origin of the term jack arch

[justhumm]

I had first heard the term "jack arch" during college, while doing some intern work on the NYC subway system. And I've recently been hearing the term (somewhat blindly) thrown around on a job in Philadelphia. I have a general working knowledge of what a "jack" arch is, but like everything else in the engineering world, it seems to have a very vague definition and the origin of the term are sketchy, at best.

The best reference for a possible origin of the term is from a book that I stumbled over:

jack arch. A flat masonry arch, specifically flat terra-cotta floor arches. One explanation for the origin of this term is the resemblance of the center "keystone" arch block to the crown on the Jack in a deck of playing cards. (Friedman, Historical Building Construction, 2010)

Can anyone offer a definition and/or origin for a "jack" arch?

Cheers...

 

[WARose]

A "jack" arch is basically a arch that is flat or has very little rise. As far as where the term originates....not sure about that. I have a reference on arches.....will check it tonight.

 

[msquared48]

This Jack-In-The Box's answer to McDonalds arches.

Mike McCann, PE, SE (WA)

 

[msquared48]

http://en.wikipedia.org/wiki/Arch

Mike McCann, PE, SE (WA)

 

[JStephen]

One of the definitions of "jack" is:
something that supports or holds in position: as
a : an iron bar at a topgallant masthead to support a royal mast and spread the royal shrouds
b : a wooden brace fastened behind a scenic unit in a stage set to prop it up

Where I hear this is a "jack rafter", with the term being used in a little different sense from normal structural use.

When you draw things, you can call it "Item X" or "Arch per Detail C" but the guys out building it are going to give it a name if it doesn't have one, and trying to guess where that came from 500 years later might be difficult.

 

[IRstuff]

Most etymology sites claim that the term is only about 140 yrs old.

"Jack" is often used in the context of small; see first entry in bibliography:

https://www.nh.gov/dot/org/projectdevelopment/environment/documents/NHJackArchBridgesReport.pdf

TTFN
faq731-376

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[msquared48]

A Jack rafter iconfiguratiovving less length than a normal rafter as in our framing into a hip.
Logically applying the term, a jack arch is one having less arch or rise than other arches, as in a flat configuration

Mike McCann, PE, SE (WA)

 

[justhumm]

Hmmm. I'll have to skim through this when I have the chance.

Aitken, T. Road Making and Maintenance: A Practical Treatise for Engineers, Surveyors, and Others.
Philadelphia: J.B. Lippincott Company, 1900.

[URL unfurl="true"]https://archive.org/details/roadmakingandma00aitkgoog[/url]

(Click "All Files: HTTPS" - on the left - to find the PDF version)