I don't know why bridges are designed as they are. Most around here are
steel I-Beam frames on concrete forms. Perhaps they don't want heavy
rains to cause water or runoff from pouring down on whatever is under
the bridge .... like cars traveling at 70 miles per hour on a highway.
All I know is during the summer it is routine to see half of a highway
blocked off while a crew is sandblasting and then repainting the steel
frames of bridges. The only type of construction work on bridges in
Florida that I ever saw was new construction and changes to roadways.
Come to think of it, I never even saw any repaving being done although I
am sure it is done from time to time.
They resurface roads fairly often here,. We had a "lift" on the little
street in front of my house about 10 years ago and we are supposed to
be on the schedule for another one soon.
Maybe you didn't see the bridge maintenance because they do it from
under the bridge. One problem that causes the requirement for total
replacement is those prestressed concrete beams. They do OK until you
start getting salt water intrusion, then they are goners. There is no
easy way to swap them out. That is what happened to the Sanibel
Causeway. They just built another one.
On a lot of the roads, they rebuild the bridge as part of adding
lanes. They build the second span, divert to it and rebuild the old
one.
I also think part of the road maintenance problems are the "prevailing
wage" seems to be the highest amount ever negotiated by a union. Also
seems as if some technology is not allowed. When in Canada 10 years ago,
there was a company "asphalt recycling company" ARC that used an infra red
heater that took the asphalt roadway up, chopped it up, added a binder and
relaid the road. 4.5 lane miles a day. Here it takes a week to do a half
mile of road.
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