>>When a bridge fails it seems to me that it would not fail in such a catastrophic manner. One end or the other but not he length of the span. The center pylons everything is gone. It looks, to my untrained eye that it was blown up<<
That hasn’t occurred to me at all.
We should know THAT pretty soon this AM. Ay engineer should be able to determine that in a few minutes or even seconds.
For this kind of thing I have learned to wait until some info is available.
It might not take a very big bomb if placed right to cause a tremendous amount of damage in a pre-stressed concrete structure.