Go BottomWorld s longest rafter
 | hardwood
Join Date: Dec 2002 Posts: 3583 iowa 
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2009-01-04 159048
A couple nights ago I watched something about colossal building type stuff on the Science Channel. The world's longest self supporting rafter is 475 ft. long, it's holding up the roof on a new convention center somewhere in South Korea. It was welded up from steel components on site and built in place. The bottom stretcher is in the concrete floor, and the ends of the rafter connect to it under the floor. And I thought 90 footers were long. Frank.
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 | candoarms
Join Date: Mar 2007 Posts: 1932 North Dakota 
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2009-01-04 159049
Frank,
I like watching those programs on the Science Channel.
In one such program they interviewed an engineer who discussed the new possibilities available to him, due to the powerful computers we have these days.
If not for the ability to test and prove these concepts in virtual reality (computer modeling) no investor would ever take the risk of putting up the money for the full-scale buildup.
He discussed all of the things he had to go through to prove to the investors that his design concepts would actually work. (trash in = trash out)
If not for computers.........
Joel ....
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 | earthwrks
Join Date: Dec 2003 Posts: 3853 Home Office in Flat Rock, Michigan
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2009-01-04 159059
Hopefully I got my numbers right, but when I was in the auto industry before computer design analysis the Feds required something like 25 completely built car crash tests. A typical car 10 years ago cost about $1 million per copy. Then computers came into full swing. They relaxed the requirement to just 5 cars.
Going back to Hardwoods post, my contention with modern engineering is: It doesn't matter how well it designed--it matters how well and how it's built. Case in point the Petronis(sp) Towers has one tower that had 5 floors that had faulty concrete that had to be removed and replaced before construction could continue. ....
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| hardwood
Join Date: Dec 2002 Posts: 3583 iowa
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2009-01-04 159068
Maybe someone else who saw the same program can help me a bit here. The original design was updated by another engeneering firm who removed several thousand puonds of steel reenforcment plates at the welded joints of the rafter. Their contention was that the plates didn't add enough strength to compensate for their own weight. Anybody wanna sit under this deal during a windstorm? ....
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 | AnnBrush
Join Date: Mar 2004 Posts: 463 Troy OH 
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2009-01-05 159083
"my contention with modern engineering is: It doesn't matter how well it designed--it matters how well and how it's built"
How well it is built will not overcome an inherently faulty design.
The perfect design relies completely on the construction being performed to the specs that were inherent to the design.
The two concepts go hand in hand. In the first instance I suppose you could use the carburetor as an example when employed in mass production vehicles. The absolute best built carburetor is easily surpassed in reliability by a simple (perhaps even averagely built) fuel injection system, today you don't see any carburetors in vehicle production, the design is just not durable enough. On the other hand optical lenses used in most scientific instruments are relatively easy to design but require extremely tight manufacturing tolerances to work properly and the care and expertise required in manufacture is the primary reason for their high cost. ....
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