Armory Structure 5

[KCRatnayake]

I am in the process of designing a police station. There is an armory in the design. I know we'll have to use concrete walls right round this. Can you tell me any other factors that I have to consider in designing this? Useful link is appreciated.

Clefcon

 

[concretemasonry]

Probably either reinforced concrete or reinforced masonry, depending on the use and appearance. Often one side of the wall has finish and appearance requirements (hallway, office, etc.)

I have seen some with coarse textured block grouted solid to decrease the noise level when the pricy panels are not in the budget.

Depending on the possible use on either side of the walls you could be seeing "high security prison" type construction with steel as close as 8" o.c. There are special block made to permit construcion without any lifting over steel in place. Usually requirement is part of the initial criteria.

If there are concrete slabs, the non-bearing walls may have some very important security connections at the slab above (depending on construction sequence).

You can expect some unique requirements depending on the use of the facility. If it is just administrative/target range/ book 'em and keep them for a short time facity, then not many unusual requirements.

Always an interesting building to plan/design. - I worked with a construction manager/architect of a high security prison and attended the "grand opening" for the influentials and ex-con consultants. - We had the opportunity to spend the night in a cell!

 

[UcfSE]

I would check with the building department. You may also try to find some of the DoD standards, or similar brnach of government if you aren't in the US, that are in the public domain. Those may provide some guidance for considerations in case you can't find anything specific.

 

[msquared48]

An Armory strikes me as needing even tighter requirements than a prison, especially nowadays. I have done one prison before, and have been in the military Corps of Engineers. My guts tell me that I would expect 12" thick concrete walls with three layers of a 4" staggered grid of reinforcing, probably #5 bar minimum. I would spec 5000 psi concrete. But, yes, check with the local BD or Police agency requirements. They may have their own standards.

To me, CMU would be a definite no-no due to the tight grid and the relatively low strength of the block.

No strength worries here, eh?

Mike McCann
McCann Engineering

 

[JAE]

Do you have a blast issue here? We once did a munitions maintenance facility for the military - sheesh - concrete walls on either side of 3 feet of earth fill creating a sandwich wall to resist blast of munitions within.

Also, many times you can design into it a blow-off section (say in the roof) that will fail first (on purpose) to direct any blast forces away from personnel.

 

[kxa]

JAE

Is there any publication that provides pressure equivalent for different types of blast or even method of designing the walls, floors, etc.?

 

[JAE]

We got an Air Force Blast TM manual and tried to go through it to figure out the blast forces, etc. Quite the book. Very complex and we quickly "determined" that our scope of services didn't include doing this. You had to know the actual type, position, etc. of the munitions to do any good. What we ended up doing is use a similar design that they had earlier approved.

This paragraph is taken out of the manual: TM 5-809-6/AFM 88-3, Chap. 6 which is found here:

http://www.usace.army.mil/publications/armytm/tm5-809-6/chap9.pdf

[blue]9-2. Blast-resistant construction
Design of structures to resist the effects of accidental explosions will be in accordance with TM 5-1300/NAVFAC P-397/AFM 88-22. The reference is mandatory for explosive safety design. Design of structures to resist the effects of conventional weapons will be in accordance with TM 5-855-1, and design of facilities to resist the effects of nuclear weapons will be in accordance with TM 5-858-1, TM 5-858-2, TM 5-858-3, TM 5-858-4, TM 5-858-5 and TM 5-858-8. The design of blast-resistant structures must consider the transient loadings and dynamic response of the structure that results from the specified design event. Blast-resistant design is often required in conjunction with the construction of weapons system facilities, both developmental and operational, as well as for structures designed to resist the effects of intentional attack.[/blue]

 

[kxa]

Thanks. Sounds very involved. Is there any minimum design pressure or minimum std of protection?

 

[JAE]

No minimum pressure. Basically, as I remember it, you have to identify all the applicable munitions to be stored, and perhaps quantity, and then there is some format where you develop a blast pressure for design. I recall this had large steel blast doors, and earth sandwiches for both walls and roof.

Sorry I can't be more specific - it's been a while .... and I've tried to forget it.

 

[MarcbSE]

The big issue is the type and quantity of munitions stored in the Armory. I've designed several "blast resistant" storage facilities for the Army and the design is quite involved. You have to consider a dynamic blast pressure and I would expect 12" thick (minimum)reinforced concrete walls with (2) mats of steel on about 4 1/2" spacing both ways and staggered from face to face. However, this would apply mostly for larger arms. In a police station I would not expect this type of explosives to be present. Most likely they are calling it an "Armory" but is only used to store small arms. In this case I would use basically the same design used for a prison while taking into account the DoD Antiterrorism design specifications.

 

[KCRatnayake]

Thanks folks,
This was very helpful.

Clefcon

 

[BSE05]

The NFPA has design criteria for most situations of this type. Try calling them in Quincy, MA I believe.

 

[twinnell]

We have done 4 or 5 armories for Fort Bragg and they told us what they wanted. 8" reinforced masonry with #4@8" OC. 8" thick concrete ceiling slab. Terminate wall steel in ceiling slab with hook. 2 No. 9 wire horizontal joint reinforcing @ 8" O.C.

There is an Army COE documents or DOD documents out there that explain all this...can't find mine.

 

[civilperson]

Do not forget ventilation of this reinforced space! (Sprinklers and floor drains are nice.)

 

[BSE05]

The building code, under high hazard occupancy, will point you in the right direction. In my experience not too many architects understand this section. Over the years I have been involved in many different high hazard occupancies and learned to do the code reviews for all the disciplines (A/E firm). Explosives are high hazard, but it depends on the total quantity stored what design criteria needs to be followed to meet code.

If required to resist explosion NFPA has a section on damage limiting construction due to deflagration that will give you design criteria and how to determine resistive/relief forces.

Ask your architect to review the code for you, but do it yourself as a good check against liability.