The steel truss cantilever bridge was a major engineering breakthrough when first put into practice, as it can span distances of over 1,500 feet (450 m), and can be more easily constructed at difficult crossings by virtue of using little or no falsework.The engineers responsible for the bridge, Sir Benjamin Baker and Sir John Fowler, demonstrated the structural principles of the suspended span cantilever by sitting in chairs and supporting their colleague, Kaichi Watanabe, in between them, using just their arms and wooden poles.Steel truss cantilevers support loads by tension of the upper members and compression of the lower ones.Commonly, the structure distributes the tension via the anchor arms to the outermost supports, while the compression is carried to the foundations beneath the central towers.Many truss cantilever bridges use pinned joints and are therefore statically determinate with no members carrying mixed loads.
The structural principles of the suspended span cantilever bridge
The old eastern span of the
San Francisco–Oakland Bay Bridge
, pictured in August 2014, is deconstructed in an order nearly reverse that of its construction. Similar temporary supports were used under each anchor arm during the bridge's construction.