Talk:Counter-arch

Is Enneüs Heerma Bridge a good main image?
I'm not clear that the main image in this article - of an inverted arch in the Enneüs Heerma Bridge - is a good or even correct example of a counter-arch. I'm not actually sure if it's structural in that bridge, or maybe just decorative.

If a counter-arch is "built adjacent to another arch to oppose its forces or help stabilize it," then its forces should act in the opposite direction of the adjacent arch. This feels intuitive for arches built next to each other that are both upright, as in an arcade: one arch is pushing outward at its base, so e.g. on its left side there are leftward forces; and the adjacent arch's right side exerts rightward forces which counteract that. Similar for a flying buttress, which the article mentions.

But since the arch in the bridge photo is inverted it seems it would do the opposite. Arches normally push outward at the base because gravity is pushing the top of the arch downward, putting the arch in compression and transmitting the downward force to the ends of the arch where it pushes both down and outward. In an inverted arch, it seems like since gravity is pulling the center of the arch downward, the arch would be in tension (not compression), and thus at the ends of the arch the forces would be down and inward. Placing an inverted arch next to an upright arch thus feels like it would amplify, not counteract, the upright arch's forces. Images in the inverted arch article itself always show the arch directly beneath the upright one, not next to it - in that configuration, the forces would indeed cancel out.

Maybe there's some less obvious physics to how the inverted arch pictured in the Enneüs Heerma Bridge works to counteract the other arches... but it feels unclear enough that it needs some additional explanatory text if so. Or ideally it should be replaced by a different image that illustrates a more typical, canonical usage of counter-arches... Ytpete (talk) 18:48, 2 July 2024 (UTC)


 * This article has a lot of issues, starting with an almost total absence of readable text. I agree with your reasoning that the illustration should be replaced, too. Викидим (talk) 19:26, 2 July 2024 (UTC)