If masonry is able to withstand the weather an order of magnitude longer than steel - wouldn't it make sense to reinvent masonry building techniques for building stuff that's expensive to close down? I get that labor cost is prohibitive for this kind of stuff - maybe we will see a renaissance of masonry once we have flexible enough robots to handle it?
I'm not an expert on this, but I wouldn't know of "stuff that is expensive to close down" relative to the extra costs of a masonry bridge.
Let's consider the Golden Gate Bridge as an extreme example (extreme because lots of traffic across it has no reasonable alternative routes). If we needed to replace it, we could build a replacement bridge next to it, connect roads, and then open them over a weekend with little disruption.
If we chose to shove the new bridge in place of the old one in a week or so, that would have to disrupt traffic, but I doubt it would be more expensive than building _and_paying_for_ 20+ piers instead of the two we have _now_ (looking at http://en.wikipedia.org/wiki/List_of_longest_masonry_arch_br..., we cannot build masonry spans over 100m. The arch bridge is the best we can hope for when using stone because stone isn't strong in tension).
Also, such a disruption, announced years in advance, need not be that much of a disruption. People will take a few days of, stay with friends or family, maybe a temporary camp will be set up, etc)
On the other hand, that Wikipedia page mentions that many 50m+ stone arches have been built in China since 1950.
The Golden Gate Bridge is actually a lot less critical than you might imagine. For a really critical bridge, consider the neighbouring San Francisco/Oakland Bay Bridge, which carries about twice the daily traffic. And in fact, the eastern span of the Bay Bridge was replaced last year.
The reason many stone and masonry structures are still standing is two-fold.
One: most of them are not impressive from a structural point of view. Two: most of them have been retrofitted so many times that they're hardly the "original" structure.
