Analysis

Classification Is For Us Only

Or, more directly: physical objects don’t care how we classify them. When I talk about structures here (or elsewhere) I try to classify them in a way that would be useful to a reader: a building has a frame or it has bearing walls, a bridge has a Pratt truss or it has a Howe …

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Engineering Visible

Structural engineering for buildings may be generally hidden, but there are a lot of exceptions. I’ll exclude exposed wood joists in small buildings from being exceptions since those buildings were not, until relatively recently, designed by engineers. But, for example, plenty of concrete factories have exposed structure (albeit opaque structure that is difficult for non-engineers …

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Another Weirdo

That’s the 1871 Ponakin Road Bridge over the Nashua River near Lancaster, Massachusetts. It’s not unique but it’s close enough that I’ve never seen this particular form before. The HAER description calls it a “Post truss,” named after Simeon Post. Supposedly these were common in the 1860s and 70s, which means most of the bridges …

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Without Visual Hierarchy

Vierendeel trusses are misnamed. They’re really frames, not trusses. In ordinary trusses, most or all of the members are designed for primary stress consisting of axial load, while every piece of a vierendeel, by definition, has bending. But they have been used (when they’ve been used, which is not that often) in the same places …

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Toward The Perimeter

I want to illustrate something I said in passing yesterday. In describing how to make columns stronger by decreasing their slenderness, I said “pushing the material from the center of the section to the outer edges increases the radius of gyration without increasing the weight.” The picture above is from the Lenox Avenue branch of …

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