Designing buildings for Tornadic Winds
Designing buildings for Tornadic Winds
(OP)
I am working on an steel-framed office building (5-6 stories) that has to be designed as an essential facility (requirement by client). I would really appreciate if anyone out here could through some light on designing such a building for Tornadic winds. I did a bit of code review on this and I am totally confused. Is it even practical to design such a building for such high wind velocities?? If yes, where can I find the design criteria. ASCE 7-05 commentary does have some information regarding tornadic wind velocities to be considered. But, I couldn't find any information on how to calculate pressures (both MWFRS and C&C) and load factors to be used in the final design. I would really appreciate your thoughts and comments on this. Thank you.






RE: Designing buildings for Tornadic Winds
The issue with tornadoes isn't so much of the wind speed either, but more with the openings and penetrations that are created in your building by debris. These then cause pressure buildups as you approach a partially enclosed building envelope. But since they are not predictable, they are nearly impossible to design to. I'm not sure ASCE-7 made any load combinations for a Volvo flying through your third story windows.
RE: Designing buildings for Tornadic Winds
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RE: Designing buildings for Tornadic Winds
This can be had at the link.
Maybe only critical items need to be placed in the safe room rather than design the entire building for a torndao.
As others have stated, internal pressures can be come significant for a direct hit by a tornado.
RE: Designing buildings for Tornadic Winds
RE: Designing buildings for Tornadic Winds
If the owner wants the facility, or parts of the facility, designed to withstand a tornado, that is another issue. And a question that should be asked of the owner. What is he/she intetending when they say they want their facility to be 'essential'.
FEMA 361 is guidance for the design of tornado shelters. FEMA 453 mentioned above if for shelters offering protection from man-made events.
We have been asked many times if it is practical to design multi-story buildings to meet FEMA 361 guidance (we are located in the midwest, and tornados are an issue around here). Our response always is that yes, we can design a multi-story building to FEMA 361. The only problem is the owner likely cannot afford it.
The best solution is to locate the shelter underground. If that is not feasible, 1 story 'protected areas' on the ground floor are the only practical solution.
JMHO.
RE: Designing buildings for Tornadic Winds
But designing a massive chunk of concrete with no openings for a tornado and an occupied building for a tornado are two different issues. I'm not sure you could design a 5 story building for these forces.
RE: Designing buildings for Tornadic Winds
lkjh345, as stated by bnickeson above, check out ICC 500. This document is based upon FEMA 361 and essentially provides a "code-language" specification on shelter designs vs. 361's "guide-language".
RE: Designing buildings for Tornadic Winds
RE: Designing buildings for Tornadic Winds