[2020] Rebuilding bridge - I'm confused...

The devs may be cheating with their buildings. Not just because structural integrity isn't computed until something is disturbed, but with actual magic blocks that defy normal SI rules. You can cheat too if you want, with "Floatation Block" and "Floatation Pillar 100" which are available at least in the POI editor. The description for these blocks says "This block will provide full support no matter where it is placed, just like it was placed on bedrock."

As for working within the system... some of your screenshots aren't working, but you should remove the dead weight. Those wooden catwalks on top aren't helping. Neither are most of the ramp blocks.

I would suggest starting with a flat, horizontal beam that covers the span. Make it out of 100% metal rivet blocks - you can paint it later if you have to. You should be able to extend 16 blocks from each side at max, which looks possible when eyeballing it. Don't do a support column, because you want to know exactly when it's overloaded. Don't start at one end and work your way to the other, either. You'll have to build out from both sides separately and meet in the middle.

Then widen the beam into a 2-block-wide beam, a 3-block-wide beam, and so on until you match the width of the bridge. Again, keep using metal blocks for everything, even if you want it to look like concrete or asphalt later.

Once you have the platform part of the bridge done, you're basically done with the engineering part. You can confer a bit more support under where it attaches to the ground, but that's it. Everything else you're going to put up on the sides of the bridge, which looks like 'structural support', is for show. So make the vertical beams out of hay bales or wood, because they're lighter. Add it bit by bit, and if you're lucky you'll get the shape you want before it collapses. Keep flying, because your character weighs something, too.

If all goes well, you'll have a horribly unsafe structure that will crumple like a house of cards the first time a zombie breathes on it.

Originally posted by The Giving One: From what I have seen and what I know, these bridges are "designed" to fall fairly easily, for maybe just that reason. Sure, it's up to the player to figure out how to reinforce it so it will be solid and structurally sound, but that's easier said than done, and can still leave it weak for zeds to take down.

I found this out once on one of these bridges also. I walked up to it and just struck it once with a stone ax and the whole thing collapsed, on a new map and on day 1.

I don't know the developer's original intentions. But if I had to guess, I suspect that the world builders knew that they wanted a canyon with a bridge in the game. The programmers told them early on that there's a 16 block technical limit on how long a span can be (so that calculations only have to extend to 1 chunk away at most). So they made the canyon as big as they could (because a canyon needs scale to be believable), while keeping the bridge across it at a plausible size for this world.

In other words, I hypothesize that the fact that this bridge, or any bridge of that size, is so fragile is less about what the player can do with it, and more about doing the best one can within the technical constraints.