Hurricane design criteria

[steve1]

I am putting together structural design criteria for an industrial building, housing a turbine generator that will be constructed along the eastern seaboard of the U.S. The owner has required that the facility remain operational after a category 3 hurricane. The site is alongside a river near the mouth. The site is on a side sloping hillside, and has good quality ledge near the surface. Do to the tidal surge the one storey building will have its finished floor elevation raised above the tidal surge. As a result along the low side of the building the top of the foundation wall is projected to be seven and a half feet above grade.

Considering the criteria for the design of the foundation wall to resist the the tidal surge I have researched both the state building code (modified IBC) and the Florida building code, along with ASCE 7, and numerous FEMA publications. I have plenty of information concerning wind forces, wind generated missiles, and height of tidal surge.

What I have not found is information directly related to the hydrodynamic effects of the tidal surge or water borne debris (water born missles?) that may impact the structure during the tidal surge. Does anyone know if these effects should be considered in the design? If so what would be the reference documents?

 

[SlideRuleEra]

steve1 - What you are describing sounds like a "storm surge". The low pressure and circular wind pattern of a hurricane cause a rapid VERTICAL rise (and later a rapid fall) in water level as the eye approaches and crosses the coastline. The vertical magnitude of this storm surge can be predicted with reasonable accuracy for a given location.

The storm surge is superimposed on normal tidal action, then wind-driven waves are superimposed on the cumulative total (tidal action + storm surge). The primary concern is the wave action at this maximum water level. However, you could certainly have impact from water borne debris moving due to tidal/wave action. You may need to consider hydrostatic forces if the foundation is to keep water from going into the structure.

As you have discovered, I doubt if any of this is addressed by current codes or definitive reference documents. FEMA normally addresses relieving the hydrostatic pressure that can come from rapid water level rise (storm surge). Break-away walls, etc. let the water pass through/under a structure and "hope for the best" when it comes to debris impact.

Like many aspects of industrial design, you will most likely have to rely on engineering judgment, rather than guidance (or restrictions) offer by codes.

http://www.SlideRuleEra.net

 

[MikeHalloran]

Does that river carry barge traffic?

Try usace.army.mil.




Mike Halloran
Pembroke Pines, FL, USA