## The Roof of the Taq-i-Kisra

A higher resolution image, from a slightly different viewpoint

The roof of the Persian Throne Room of the Taq-i-Kisra, now in Iraq, is the best surviving example of an ancient large span structure built to a catenary profile, the shape that will minimise bending moments in a structure of uniform thickness, standing under its own weight.

The red line added to the photograph is a catenary, and the blue line a parabola with the same span at first floor level. The plot suggests that the roof shape from first floor level does indeed approximate a catenary, although the low resolution photograph and irregular outline of the end face of the structure make it difficult to be certain.

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### 7 Responses to The Roof of the Taq-i-Kisra

1. Looks like a cantenary on the inside and a parabola on the outter surface. Looks a bit like a bit of thickening in the structure at the base of the arch

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2. Fisher says:

Hey
You’re not likely to check this anytime soon, but if you do, could you please email me the link of the second picture untouched, or it itself
its for a school add maths project

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3. dougaj4 says:

Hi Fisher

This is the link I used:

If you are working on arches you might be interested in this post as well:
https://newtonexcelbach.wordpress.com/2009/06/16/elegant-proofs-4-the-optimum-shape-of-an-arch/

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4. Fisher says:

Thanks a lot, it’ll help a lot

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5. Sam says:

Hey,

Just a minor correction, Taq-i-Kisra is in Iraq not Iran although it was named after a Persian emperor.

http://en.wikipedia.org/wiki/Taq-i_Kisra

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• dougaj4 says:

Thanks Sam. I have corrected the text.

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