King Post Truss Bridge
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The Kingpost truss was adapted to
support the shorter bridge spans. It was probably first used with
small open-work bridges, and it represented quite an improvement
over stringer bridges, in which the trunks of trees were simply
thrown over a stream. In the Kingpost truss, a timber called the Kingpost, is in effect, suspended by its top end by two diagonal timbers whose ends are braced on the ends of the chord above the abutments on each stream bank. The center of the chord is suspended from the Kingpost. The weight of the bridge is transmitted to the ends of the chord through the Kingpost braces. The Kingpost braces are said to be in compression, squeezed between the chord-ends and the Kingpost by the weight carried by the Kingpost. The Kingpost, being stretched by the weight of the roadway and the outward thrust of the Kingpost braces, is said to be in tension. The chord is in tension as well, supported at the abutments and by the Kingpost and stretched by its own weight and the weight of the roadway. As long as the truss, its joints, and its timber members are strong enough to bear the stresses of compression and tension, the bridge will stand.
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King Post Truss Bridge built by Ian Galbraith (New Zealand) Top View |
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King Post Truss Bridge built by Ian Galbraith...in position on his layout. |
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See the sideshow "King Post Truss Bridge" |
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King Post Truss Bridge built by Ian Galbraith (New Zealand) for a friends layout. |
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