The Evolution of Bridge Technology
Historic bridges tell us about the people who built them,
what materials were available to them, and how they
thought about shaping and joining together those materials.
As such, a bridge is a direct reflection of the knowledge
and skills of its engineer or builder, and of the society and
culture that sponsored its construction.
The evolution of bridge technology in America is a story that
begins with colonial carpenters and masons building mostly
short-span bridges of timber or stone using traditional
methods. From 1800 to 1860, the growth in overland trade
and the introduction of turnpikes, canals, and railroads
prompted experimentation and investment in longer bridges
to span America's wide rivers. This led first to the
development of wood truss bridges, often covered with
siding and a roof to protect the load-carrying trusses,
and second to the use of iron for greater strength and
capacity. Along with these new bridge types came a rapid
growth in engineering knowledge and the establishment of
the first college programs to train professional engineers.
The second half of the nineteenth century saw the growth of
the bridge industry with hundreds of companies marketing
prefabricated, metal-truss bridges. These bridges, often
sold by catalogue, were pre-made in factories and shipped
to the bridge site for final assembly. They reflected an
amazing diversity and ingenuity of engineering, and a
distinctly American approach to bridge building.
During the first half of the twentieth century, the
automobile and truck brought about the need for highways
and bridges better suited to safe, high-speed, motorized
travel. The bridge-building materials of choice were
reinforced concrete and steel for economy, permanency,
and strength. The federal and state governments established
highway agencies with chief engineers who promoted the use
of standardized bridge designs in the development of state
highway systems. Most of North Carolina's historic highway
bridges date from the late 1910s to 1950s, and the era of
federal and state-sponsored improvements.
To further explore the types of bridges built in North
Carolina and their technology, search and click through the below titles.