After Corbu » disasters

Counter-revolutionary design

Quixote — Fri, 11 Sep 2009 02:55:00 +0000

What If New York City 3 by Studio Lindfors

This is pretty awesome, but it would make it much harder to use the political & economic disruption of a precipitous rise in sea levels to stage a world revolution.

[vis BLDGBLOG, so so long ago]

Engineering Confessions

Quixote — Tue, 23 Oct 2007 10:23:30 +0000

Spending most of my time around engineers, I forget that certain things aren’t common knowledge. For example, I recently had to explain that buildings are not designed to survive earthquakes. Rather, they are designed to not kill people during earthquakes, then afterwards we’ll knock em down and rebuild.

Engineers make this sound noble: “We’re in the business of providing life safety.” They even get a bit of a chip on their shoulder about it: “How many thousands of lives do we save every year? Yet they pay us less than doctors. Totally Unfair.”

The reality is that it wouldn’t be economical to design structures to stay elastic (read: not break) during seismic events; the steel and concrete involved would be daunting. Instead, buildings are designed for 15-25% of the expected major earthquake force, and above that they bend, crack, yield, etc. All that deformation dissipates energy…and tends to destroy the structure. Occupants are (usually) fine, but fixing the damaged building is more expensive than it’s worth.

Thus, all our time is spent designing things that are meant to fall down, either through tectonics or dynamite. Nothing we do is permanent; the skyscraper cannot hold; every tower inherently is of Babel.

Let Malibu Burn

Quixote — Sun, 21 Oct 2007 20:21:20 +0000

It’s on fire again today, and while I hope everyone got out safely, it seems like a good time to remember: The Case for Letting Malibu Burn.

Alternative 9/11s

Quixote — Thu, 13 Sep 2007 10:00:42 +0000

An Absolution Revolution tells of Mel Gibson’s defeat of the English at the Battle of Stirling Bridge in 1297. This is similar to my approach to dealing with 9/11, which is to talk about the lesser known atrocities of the date, and try to counteract America’s 9/11 hyperbole via context. Except Jason went with a victory rather than a tragedy, which is subtle, but still flamethrower analogizing. Of course, it’s entirely possible he just wants to talk about a historically significant events of the date, but I’m skeptical.

It’s a beautiful day for a coup

Quixote — Tue, 11 Sep 2007 11:10:20 +0000

I looked down at the calendar to check the date and, lo and behold, it’s September 11th, the 34th anniversary of the US-backed coup that toppled President Salvador Allende and brought Pinochet to power in Chile. That act of terrorism resulted in thousands of deaths and made political prisoners of thousands more.

Of course, 6 years ago a more famous act of terrorism had worse results: tens of thousands dead in New York, Afghanistan, and Iraq and hundreds of political prisoners at Guantanamo. The toll of the attack didn’t have to be this severe, but we let it get out of control — we let a horrible tragedy become a coup.

6 years ago we had a moderate, incompetent president who couldn’t move conservative legislation and compromised with liberal institutions like Ted Kennedy to pass education ‘reform.’ Then: the September 11th attacks, and everything changed. Ever since, our country has been ruled by an extremist, incompetent president who steamrolls bills past weak, assenting legislators.

Maybe this will change now that Democrats are starting to put the “fuck you” back in “opposition party” with their wonderful investigations. Maybe they’re ready to end the coup. But first they have to realize that this man is just as much a hack as this man turned out to be, and call him on it. Military uniforms are not inoculations against becoming Bush cronies; this war remains past its sell-by date, no matter who is trotted out to ask for another six months.

Bring the troops home now.

WTC Steel

Quixote — Mon, 27 Aug 2007 17:02:05 +0000

Warped, yielded steel from this issue of Engineering News, picture taken at the WTC. It somewhat illustrates what I was talking about below — the wide flange is bent and it look like some type of edge connection broke off, but the beam as a whole is still in one piece. Mostly, I just think its kind of beautiful as an industrial artifact.

Sunday Conspiracy Blogging

Quixote — Mon, 27 Aug 2007 05:02:04 +0000

By linking to this Robert Fisk article about questioning the 9/11 explanations, LitBrit produced quite a bit of commenter angst over at the House that Klein Built. As an engineer, I find the discussions of 9/11 steel collapse fascinating, and at the risk of revealing ignorance within my own field I want to wade in a bit here.

Fisk’s version of the “Steel shouldn’t have failed” complaint:

If it is true, for example, that kerosene burns at 820C under optimum conditions, how come the steel beams of the twin towers – whose melting point is supposed to be about 1,480C – would snap through at the same time?

Apparently he’s mixing in issues about how fast the various buildings collapsed, but I’m setting that aside to focus on the tempature-induced steel collapse. The accepted explanation for this is laid out by Popular Mechanics:

“Steel loses about 50 percent of its strength at 1100°F,” notes senior engineer Farid Alfawak-hiri of the American Institute of Steel Construction. “And at 1800° it is probably at less than 10 percent.” NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.

And PM quotes other experts who explain that the kerosene fire would have spread to the office finishes, which burned as hot as 1800°F. All this makes intuitive sense, and I trust AISC — they wrote my steel manual. What I don’t understand is how the steel “snapped.” Also from the PM article:

“I have never seen melted steel in a building fire,” says retired New York deputy fire chief Vincent Dunn, author of The Collapse Of Burning Buildings: A Guide To Fireground Safety. “But I’ve seen a lot of twisted, warped, bent and sagging steel. What happens is that the steel tries to expand at both ends, but when it can no longer expand, it sags and the surrounding concrete cracks.”

This is exactly as I’ve been taught. A Temperature change loads a steel member, reducing it’s capacity until it fails. It’s important to understand that engineers use “fail” in a very particular way, and it is distinct from “fracture.” Here’s the stress-strain curve for steel at different temperatures, taken from this article:

Stress just means force per area and strain is basically elongation. So, as you load a member more, it deforms more. Note that, at every temperature level there is a point where increasing the load is not necessary to cause the steel to continue elongating. A member has “failed” when it has passed the initial near-linear portion of the stress-strain curve, and begun deflecting at great rates. The steel warps and bends, and is structurally useless. Eventually it will fracture, but it’s rare; long before a beam actually cracks through, its connections to adjacent members will break.

Connections are always the weak point of a structure. They experience higher forces since loads flow across them in three dimensions. Welding can weaken steel, lowing its capacity. Lines of bolts reduce the cross-sectional area of a member, creating a failure plane.

So: it would be extremely surprising if steel members snapped through as a result of temperature increase and excessive load transferred from neighboring columns. I’m betting people throwing “snap” around are referring to connections failing, causing steel elements to break apart from each other. Which, since connections are weak, occur at lower loadings than you might expect by just calculating the capacity of a system.

Of course, this doesn’t address the fact that fireproofing should have caused the collapse to take longer and I don’t know that a plane crash could have scraped off enough of it to make a huge difference. But I’m hardly knowledgeable about plane crashes or fireproofing, so on this I trust the experts.

However, I do have an alternative explanation for how the fireproofing was overwhelmed and the steel collapsed:

(God this image is horrifying. I mean, of course women do construction in a low-cut micro-dress with sky-high heals, but that tool belt is just not going to cut it.)

Riveting

Quixote — Thu, 09 Aug 2007 10:25:50 +0000

Money quote from today’s New York Times article about the Minnesota bridge collapse:

“Bolts are better,” Mr. Peterson said, “but we wouldn’t consider anything wrong with rivets.”

Yeah, except for the rivets not being strong enough, there wasn’t anything wrong with them at all…

Strange thing though: the NTSB let everyone know that something may have been wrong with the bridge gusset plate design (a conclusion they arrived at in record time), but didn’t say what the problem may actually be. This makes the announcement useless as a safety precaution, as the problem certainly can’t be fixed on other bridges if it’s unclear what’s wrong.

However, the announcement does work well as a political precaution, helping to deflect criticism of Republican infrastructure cuts. Funny how that worked out…

“God Hates Minnesota”

Quixote — Thu, 09 Aug 2007 04:28:14 +0000

Fred Phelps is an asshole, and while there is no law against being an asshole, there is one against protesting at funerals in Minnesota, thank God. I have little doubt that this kind of over-the-top nuttery pushes the country to be more accepting of gays and, in this case, Minnesotans, but that is cold comfort to victims of Phelps’s hate.

Boom

Quixote — Sat, 04 Aug 2007 21:38:50 +0000

The Alvarez Hypothesis claims that sixty million years ago an asteroid 80 miles across hit the Yucatec peninsula in Central America. It threw up fifty trillion tons of dust and ashes into the air (note: speculative statistic), blotting out the sun and causing a worldwide mass extinction.

People, those of us who think about the impact at all, tend to regard it as a good thing since it got rid of those pesky dinosaurs and allowed our rodent-like ancestors to evolve into people—a win-win. I think that spinning an asteroid impact as favorable is indicative of either clueless optimism or disgusting vanity—your choice.

One of the pieces of evidence for the hypothesis is the distribution of cenotes—huge, circular sinkholes filled with fresh water—which form a circle around the believed impact area. The cenotes were sacred sites to the Mayan peoples who have lived on the peninsula for thousands of years. Some were sources of water for towns, while others witnessed human sacrifices

Today they also serve as spring break swimming pools for the ‘Girls Gone Wild’ set of rich Americans. I believe this refutes the claim that society is engaged in inexorable progress towards a better world. Clearly real progress is going to require more effort.