In architecture a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in forces in the members which are either tensile or compressive forces. Moments (torques) are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes.
A planar truss is one where all the members and nodes lie within a two dimensional plane, while a space truss has members and nodes extending into three dimensions. The top beams in a truss are called top chords and are generally in compression, the bottom beams are called bottom chords and are generally in tension, the interior beams are called webs, and the areas inside the webs are called panels.
The Forth Bridge is a cantilever railway bridge over the Firth of Forth in the east of Scotland, to the east of the Forth Road Bridge, and 14 kilometres (9 mi) west of central Edinburgh. It was opened on 4 March 1890, and spans a total length of 2,528.7 metres (8,296 ft). It is often called the Forth Rail Bridge or Forth Railway Bridge to distinguish it from the Forth Road Bridge, although it has been called the "Forth Bridge" since its construction, and was for over seventy years the sole claimant to this name.
The bridge connects Scotland's capital city, Edinburgh, with Fife, leaving the Lothians at Dalmeny and arriving in Fife at North Queensferry; it acts as a major artery connecting the north-east and south-east of the country. Described by the Collins Encyclopaedia of Scotland as "the one immediately and internationally recognised Scottish landmark", it is a Category A listed building and was nominated by the British government in May 2011 for addition to the UNESCO World Heritage Sites in Scotland.