I mean the steel structure above the piers, the piers or pillings are usualy concrete, and the footing of the bridge is usualy steel imbeded into the concrete. Where they merge however, you have to different materials joined, and that is usualy the weak spot. A meter or so up and you have all those stresses. The charge on the concrete pilling is more to cause a shacking of the bridge once its been damaged to help loosing up what has already been damaged or weakened by the prior explosives so that gravity can do its job.
Also, look at places where a steel pole is imbeded into concrete, there is always rust on the steel, again a weak spot that should be checked and exploited.
__________________
"God bless America, the land of the free, but only so long as it remains the home of the brave."
|