seismic design

(Thanks to my new Moleskine, I was able to scribble a note to myself about this interview at a stoplight on the way home from school Friday)

This a portion of “Designing a Bridge for Earthquake Country”, an NPR Science Friday Interview with Dr. Marwan Nader, lead design engineer of the new span of California’s Bay Bridge.


In the interview, Nader describes that the Bay bridge is built on a foundation of soil, not rock, which amplifies seismic motion – a problem in California. The new Bay Bridge has not just been designed, but seismically designed as a self-anchored suspension bridge, which differs from the ground anchorage of a typical suspension bridge. Nader explains that instead the cable is anchored to the deck of the bridge, so the loads the cable bears go to the deck. Another difference is that the cables are three-dimensional, instead of the vertical cables on typical suspension bridges, which satisfies the need for design equilibrium.

(images from Wikipedia: self-anchored suspension bridge) The above image is of a traditional suspension bridge. Note that the anchors are in ground.

Versus this self-anchored suspension design in which the cables are anchored directly to the deck.


FLATOW: …also, I noticed from the design is that the bridge is made in difference pieces so that parts can move independently of one another, correct?

NADER: That’s correct.

FLATOW: Doing so, so that when the Earth shakes, it all just sort of floats.

NADER: Right. The seismic design, the way we understand it, is basically there are effectively two ways to resist the motions. One is to really design a bunker, which effectively is very strong to take the forces…

FLATOW: So you’re fighting nature.

NADER: Yes. And what you’re doing there, is you’re really taking on whatever the motions are. And the earthquake has a very interesting characteristic to it. It’s like a musical, effectively. It’s got areas where there’s a lot of energy, which is at the frequencies that are very, very low or very, you know, very, very high. Excuse me. And then that’s where you’re getting the most energy. And then as you get the structure to be more flexible, that’s where the energy gets smaller. So if you are a little bit careful about it, you can actually design your structure to be in the areas where the earthquake is less damaging. And by making that structure tuned to what Mother Nature’s going to apply, you actually avoid that ground of the force.

The other aspect of it is designing components, if you will, that are made to take on the damage. Like when we drive cars. If you think about it, cars – we know we drive cars. We know that we’d like not to get into accident, but we planned for that accident. And the idea…

FLATOW: It’s like crumple zones.

NADER: Exactly. And the idea behind it, is you get the damage to occur in areas where you keep the car functional to the extent possible when it’s a midsized type of accident that you have. And the idea is that the fenders take all the damage. Very similar to that, is our bridge is designed that way. We actually looked at specific areas which we said that’s where it makes sense to have the damage occur. We designed those elements to take on that damage, and thereby protecting the more important elements to it.

FLATOW: So you can replace those damaged pieces later on.

NADER: Exactly. The idea is that, after an event, the bridge is still functional. We would go in – obviously, the engineers at that time would go in and do a, you know, an inspection, evaluate – there will be damage, but it will be in a form where you can actually make it available so that emergency traffic can be – immediately after that, go on it, and shortly after that go through normal traffic.

The bridge

Please don’t read this as writing is the bridge to ______________; I’m more interested in the design of the bridge itself. I don’t know much about the engineering of bridges, but this idea really struck me as something interesting for the design of composition, and as something that fit within/alongside my ideas of page tectonics: seismic design. Here is a new metaphor for conceptual use. Designs that are functionally flexible, that can withstand shifts and even damage when the larger body (composition) moves. Where would such a design allow us to go that we couldn’t reach before?


5 thoughts on “seismic design

  1. There are also some interesting points on design in another science friday podcast found here

    I believe that the only bridge that they talk about it the Brooklyn Bridge, but that was probably the most interesting part of the talk. It mostly focused on how the bridge was designed for the contrator to cut corners and mess up, but still be extremely reliable. How the potential for failure was built into the design. pretty cool.

    Also, something to look for in the future, as far as structural design/engineering might be the moving of the NASA spacecrafts. Most specifically the Endeavour. It will be moved to LA, and they are hoping to display it vertically, as if prepared for launch. Being so close to a fault line, and frequently exposed to seismic activity, will create a lot of interesting obstacles should they choose to move forward with the vertical display of the shuttle.

    Additionally. This is Clay, not Chelsea.

    • Cool, thanks! I’ll have to check these out.

      I mean, it’s hard not to think about engineering or construction when considering materiality because the design and the materials mean everything or the structure won’t function. It’s not perfection or surface aesthetics, it’s what it can do because of its construction, even in less than perfect/pristine/”real” circumstances. I’m not sure we think about composition in this manner enough, as what compositions can do socially (in their activity/action).

  2. My initial thoughts went to signposts and other writing strategies for signaling movement(s) to readers, which don’t necessarily accomplish what I think you’re talking about, but I know often help me to begin rearranging other components while feeling safe that the other parts will “withstand” the movement. I’m curious as to how this metaphor applies to the kind of rigid composing we often do in composition classes, versus, say, a piece I might compose that is intended to undergo rigorous movement a la the fluxus poster you made and those you and Chelsea helped my students with. I would imagine it’s not necessarily different. I’m also curious to know if you see this as an “always already” kind of thing, that we’re always doing this and should perhaps pay more attention to it, or if it’s an alternative to some other theory/practice of composition, etc.

  3. I guess I was thinking about this in terms of how we envision the writing we do in classes (obviously speaking of writing in pretty broad strokes here/painting generalizations). So, designing writing that can situate itself as connected to the course’s goals/outcomes, other scholarship/ideas, the self (s), which all have larger connection/relations, instead of just viewing its structure as self-contained or self-anchored. In these connections that extend out and come back (like the three dimensional cables) the writing is more active, permits travel (beyond a singular context) because it’s not just anchored to Composition’s bedrock in what is supposed to be (but can’t be) a fixed/stable/rigid position.

    Haha, now that I’m writing this out I realize that this is all traceable/connected to all of the Bruno Latour I’ve been reading lately (The Compositionist Manifesto) – Actor Network Theory. So it’s not really an alternative to a theory of writing/composition, but another conceptual borrowing from, how would Latour be classified (even though I kind of resist it), sociology of science.

    I don’t think that this isn’t happening, but I don’t think that it is either.

  4. The bridge is almost a boat! Good find, Jana. It reminds me of the bit we heard in Alma about scaffolding. Scaffolding has, of course, become a go-to structural metaphor for the teaching of writing, but I would say we are too infrequently pulling the scaffolding apart to consider whether the metaphor is any good. For example, on Friday morning, I saw a pair of contractors atop a scaffold in one of Pray-Harrold’s lecture halls. They were attending to something high on the wall–a light fixture, maybe the screen-lowering aparatus, who knows. But the scaffold was put to a mundane use in this case. It may as well have been two ladders. Reading Gewande’s Checklist Manifesto (stop me if I’ve already told you this), I was struck by the role of bracing as a lasting and in-built structural ally, particularly for high-rise construction. Bracing is not scaffolding, but neither is it anchored to the ground, exactly, except via intermediary structural supports who route weight to the foundation and footings. Anyway, your entry here got me thinking about how these self-pinned structural supports might function to lend strength, flexibility, and safety (via buoyancy) both for instruction and for the thing itself.

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