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Re: Catenary Shape

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I was in the Peace Corps (a long time ago in a galaxy far away...) looking
for appropriate building technologies.  In North Africa I came across a
local masons way of building barrel vaults.  He drapes a string line in an
attractive shape (usually with a traditional rise and run ratio) places a
form of lattice work or, now, plywood behind the string and traces the
outline to the form.  Turns the form over and starts laying rammed earth or
mud brick to the outline.  There are variations on the theme (one of which
was/is a dome) but it works for them and they didn't seem familiar with the
term "Catenary".


-----Original Message-----
From: Charles Greenlaw <cgreenlaw(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Thursday, April 08, 1999 2:45 PM
Subject: Re: Catenary Shape

>Nels, there is an analog method that I saw in a fine documentary film on
>Spanish architect Antonio Gaudi, who designed irregular dome roofs on
>columns of sporadic location and tilt.
>As you note, the situation can be turned over and modeled as a real,
>physical model, as a tension structure of flexible elements and
>weights, where all these elements find their way into the position of least
>energy. The film showed such a model, and I got the idea that Gaudi scaled
>the geometry and tensions that resulted and built to it. Here, you may be
>working with a different array of what's fixed, and what's variable to
>experiment with. But "modeling" is still the essence of it.
>In the theater, I kept thinking, "Jack Barrish has got to see this." When
>the lights came on, there was Jack and a party of his friends. Jack died
>recently, and memorial services are Saturday in Sacramento. He was
>of our local SEAOC Section in 1952, and of the statewide SE Assn in 1970.
>Charles O. Greenlaw, SE   Sacramento CA
>At 10:34 AM 4/8/99 EDT, you wrote:
>>I'd like to find a thorough reference on catenaries.  Specifically, I need
>>be able to determine the shape of a flexible tension element as a function
>>the load that it supports.
>>Actually, I'm working on strengthening an existing unreinforced stone dome
>>roof.  The profile of the neutral axis of a dome as a compression element,
>>regardless of its shape, has the shape, inverted, of a flexible tension
>>element supporting the same load.
>>Nels Roselund
>>Structural Engineer