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Re: Compression flange bracing

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>Anybody have any thoughts on the validity of counting friction for lateral
>support? I can't imagine AWWA recommending this design approach without some
>sort of basis.
There must be something more to this. First, friction is limited to a 
load equal to the product of the friction coefficient and the normal 
force. Just figuring out the friction force isn't easy, given the 
difference in stiffness between plate and steel, so you have some 
problems determining if you have enough friction. Second just laying the 
tank roof over the supports seems uneconomic, since attaching the 
stiffeners to the roof makes for a much stiffer and stringer structure 
than the two acting separately, at the cost of some stitch welding. Looks 
like you might also get into problems with uplift, since the roof 
wouldn't be stiffened. I expect the AWWA limited this provision in some 

My practice has always been to ignore friction unless it works against 
you--never assume it'll help. (Paraphrasing Kathryn Hepburn in 'The 
African Queen:' 'Friction, Mistah Allnut, is what engineahs were put upon 
this earth to ovahcome!')

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)