box.  FM 1-44 requires the walls to be non-bearing and have a steel or
concrete frame backup.  I will have a steel frame backup.

I would like some feedback from others who have designed explosion
resistant construction.  I?m wondering about lateral stability of the
mechanical room framing.  For wind and seismic loads the 3 sided box works
great for lateral stability.  Can the walls also be used for lateral
stability during an explosion?  Section 3.1.8 ?Pressure Resistant
Construction Details? of FM 1-44 seems to imply there needs to be a frame
to backup the wall panels.  Section 3.1.9 ?Steel Walls and Framing?
discusses steel frame backup for concrete masonry but does not mention
concrete walls.  Can the walls also be used for lateral stability, or do I
need a braced frame in the backup steel?

A parallel consideration is the roof deck.  Is a regular roof deck with
insulation typically provided, or is concrete filled deck typically
provided in explosion resistant construction?  I?m wondering if the roof
diaphragm would be in tack sufficiently to provide a diaphragm after an
explosion if it is not filled.  It seems to me the weight of the concrete
will help resist the uplift of the explosion force so that the diaphragm
will remain in tack and able to resist shear.  The negative factor is the
added cost from concrete and the steel and foundation to support the
weight of the concrete.  If the roof is not designed to release pressure,
should it be concrete filled?

FM 1-44 does not mention how to determine the forces needed for lateral
stability.  It seems to me the forces on the 2 side walls of the 3 sided
box would primarily be equal and opposite.  The back side of the box that
separates the warehouse from the mechanical room would have the force of
the explosion of 70 psf.  What other ways are there of looking at the
lateral stabilizing force for the overall system?

Thanks for any insight you may be able to give.


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