spherical shell - show forces

this not a typical grasshopper related question but i thought i could give it a try.

i would like to understand how in a spherical shell in the horizontal rings in the upper part there is stress while in rings below there is tension. this flip take place at 51,8º angle.

im mean somehow its clearer if im thinking the shell as something with certain thickness

like a dome structure.

maybe someone could help me out with a simple explaination (in gh :-) ?

Replies to This Discussion

Permalink Reply by Chris Tietjen on February 25, 2011 at 2:34pm

Here's a link to a web page that might hold some insight to this problem. Arches As I read it it seems that the line of thrust for an arch is always a catenary and needs to be in the middle third of the arch section for forces to remain compressive or at least 'well behaved'. In the case of the circular arch the line of thrust tends to fall outside of the arch section and this introduces the tension. The angle where this happens probably is related to the point on the circular arch where the catenary crosses to the outside of the arch section. Mostly guessing about this though so don't build anything :)

Chris

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