Tornadoes and Concrete

[Simon Timm]

In the fujita and advanced fujita scale, (E) F5's are defined as severely damaging reinforced concrete. I personally have never observed this occurring(though I live in Wisconsin and I have only observed weak tornadoes), I have only seen pictures and read a few reports of reinforced concrete being severely damaged.

Here is one case in Wichita Falls tornado, where steel Reinforced McNeil high school was destroyed

http://www.srh.noaa.gov/oun/wxevents/19790410/burgess.php

In what tornado cases have you observed the destruction of a steel-reinforced building?

 

[Jason Foster]

Not all walls are created equal.

"McNiel Junior High, a new concrete/steel-reinforced building was not built well enough to provide safe shelter from the tornado. The Southwest National Bank Building was totally destroyed except for its concrete vault, a proxy for an above-ground shelter." -- Quote taken from link.

I think the idea here was that the structure of that particular building was not enough. In general, concrete reinforced with typical rebar in a wall of about 8" thick or more, and having a surface area that is not expansive enough will withstand high winds included and F4 or F5. It is true, as the report indicated that not all wall, even concrete reinforced one, will withstand 200+ mph winds. It is important that any structure that is designed to survive such conditions have the least about of surface area perpendicular to the strongest winds. smaller structures or thicker walls may be required.

I'll look into deeper, maybe add more later. Perhaps you can pose this question to Tim Marshall, a structural engineer, and known tornado damage analyst, who can comment further. I'm an architect and have limited detailed knowledge on the subject.

 

[STurner]

I believe the high school in Greensburg was made out of three layer concrete load bearing walls and mortar and about two-thirds of that building was completely destroyed. I also believe the Parkersburg tornado completely destroyed a steel-reinforced structure.

 

[Greg Higgins]

Back on 10 Apr 1979, I was a brand new EMT (hired as we watched the tornado come through town) and one of the "high" moments of the evening is when we got to the Southwest Bank and discovered survivors where we were sure we would find victims. I know there are pictures that exist of the vault and as I recall, there was a hadite block wall around 2 sides of the vault, which itself was steel.

Greg Higgins

 

[Dennis Sherrod]

I am not sure if this may be helpful to look into or not. March 1, 2007, a low end EF-4 struck Enterprise, AL. partially destroying a concrete / brick high school killing 9 students. I have not looked into the exact construction, but do know that some of the high school was destroyed. There may be some useful info from that.

 

[scott r currens]

I've never heard of steel-reinforced concrete losing its structural integrity as a result of a tornado. I'd bet that any steel-reinforced concrete buildings that were destroyed in a tornado were not destroyed as a result of the steel-reinforced concrete losing integrity. I seems more likely that windows, roof's, and non-reinforced walls are what failed with in those structures. If I am wrong I would love to see images of that damage.

 

[Simon Timm]

I did find this image of what looks like a warehouse in Memphis Tennessee that was destroyed by the tornado this year

http://www.flickr.com/photos/mckeephotographer/2705536226/sizes/l/

 

[STurner]

I believe Simon that the Oakfield, Wisconsin F5 tornado on July 18, 1996did some very intense damage although it was pretty narrow. I think it cleaned four homes that were very well-built off their foundations and in addition I believe it bent or snapped rebar from the base of one of the homes foundation.

 

[Dann Cianca]

It would be interesting to see if similar buildings would fare the same in different debris situations, i.e. just vegetation or a lot full of cars. There's an obvious assumption ...

 

[mike scantlin]

I believe Simon that the Oakfield, Wisconsin F5 tornado on July 18, 1996did some very intense damage although it was pretty narrow. I think it cleaned four homes that were very well-built off their foundations and in addition I believe it bent or snapped rebar from the base of one of the homes foundation.

I couldn't imagine rebar being snapped by winds alone.

I'm sure any damage done to steel re-enforced structures would be done by large debris, not the winds.

Kind of off-topic, but how does this play into the Ratings?

* Let's say there's a Large tornado out in a field. In this field, there is a car and a steel re-enforced wall. If the tornado, not capable of destroying the wall alone, throws the car into the wall knocking it to the ground, how is this rated?

I know that it's still the tornado causing the damage, I'm just wondering what thought processes go into rating damage like this.

 

[Jeff Duda]

I couldn't imagine rebar being snapped by winds alone.

I'm sure any damage done to steel re-enforced structures would be done by large debris, not the winds.

Kind of off-topic, but how does this play into the Ratings?

* Let's say there's a Large tornado out in a field. In this field, there is a car and a steel re-enforced wall. If the tornado, not capable of destroying the wall alone, throws the car into the wall knocking it to the ground, how is this rated?

I know that it's still the tornado causing the damage, I'm just wondering what thought processes go into rating damage like this.

Sounds like the beginning of a philosophy discussion titled, "If a tornado breaks a tree in the woods and no one is around, did it make a sound?"

 

[Sean McMullen]

I remember one of the first chase videos I got was "Chasers of Tornado Alley". In the video, Greg Stumpf comes across a concrete road that had been peeled back by a tornado. I don't recall if it was steel reinforced like a highway or an interstate though, maybe if Greg were reading this he might be able to explain.

 

[Greg Stumpf]

I remember one of the first chase videos I got was "Chasers of Tornado Alley". In the video, Greg Stumpf comes across a concrete road that had been peeled back by a tornado. I don't recall if it was steel reinforced like a highway or an interstate though, maybe if Greg were reading this he might be able to explain.

IIRC, not having watched the program in many years, I was referring the asphalt peel on Hwy 86 just east of Dimmitt, TX on 2 June 1995. I have a portion of the peeled asphalt in my office, and it was about 3" thick. The specimen is next to another asphalt peel I collected from 3 May 1999 SW of Bridge Creek, OK. The Bridge Creek asphalt was about 1.5" thick.

Neither were steel reinforced concrete roads. I have never witnessed a concrete road "peel", and I would suspect it would be extraordinary given the theoretical upper limit for tornado wind speeds.

Other asphalt peels I have witnessed were in Jarrell, TX (5/27/97), Kellerville, TX (6/8/95). Both were about 1.5" thick as well. I did not collect specimens of those two events.

 

[Stephen Levine]

Monolithic Domes are rated for F-5 tornado damage and are proven to be safe tornado and hurricane proof homes.
For more information, go to their web site www.monolithic.com.

I once saw a picture on their site of a dome home that took a direct hit by a tornado. A telephone pole was laying against the roof. There was zero damage to the structure.

Someday I would like to build one.

 

[STurner]

Yeah I am no expert but would think it would take more than windspeed alone to snap rebar. I think it would have to be blasted with debris and winds to do that type of damage. I still think that even that still would take a violent tornado to do that type of damage to rebar on the foundation of a well-built home.