Design

Overlapping Developments

Everyone seems to love covered bridges, but profile photos of them tend to be very boring: you’re looking at a plank wall. For most bridges, that’s one of the best angles. In any case, that’s the Bunker Hill Bridge over Lyle Creek, in Catawba County, North Carolina. And the inside view shows why I’m writing …

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Whether You Want To Or Not

Some days, the new thing I learn that day is something that is annoying to the point where I regret wasting the 30 seconds it took to learn it. Today, I learned what a “half-hip Pratt truss” and I’m going to inflict it on anyone reading this. The two most common configurations in US bridges …

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It Takes A System To Be Ordinary

The Wilson Shute Bridge over French Creek, south of Meadville, Pennsylvania is similar to a lot of the truss bridges I’ve discussed here. It was a steel Pratt through-truss, constructed in 1889, listed on the National Register and surveyed by HAER in 1988, and demolished in 1997. As the pictures below show, it made heavy …

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One And A Half Decks

The vast majority of road bridges have a single deck; a few are double decked. The 1895 Falls Bridge, across the Schuylkill River in Fairmont Park in Philadelphia is an interesting exception. It has the structure needed for two decks, but the upper deck was never built, leaving a bridge that looks curiously top-heavy. Fairmont …

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The Morgan Library

Structural engineers working on buildings get used to anonymity. Even if a building has a daring structural design, most (or, often, all) of the press will name the architect rather than the engineer. In renovation projects, which make up nearly all of our firm’s design work, engineers are even less likely to receive much recognition. …

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