Wall Panel Ballistic Resistance

[Galambos]

We are currently retrofitting a warehouse to a datacenter and received a request from a future tenant to identify the "ballistic resistance" of our exterior walls.

Does anyone have a resource they can point me to?

I found UL572 that describes what each level is, but as far as classifying a wall, I'm stumped.

Thanks!

 

[TomDOT]

Mock up a wall, then shoot it with various calibers. See what is required to penetrate.

 

[Galambos]

Thanks for the input. Anyone else?

 

[TomDOT]

It's what I did with a new (polymer) sign substrate when there were concerns about "ballistic impact" when compared to aluminum substrate. The polymer signs actually stayed more legible, as they punched out more cleanly instead of dimpling.

 

[Althalus]

Galambos,

Actually, Tom got it right. The equations are simply too complex and the variables too unpredictable to do anything theoretical with any degree of accuracy. Almost all ballistic ratings are done through empirical methods rather than theoretical ones.

But here are some rules of thumb.

Wood walls:
.....1) A 1/2" OSB or Plywood usually stops a .22 or a .38 regular.
.....2) 9 mm hollow points will usually not penetrate 1/2" plywood + drywall.
.....3) Anything larger or higher velocity 9mm jhp will probably go through the wall unless it hits a stud.

I'm assuming you don't have steel walls 1" thick or better. Anything thinner and it's a crap shoot. Angle, powder charge, caliber, tip, etc. all enter into it.

Concrete & Masonry:
1) For the most part an 8" thick grout-filled masonry wall can resist handgun fire including *most* armor piercing rounds and most lower caliber rifles.
2) A sand-filled 8" masonry wall will be a little better at ballistic rating, but it is not as strong structurally (obviously).
3) An 8" thick 4000 psi concrete wall will resist all but the most powerful firearms. A high powered 30-06 (Moose round) or a 50 caliber or armor piercing versions of some mid-range rifles.
4) If you want complete protection from all firearms, you need the following:
....a) 12" 4000 psi concrete.
....b) One grid of #4 rebar at 8" o.c. at each face.
....c) The grids on each face must be offset from each other by 4".

It will take a missile or something of equal power or penetration to get through this wall.

ALTERNATIVE: Build a concrete dome. A 40' dia dome at 6" at the base and 3" at the top will resist the same as the 12" thick wall described above. The rebar will be one layer #4 at 12" o.c. and tie to a layer of hardware cloth. If you increase the dome diameter, the thickness will increase proportionally.

If you want to repel missile fire, be prepared to use a lot of steel and concrete -- or bury it underground.

If you want an actutal reference, you're out of luck. I don't believe there is a reference for the information your post indicates.

 

[Galambos]

Good input, but Tom was partially right:

per NCMA

http://www.ncma.org/resources/design/Technical FAQ/BulletBalistic Resistance.aspx

Suprisingly, ACI has less information:

http://www.concrete.org/FAQ/afmviewfaq.asp?faqid=10

 

[dik]

Althalus... I wouldn't want to be standing behind your 1/2" OSB or plywood... unless you're using 22 shorts (if still available) that might stop them. Using regular velocity long rifle cartridges, most 22 bullets will go through 1/2" plywood to about 75 yards. 5/8" mild steel will allow some 30-06 level of attack and will 'embed' a .308... my .338 would punch a clean hole through the 5/8" mild steel... These are regular hunting rounds.

An architect I worked with had a couple of Lexguard samples... one that was taken to a range and the salesman embedded a .45 pistol slug in it... the Architect was tickled pink that he had 'bulletproof' glass... I took his clean sample and put a .338 through it... he was mildly upset that I had ruined his bulletproof glass... just depends on the level of attack...

Dik

 

[Gumpmaster]

Check out UFC 4-023-07, Design to resist direct fire weapons effects. There are actual codified design proceedures to do what you want. Not much guessing necessary. Equation 5-3 gives you the required steel thickness to prevent penetration. Equation 5-1 gives you the required wood thickness. There are other design strategies you can employ as well (also included in the UFC).

 

[IRstuff]

Your client has given you a bit of an open-ended peoblem. He needs to bound the problem by specifying which type of ammunition he wants to stop, and which he's willing to accept the risk of penetration. Defense against unintentional impacts will be quite different than intentional attacks.

Or, is he just idly curious?

FYI, the UFCs can be downloaded from here:

https://pdc.usace.army.mil/library/ufc/

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[Althalus]

@dik,

You know I respect your comments. But I wonder if you're using the same powder I am. I regularly go plinking with my .22 rifle against a 1/2" plywood board. They leave chips, but don't penetrate unless I get near the same spot several times. I'm probably about 30 yards from the board.

 

[WARose]

Bechtel put out a paper some years back that has been widely used in the Nuke business to estimate required penetration for projectile impact. It was called 'BC-TOP-9-A: Design of Structures for Missile Impact'. I think they put out Rev. 2 in 1974, and I’m not aware of any past that.

 

[FRPNerd]

Check out the Composite Armor Flyer at Strongwell.com.....

This will guide you some on the UL Standard, and then let me know if you want to purchase some panels for a retrofit application.