Girders

Girders that are fixed at one end and free at the other are called cantilevers, and with these it is usual to arrange pairs of cantilevers end to end so that they may balance each other. The Forth Bridge gives the finest example of the use of cantilevers, the spans being built of huge cantilevers 600 feet in length with their free ends pointing towards each other and arranged to carry a steel girder of the ordinary type between them. In the cantilever the bending stresses increase from the free extremity towards the fixed end. The booms are therefore made widest apart at the piers. [Bridges, article and plate.]