Cantilever

A cantilever is a structural element fixed to a support at only one end and left unsupported at the other, often projecting outward from a vertical wall. It can take the form of a beam, a plate, a truss or a slab, and when a load is applied at its free end the cantilever carries that load back to its support by developing shear stress and a bending moment along its length. Cantilever construction lets a structure overhang open space with no external support beneath it, which is why the form is common in cantilever bridges, balconies and corbels. The Forth Bridge in Scotland is a well known example of a cantilever truss bridge, built as a pair of cantilevers each supporting one end of a central connecting span. In traditional timber framed building a cantilevered upper floor projecting past the floor below is called a jetty or forebay, and the southern United States has a historic barn type, the cantilever barn, built the same way in log construction. Cantilevers are also used temporarily during construction, letting a bridge be built out from each bank over a river or valley where falsework cannot be placed underneath, with the two advancing cantilevers finally jacked together and joined under compression.