Stitch in time saves nine – 2nd in a series on cliches that made our country strong
Things we used to say: “A stitch in time saves nine” (Labor Day edition)
A few weeks ago I was walking across a multi-level bridge on a tour of Chicago. Bridges – in fact structures of all kinds – fascinate me and I like learning how they stand, and how they fall. So naturally I was looking at the structure, figuring out how the loads were distributed, how they were sent to ground, and if there was any redundant load-path to ground. And following the load from the span to where it connects to ground support I looked up and saw this:
You are looking at a link, between the bridge support (left side) and the bridge span (right side). The link consists of a pair of vertical steel bars with 2 holes, bolted onto the support and the span I-beam respectively. The span literally hangs from the support; load applied to the span is conveyed to ground via the lower bolt, the link, then the upper bolt. I’m going to describe the best of my understanding of this structure, and if any inspectors or engineers happen by, feel free to expand or correct in the comments.
Since the bridge span consists of many I-beams in parallel, each with one link at each end, we would not expect all the links to fail at once unless they were in such bad condition that a cascading failure became possible. The challenge is that these links necessarily exist near where the span connects to the support, so road salt can fall right on them from the road above. The links and bolts themselves seldom break. A common failure mode of this kind of link is that expanding rust on the beam forces the washer outward, shearing off the cotter pin that holds it in place, allowing the bolt to migrate horizontally and leave the I-beam unsupported. Mitigations include regular inspection to insure that the pins are intact (as these are), holding the bolt in place. Application of water-repellent grease isn’t a bad idea either.
OK, fine, that’s cool. This bridge support is actually in fair condition structurally even though it should be watched carefully on account of the rust. The problem is there are hundreds of these links on this one complex bridge alone, and Chicago has more bridges than any other city anywhere. Some of them are of different designs and could have different failure modes. Bridge inspecting is, to say the very least, a full-time job, and it is not without political pressures. Add sewers, water mains, buried power lines, buildings, and roads and you need a lot of people who just go look at things and make predictions about them. And the looking sometimes involves advanced imaging and analysis techniques, plus knowledge of chemistry, engineering, physics and even technology history. People who can do that don’t work for minimum wage. (They don’t exist in isolation from a working education system either, but I’ll cover that later in this series.)
Roads, bridges, electrical grid, water mains, sewers, schools, dams and river engineering projects of days past contributed in two ways to our economy. First directly, in the wages of the people who designed them and built them. These people spent their wages, creating a cascade of economic activity from service to manufacturing. And second, the infrastructure itself reliably enabled economic growth – something politicians were pleased to attribute instead to their charm and ideologies. Today that same infrastructure is falling into disrepair, as thoroughly documented by the excellent Slactivist series you will find in the Notes section.
We are in effect resting on past accomplishments – infrastructure built from the 1930′s through the 1970′s. No politician wants to hear from the bridge inspectors that they must sell a multi-million dollar “expense” to the taxpaying, voting public. We’d rather be afraid of swarthy foreigners than rusting bridges – even though in the long run the rusty bridges are a much greater hazard to our economy. Infrastructure is one of several necessary conditions for a sustainable economy.
Is there anyone alive who really thinks it is better to wait for disasters than to prevent them? The only explanation I can conjure for our national behavior is that we’ve become accustomed to not thinking it through. Strong infrastructure makes for strong economies – and the opposite is true when infrastructure is allowed to fall apart. By the time disaster strikes, the economy is immune-compromised, vulnerable. We have stopped telling ourselves; “A stitch in time saves nine”, dismissing the old aphorism as a cliche. There is another cliche that now applies: “better late than never” – but late unpredictably turns into “too late” so we’d better start right away.
- Slacktivist: “We have people who desperately need work to do. And we have work that desperately needs doing. I wrote about some of that work in a series of posts last year — 1. Water; 2. Sewers and storm drains; 3. Offshore wind farms; 4. The Grid; 5. Bridges — but those posts barely scratched the surface of the necessary and urgent work that remains undone…”
- CBS News: We train politicians not to prepare for disasters (video)
- Kevin Drum: My jobs plan, a trillion dollars for infrastructure
- TP Report: As their states’ bridges and roads crumble, GOP remains opposed to infrastructure investment.
- Reuters: Greg Easterbrook says Federal Construction Spending doesn’t translate to GDP growth – but the examples he gives sound like a better argument for project-management and penalty clauses than for throwing out the idea of infrastructure spending
- Almost on-cue, a perfect example: The Sherman-Minton bridge in Louisville, shut down for structural defect. Didn’t collapse, no disaster, except the economic one that issues from shutting down a major route.