Hello, Alan. Modern bridges in America do not have wooden structures over them. There are historic bridges, which we call 'covered bridges' that have roofs over them, to keep off rain, ice and snow. They are considered charming and quaint, rather like thatched cottages.

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A few months ago I read a book by Phillip Wearne called "Collapse: why buildings fall." I recommend it to everyone. It's on Amazon, or your library might have it. Mine did. It covered buildings, yes, but also bridges and a drilling platform.