Friday, August 22, 2008

Report on the collapse of World Trade Center #7

It's got something I hadn't thought of for some reason: the thermal expansion of the steel beams.

Should have occurred to me before. People generally don't realize just how much a big piece of steel increases in length as heat rises. First time this whacked me was the first time I hardened & tempered a broadsword. I've got a long, narrow forge just for hardening & tempering, and the blade fit in with room to spare. Until it got up toward critical temperature; it stretched enough that I had to cut more than an inch off the tang(oversize, so not a big problem) for it to fit. Now think of a beam many feet long and weighing many, many pounds, coming up to high heat... I don't know the formula to figure it, but the increase in length would put enormous strain on that beam and anything it was connected to. Enough, unsurprisingly, to make connections fail. And that triggered a cascade of failures.

I'm sure the truthers have another explanation, probably involving a SEAL team with cutting torches on a suicide mission or something.

6 comments:

DJMooreTX said...

This brings to mind one of the few times Dark Knight failed to keep my disbelief suspended, even given that it's a live action comic book: there's a scene where a building complex gets blown up. The trick is, there's several explosions in sequence, and all the explosives were supposed to have been planted surreptitiously -- and I think, in the context of the movie, in less than a day.

The truuffers fallout made me aware that pulling off that kind of destruction takes weeks of very obvious preparation.

jetfxr69 said...

Equation for thermal expansion:

Lf-Li=a*Li*(Tf-Ti), where L is Length, T is Temperature (in C or K), the subscripts indicate 'initial' and 'final' as appropriate, and a is a constant for a given material.

See http://www.engineeringtoolbox.com/thermal-expansion-pipes-d_283.html

Sigivald said...

That reminds me of the JOM's explanation (which AFAIK is the same as the official one) for the collapse of the WTC towers themselves.

Very long beams with uneven heating, and thus warping, which just led to all sorts of nasty concentrated stresses and unpleasantness.

Then the big badda-boom.

Fire said...

HHHHHMMMMMMM,

Heat + Expansion = the beginning of a good story.

Heat + Warping = lots of laughter.

Firehand said...

Jetfxr, I've still got the headache from trying to work that.

Yes, Fire, heat and expansion can be kind of fun, but keep your warping to yourself.

Fire said...

Rest assured...I don't want to see it warp at all. That would just freak my ass out! Now the expansion....I marvel at how that works. (tongue in...well, cheek)