Comment on Would it be better to just have a lot of society be underground?
iocase@lemmy.zip 3 days agoThe city burned down which allowed these sweeping changes to happen. The minimum height is set by preventing yearly flooding due to heavy rains and strong tides since the area was filled in tidelands. The maximum was set by the rest of the city and its Hills. This is an engineering problem so you solve it the way an engineer would.
The way you would do this for a modern city is by first considering geography and your design requirements. “How much do we need to raise it and why?” If you only need to fit utilities in there and nothing else your necessary lift isn’t that high. Maybe a few meters. If you want to also cram cars or trains down there so you can build to viaduct top lighter by mandating no cars, and to make it a walkable city, you can set a higher requirement. You’re basically building a bridge that spans the entire city and the same calculus works for a viaduct city as it does for designing a bridge. Your biggest expenses are regrading, foundations, redoing drainage, and routing utilities into the viaduct passageways and abandoning existing utilities in the ground from the old city. That’s all if you can avoid eminent domain or conflicts with property owners.
All of this is obviously way easier to do with a newly built city from day 0, or a city that burned down. The reason it happened in Seattle is because residents were sick of yearly flooding and they needed to rebuild with fireproof materials anyways. So why not solve both?
WhyJiffie@sh.itjust.works 3 days ago
how do you replace viaducts? Would that need demolishing buildings on top?
iocase@lemmy.zip 3 days ago
Afaik you build buildings on raised foundations and the viaduct decks span the gap between buildings creating a raised “ground floor” above the actual dirt. They eventually do wear out given enough loading cycles accumulating fatigue in the metal reinforcement, but can last a hell of a long time if you keep heavy vehicles off of them.
In an ideal world the viaduct top is for pedestrians or bicycles only, and there’s enough space underneath for logistics to supply businesses from loading docks at their basement. Overhead LRTs would be a natural pair with viaducts since you can just build the LRT piers to put their load path into the viaduct columns (which you also engineer to be larger.) that way you can separate all traffic types by verticality instead of all sharing the same grade.
The big benefit there is the viaduct deck doesn’t fatigue hardly at all. Maybe emergency vehicles allowed up on the deck? Otherwise it’s just bicycles or pedestrian traffic.