The strength of a cantilever bridge can be increased by the use of trusses. A truss is structure that consists of a number of triangles joined to each other. The triangle is an important component of many kinds of structures because it is the only geometric figure that can not be pulled or pushed out of shape without actually changing the length of one of its sides. By combining a number of triangles into a single unit, the unit is given a great deal of strength.
The cantilever beam, end beams, and joining beams in a cantilever bridge are often strengthened by adding trusses to them. The trusses act somewhat like an extra panel of iron or steel, adding strength to the bridge with relatively little additional weight. The open structure of a truss also allows the wind to blow through them, preventing additional stress on the bridge from this factor.
Trusses are used not only in cantilever bridges, but in all other kinds of bridges also. In fact, you have probably noticed the complex pattern of intersecting triangles on bridges over which you have passed. These truss patterns are one of the most efficient ways of adding strength to any type of bridge an engineer designs.