Coastal Engineering, Flood Proofing a Building 1

[Michael55]

Can anyone lend any insight into a slab on grade, pre-engineered metal building design. Local code calls for a flood water depth of 4' above the finish floor elevation which will create considerable floatation uplift. My client wants to flood protect this new building with exterior walls and flood doors as part of the building design such that he can build on his site with no fill dirt required. Any thoughts regarding an economical design? (thick mass concrete floor slab, helical piers, etc?)

Thanks.

 

[SlideRuleEra]

"FEMA Flood Mitigation Handbook" has a few basic considerations

http://www.conservationtech.com/FEMA-WEB/FEMA-subweb-flood/01-06-FLOOD/4-Buildings/A.Inundation.htm

Also, you may want to look in "FEMA 55, Coastal Construction Manual, Third Edition", which I recently put on my website
thread194-174585

http://www.SlideRuleEra.net

 

[structuralaggie]

If you are building in the flood plane, don't you have to provide flood vents and / or break away walls?

 

[swivel63]

yea, that's what i thought.....we had a similar issue on another project and basically had to provide exterior walls that could be knocked over in the event of a surge (i think).

 

[Michael55]

Thanks for the suggestions. I guess my real thoughts on this are as follows:

The local code is based on FEMA Publication EP1165-2-314 Dec15, 1995.

The local bldg code allows a commercial building finish floor elevation below the design flood water level provided that the building is "flood proofed". The flood proofing will consist of waterproofed exterior walls and flood doors to a height which is 1' of freeboard above the design flood water elevation.

Assuming a 50'x50' (2,500 sf) building, with a water height of 5' all around the exterior perimeter, is the total flotation uplift equal to 50x50x5x62.4 = 780 kips?
If so, then the code requires a safety factor of 33% yielding an uplift pressure of 1,037 kips total.
Is this correct? If so then resisting this with a mass concrete floor slab is not very economical. (would require a thickness of nearly 3')

Thoughts?

 

[civilperson]

Fill to a height 1' above the flood elevation is cheaper than the flood proof components envisioned and easier to sell to building officials.

 

[SperlingPE]

Concrete cost: 50*50*3 divided by 27 = 278 yds^3
278 * $100 = $27800

What is the cost of dirt work in your area?

This is a pretty simplified look at the economics.

 

[structuralaggie]

Piers? They can take a lot of uplift is so desinged.

If this is for the coast and the flood zone is from tidal surge, take care in the design. The water may not just come up statically. Hence my question about break away walls. Waves can create tremenduos loads.

 

[boo1]

also see FEMA Recommended Residential Construction for the Gulf Coast: Building on Strong and Safe Foundations:

http://www.fema.gov/library/viewRecord.do?id=1853