First, the deck carries the load of all the traffic on top of it. The deck can be supported by a variety of means. The smallest, simplest bridges (i.e. highway overpasses) carry the weight through the flexural (bending) strength of the steel or concrete underneath they deck. read more
A bridge supports loads by transferring the weight through trusses, cables, columns and anything else you see on a bridge. These channel the loads down into a medium that can usually take the load, either the bedrock or into foundations. read more
The most obvious way truss bridges support weight, or load, is to have some sort of solid deck spanning between two trusses, or possibly cantilevering from one truss. This deck can be a stiffened steel plate or solid reinforced slab, with transverse beams between the trusses. read more
The design of a truss, which is usually a variant of a triangle, creates both a very rigid structure and one that transfers the load from a single point to a considerably wider area. While truss bridges are largely a product of the Industrial Revolution, our next example, the arch, dates back much further in time. read more