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tornadoes: seaoi presentation

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Title: tornadoes: seaoi presentation

i attended an seaoi presentation (given by gene corley? is gene here?), on the tornadoes in kansas/nebraska a while ago. some interesting conclusions. if i recall correctly, they were the most powerful tornadoes ever recorded to date. They had the highest wind speed measurements taken, at least to the point until the monitors became non-functioning.

1. most of the telecom structures (towers, antenna arrays) were lightly damaged.
2. water towers were also lightly damaged.
these structures are obviously designed for higher survival wind speeds, and they performed as designed.

3. most of the houses that were NOT destroyed/blown away/separated from their foundations had appropriate anchor bolts with nuts AND washers. This is not to mean that they were not damaged, but that they were still on their foundations.

The inference can be made that those that were destroyed/blown away/separated did not have adequate anchor bolts and/or missing nuts and washers.

I have inspected MANY wood framed structures (mostly single family and lt. comm.) that contractors have built with the code specified "anchor bolts" but without nuts or washers, they seem to think that a house weighs enough to resist wind uplift...local code officials seem to miss these too. We too often assume that anchor bolts imply nuts and washers (granted, my experience is limited to the midwest, and it's pretty much boca here).

4.  the estimated wind pressures as i recall were about 100 psf in the tornado damage zone. (i can't remember how they derived these numbers).

5. basement tornado shelters can be built economically. pretty much a concrete/reinforced cmu bunker with a door that opens IN adds about $1000 to construction costs.

dp