> Let's define an ideal arch as one that doesn't have a tendency to fall apart sideways, outward or inward. This means no shear (sideways) stress between blocks, and that means the pressure force between blocks in contact is a normal force -- it acts along the line of the arch. That should sound familiar! For a hanging string, obviously the tension acts along the line of the string.

> […] the ideal arch shape is a catenary.

Source, ch 1 from a textbook on mechanics:


Repost, forgot the image, sorry.

> In fact, Gaudi designed a church in Barcelona using a web of strings and weights to find correct shapes for the arches -- of course, the actual building would have a shape like the reflection in a horizontal mirror above the strings

Also from ch1 of that mechanics textbook:

Woot Gaudi!


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