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RE: Blast Resistant Building Design for Blast Containment

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Bill,

I checked with some of the engineers in our office who have experience in
design of blast resistant test cells regarding using tilt up precast
concrete construction.  Their opinion is that it may be technically
feasible but the panel thicknesses are going to be well beyond standard
tilt up panels which affects costs and as you and others mentioned the
connection details are real challenge.  Also, shear design requires lacing
reinforcement when the scaled distance Z < 3 which further complicates the
design.

I am not aware of any 'cook' book approach that can be used to calculate
the blast loads on the access door behind the labryinth walls due to the
complex reflection effects that take place.  There are some PC based codes
available for predicting the blast loads from government sources that you
may be able to apply.  You have to check with your contracting officer to
see if you have access to these sources.  Basically, the test cell would be
divided into multiple 'analytical' compartments connected by vent areas but
there are limiting parameters (such as length to effective diameter ratio,
... etc.) that may rule out the use of these codes.  You may also need to
consider the mass of the vented panels.  We are using computational fluid
dynamics (CFD) methods for these problems now with an in-house PC based
program.  Otherwise, you will probably find yourself making conservative
assumptions.

Walt Sawruk
EQE International, Inc.
Shillington, PA
email: ws(--nospam--at)eqe.com


At 10:05 AM 28-12-1999 -0600, you wrote:
>Wanted to make sure someone was listening before I drug out the story.
>
>We've got a "test cell" building to design. Four test cells, three small
>(0.7 kg TNT equivalent) and one large (1.4 kg TNT equivalent). They are
>adjacent to a lab space that is expected to be occupied.
>
>The outward facing walls we will make "blast vented" so that the impulse
>from a blast will be limited (at least that's my understanding of how this
>works). There will be a wall stood off from this wall to shield property and
>living organisms from any debris that might be blown outward.
>
>The common wall with the occupied lab space is my concern, however.
>
>An additional complication, at least the way I see it, is that there is a
>"blast lock" in one corner of each cell, such that someone can go through a
>door from the lab to the lock, then turn 90 degrees to go through a blast
>door into a cell. Each cell is thus an irregular "ell" shape, to accomodate
>the lock.
>
>The client wants to use all "tilt-up" construction (which I don't see as
>viable for the test cell portion of the building). Is this possible, in your
>opinion?
>
>Also, how much help is the "blast vent" wall panel array? How much can it be
>expected to mitigate the blast impulse overpressure acting on the other
>walls?
>
>How about the wall joints? The only other deal like this that I've ever done
>we used non-reentrant corners. This has 'em all over the place.
>
>I wonder if some sort of "composite" R/C wall, maybe with a sandwiched layer
>of something like styrofoam (deformational) or lead shot (mass) would help
>to cushion the blow?
>
>Finally, how would you approach this analytically? Is there a simplified
>analysis that you could use? We have the Army TM 5-1300 manual(s), but I
>haven't perused them enough to tell if they give guidance in this regard.
>
>Any thoughts you'd have along these lines would be much appreciated.
>
>Thanks and regards.
>