- A truss is an arrangement of structural members that are connected together to form a rigid frame work.
- Trusses have been used extensively in bridges since the early 19th Century.
- Truss bridges are usually categorized in two different ways according to the location of the deck and according to the orientation of the vertical and diagonal members.
- The Structural Stability of a truss is stable if all of its members are arranged in a network of interconnected triangles.
- The triangular arrangement of members ensures the rigidity of a truss structure.
- To fix an unstable truss, look for any "panel" of the structural model that is not a triangle, then add one or more members to transform that panel into a series of interconnected triangular shapes.
- Modern trusses are made of structural steel.
- Some other types of bridges include arch, suspension, cable-swayed, and beam.
- Dunlap’s Creek Bridge was the first iron bridge built in the United States.
- The bridge was a vital link in the newly constructed National Road, which was the first important road built with Government funds.
- Dunlap’s Creek Bridge consisted of five parallel cast iron tubes spanning 80 feet.
- Dunlap’s Creek Bridge was built by Captain Richard Delafield of the Corps of Engineering.
- Dunlap’s Creek was designated a National Historic Civil Engineering Landmark in 1978.
- Truss bridges are usually categorized in two ways depending on the location of the deck and orientation of diagonal and vertical members.
- The deck truss has its deck located at the top chord.
- A through truss has its deck located at the bottom chord.
- A pony truss is like a through truss, but not as high and has no lateral bracing.
- Truss configurations are based on orientation of members.
- A number of standard truss configurations are commonly used in bridge structures.
- These configurations are defined primarily by the geometry of their members.
- Three of the most common standard configurations are Howe, Pratt, and Warren trusses.
- These trusses are named after the 19th century engineers who developed them.
- The major components of a typical truss are verticals, chords, diagonals, floor beams, deck, pinned support, roller support, and abutment.
- Loads include the weight of a bridge and vehicles that are on them.
- Loads can also include weather, such as snow.
- These forces must all be considered when developing a bridge.
- Yield stress is the strength of a metal.
- The strength of a metal must be determined before building a bridge.
- Supporting structures, such as beams and wires, are used commonly in bridges.
