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RE: We're Not Getting Older, We're Getting DUMBER

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I had a call from Mike to bring me up to speed on this.
It appears I misunderstood him or he used terminology
I wasn't familiar with, but all this time I believed it
was a transmission tower in the states.  Maybe there
were too many beers in the way - just joking.  But he
said yesterday that they did over-estimate the dead load
but also seriously under-estimated the wind loads and
the effect of turbulence around closely spaced towers.
So the Brits as a result promptly jacked "up their wind
loads by 150%". Again this was in a casual phone
conversation, so don't quote me. I don't want to be
guilty again of mis-quoting.  Sorry about all that.
I will go back now to doing calcs, some in ASD and some
in LSD.
Gary


On 26 Jan 2006 at 11:04, Robert E Shaw Jr wrote:

> I emailed Mike. He's checking to se how his name was involved, but he
> provided this information (a copy of an article) about what the reference
> was to. It looks like it was the load side, not the resistance side, that
> had the effect of causing the collapse.
> 
> Bob Shaw
> SSTC
> 
> Ferrybridge Cooling Towers Collapse
> 
> On the 1st November 1965, during high winds, three out of a group of eight
> cooling towers at Ferrybridge 'C' Power Station collapsed, with the
> remaining towers sustaining severe structural damage. The towers, each 375
> feet high, had been constructed closer together than was usual and had
> greater shell diameters and shell surface area then any previous towers. The
> design and construction contract for the towers had been given to Film
> Cooling Towers (concrete) Ltd. in 1962.
> 
> High winds were considered to be the trigger for the collapse, but an
> inquiry found the exact cause to be an amalgamation of several other factors
> in their design: 
> 
> British Standard wind speeds had not been used in the design resulting in
> the design wind pressures at the top of the tower being 19% lower than it
> should have been.
> 
> Basic wind speed was interpreted and used as the average over a one minute
> period,
> whereas, in reality, the structures are susceptible to much shorter gusts.
> 
> The wind loading had been based on experiments using a single isolated
> tower. The
> grouping of the towers created turbulence on the leeward ones - the ones
> that did actually collapse.
> 
> Safety margins had not really covered any uncertainties in the wind
> loadings.
> There had been, it was decided, a serious underestimation of the wind
> loading in the initial design.
> 
> Fortunately, no one was killed or injured in the accident.
> 
> 
> 
> 
> -----Original Message-----
> From: Gary Hodgson & Associates [mailto:ghodgson(--nospam--at)bellnet.ca] 
> Sent: Thursday, January 26, 2006 8:16 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: We're Not Getting Older, We're Getting DUMBER 
> 
> Chris,
> I recently quoted a transmission tower that failed when
> designed by ASD where they say it probably would not
> have failed if designed by LFRD.  My source (they) was
> Mike Gilmor at the Canadian Institute of Steel
> Construction-phone 416-491-4552.
> Gary
> 
> 
> 
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