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2002, Bigelow Middle School, Engineering Technology Department



Bridge Truss Designs

Describing Factors
The four main factors are used in describing a bridge. By combining these terms one may give a general description of most bridge types.

  • span (simple, continuous, cantilever),
  • material (stone, concrete, metal, etc.),
  • placement of the travel surface in relation to the structure (deck, pony, through),
  • form (beam, arch, truss, etc.).

The three basic types of spans are shown below. Any of these spans may be constructed using beams, girders or trusses. Arch bridges are either simple or continuous (hinged). A cantilever bridge may also include a suspended span.
simple spans continuous spans
cantilever spans cantilever spans with suspended span

Comon Travel Surfaces
deck configuration
pony configuration
through configuration

Arch types
solid-ribbed tied arch, bowstring arch cantilever spandrel-braced arch
trussed deck arch brace-ribbed arch, trussed through arch
closed spandrel deck arch open spandrel deck arch


Simple Truss types  
kingpost truss
queenpost truss

Pratt Truss types
Pratt truss
Parker truss
Baltimore truss
Pennsylvania truss, Petit truss

Whipple Truss types
Whipple trapezoidal truss Whipple bowstring truss

Warren Truss types
Warren truss subdivided Warren truss
double Warren truss quadrilateral Warren truss

Other Truss types
Howe truss Howe truss with counter braces
Howe truss with timbers and iron rods lenticular truss, Pauli truss
Wichert truss Bollman truss
Fink truss cantilever spandrel-braced arch
cantilever through truss cantilever through truss, symetrical

Suspension types

The longest bridges in the world are suspension bridges or their cousins, the cable-stayed bridge. The deck is hung from suspenders of wire rope, eyebars or other materials. Materials for the other parts also vary: piers may be steel or masonry; the deck may be made of girders or trussed. A tied arch resists spreading (drift) at its bearings by using the deck as a tie piece.
suspension trussed arch
solid-ribbed arch, bowstring cable-stayed

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