×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Debate Over Superdome as Hurricane Shelter

Debate Over Superdome as Hurricane Shelter

RE: Debate Over Superdome as Hurricane Shelter

Well - I guess I just can't see the dome getting blown away.  Most major structures are designed for standard wind in the wind zone and NO is very close to the coast so at least a 120 (the article says 130) mph wind would have been used.  In addition - the shear size of the dome and the way its built would suggest that the overall stability of the dome isn't in question - as the primary wind would average smaller than the peak hot spots (component wind)that usually cause so much damage in homes and smaller structures.

In addition - being within an urban setting, the wind speeds are knocked down from the weather service speeds which are taken at specific "clear" zones at a set height above the ground - so the real wind hitting the dome wouldn't be the 165 mph speeds that you hear bandied about on the news.  

RE: Debate Over Superdome as Hurricane Shelter

Here's a link to a wind speed map of Katrina.

Note that the Category 5 is 135 knots which equals 155.5 mph.  Note also that this speed is at about 1800 km above ground.

Wind Map of Katrina

RE: Debate Over Superdome as Hurricane Shelter

(OP)
Good point but remember we design for 3-second gust not sustained wind speed.  So lets say the winds reduce to 150mph sustained when it hits New Orleans.  This translates to a 3-second gust of around 190mph.

Look at Table G-1.

http://floridadisaster.org/bpr/Response/engineers/documents/2004SESP/Individual%20Elements/2004-SESP-AppxG.pdf

Some spooky stuff in that table.  What are we really designing for?  Hope you sleep good tonight knowing your building are underdesigned.

RE: Debate Over Superdome as Hurricane Shelter

The speed can't be at any altitude, especially that high. I think this chart is a ground level speed as they compare this to a giant force three tornado that last for hours instead of seconds.

I know that in IVAN I was measuring sustained wind speeds in excess of 120 MPH for several minutes at 16 ft.  The wind never dropped under 100 MPH for over 1 hour, that’s all I could measure because my anemometer went away.  I was told, never checked, that this the standard height for a wind gauge.

The Superdome was designed and built when it wasn't surrounded by tall buildings.  It was the highest thing around.  There was some discussion during the construction of the Dome as to the actual design speed.  I know we had to upgrade the plant site form 100 MPH to 135 MPH. Apparently 100 MPH was the accepted standard for many years.

RE: Debate Over Superdome as Hurricane Shelter

It's a nice looking structure (http://www.superdome.com/site.php).  Would they have done wind tunnel testing to develop the winds loads on this building due to its unusual shape?  If so, it would be interesting to know what wind speed they used.

In Australia, we get some pretty severe Category 5 tropical cyclones on our mid- and north-west coast.  Structures that have a special post-disaster function are designed for an ultimate limit state wind speed of up to 99m/s (221mph), based on an annual probability of exceedance of 1/2000.

RE: Debate Over Superdome as Hurricane Shelter

Most domes are designed with wind tunnel testing.  At what design speed I'm not sure for the New Orleans Dome.

RE: Debate Over Superdome as Hurricane Shelter

(OP)
Yes, but how you accurately perform a wind tunnel test on a structure back in the 1970's with new structures now adjacent to the Superdome?  The necking of wind between buildings can really increase pressures on adjacent structures.  I just heard on the news that the occupants inside the structure can see some daylight thought the Superdome’s roof.

RE: Debate Over Superdome as Hurricane Shelter

It's also a bit tricky modelling for wind tunnel testing; in particular for 'funny' shapes.  Some of the coeficients aren't scaleable.

Dik

RE: Debate Over Superdome as Hurricane Shelter

What about impact loads from airborne debris?
How resistant is the structure to puncturing?

RE: Debate Over Superdome as Hurricane Shelter

Great discussion.  Funny how we engineers ponder these things.  This morning I found myself wondering just how many older structures could sustain a category 4 or even a 5 hurricane.

I've never designed a dome, but having visited a few I would still think that the dome would be a safer place to go than most structures.  If it's like any of the ones I've seen it has huge concrete beams and columns inside, which I would think would be great things to take shelter  under/beside in the event of a hurricane.  But I wouldn't want to be out in the middle of the dome with just the roof over my head.  I would think that would be the weakest link.  

I'm curious to see how much damage it does sustain.

RE: Debate Over Superdome as Hurricane Shelter

Lets think about this a second.  Obviously someone has given the city the ok to put people in the superdome.  I would find it very odd that they would pile thousands of people into an unsafe structure.

Lets also not forget about all of the redundancy of a building of this caliber.  Obviously this structure has a specified lateral supporting system.  But factor in all the other structural elements that aren't accounted for.  Plus all the factors of safety and so forth. I've seen alot of unsafe structures (unsafe according to the building code) sustain substantial lateral loads.

Just my 2 cents.  

RE: Debate Over Superdome as Hurricane Shelter

News
Hurricane Katrina ripped two holes in the curved roof of the Louisisan Superdome, each about 15 to 20 feet long and 4 to 5 feet wide.


RE: Debate Over Superdome as Hurricane Shelter

Are any of the buildings in the hurricane region rigged up to provide data for design codes after the storm?

RE: Debate Over Superdome as Hurricane Shelter

I don't know how the dome exactly works, but it sounds like a couple of roof panels may have blown off.  I can't imagine the wind "ripped out a chunk of concrete".  Yeah, they'll get wet, but it doesn't seem like a real structural problem.

RE: Debate Over Superdome as Hurricane Shelter

Here's the link to the Drudge article on it:

Superdome

It may not last long on the net but view it while you can.

RE: Debate Over Superdome as Hurricane Shelter

"Lets think about this a second.  Obviously someone has given the city the ok to put people in the superdome.  I would find it very odd that they would pile thousands of people into an unsafe structure."

If you read the articles relating to the discussion, the problem they have is there isn't anywhere else that's any safer.  Any place low will flood, and other buildings aren't designed for any higher wind speeds than the Superdome.  Whether it's safe is immaterial, it's still safer than the alternative.

RE: Debate Over Superdome as Hurricane Shelter

I heard that they were putting people under the upper seating overhangs, so any roof debris or rain would fall on the football field, not on the inhabitants.  So essentially, they are covered with hard material all around and the small holes in the roof panels wouldn't pose any significant risk.

RE: Debate Over Superdome as Hurricane Shelter

If you look at the pictures of them, in yahoo, for example, they were actually sitting on the field, but after some of the roofing came off they moved them to safer areas. Who wouldn't prefer sitting on soft grass to hard seats and floors?  But still, if it were me I would have felt uneasy on the grass under the main roof.

RE: Debate Over Superdome as Hurricane Shelter

I read an account that stated that they had to move the people under the damaged areas, but I don't necessarily believe anything I read in the news media without some other type of verification.

The superdome was built after Betsy and Camille, both worse storms than this one as measured by low pressure measurements, so I would imagine that it has a pretty stiff wind loading rating in its design.

rmw

RE: Debate Over Superdome as Hurricane Shelter

It's nice that he referred to "engineers" eventually looking at the roof to see if its safe.  Many times its "architects".

RE: Debate Over Superdome as Hurricane Shelter

Any ideas of the design requirements of the building?

RE: Debate Over Superdome as Hurricane Shelter

One of the major problems with Hurricanes is not so much the high wind but the storm surge.  With all the redundancy in typical structures they can survive wind loads above their orginal design loads.  I don't know of too many buildings which have been design to resist a 25' high wall of water.  Note I don't know how high of surge that Katrina produced but I seriously doubt my house could survive what ever the actual storm surge was.

RE: Debate Over Superdome as Hurricane Shelter

RARSWC, you bring up a valid point.  However, unless the home is directly next to a broken levee/seawall, the water rises fairly uniformly around the house, meaning there isn't a net force on the house.  A problem would be if your home was watertight, and the water on the outside rose while the inside was dry.  So basically, before you leave, I'd recommend opening the windows and doors.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources