Bridges presentation
capitalized on the availability of cheap timber. When the American iron industry caught up with
Europe's by the mid-19th century, bridge building took the direction of composite pin-connected
trusses, with sophisticated castings for joint blocks and compression members, and forged eyebars
and wrought-iron rods for tension members, all fabricated to high tolerances. This allowed them to
be assembled easily and inexpensively in the field by unskilled labour using simple tools and
erection techniques. The system prevailed in the USA because that country lacked a skilled labour
force, and the remoteness of many bridge sites hampered the use of sophisticated machinery or the
shipping of large bridge parts over long distances. A spirited debate ensued between England and the
former colony during the last quarter of the 19th century over which system was best: easily erected
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