Quote:
Originally Posted by Reecemartin
Since Ive been trying to better understand what future construction will be needed to maintain the Expo Line I found this page on the concrete guideway structure used in the Millenium Line: http://www.cement.ca/en/Public-Transit/Skytrain-Millennium-Line.html
It turns out the guideway are designed to last 100 years (not sure where things would stand after that long). Would be interesting to see longevity estimates for the Expo Line to get an idea of the improvements made.
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Watch any documentary like "Life after People" or "Population Zero" to learn just how long concrete will last. It turns out that reinforced concrete has a much shorter lifespan than straight cement (portland cement, roman cement.) The really interesting part about it is that reinforced cement lasts forever until it gets wet.
So in our climate, it's very likely that things made out of reinforced concrete will disintegrate much faster than say... Nevada. However our stuff will last longer because we don't use as much road salt as the rest of the province or the country.
That said, 100 years is a relatively conservative measure. Since most of the Millennium Line is in the middle of road, while the Expo line is down a former rail ROW, the Expo line might actually last a little bit longer save for the initial segment down Terminal.
The key thing is maintenance. Concrete buildings don't last for 100 years primarily because they allow water to pool on the rooftops, thus the water gets into the concrete and then the rebar oxidizes and expands, destroying the concrete. I'd assume that the concrete used for the guideways is either more water resistant (given our climate) or has proper drainage so that water doesn't have time to soak into the concrete.
Even if the guideways only last 100 years, they can be replaced in pieces.
Compared with at-grade LRT's that aren't even designed to last 30 years. You run them into the ground and then have to replace the rails and LRV's even if you maintain the LRV's, because the capacity will need to be improved anyway.