“For the same amount of effort, a terrorist with the ability to do this could have placed charges in an office building parking garage at night. Had a much lower chance of detection, been able to insure that the entire building collapsed and kill hundreds of people.”
I don’t understand why you (and others? it was way earlier) seem to think it’s easy to blow up a building, without all the knowledge of where best to put the charges.
I don't think it's easy, but neither is setting the charges for a bridge.