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RE: Mechanical Room Explosion Resistant Construction

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My experience with this type of facility is to provide a braced steel
structure independent of the blast resisting walls.  If the machine room
is new and the adjacent buildings are existing then you're going to have
to design the blast resisting walls as freestanding cantilevered. If the
adjacent construction is also new and the wall does not have to function
as a FM MFL firewall then you should be able to connect the blast
resisting wall to the other adjacent structures so that it does not have
to cantilever.

The blast relieving wall should be constructed with insulated metal
panels using quick release connectors manufactured by I think Fabcon?  I
believe FM also requires that you connect cables to the panels so that
when they blow off they don't go sailing off down the road.

D. Matthew Stuart, P.E., S.E., F.ASCE, SECB
Senior Project Manager
Structural Department
Associate
Schoor DePalma Engineers and Consultants
200 State Highway Nine
Manalapan, NJ 07726
732-577-9000 (Ext. 1283)
908-309-8657 (Cell)
732-298-9441 (Fax)
mstuart(--nospam--at)schoordepalma.com

-----Original Message-----
From: seaint04(--nospam--at)lewisengineering.com
[mailto:seaint04(--nospam--at)lewisengineering.com] 
Sent: Monday, June 11, 2007 8:51 PM
To: seaint(--nospam--at)seaint.org
Subject: Mechanical Room Explosion Resistant Construction

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.

Rich


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