The blatantly easy way of doing it is a little crude, but very effective.
In your intro put a gamelogic at the base of one of the pillars and give it a name.
Then during your intro have a trigger, or script with this line;
bomb= "Laserguidedbomb" camcreate (Getpos GameLogic)
And there you have it. Its crude but it works wonders. When that line is called it will blow up the bridge into smithereens. More bombs and game logics for more pillars etc. There are much more elegant ways of doing it (without the game logics) but this way will work just fine.