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Introduction to Bridges
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It is probable that primitive humans first discovered bridges by chance. Perhaps a river carving its way through an area formed a natural bridge.
Or maybe a vine became tangled in two separate trees, or a tree fell
across a stream. Whatever occurred,
it was observed and learned from.
The
American bridge builder and engineer, David Steinman, speculates that nature did
in fact provide the inspiration for the three major types of bridges—the
corbelled arch, beam and suspension bridge, and that prehistoric man had found
and used these. But
one day a superman, who possessed extraordinary intelligence for his day,
discovered that he was stranded without any of these bridges of nature to aid
him at a time when he needed one badly. In
a moment of brilliant thinking, he recalled the shape of such a structure—of,
for example, the tree-trunk kind—and therefore he asked himself why he could
not make or creates such a span. Over
a century earlier, Thomas Pope, writing his own history of bridges in the early
nineteenth century, commented:
That
Bridges were requisite in the earliest periods of time, we cannot doubt, from
the knowledge we possess of the common operations of nature. Seas, Lakes, Rivers, Brooks, and Swamps, must have existed formerly as
well as now; and man, in his common pursuits, must have invented means of
surmounting these obstacles to his correspondence with his fellow man, and
keeping up the chain of connexion so necessary to his existence, as well as to
his gratification.
We
know that certain natural bridges were formed, that sustained themselves by the
geometric principles of the arch. Such
bridges, as those formed in
By
the same token, ropes and vines were used for carrying people over ravines and
canyons. Perhaps someone first swung
from one point to another, and later kept the vine or rope attached to two
points so that cargo or persons could slide along from one end to the other.
Eventually, these supports would hold another vine or rope over which
people would walk, ultimately becoming a “roadway” in itself. Such may have been the origins of the suspension bridge.
The
Romans, while certainly not the originators of the arch (credit has been given
to the Babylonians for that), can fairly be said to have perfected its
application and principles. Some of
the stone arch bridges built by Roman engineers survive to this day.
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