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Old 19th June 2007, 11:35 AM   #265
Newtons Bit
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Originally Posted by Doug Plumb View Post
By 6 and 20 times the gravitational load, I mean 6 and 20 times the gravitational load. If there is a live load then it is typically much less than 6 and 20 times respectively the gravitational or "dead" load. Live load occurs from wind, earth quakes, etc - its vibrations. Wind wasn't heavy that day.

I get those figures from Jim Hoffman and from an engineering report referenced in David Ray Griffins book from ASCE.

I don't believe that any of you have read the full NIST report.
I don't think you've read ASCE7 which defines what those loads are.
Originally Posted by ASCE7-02 Section 4.1
Live loads are those loads produced by the use and occupancy of the building or other structure and do not include construction or environmental loads such as wind load, snow load, rain load, earthquake load, flood load, or dead load
You may think you're hot stuff in EE, you may even be the best EE in the world. But you still don't even know basic definitions of loading for structural. The perimeter columns are moment frames, their design is not controlled by vertical loads, but rather bending moments.

If YOU had read the NIST report, you would have learned that the core columns had a demand to capacity ratio (DCR) of less than 1.0 in some areas in modern allowable stress design (ASD) and a dead + live load combination. The current "Factor of Safety" for ASD with a DCR of 1.0 is 1.65. The deadload near impact was about 50 psf and the design live load was 100 psf. Due to the area, the live load was reduced to 50psf for column design, hence, live load is approximately equal to dead load. You can do the arithmetic and figure out that the structure could actually handle THREE times the dead load.

Stop making things up.
"Structural Engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze so as to understand forces we cannot really assess in such a way that the community at large has no reason to suspect the extent of our own ignorance." James E Amrhein

Last edited by Newtons Bit; 19th June 2007 at 11:45 AM. Reason: spelling ]=
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