The whole promise of engineering is not to build a bridge that stands but to build a bridge that barely stands. It is not a good idea to build a bridge that last 500 years. You likely destroyed valuable resources to build one. Build a bridge that lasts 100 years and save those resources. In 100 years the technology to build bridges improves so much that it is lot easier to build a new one. At least in most countries like India.

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throwaway27448 6 hours ago | parent | next [-]

> In 100 years the technology to build bridges improves so much that it is lot easier to build a new one

This hasn't even been true for 200 years lol

	▲	Hugsbox 2 hours ago \| parent [-]
		We don't build better bridges than we did 200 years ago? Forgive me if I'm wrong, but it seems like we build bridges right now that would have been unthinkable 200 years ago

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matheusmoreira 6 hours ago | parent | prev | next [-]

Nobody is going to tear down old bridges and rebuild them at enormous costs just because technology changed. Some things can't or won't be redone and so it's worth it to build it to last and getting it right on the first try.

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dev_l1x_be 6 hours ago | parent | next [-]

This is exactly what we did with houses, buildings. We had perfectly functional 100+ years old fully functional, gorgeous buildings and we replaced those with brutalist concrete/glass barely functional garbage.

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otherme123 6 hours ago | parent | next [-]

In Europe we have plenty of old buildings. The good ones (i.e. made by very wealthy people) tend to be decent, with a skew towards huge living rooms but tiny rooms. The cheaper ones are a mess to mantain: cold in winter, hot in summer, expensive to renovate (it could be more expensive to renovate than to build a new one), bad to no isolation, in my region terribly humid, usually too dark with minuscule windows for modern standards.

With roman buildings that last 2000 thousand years we are looking at survivor bias. Near me there are some roman ruins from a (cheap and small) public bath that are barely distiguishable from a pile of bricks. The are some nearby pre-roman ruins in better shape.

	▲	modo_mario 4 hours ago \| parent [-]
		>cold in winter >in my region terribly humid You need to actually reduce draft a bit (often old houses like mine tend to accumulate flaws that the elderly living there before didn't fix anymore.) and use a heating sources that matches. Having a fireplace is fine. It could overheat the house whilst also keeping air dryer and it's essentially renewable (compared to the alternatives and houses made of more plastic insulation than anything else) if you don't mind air quality dip in winter. That said i can see how that's no longer an option in places that have drastically increased their population

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matheusmoreira 19 minutes ago | parent | prev | next [-]

Those are houses though, private property. Not government infrastructure.

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wbl 5 hours ago | parent | prev | next [-]

There are exactly 3 old buildings in Warsaw thanks to the Germans. Brutalism exists because a generation who grew up in rubble wanted solidity.

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ascorbic 6 hours ago | parent | prev [-]

They weren't torn down because there was better technology available. They were torn down because they were falling apart, or were no longer meeting the needs in that location. I love old buildings – my house is 250 years old – but there's no denying that generally they are less suited to current needs than newer buildings.

	▲	benj111 2 hours ago \| parent [-]
		Older buildings are generally more flexible though. In the UK, within living memory electricity has become widely available, TV has, gas, internet etc etc. and yet we still build houses without the assumption that some cable isn't going to be modified in the wall some how. There's fairly modern houses that didnt have the 2 courses of brick added to the loft to allow 300mm of insulation to be installed. We are now building houses with gas boilers, knowing that they will have to be swapped out probably before the life of the boiler runs out. And I bet the radiators and piping aren't sized to make that possible. That the circuit isn't sized for that. Yes none of this is easier in a 250 year old house, but it isn't harder and 250 year old houses hadn't really changed appreciably for a few centuries so it isn't as if there would be an expectation that you would be installing new things in the wall every decade.

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gus_massa 5 hours ago | parent | prev | next [-]

Usually you need wider bridges, so the old bridge needs a replacement or a second bridge on the side.

	▲	matheusmoreira 15 minutes ago \| parent [-]
		If the bridge became a bottleneck, then there is an actual reason to replace it. People aren't doing it on a whim because technology changed.

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Zardoz84 5 hours ago | parent | prev [-]

But we are currently doing it when a bridge can't handle modern traffic levels because it was designed thinking in 50's traffic (single lane for each direction without peatón or bicycle ways to 4 or 6 lanes and pedestrian and bicycle ways).

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culi 4 hours ago | parent | prev | next [-]

Modern concrete includes plastic fibers like polypropylene, fly ash (a great source of arsenic, lead, and mercury), silica fume, formaldehyde, and often even PFAS

This type of concrete does not give us any more flexibility in the future to rebuild or upgrade because doing anything to it could turn it into an environmental and public health hazard

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dizhn 3 hours ago | parent | prev | next [-]

Aren't structures like bridges tested to at least 1.5x design parameters? In our field it's usually 2x (pressure and lifting lug strength).

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croes 6 hours ago | parent | prev [-]

Sometimes knowledge gets lost and newer doesn’t automatically mean better

	▲	culi 4 hours ago \| parent \| next [-]
		In fact, the dominance of concrete is surprisingly political. It has a lot to do with Cold War geopolitics https://www.listennotes.com/podcasts/the-conversation/keepin...
	▲	hkt 3 hours ago \| parent \| prev [-]
		Case in point, Roman concrete