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One often gets the "nothing like this will be built again" feeling around these kinds of engineering projects from the 20th century, since modern constructions tend to have a very different feel, more sleek and less massive. Also true with things like transit infrastructure: even though a modern subway or elevated train line, like the Copenhagen metro (which has both), is better in just about every way from the old style of construction, it subjectively doesn't have the same impressive feel of something like the NYC subway or Chicago El, with their massive steel columns and hundreds of thousands of rivets.

"with their massive steel columns and hundreds of thousands of rivets"

We have a fantastic example of that near Edinburgh:


Wasn't that bridge intentionally designed to not only be robust, but to look as imposing and robust as possible, in order to reassure the public since the previous bridge in the location had collapsed?

Yes they certainly succeeded in making it look robust! You are correct in saying that this desire was based on a previous accident where a bridge collapsed - although it a bridge in a different location (over the Firth of Tay at Dundee rather than the Firth of Forth near Edinburgh).


One interesting thing if you like Science Fiction is that Iain (M) Banks grew up in North Queensferry, which is right under the north end of the Forth Bridge - which completely dominates the wee town. I remember hearing in an interview that Iain claimed that his fascination with megastructures (e.g. Culture GSVs and Orbitals) probably came from growing up in an environment dominated by a Victorian megastructure.

He even set one of his novels on a fictionalized mega-sized version of the Forth Bridge:


Reminded me of the first arch bridge in the world to be made of cast iron, built in the 1770s and still standing: http://en.wikipedia.org/wiki/The_Iron_Bridge


It just feels like these structures were built to last a lifetime and then some. Most of the stuff being built nowadays appears as though it already has a due date of "the not to distant future" to be torn down and replaced.

At least here in the US, the architecture just feels like everything else around me - it's disposable.

For a lot of infrastructure, the ability to more accurately model and calculate the performance of structures has meant that they don't need to be overbuilt so much. The less you overbuild a structure, the less it weighs, and the less structure you need to build - a virtuous cycle.

If you look at the last 400 years of bridge design you can see the transition from overbuilt compression structures to gossamer suspension bridges. This is a good thing, but it's easy to mistake old, overbuilt structures as being more "robust" when what they really are is an inefficient design meant to avoid failures due to a weak understanding of how the materials and structure will perform under use.

I agree that there is a vast increase in productivity and saved resources from better modelling and understanding of the materials.

But you cannot ever convince me that our steel suspension bridges are going to last for centuries like our stone bridges from the 15th century and onwards.

The thing is, their goal wasn't to last for centuries. Their goal was just to not fall down, and because people back then didn't have the modeling abilities we have now, their solution was to be very conservative in their design and overbuild everything. If we wanted to make bridges that would last a long time, we could almost certainly do it more efficiently now.

Yes, stone will last longer, simply because it doesn't get eroded by the elements as quickly as possible. But it's also simply not usable as a construction material for bridges beyond a certain size and span, because it's only good under compression and even then its own weight starts to become a limiting factor as you get larger.

By the 1940s, a stone bridge that might take 100 man-years of labor to create could be replaced by a bailey bridge that goes into place overnight. I'm sure if we wanted to create a bridge that lasts 300 years, we could dedicate more resources to it, but it would be grossly wasteful to do so - you don't know how long the current requirements are going to even be relevant. It's better to build a bridge that lasts for 50-60 years, and have the option value of replacing it with a better structure down the road.

>>>>>> It's better to build a bridge that lasts for 50-60 years, and have the option value of replacing it with a better structure down the road.

And then we get to where we are now a lot faster. . .


"Over 90,000 miles of roads and 71,000 bridges are in dangerous disrepair, according to a 2010 U.S. PIRG study."

I guess the key difference is the sense of massive person power one gets from those older projects. Rivets and the like bear the unmistakable mark of human assembly.

That said, I still find modern day mega engineering projects similarly impressive. The Large Hadron Collider and the current construction of the ITER in France come to mind....


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