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[SEAOC] Re: [SEAOC] Quartering wind

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John Pepper wrote:
> I have found that quatering wind is usually, (almost always) contorls the
> design for the elements that are resisting lateral loads in more than one
> directrion, such as shearwalls and frames that are not planar or foundations
> that connect such elements.
> It gets more intresting in non square building such as rectangular or those
> of irregular shape.
> I have designed a lot of high rises in a "Y" shape for maximizing ocean view
> with searwalls perpendicular to the "Y" legs in each wind, most often with
> diffrent stiffness and diffrent tributary area as well as lower floor
> discontinuies. In these cases, taking the normal x and y wind sepearatly is
> not even close, since wind some where around a quatering wind will control
> and torsion can be a major factor. Fpor this, we do an anlaysis every few
> degrees around a circle to determine the criticlal wind direction, which is
> not the same for each wall.
> The same principles apply for earthquake design.
> We have also found that wind tunnel testing of tall, irregualr shaped
> building will present a great savings over standard wind design using ASCE-7.
> John Pepper
> The Pepper Engineering Group, Inc.
> 20895 East Dixie Highway
> Aventura, FL 33180
> pepper(--nospam--at)
> ...
on each connection, for each floor. He discovered the weakest point was on the 30th floor. One of the problems 
was the approach of hurricane season on the east coast. It seems that the failure of one connection on the 30th 
floor might collapse the building with a sufficient wind, which in this case, left un-repaired, was a 17 year 
wind. One interesting feature of the article was that LeMessurier had designed a tuned mass damper, a 410 ton 
block of concrete on a film of oil, positioned by horizonal springs. This gave him the extra stability of a 55 
year wind storm. But mostly, it was installed for the comfort of the tenants. Leslie Robertson, an engineer 
hired by Citicorp,(an a consultant to the World Trade Center bombing for the FBI), insisted on round-the-clock 
monitoring of the damper until the necessary repairs could be made.

My own feeling on this most interesting article is what must be true of most crises: the well-meaning but 
flawed intentions of those who are trying to help, but shouldn't: CitiCorp, and Hyatt walkway plan change. I am 
sure each of you has similar, if less dramatic, incidents in your professional lives.