Try FEMA 361: Design and Construction Guidance for Community Shelters
It is more aimed at larger shelters, but may give you the guidance you need for a small shelter. It talks about determining extreme load cases, impact requirements, etc...
I believe it is free to order from FEMA's website.
I believe another appropriate document is FEMA 315, which is a commomly used prescriptive standards developed abot 10 years ago and is being used with increasing frequency. It is appropriate for freestanding and interior shelters (above and below grade).
The thrust of the protection is obviously protection from projectiles since the structural concerns are obviously less and are addressed. Much of the basis is the projectile testing program of assemblies at Texas Tech in conjunction with FEMA.
The document also provides some good guidelines on size, doors, door swing direction, hardware, roofing and ventilation.
I understand there may be some consideration on modifying the standard for interior basement structures.
Just go to the FEMA site (fema.gov or fema.org, I believe) and you can download the .pdf documents.
I just checked out FEMA 315. It is listed as "Seismic Rehabilitation of Buildings: Strategic Plan 2005" on the FEMA website. Are you sure about that number?
I will check on the number. I may have been confused about the number and could not find the CD I got from FEMA. I beleive in their site they refer to the subject as "safe cell", "safe room" or something similar.
As I mentioned, the main criteria is the wall construction is critical for projectile protection and the structural just follows, but is usually a moot question if the FEMA standards are followed.
There is also another document (FEMA 320) that is for building safe rooms is houses. The wall details for 8" reinforced block and 8" reinforced concrete are very similar with the same roof and foundation structure. The is also plans for wood construction consisting of two layers of 3/4" plywood and sheet of steel with double 2x4s and an interior finish.- I understand some of the codes are considering reducing increasing the steel reinforcement spacing for many conditions.
FEMA 320 is not a code and is not written in code language. It is a guide based on extensive testing at Texas Tech and elsewhere for the past 10 to 15 years and oriented toward life safety and elimination of any projectile penetration, which is the most common hazard/risk.
It is a guide and not a structural design, but following the size recommendations and construction, any necessary structural calculations will be minimal with proper assumptions and an ability to come up with realistic wind loads for an F5.
For the structural portions follow the local building code and use ACI 530 for guidance.
