Interior structure of a covered bridge that uses a queen-post structure
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Ancestor | Truss bridge |
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Related | None |
Descendant | None |
Carries | Pedestrians, , vehicles |
Span range | short to medium |
Material | wood planks |
Movable | No |
Design effort | medium |
Falsework required | Sometimes |
A queen post is a tension member in a truss that can span longer openings than a king post truss. A king post uses one central supporting post, whereas the queen post truss uses two. Even though it is a tension member, rather than a compression member, they are commonly still called a post. A queen post is often confused with a queen strut, one of two compression members in roof framing which do not form a truss in the engineering sense.
A queen-post bridge has two uprights, placed about one-third of the way from each end of the truss. They are connected across the top by a beam and use a diagonal brace between the outer edges. The central square between the two verticals is either unbraced (on shorter spans), or has one or two diagonal braces for rigidity. A single diagonal reaches between opposite corners; two diagonal braces may either reach from the bottom of each upright post to the center of the upper beam, or form a corner-to-corner "X" inside the square.