ABSTRACT
Modern highway trusses are usually either continuous or cantilever bridges and are typically Warren trusses with or without verticals. By the mid-20th century, the Warren truss with verticals was a dominant form of truss configuration for highway bridges, and the Warren and K trusses were dominant in railroad bridges. The truss bridge behaves much like a closed box structure when it has several planes capable of resisting shear and end portals sufficient to transmit shear back into vertical loads at the bearings. The truss bridge is usually characterized by a plethora of bracing and wind-carrying members in addition to those members seen in front elevation. An influence line is a graphical presentation of the force in a truss member as the load moves along the length of the structure. If the truss is statically indeterminate, then the influence lines will be a series of chords to a curve, not a straight line.
