Weather or not an object can be destroied in AH1 depends on what kind of object you make it. A structure can be destroied by either team, bombable only by nme and a barrier cant be destroied. A bridge can be any of these and still be usable as long as it has a rood, river or track under it. If its not over a water tile it doesn't need a road. Blowing it up will stop GVs from crossing and kill any GV that may be on it, but a convoy will still cross.