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RE: How to design Reinforced Blast Doors

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Kapil,
OK.  That answers some questions.  Doors like this are much more economical just cutting them from a solid steel slab.  Welding on all of the reinforcement for a built up door will drive the cost way up, but the example is still valid.  The numbers are just a lot bigger. 
 
The reinforcement will act no differently than something like a double tee concrete parking garage slab in theory.  The plate steel transfers the load to the reinforcing ribs.  You must account for the shear that will be distributed through the system.  The reinforcement for the built up door will primarily help resist the flexure, you will still need a mechanism to transfer the shear.  That could be edge reinforcement or it could resist the shear in the plate steel that forms the "flange" portion of the composite shape.  I would advise all full pen welds for a uniform stress transfer.  You will also need to perform stress relief for the built up door due to the welding.  I do not see how a built up door will be more economical than a sold steel door. 
 
This door probably should be modeled dynamically.  If you do not have the computer tools, Southern Research can perform this service for you.  These guys can do the modeling for you very quickly and efficiently using a dynamic FEA.  At least call them to get a heads up.  Tell them I recommended you to them. 
http://www.southernresearch.org/engineering/engineering-blast-mitigation.html
Dan knows more about this than I do by quite a margin.  He is a good guy to know for serious computer modeling. 

Regards, Harold Sprague


 

Date: Tue, 19 Jan 2010 08:07:25 -0500
Subject: RE: How to design Reinforced Blast Doors
From: kapil.nandwana(--nospam--at)gmail.com
To: seaint(--nospam--at)seaint.org

Thanks for your comments.


However in Problem 5A-7(A) page 1598, Pr. = 14.3 psi. In my case the reflected pressure is 332 psi. For this pressure range, can I still assume that the vertical stiffener act as a supported edge and then perform the analysis assuming the door to be supported on three sides. 

Also, I do not understand how can it be assumed that the angle is supported at the ends, when in fact it is just welded to the plate and not supported at all. 

Thanks alot for your help. Waiting eagerly for your response.

Kapil 



RE: How to design Reinforced Blast Doors

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  • To<seaint(--nospam--at)seaint.org>
  • SubjectRE: How to design Reinforced Blast Doors
  • FromHarold Sprague <spraguehope(--nospam--at)hotmail.com>
  • Date: Mon, 18 Jan 2010 21:14:25 +0000

 
I presume that you are following the example in Problem 5A-7(A) page 1598.  If so, just go back to step 17 and use the composite properties then follow it through until you get to step 18 where you calculate the rotation of the composite door.  Repeat the process with added stiffening or reduced stiffener spacing and the resulting composite section properties until you limit the rotation of 3 degrees or less.  

Regards, Harold Sprague


 

Date: Mon, 18 Jan 2010 13:18:11 -0500
Subject: How to design Reinforced Blast Doors
From: kapil.nandwana(--nospam--at)gmail.com
To: seaint(--nospam--at)seaint.org

Hi,

I am currently working on designing a blast resistant door per TM5-1300 (Now UFC 3_340_02) Manual. The parameters (Blast door is double leaf 187.5 X 196 in, each leaf supported on two sides)are such that using a 2" thick steel plate results in support rotation angle of 3 degree. Now, customer spec requires the limit on rotation to be 2 degrees. We do not want to increase the plate thickness to more than 2", so, I was thinking of using stiffners to reduce the angle of rotation, but the problem is, I don't know how to analyze a blast door with stiffeners.

I am comfortable using TM5-1300 for a monolithic plate but unsure how to analyze a stiffened structure. Can someone help me in locating a reference example from which I can learn the analysis method for stiffened door ?

Thanks,

Kapil 



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