January 2015

Ransome Bar

by Don Friedman on January 21, 2015

We ask for probes on a regular basis, usually to find out what something useful about unknown hidden structure. On a recent project we asked for probes through a cellar slab. Our instructions were to remove the concrete while leaving the rebar in place, so the final probes looked like this:

IMG_0917

The rebar that was exposed is square in cross-section, and twisted along its length. This style is known as Ransome Bar after its inventor, Ernest Ransome.

The twist was Ransome’s method¬†of solving a basic problem of reinforced-concrete construction: how do you get the rebar and concrete to act together? When there is tension in the bars, they tend to slip relative to the surrounding concrete, destroying the composite action that is the basis of the combined material. The general solution to this problem has been to use “deformed” bars, where some kind of geometric irregularity is used to provide the bond between the steel and concrete.

Ransome was one of the first designers and builders in the Untied States to successfully create large reinforced-concrete buildings and his bar was popular for more than 30 years, into the 1910s.¬†Interestingly, Ransome bar fell out of use because it was too good. The helical twist produced far more bond strength than is needed and cost more than other methods of creating deformation. So we don’t see new Ransome bar but when we find it in old buildings we know that we don’t need to worry about bond strength.

Bad Art

January 9, 2015

Another thirty-cent postcard find: the worst illustration of the Woolworth Building I’ve ever seen. Here’s the postcard version: And here’s reality in the same era: Given that the postcard was published by the Success Postal Card Company, which was located in New York, there’s really no excuse for this. It’s a terrible representation. The only […]

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Used Books

January 7, 2015

You can find great stuff for thirty cents at used-book stores. Here’s a postcard of our home, with a picture taken in the brief window of time between the completion of the Trinity Building (111 Broadway) and the construction of its fraternal twin the U.S. Reality Building (115 Broadway). In other words, this view only […]

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Michael Lo

January 6, 2015

Marie and I are proud to welcome Michael as a partner at Old Structures.

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