Covered Bridge Terminology  
abutment - the structure that supports the end of the bridge or accepts the thrust of the Burr arch and supports and retains the bridge approach
approach - the road surface leading into the bridge
bolster beam - a timber between the abutment and truss which extends beyond the abutment. Commonly found in Town truss
camber - a built in, upward curve of the bridge
chord - the horizontal members, upper and lower, of a truss system extending from end to end
deck - the surface of the bridge that carries the traffic
floor beam - a transverse member between the trusses that supports the decking and live load
gabion - a galvanized wire box filled with stones used to form retaining walls along
a stream or bridge
parapet - a wall rising above the road level, usually as an upward extension of the wingwall
pier - structure(s) located between the abutments to support a multi-span bridge. Additional support to an existing span. It may be original or added later
portal - the opening at either end of a bridge, the face of that opening
post - a vertical member which is perpendicular or near perpendicular to the bottom chord
runners - lengthwise planks laid over crosswise planks in the tire track area of the bridge deck, probably added sometime after the invention of the automobile to reduce
noise from the loose planks
span - the horizontal distance between two supports of the bridge
trunnel, tree nail - a wooden peg, usually oak, used to fasten timbers in bridge building, sometimes 
replaced with galvanized steel bolts
wingwalls - extensions of the abutment which contain the fill of the approach
All Terminology information listed above comes from the book "Pennsylvania's Covered Bridges, A Complete Guide" by Benjamin D. Evans and June R. Evans

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