ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Conspiracies and Conspiracy Theories » 9/11 Conspiracy Theories
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Reply
Old 24th May 2015, 12:10 AM   #41
Jango
Graduate Poster
 
Jango's Avatar
 
Join Date: Dec 2014
Location: United States of America
Posts: 1,688
Oh God...
Jango is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 24th May 2015, 12:17 AM   #42
ozeco41
Philosopher
 
ozeco41's Avatar
 
Join Date: Mar 2009
Location: Moss Vale, NSW, Australia
Posts: 7,418
Originally Posted by Jango View Post
The pleasure was mine. Thank you.
Mutual.

And my thanks to all those members who left the thread free of noise for the duration of my explaining.

We got it all in one noise free page - must be some sort of a record.
ozeco41 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 24th May 2015, 12:18 AM   #43
ozeco41
Philosopher
 
ozeco41's Avatar
 
Join Date: Mar 2009
Location: Moss Vale, NSW, Australia
Posts: 7,418
Originally Posted by Jango View Post
Oh God...
..our help in ages past.
ozeco41 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 24th May 2015, 12:41 AM   #44
Jango
Graduate Poster
 
Jango's Avatar
 
Join Date: Dec 2014
Location: United States of America
Posts: 1,688
Originally Posted by ozeco41 View Post
Mutual.

And my thanks to all those members who left the thread free of noise for the duration of my explaining.

We got it all in one noise free page - must be some sort of a record.
Perhaps we can expand to Building #7?

From what I have read and seen, the formula for collapse was damage from debris and fires. IIRC, column 79 failed and global collapse began. Does your explanation for the Twin Towers apply to Building #7 or are there significant differences?
Jango is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 24th May 2015, 12:46 AM   #45
Jango
Graduate Poster
 
Jango's Avatar
 
Join Date: Dec 2014
Location: United States of America
Posts: 1,688
Originally Posted by ozeco41 View Post
..our help in ages past.
If I were from the east coast, like New Jersey or New York, the way I meant it would have been spelled out 'Oh Gawd'. But I am not from the east coast. I am from the Midwest.
Jango is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 24th May 2015, 01:03 AM   #46
ozeco41
Philosopher
 
ozeco41's Avatar
 
Join Date: Mar 2009
Location: Moss Vale, NSW, Australia
Posts: 7,418
Originally Posted by Jango View Post
Perhaps we can expand to Building #7?
I cannot explain it with the assured rigour I can for the Twins.

Sure I can critique the arguments both ways. And there is also a lot of the debunker argument which fell for the traps inherent in the truther claims.

Originally Posted by Jango View Post
From what I have read and seen, the formula for collapse was damage from debris and fires...
It was a steel framed building subject to unfought fires. Odds on it would collapse. It did. Steel framed buildings subject to fire rely on conduct of active fire fighting methods. The designs are premised around 1, 2, whatever hours fire resistance - to give time for occupants to escape and ACTIVE fire fighting started. The occupants escaped. The decision was taken to not start active fire fighting. That left the building to take its chances. It lost. No big deal in logic. The sort of choice firies make every day in bush fire situations - which houses to save and which ones to let go - except a few more decimals on the size and cost.
Originally Posted by Jango View Post
IIRC, column 79 failed and global collapse began.
Broadly that is the NIST explanation - I have a minor pedantic disagreement which changes nothing of consequence.
Originally Posted by Jango View Post
Does your explanation for the Twin Towers apply to Building #7 or are there significant differences?
No. Totally different.
ozeco41 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 24th May 2015, 08:12 AM   #47
Oystein
Penultimate Amazing
 
Oystein's Avatar
 
Join Date: Dec 2009
Posts: 16,234
Originally Posted by ozeco41 View Post
...
My Objective - to explain the cascade failure process of WTC1 and WTC2 "initiation stage" up to the point where the Top Block was falling AND ROOSD/Three Mechanisms progression was under way.

I will not be addressing CD claims which means that I must allow for CD options in the mix of contributors to collapse. The understanding of cascade failure is not affected whether or not there was CD. (Think about that before (any of) you ask )
...
Detailed explanation finished by Post #37, therefore thread OP plus following posts now ripe for an # oysteinbookmark.

Thanks ozeco41 for the effort, and thanks all who took their comments to the Peanut Gallery and kept the first page clean
Oystein is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 25th May 2015, 09:44 AM   #48
Newtons Bit
Penultimate Amazing
 
Newtons Bit's Avatar
 
Join Date: Apr 2007
Posts: 10,016
Originally Posted by ozeco41 View Post
Weakening Factor #2 - Changing Effective Length
Most people will probably have good gut feel for this one - a long thin rod, pole or bar will bend more easily than a short stocky one:

The issue for WTC collapses is that some columns - e.g. the "inward bowing perimeters - had their effective length increased by failure/removal of bracing:
http://conleys.com.au/webpics/columnEL200.jpg

The effective length "as designed" is on the length. And the "effective length" of the column is 1 - each storey. Cut out the bracing as shown on the right and the effective length becomes 3.

And the strength of the column is inversely proportional to the square of the EL. So increasing length by 2 reduces strength to 1/4 and increasing by 3 reduces strength to 1/9th.
No. The strength of the column is not "inversely proportional to the square of EL". The columns near the plane impact have a small effect length and as a result are inelastic. You're using elastic behavior. This is the actual formula for nominal compressive capacity from the AISC Specification:



The perimeter columns have a r~=5.5in, which makes the slenderness ratios:
KL / r (L= 12'4") = 26.9
KL / r (L= 37'0") = 80.7

Which is less than the limiting slenderness of 4.71 SQRT(E/Fy). Equation E3-2 controls and as a result, the difference in nominal compressive capacity is in the ballpark of 20%.
__________________
"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
Newtons Bit is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 25th May 2015, 10:05 AM   #49
ozeco41
Philosopher
 
ozeco41's Avatar
 
Join Date: Mar 2009
Location: Moss Vale, NSW, Australia
Posts: 7,418
Originally Posted by Newtons Bit View Post
No. The strength of the column is not "inversely proportional to the square of EL". The columns near the plane impact have a small effect length and as a result are inelastic. You're using elastic behavior.....
Yes---of course---BUT...
Remember that my explanation was for Jango - AFAICS a non-engineer and I needed to get some broad concepts across.

I only listed a couple of the "building block mechanisms" and didnít explain the common error(s) made with perimeter inward bowing. If Jango asks for more explanation I will provide it - No point me confusing the lay person with lots of engineering details which don't change the broad message.

My objective was (and still is) explaining to the relative novice - not making a doctoral dissertation which can withstand detailed professional scrutiny by those who shouldn't need my explanation.
ozeco41 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 25th May 2015, 10:25 AM   #50
Newtons Bit
Penultimate Amazing
 
Newtons Bit's Avatar
 
Join Date: Apr 2007
Posts: 10,016
I don't believe you. Either you're intentionally misstating your case to make it sound better or you didn't remember that elastic buckling was a thing. Personally I think the former is much more likely than the latter.

This statement of yours:
Quote:
And the strength of the column is inversely proportional to the square of the EL. So increasing length by 2 reduces strength to 1/4 and increasing by 3 reduces strength to 1/9th.
is 100% false in the context of your example. If you just wanted to explain the basics then you could have explained that the compressive capacity is some function of the length and that increasing the length reduces the capacity. That'd be fine. That would actually achieve the objective you're claiming you set out for. But by using the providing the terms that you did, terms for elastic buckling that do not apply in your example, you're misleading him. And, in my opinion, it seems to be intentional.
__________________
"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
Newtons Bit is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Conspiracies and Conspiracy Theories » 9/11 Conspiracy Theories

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 11:56 AM.
Powered by vBulletin. Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.