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Re: Bomb Shelter

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Forrest
Your point is noted. But could you please elaborate more on this "CONCRETE FLANGE" that you are proposing? Thank you once again.
SYED FAIZ AHMAD

From: Forrest Braun <fbraun(--nospam--at)bbfm.com>
Reply-To: seaint(--nospam--at)seaint.org
To: seaint(--nospam--at)seaint.org
Subject: Re: Bomb Shelter
Date: Fri, 01 Jun 2001 16:09:34 -0800

Syed

Using epoxy concrete may not be the best solution for what are probably
heavy doors since the epoxy could have significant creep, and your
anchors will be in tension. Heat may also be a concern although from a
blast that time period will be short.  Any resulting fire in the
aftermath though could be long enough to affect the epoxy.  A high
strength cement or concrete grout would be a better solution especially
if the existing reinforcing can be exposed to allow the new grout to
completely surround the bars.

Try to avoid cutting any of the existing bars.  It will probably be
necessary to cut a few to fit the hardware.  Any bars that need to be
cut should be re-established if at all possible since this will be a
high stress point.  Mechanical bar splicers, or welding (if weldable
bars or appropriate precautions taken) I should think would be better
than lap splices.  All of these take up space or may require additional
demolition of concrete so you will need to look at these options
carefully.

An alternate to potentially affecting the integrity of the existing
concrete may be to add a concrete "flange" of appropriate depth and
width to the blast side of the wall to accept the door hardware.  This
flange could then be doweled into the existing concrete thus providing
greater flexibility in maintaining the existing bars.  Just a thought
though.

syed faiz ahmad wrote:
>
> Gentlemen/Women
> I have a problem which i want to share discussions with our fellow learned
> engineers on the List.
> We built an underground bomb shelter which have wall openings provisioned
> for the Blast resistant doors. There were no provisions left for "hold
> fasts" for fixing the blast doors at the time of casting of this bomb
> shelter. The peripheral walls of the shelter are 700 mm (2 ft-4 in) thick & > the intermediate walls receiving these doors are 300 mm (12-in) thick.The
> top & bottom slabs are 700 mm (2ft-4in)thick. These doors are basically
> leading to escape shafts & also serving some rooms. The blast doors have now
> been received so we know now exactly the number & location of the "hold
> fasts"; this information was not available at the time of concreting, that
> is why no provisions could be made for "hold fasts" then. We are now
> intending to break open portions in the walls to fix these hold fasts & fill > back the openings with epoxy concrete.These are bomb shelter walls so there > are of course, a jumble of rebars. This will involve cutting of some of the > rebars as well.There is no way to do some analysis because these are bomb
> shelters designed by some Consultant some 15-20 yers ago and are being
> copied generation to generation. No data on these blast forces are available
> which would basically be generated by surrounding air after enemy air
> attack. So,as you see, we have to work empirically on pure engineering
> judgements.I know from research, structural elements repaired with epoxy
> concrete become very strong & under load tests it yields from some other
> locations & not at the locations where it was repaired using epoxy concrete.
> This is satisfying to me & i can try & sell this to the supervising
> Consultant. But there could be questions on its integrity to resist blast
> pressure, especially because weak points have been created , interms of
> openings made in walls to fix the "hold fasts". So,my question is: do other
> fellow engineers agree with this procedure Or they would like to suggest
> some better  or alternative recourse?
> SYED FAIZ AHMAD
> SENIOR STRUCTURAL ENGINEER
> SAUDI OGER LTD
> RIYADH, SAUDI ARABIA
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--
++++++++++++++++++++++++++
Forrest T. Braun, P.E.
BBFM Engineers, Inc.
Ph (907)274-2236
Fx (907)274-2520
Anchorage, Alaska
http://www.bbfm.com
++++++++++++++++++++++++++

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