Wave Loads on Vertical Walls

[mahagna]

Hi all, I'm assisting on a project where we were asked to look into wind and seismic anchorage for an exterior storage tank at a facility.
While gathering the typical design criteria, I noticed the site location was in a flood plain, close to a coast.
I have never done flood loading on a structure before, but in the interest of being thorough, I wanted to look into it and compare it to the seismic and wind loading.

The tanks are flat-sided, so I used the breaking wave load on vertical walls equation - which gave me a load of 31 K/ft.... For an 18'-0" long unit that's 564 K of force.
I don't have a sense of whether that number is at all reasonable but it is way higher than the wind loading we've calculated for the unit.

To provide some other info, the BFE is 16', the G elev is 2' and we've been asked to design for Risk Category III for both wind and seismic, so I did the same for flood.

Can anyone give me some guidance if this is really how high flood wave loading gets or if I've gone astray somewhere?

 

[phamENG]

16 feet!? Is it behind a dam? There's got to be something off about that. Can you post a clip of the flood map?

Wave forces are no joke. Wind does a lot of damage to a building...waves level them.

 

[mahagna]

Attached the FEMA map with a highlight of the zone... right off the Gulf of Mexico.
I think I need to get in touch with the client - looking at pictures of the site on their website, there is a braced wall around the perimeter of the site, perhaps that offers some protection to things within.

 

[phamENG]

Wow. That's nuts.

But...you're in an AE zone. So breaking waves aren't really going to be an issue for you. Breaking waves are a design consideration in the VE zones, but in AE you just need hydrodynamic loads from flowing water. Still not small, but won't be nearly as bad as an 11ft waving crashing against the side of the tank.

 

[mahagna]

That simplifies things a bit...I'm assuming hydrodynamic loads from flowing water still need to be applied concurrently with hydrostatic load, similar to the breaking wave equation?

 

[haynewp]

Where does it say that you can ignore breaking waves in AE Zone?

 

[phamENG]

Fair point, haynewp. There's no LiMWA delineated on that map, so those would be Coastal A zones and there is some consideration for the waves. But they'll be less than 3 feet in height, which will still reduce it by quite a bit. You won't need to use 0.78d[sub]s[/sub] to determine the wave height. Just set it at 3ft.