May 2016

Comparing New And Old Skyscrapers

by Don Friedman on May 31, 2016

“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 their favorite building the tallest in the world, or in some other way feels right to them. Given that, this entire post is either nothing more than fodder for arguments or it’s just my opinion. Or both.

How subjective is the word “skyscraper”? When it first entered use with reference to buildings, in the 1890s, it meant buildings that were maybe 12 or 14 stories high. In current use, those buildings are probably not even counted as short skyscrapers. (Musical interlude: Oklahoma is set in 1906. As I mentioned before, there’s no way that people in Kansas City thought that a 7-story building was a skyscraper in 1906 because they’d had a 12-story building there since 1888.)

There has been a resurgence in recent years of new buildings breaking records for height. If you like skyscrapers, that’s great. Most of the new very, very tall buildings are not in the U.S., and if you’re a fan that’s great, too, since it means more tall buildings wherever you travel.

Closer to home, we’ve been having a resurgence of merely-very-tall building construction here in New York. Four, or maybe five apartment houses over 1000 feet tall are up or in progress on 57th Street, and more scattered around town. These buildings are not as tall as the current record-holder, the Burj Khalifa, but one of them – The “Nordstrom Tower” – will be taller than the Willis [nee Sears] Tower in Chicago and thus will be the tallest building in the U.S. (I, personally, think that the claim that the uninhabited spire on top of One WTC makes it the tallest is ridiculous.) More interestingly, the new buildings in town are amazingly slender.

Fortunately, I don’t have to dive into the details of this topic, as an exhibit at the Skyscraper Museum has done it for me. In short, unlike the slendernesses of 6 to 8 of most of the previous generations of skyscrapers, the new crop here has slendernesses as high as 23. Since I’m interested in old buildings, how does the current crop compare to the past?

There are pre-1900 champs like the Gillender Building (at the corner of Wall Street and Nassau Street, torn down 13 years after completion for the larger Bankers Trust tower), with a slenderness of 10.5:

The shaft of the Singer Building tower was 65 feet on each side, and the building was 612 feet high.

But the best example of an old building that rivals the current towers as a straight up-and-down and slender building  is the old One Wall Street, AKA the Chimney Building, which was 18 stories high and slightly less than 30 x 40 feet in plan area:

There are other very slender buildings from before 1910, but this one simply does away with everything nonessential. It may not have been very tall by our standards, but it seems to me to be pointing at the future.

Road Trip: Much Simpler

May 27, 2016

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

May 26, 2016

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

May 25, 2016

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?

May 24, 2016

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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Grandfathering Structure

May 23, 2016

The Times published an interesting article last week on the topic of existing buildings that do not meet current zoning. The title tells the story: “40 Percent of the Buildings in Manhattan Could Not Be Built Today.” The term for legal protection for existing conditions that cannot be legally created now is “grandfathering” Rather than discuss zoning, I […]

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Different Ages

May 20, 2016

I spent part of yesterday traveling on the Morris and Essex line of New Jersey Transit, which was originally part of the Lackawanna Railroad. The Lackawanna is a favorite of mine in a historical sense because of its name and its mascot, Phoebe Snow. The trip got me thinking about the various ages of the […]

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Road Trip: The Tower Bridge Is Weird

May 19, 2016

Another snap from London: That’s the Tower Bridge as seen from the walkway to the Tower of London. Structurally, we’ve got a double bascule roadway at the center span, a truss walkway high above (so that pedestrians can walk across even when the road span is raised), and suspended side spans with inverted three-hinged arch trusses […]

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New York City Preservation

May 18, 2016

It may come as a shock, but I’m a fan of analysis rather than guessing. I’ve been having a fun time reading Historic Preservation: At the Core of a Dynamic New York City, a report from the New York Landmarks Conservancy, and also an article from the Architectural League, How Many Row Houses Are There In New York […]

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Historic Structural Detail: Stairs

May 17, 2016

A lot of old buildings with wood-joist floors have their stairs contained within brick enclosures. It’s an early form of fire-resistant egress path. So how do you create a non-flammable stair under those circumstances? Here’s the top side of the stair, looking down (my apologies for the vertigo): And here’s the underside, looking up: Each […]

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