absolutely ...
but either mistakes in design OR improper construction OR improper materials OR unaccounted corrosion/lack of proper maintenance can lead to a failure.
My guess would be improper materials or corrosion/lack of maintenance.
In the 1980’s (early) - a 30 - 40 year old bridge span in Connecticut, part of I-95, fell into a river - and IIRC - it was poor maintenance (or marginal design combined with poor maintenance) that lead to the failure.
Mike, PE
“but either mistakes in design OR improper construction OR improper materials OR unaccounted corrosion/lack of proper maintenance can lead to a failure.”
You are absolutely correct. These things can all happen, and do...just not often. As you know, design goes through many levels of approval, construction methods are inspected by PEs, a percentage of all steel materials from the warehouse or mill are inspected for bad spots, and all specs and general notes have guidelines for storage and handling of all material. Again, you are right, one of these things could happen, I just don’t want people to think that the load of gridlock traffic isn’t taken into consideration when designing a bridge.
Do me a favor, after looking at the long shot:
Try to explain to a know-nothing non-engineer like myself, how the physics would work. I understand one side of the bridge automatically would drop the other; I even get the pulling in or slanting out of the two sections right before the river; but that far back with both branches above the ground intact? Could it be those sections were updated that still stand above ground yet those arched over the water were old (with an old type of iron work... maybe rust as well)? Just seemed like a strange place for the momentum to stop.