FEMA 361 Storm Shelter Opening 1

[kennyb04]

I have designed a safe room within a building to FEMA 361 wind speeds. It is not the entire building, but just one room within the building about 9'-0" X 12'-0", solid grout masonry walls with concrete cap. The architect/mechanical engineer is wanting to place an opening in the concrete cap for an exhaust duct about 12"x6". It really isn't very large, but I can't find what FEMA allows for this or if ICC500 says anything different. My main concern is if there is a design level tornado and the mechanical duct is ripped off and the opening in the roof is left. I suppose some rain would make it's way in but the opening would not affect the strength of the room as we used an atmospheric pressure coefficient of 0.18.

Doors and window openings require special tested doors and windows for impact but would the exhaust duct require any special testing? Would it have to actually stay on in the tornado event or is the roof opening without protection (assuming the exhaust vent came off) be ok? Any thoughts are appreciated.

 

[JAE]

ICC 500 states that penetrations through the shelter envelope larger than 3 1/2 sq. inches or 2 1/6" are to be considered as openings and then refers you to their section 306.3 for requirements for protection.

306.3 then refers to 306.4 where opening protective devices such as shutters or protective screens need to be tested for missile impact.

Chapter 8 of ICC 500 outlines the testing procedure for these systems.

I would think that there might be companies that provide various types of venting protection system (louvers, baffles, grating, etc.) that might work.

 

[concretemasonry]

Your main concern is trying to engineer a structure with prescriptive standards that have been thoroughly tested for projectile penetration and not just structural requirements because of the short term critical situations. Your opening is quite small and the are ways to use some of the FEMA requirements for "safe cells" that address the doors/hardware and openings for a relatively short term event.

An opening must be provided that meets the rebar spacing and thickness even for ceilings/roofs since what goes up comes down and the underlying concept is life safety. Projectiles are the main cause of death, even in structurally sound areas.

Provide a steel frame for the opening that is integrated with the slab (minimally/normally 8" thick with steel at 8" o.c.) and reinforcement and make sure the insert in the opening meets the FEMA requirements and is attached properly. Normally, most code standards revolve around the historic testing that has been done for decades to provide projectile protection and not just structural codes.

Since tornadoes are a life safety situation, a "structural failure" from cracks or deflection are not important as long as people can exit alive and unharmed.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[ttobin]

I have just finished two FEMA 361 rated facilities for telecommunication applications. We followed the letter of the law on the FEMA design criteria. After we had the calculation run by a S/E with proper foundation anchors and depth we met the FEMA361/320 requirements. This did not surprise me due to the repeated calculations we have had done on our buildings and the windload capacity we have met for years.

This unit was unique in that it was a two piece unit that we took into an existing facility. I used all certified and labeled doors and hardware. We are a welded design.

Question: I now have other counties looking for emergency storm shelters. These would be for human protection. I have monitored the Texas A&M testing process with the 100 mph 2x4. I don't see that being able to pentrate our 12 gauge steel. Dent maybe. Is the FEMA standards enough? I am creating a video to put up on You tube tonight.

Tim Tobin
Eagle Companies

http://www.eng-tips.com/viewthread.cfm?qid=336825

 

[JAE]

The other countries may or may not have tornado guidance, codes, requirements. You'd have to check with the actual governing authority on the validity of FEMA standards in their domain.