School Used as Emergency Shelter - Any Design Changes?

[dhoward26]

I recently completed the structural design of my old grade school.

The school has came back and said they want to use the new school as an emergency shelter in the event an emergency comes up.

Are there any changes structurally I would need to do to my design?

To me, it would seem it is just back-up power (redundancy), lighting, food and water storage that need to be considered and nothing structural.

Thank you,

D

 

[Teguci]

Have a look at ASCE 7 section 1 regarding importance factors.

 

[flight7]

Assuming your project is subject to ASCE 7, the occupancy category might change to IV. This includes "designated earthquake, hurricane, or other emergency shelters." Does the owner's intention fit this description?

 

[dhoward26]

Thanks for the help. It changes the lateral loads substantially with the change from category III to IV after reviewing the ASCE-7.

 

[MiketheEngineer]

And I might add a bit of a cushion....

 

[boo1]

flood height?

 

[Ron]

Not sure where you're located, but in my area (Florida), when we are considering emergency shelter applications, we typically take the wind design for coastal areas to a Category 5 storm rather than the typical code application (Cat 2,3, or 4 in most areas).

If you have seismic considerations, you might increase your seismic loading similarly.

 

[dhoward26]

It's in North East Oregon. We're pushing for them to not go this route as the design is already done and the contractor has already made his bid. This change would have a pretty substantial affect on the cost of the school.

 

[connectegr]

We recently worked on a school, which designated only the gymnasium as a tornado shelter. The design significantly changed the structure.

http://www.FerrellEngineering.com

 

[Forensic74]

Gymnasium as a tornado shelter, I really hope you advised them against this.

This is a loaded question because the owner's expectations of a shelter are usually very different than what can be provided.

 

[JAE]

We've done numerous elementary school gyms as shelters - can be done - just need to deal with the loads, indirect gym entries, etc.

 

[Forensic74]

Really? Arent the pressures for a true tornado shelter enormous in FEMA 361? Would think it'd be nearly impossible to meet for large spans/walls.

 

[concretemasonry]

Emergency shelter suggestions for groups have been developed by FEMA (fema.gov, I believe).

They do not address the structural systems of a gym or other vulnerable structures. The concept is life safety/survival under severe conditions. Obviously a tall floor space would be bad choice, but the lower areas with more stability and less exposure make more sense.

Most of the suggestions (not a code) are based on life safety and protection from winds and especially projectiles, because FEMA has a great background in that area. For residential protection from projectiles and debris (the largest cause of deaths), there only a very few select wall systems recommended because of the extensive testing over the last 15-20 years or so. These can be used or existing walls can be modified to approximate the results, but not quantified.

It is well worth the time to look over the concepts and see how they apply.

Dick

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

 

[racookpe1978]

For a school/shelter in a hurricane-threat area (not Oregon ?) wouldn't the windows have to be addresses against flying debris?

Than again, my old grade school was built pre-air conditioning and pre-Columbine (warfare) problems, so maybe new schools have "no" outside windows .....

 

[dik]

dhoward26...
Has the contract been awarded? You mentioned you had bids. Change is significant that re-tender might be in order.

I would suggest that you do not 'push for them not to go this route'... in the event that there is a problem and collapse, you may be in for serious law suits.

If the school wants this, then deal with it as a significant change.

Dik

 

[JAE]

MainMan10 - this was a no-window smaller elementary school gym - 12" fully grouted CMU with rebar in every cell. Heavy roof system tied down to the walls with extended anchorage (about 3 to 4 feet down the wall). It was based on 200 mph now that I think about it. Yes the loads were large but not to the extent we couldn't design for them.

FEMA 361 does address the structural design of buildings used as community shelters. It deals with both loads and projectiles. ICC 500 is the newer "code" version of the FEMA guidelines.

 

[Duwe6]

Watch the detailing and construction of the roof-to-wall connections, and the roof attachment to the purlins. A gym is a poor choice with the best installed work.

There is a *very valid* reason that hallways and bathrooms are the traditional areas of choice for 'hardening'. Your customer is trying to "reinvent the wheel". Sometimes [almost always] the 'usual & customary solution' represents an optimal design.

Wheels are round for a reason.

 

[MiketheEngineer]

I agree w/Duwe6 - small halls and baths are naturally "hardened" Just beef them up a bit and designate them as the "emergency" area.

Done all the time.

 

[lutein]

We typically design emergency shelter in accordance to FEMA 361. All windows/doors should comply to FEMA 361 for missile impact resistant. Otherwise, pending on the opening, the roof may have to be designed for partially open C&C wind, which is much larger.

Also - Check with the owner to determine the tornado category, typically in fujita scale, F1, F2, etc. go to national weather website to find the corresponding 3-sec guest wind speed.

 

[concretemasonry]

The projectile criteria is a major influence on the selection of walls. It is NOT a structural criteria, but is based on actual standard penetration tests (12' long 2x4 fired from an air cannon at about 145 mph) conducted through the years at a university in Texas. The acceptable walls must meet the criteria of NO penetration. 8" reinforced (8" o.c.) concrete and and reinforced masonry were the only acceptable wall sections for many years and finally a wood wall section got approval, but it is 8" studs at 12" o.c. and sandwiched by 3/4" plywood plus steel plate.Of course, the roof must also meet the requirements.

Keep in mind this is really for tornadoes and not hurricanes that typically have much lower winds. The concept is meant to be applied to small life saving structures for survival and not for groups with longer term needs.

Windows obviously have a more relaxed threshold, because shutters or other systems are also expected to be used or required.

Dick

Dick

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