4 ms·

Meanwhile the average lifetime of modern infrastructure is what, 50 years ?

lupusreal 2y ago
Modern concrete could last as long ad Roman concrete, if not for the fact that we use rebar which inevitability corrodes and is the limiting factor in how long those structures can last. But that same rebar allows us to create structures that the Romans never could have. Concrete structures with huge spans and thin walls. It's not that we don't know how to build things which last long. Rather, we choose not to because building that way has tradeoffs we usually don't want to make. This is also the reason we make things out of concrete and rarely out of meticulously stacked rocks.
ChrisMarshallNY 2y ago
Some of the water mains that bring water to New York City, from Upstate, are probably 200 years old. Many of them are made from wood.
_aavaa_ 2y ago
Part of the shorter lifespan is that our cities grow much faster. Why build infrastructure that last 200 years if it needs to be ripped up in 50 due to no longer meeting population demands?
- Retric 2y ago
  When they transported 100% of the output of a spring there’s no need to update the infrared as a city grows there was no way to go past 100%. Dams have the same kind of limits and are regularly designed for 150+ year lifetimes. The Hoover Dam is just about to turn 90 and it’s likely to last another 100 years. Quite a lot of the built environment is designed for 100+ year lifespans. When it isn’t there’s often very good reasons. It’s kind of amazing we get road bridges to last as long as they do when you consider the physical and chemical assault they’re constantly under all while trying to minimize weight and cost.
  - lupusreal 2y ago
    Building a bridge that spans a wide road or river is extremely expensive without using iron or steel. If you do, that limits the lifespan because they corrode. We never forgot how to build stone bridges, we stopped doing it most of the time because nobody wants to pay for it.
    - Retric 2y ago
      Iron bridges can easily last 100+ years with maintenance, faster replacement is generally cheaper which is why you see exposed metal on so many highway bridges. Traffic on traditional stone bridge designs would quickly destroy them.
  - _aavaa_ 2y ago
    This is true. I was thinking of things like roads, water mains, sewer pipes, and even homes. Yeah a house that lasts 200 years sounds good in principle, until you think about the kind of material and energy efficiency advances we’ve had in just the last 25.

Modern concrete could last as long ad Roman concrete, if not for the fact that we use rebar which inevitability corrodes and is the limiting factor in how long those structures can last. But that same rebar allows us to create structures that the Romans never could have. Concrete structures with huge spans and thin walls. It's not that we don't know how to build things which last long. Rather, we choose not to because building that way has tradeoffs we usually don't want to make. This is also the reason we make things out of concrete and rarely out of meticulously stacked rocks.

ChrisMarshallNY 2y ago

Some of the water mains that bring water to New York City, from Upstate, are probably 200 years old. Many of them are made from wood.

_aavaa_ 2y ago

Part of the shorter lifespan is that our cities grow much faster. Why build infrastructure that last 200 years if it needs to be ripped up in 50 due to no longer meeting population demands?

Retric 2y ago
When they transported 100% of the output of a spring there’s no need to update the infrared as a city grows there was no way to go past 100%. Dams have the same kind of limits and are regularly designed for 150+ year lifetimes. The Hoover Dam is just about to turn 90 and it’s likely to last another 100 years. Quite a lot of the built environment is designed for 100+ year lifespans. When it isn’t there’s often very good reasons. It’s kind of amazing we get road bridges to last as long as they do when you consider the physical and chemical assault they’re constantly under all while trying to minimize weight and cost.
- lupusreal 2y ago
  Building a bridge that spans a wide road or river is extremely expensive without using iron or steel. If you do, that limits the lifespan because they corrode. We never forgot how to build stone bridges, we stopped doing it most of the time because nobody wants to pay for it.
  - Retric 2y ago
    Iron bridges can easily last 100+ years with maintenance, faster replacement is generally cheaper which is why you see exposed metal on so many highway bridges. Traffic on traditional stone bridge designs would quickly destroy them.
- _aavaa_ 2y ago
  This is true. I was thinking of things like roads, water mains, sewer pipes, and even homes. Yeah a house that lasts 200 years sounds good in principle, until you think about the kind of material and energy efficiency advances we’ve had in just the last 25.