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mikepurvisyesterday at 5:41 AM4 repliesview on HN

To build without tension you have to build structures that basically look like Roman structures [1]: a bunch of tightly spaces arches so that the entire thing is in compression, with no meaningful tension anywhere.

But it turns out that's pretty inconvenient; we really like doing dozens of feet of span for highway overpasses, building floors, and everything else. So we put rebar in all the concrete and just acknowledge that that means it has an absolute maximum lifespan of a century or two, and will certainly not last for millennia the way pure concrete in pure compression can.

[1]: https://www.theartnewbie.com/blog/rome/roman-arch


Replies

Modified3019yesterday at 7:30 AM

The “it’s built so everything is under compression” is great thing to bring up, but fyi your link is AI generated, filled with senseless repetition and “it’s not just x, it’s y”.

Looking it up on archive.org shows it was generated this year.

cm2187yesterday at 10:32 AM

They could do large arches too, see https://en.wikipedia.org/wiki/Basilica_of_Maxentius

throw0101dyesterday at 1:11 PM

> To build without tension you have to build structures that basically look like Roman structures [1]: a bunch of tightly spaces arches so that the entire thing is in compression, with no meaningful tension anywhere.

Until an earthquake occurs, and then all of those mostly-down forces turn into side-to-side forces.

Zardoz84yesterday at 6:29 AM

or go and revive Gothic architecture