March 2016

Teeth

by Don Friedman on March 31, 2016

There are quite a few design ideas that we like that are completely dependent on the skill of the laborers. Ultimately, all structural design is dependent on the skill of the laborers – it’s not like we engineers are on site actually building anything – but some details are more sensitive to skill levels than other.

When we are dealing with unreinforced brick walls, like those that make up about 95 percent of the walls in New York, our preferred detail for repairs and alterations is to “tooth in” new brick by interleaving the new brick with the old. Toothing has a number of advantages, including compatibility of materials and an even distribution of load, but it requires very careful cutting out of joints and setting new bricks in place.

Here is a picture of it being done right (and a close up), unfortunately back-lit by the outside daylight on the other side of the wall:

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New masonry walls are built with steel reinforcing, but there’s little point in putting in reinforcing that will only extend a foot or two along the wall length, so we don’t bother in cases like this.

Historic Structural Detail: The Ghost of a Barrel

March 30, 2016

Not every detail is important today, but they all exist for a reason. How did concrete contractors create round columns before reusable steel forms? The portion of this 1910s column at the top of the photo is still covered with plaster. The plaster has been removed at the bottom, showing the board marks. The vertical […]

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New Quakes

March 29, 2016

A report from the U.S. Geological Survey on the probability of earthquakes in 2016 has been getting some press. In one sense that’s surprising, because USGS documents tend to be a bit dry and technical for the average reader; on the other hand this one contains the fascinating information that the risk of human-induced earthquakes in some parts […]

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Historic Structural Detail: Heavy Metal

March 28, 2016

This: is a box girder consisting of two I-beams and two plates, all riveted together. It’s at the next-to-top floor of an old mansion, where there is a small terrace at the front because the top floor is set back several feet. The girder is below the set-back facade; the steel beams supporting brick vaults […]

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The Start Of Something

March 25, 2016

Projects are like everything else (vacations, years, the baseball season): there’s a feeling of anticipation and fun simply because they start. There’s no feeling at work quite as satisfying as walking into a building and seeing steel we designed waiting for installation.

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Failure Portrait: Crushing

March 24, 2016

Our daily work covers a number of structural materials – starting with steel, concrete, brick, and wood – and there’s a tendency to put structures in little mental boxes based on material. “Wood, therefore the loads are small” is bad logic, but it represents a lot of ordinary work. We most often see wood as floor […]

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Best for NYC: Time’s Up

March 23, 2016

The time to register for the Best for NYC Challenge ended last Tuesday. I have no idea when  the results will be announced, but I suspect it won’t be long. When they are, I’ll be linking to congratulate the winners.

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Failure Portrait: Everything

March 23, 2016

I knew before I entered this building that we would be designing a lot of repair. It turned out to be a lot of a lot. The joists are all rotted, the wall extension that’s supporting the joist nearest us is on the verge of collapse, the wall beyond is missing mortar to the point […]

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Failure Portrait: The Corner

March 22, 2016

Can you tell the difference between a break and an architectural feature? What if the failure planes of the stone are so clean that they pretty much match the finished surfaces elsewhere? There’s no embedded metal. The cracks that led to that corner piece falling off and the cracks in the main water-table stone above are […]

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Four Views on One Set of Data

March 21, 2016

Last fall, the Council on Tall Buildings and Urban Habitat – known informally as “those skyscraper people” – issued a report on the statistics of tall-building construction in New York from 1900 onwards called “New York: The Ultimate Skyscraper Laboratory.” It’s interesting stuff and well worth the few minutes it takes to read. A few […]

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