[BC] Bad tower design

[PeterH]

On Oct 23, 2009, at 11:14 AM, RichardBJohnson at comcast.net wrote:

> Don't laugh! Early Rohn towers had rivets holding cross-braces. Once
> wind pressure gets above a certain amount, these rivets (which
> operate in shear) break and the whole tower comes unglued with the
> "sprong" of a broken clock-spring!

KFI's replacement tower -- 2008, first (failed during erection) and  
2008, second (erected successfully) -- has bolted joints for the  
cross-bracing. Two bolts in each brace where it meets a welded flange  
on the vertical member and two bolts where the cross-braces  
themselves cross.

Reading from a description of the erection procedures, the bolts  
which connect the vertical members are intended to have the nut on  
the top, and the bolt on the bottom, so should a bolt fail it will  
drop free of the flange and thereby allow for inspection from the  
ground.