Saturday, May 25, 2013

Buildings, rising and falling

Like almost every other engineer on the planet, I woke up this morning fascinated by the bridge collapse in Washington State.

It's interesting that it seems like the incident was at least partly a human factors issue: Skagit River bridge collapse: Looking for a temporary fix to get traffic moving

The bridge has a maximum clearance of about 17 feet – higher than the truck’s load in this case – but the clearance curves down to 14 feet 5 inches along the sides, where the collision occurred. The tractor-trailer was hauling drilling equipment southbound.

The article makes much of the idea of putting a "temporary" bridge in place while a replacement is studied. Well, all structures are temporary, of course; the question is just how long do we expect they will last?

A friend, traveling to Boston, remembered that we spent our first years together there, and sent us a picture of the beautiful Zakim Bunker Hill Bridge. It is indeed beautiful, though we've never seen it; when we lived in Boston we used to drive over the Charlestown High Bridge, which we called the "Fitzgerald Bridge", and which surely must be in the running for Ugliest Bridge Ever.

Getting back to the Skagit River Bridge collapse, any engineering failure is important and needs to be studied. Even if the issues here are pretty simple, in other cases they are more complex. Another Christian Science Monitor article points out that studying the decay of structures is a constant process: Collapse of I-5 bridge in Washington State: no fatalities, many questions

The bridge was not classified as structurally deficient, but a Federal Highway Administration database listed it as being "functionally obsolete" – a category meaning that the design is outdated, such as having narrow shoulders and low clearance underneath.

The bridge is also classified as "fracture critical" by the National Bridge Inventory. That means the bridge is designed so that a failure in any one part of the bridge can collapse the entire span. There are some 18,000 fracture-critical bridges nationwide, of which 8,000 are also "structurally deficient," according to a 2012 review of Federal Highway Administration records by Bloomberg News.

Some failures are far more complex and need much more analysis. In the case of the horrible disaster in Bangladesh a month ago, the investigation will probably take many months or even years: Bangladesh factory collapse probe uncovers abuses

The man in charge of the investigation, Mainuddin Khandker, told BBC Bangla on Wednesday that "extremely poor" construction materials were used in the building and said the report identified five causes of the collapse.

"A portion of the building was also constructed on land which had been a body of water before and was filled with rubbish," he told the Associated Press news agency.

The 400-page report was submitted to the government on Wednesday.

Closer to home, our own bridge is still under construction, yet already we are studying its decay: Lawmakers seek probe as doubts are raised on Bay Bridge opening

"This issue does not affect the safety, strength or the lifespan of the Skyway," Caltrans said in a written statement Monday. "... Corrosion of steel tendons inside the bridge was extremely limited and was addressed."

But the construction record shows that Caltrans managers did not address frequent warnings from the agency's bridge inspectors until it was too late to head off substantial corrosion. Thomas Devine, a UC Berkeley engineering professor and a leading metallurgist, disagreed with Caltrans claims that its examination of the issue proved that the corrosion was insignificant.

Numerous scientific and methodological errors made the Caltrans findings "meaningless" and "essentially useless," Devine told The Bee.

Like other lawmakers, Cannella expressed frustration about the slow trickle of information coming out of Caltrans. "It's frustrating to me, as a lawmaker, to keep getting my information from The Sacramento Bee," Cannella said.

Sometimes a structure collapses, but the story has a happy ending: The remarkable twist to the tale of Oklahoma's tornado-hit hospital

Surveying the shredded shell of the medical centre, the two-floor structure torn apart as if a bomb had struck, it is hard to believe that there were no casualties inside.

Yet the accounts of those who rode it out inside make the story of survival all the more extraordinary. They describe people lifted off their feet and carried tumbling down hallways by screaming gusts; the thump of cars smashing into the building; shards of doorways, picture frames and tiles turned into projectiles and hurtling past them; the air choked with dust; and that all-encompassing noise -- a jet engine meeting a freight train.

That nobody suffered more than cuts and bruises is down to a combination of detailed planning, calm heads, quick thinking, selfless bravery and plain luck.

Meanwhile, new buildings continue to be built, even when it seems like there's no need: Sky High and Going Up Fast: Luxury Towers Take New York

Ultraluxury housing and construction is booming across Manhattan, which is now beginning to rival London in popularity with the world’s wealthy. The number of condominium buildings in the borough with apartments selling for more than $15 million has risen to 49, up from 33 in 2009, according to CityRealty.


As with many of these buildings, only about a quarter of the units will be occupied at any one time.

Software, of course, doesn't decay (although disk drives and flash memory do wear out, a phenomenon that we call "bit rot", though that's a gross over-simplification). But software does undergo constant change, which can introduce new problems even as we fix the old ones. So we software engineers love to study how other fields of engineering deal with failures.

And, of course, modern architecture and engineering design wouldn't be possible without software, since nearly everything is simulated and analyzed ahead of time on computers. Even software that was once considered to be just a toy is now used for serious architectural study: SimCity: An Interview with Stone Librande

Manaugh: Now that the game is out in the world, and because of the central, online hosting of all the games being played right now, I have to imagine that you are building up an incredible archive of all the decisions that different players have made and all the different kind of cities that people have built. I’m curious as to what you might be able to make or do with that kind of information. Are you mining it to see what kinds of mistakes people routinely make, or what sorts of urban forms are most popular? If so, is the audience for that information only in-house, for developing future versions of SimCity, or could you imagine sharing it with urban planners or real-life Mayors to offer an insight into popular urbanism?

Librande: It’s an interesting question. It’s hard to answer easily, though, because there are so many different ways players can play the game. The game was designed to cover as many different play patterns as we could think of, because our goal was to try to entertain as many of the different player demographics as we could.

Well, enough of all that. It's a beautiful day and time's a-wasting. We're off to go enjoy our weekend.

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