Month: May 2016

Comparing New And Old Skyscrapers

“Skyscraper” is one of the most subjective words I know. The problem isn’t that there’s no definition; the problem is that there are multiple conflicting definitions and no objective way to decide between them. People, including me of course, inevitably choose the definition that agrees with the way they see the issues, or that makes …

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Road Trip: Much Simpler

Steel framing was the first structural technology to mature. Steel construction from the 1920s is, for the most part, recognizably modern in its design and detailing. The reason I need that “most” is visible in this abutment detail from the Blackfriars Bridge: The original girder on the right ends in a complicated series of angles …

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Historic Structural Detail: Geometric Strength

Some structural forms are more efficient than others. For example, roof trusses tend to be deep (vertically) relative to their spans. Trusses can be examined at two scales: at a small scale, member by member and connection by connection, or at the overall scale, where they are analogues of beams. It’s at the overall scale …

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Easy On, Easy Off

Cast-iron facades are an early form of prefabrication. The complex architectural forms were cast in foundries in many pieces and then bolted together on site. Of course, that means that when a piece is loose, either because the wrought-iron bolts rusted or because of cracking, it comes right off the facade. Or, as seen here, falls out …

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What Does A Crack Mean?

Marie’s post on cracks and stability attracted a fair bit of notice, so I want to continue the discussion by talking about the intersection of the field investigation of cracks and analysis methods. More specifically, I want to talk about using the esoteric-to-nonengineers concept of “strain compatibility” to decide whether a crack is dangerous or not. …

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