----- Original Message ----- From: "Dan Minette" <[EMAIL PROTECTED]> To: "'Killer Bs Discussion'" <[email protected]> Sent: Monday, July 03, 2006 2:35 PM Subject: RE: Physics Prof Finds Thermate in WTC Physical Samples
> > >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On >> Behalf Of Gibson Jonathan >> Sent: Monday, July 03, 2006 12:07 PM >> To: Killer Bs Discussion >> Subject: Re: Physics Prof Finds Thermate in WTC Physical Samples >> >> >> How the debris we see falling {I would point out it's much more >> akin to >> exploding outward and then down} exterior to the building can match >> an >> interior descent flies in the face of logic. I simply cannot >> accept >> that the core structure, a thick _lattice_ of crossing steel, would >> offer the same resistance as the air outside slowing the debris. > > That's not quite what happened. [Snip-a-doodle] Doing a bit of searching I have found a few failure modes noted by NIST that have not been discussed here. http://wtc.nist.gov/pubs/NCSTAR1-3ExecutiveSummary.pdf One glaring example that we missed was "bolt hole tearing". This is where force causes the bolt hole to deform til it slips around the supporting bolt. I would suspect that this takes a bit more time than bolt shearing, but I also feel it doesn't change the math enough to matter. As for the bolts themselves, they turn out to have been stronger than original building specs called for, but again this makes small difference. It turns out that there were a very significant amount of welded joins that failed in the collapse. If you know much about welding then you are aware that the weld itself is much stronger than the base metal in the heat affected zone and it turns out that many of the welds that failed were torn in exactly that way. The base metal that gets heated by the welding rod becomes weakened by the heat. In many manufacturing processes the part being welded is then heat treated to give the heat affected zone properties similar to the base metal. this of course is not practical on a construction site. So you end up with 2 qualities of welding in a building, the high quality welding where heat treating was performed in a factory ( as a part of the normal manufacturing process for say I-beams) and welding that was performed on site as apart of the construction process. Another concept we have not discussed is load re-distribution. When some of the supports were knocked out by the impact of the planes, the load of the buildings mass was supported by the remaining structural members. NIST claims that evidence is seen that heat and load re-distribution caused not just buckling (as expected) but also necking. Necking is the thinning of a member under stress exceeding its yield strength. When impact caused the load to re-distribute, heat weakened structural members til some buckled and others necked and eventually you had a structural failure. WTC was a fairly lightweight structure for its size but the buildings were still very massive. The more one looks at the failure modes of the WTC collapse, the more complex it gets. xponent Standards Maru rob _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
