page_title: Truss
section_title: Bowstring truss
hierarchical_section_title: Truss / Types / Bowstring truss
caption_attribution_description: English: The oldest metal bridge in Virginia. Located at the Ironto Rest Area off of US Interstate 81 north. This is an image of a place or building that is listed on the National Register of Historic Places in the United States of America. Its reference number is 12001136
context_page_description: A truss is an assembly of beams or other elements that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object". A "two-force member" is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes.
  In this typical context, external forces and reactions to those forces are considered to act only at the nodes and result in forces in the members that are either tensile or compressive. For straight members, moments are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes, as is necessary for the links to be two-force members.
  A planar truss is one where all members and nodes lie within a two-dimensional plane, while a space truss has members and nodes that extend into three dimensions.
context_section_description: Named for their shape, bowstring trusses were first used for arched truss bridges, often confused with tied-arch bridges.
  Thousands of bowstring trusses were used during World War II for holding up the curved roofs of aircraft hangars and other military buildings. Many variations exist in the arrangements of the members connecting the nodes of the upper arc with those of the lower, straight sequence of members, from nearly isosceles triangles to a variant of the Pratt truss.
caption: A bowstring truss is used on the oldest metal bridge in Virginia
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