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Bridge Dictionnary
The ground
end-support of a bridge superstructure, especially to resist the
horizontal thrust of an arch and to connect bridges to its approach
ramps. May also be used to retain backfill material.
Anchor arm
The
side-span, usually of a cantilever bridge, from main pier to anchor
or abutment pier, balances the cantilever.
Anchorage
A secure
fixing, usually in mass reinforced concrete, at the extremity of a
side-span or anchor arm.
A rigid,
usually horizontal, structural element which may itself form an
entire bridge.
Bedrock
The solid
rock layer beneath sand or silt, especially in a river-bed.
Box-girder
A beam with
a hollow square or rectangular section.
Brittle fracture
The
fracture of steel elements at low temperatures or as a result of
embrittlement.
A bridge
whose deck is directly supported from pylons by straight cables
without vertical suspenders.
Cable
The staying
or suspending bridge element; in modern suspension bridges, the main
supporting cable is hung from towers, and from steel wire bound in
strands.
Caisson
A bridge
foundation, usually embedded in a riverbed by continuously digging
out the material within the bed, so that the caisson sinks.
Camber
A slight
convexity on the road surface. Also, shape given to a structural
member to offset its dead load deflection.
Cantilever
A
horizontal member fixed or continuous at one end and free at the
other.
Cantilever Bridge
A bridge
with rigid arms extending from both sides of a base, the inner ones
usually supporting a central span.
Carbon fibre
Very high-strength filaments of
near-pure carbon, suitable for reinforcement.
Cast iron
A brittle
alloy with high carbon content: high compressive strength, low
tensile strength.
Cement mortar
The mixture
of sand, cement, water and lime that binds masonry and brick.
Centre of mass
The point
of balance for any object. It's the key to structural stability. The
force of gravity pulling at a structure travels along a line through
the centre of its mass. If the resistance of the structure pushes
through this same line, then the forces are in balance and the
bridge will stay up.
Chord
The top or
bottom horizontal part of a truss.
Cofferdam
A
watertight structure allowing underwater foundations to be built in
the dry.
Composite construction
The use of
different materials, usually steel and concrete, together in a
single structure.
Compressed-air chamber
The space
at the bottom of a caisson, into which air is introduced under
pressure to exclude water so that excavation can take place.
Compression
The pushing
force which tends to shorten a member; opposite of tension.
Compression zone
The area
under compression in the upper part of a simply supported horizontal
beam.
Compressive strength
The ability
of a material to withstand compression.
Concrete
A mixture
of water, sand, stone and a binding element which hardens to a
rock-like consistency.
Counterweight
A component
of a moving bridge in which a balanced counterweight at one end of a
span falls, causing the deck to rise.
Creep
The slow
permanent deformation of material under long-term stress, as in
creep of concrete.
A
structure's own weight
Dressing
The cutting
of stone units to the required shape.
Temporary
sharing during construction.
Fender
A
protective enclosure around a pier structure.
Fill
The
material, usually rubble or earth, used to fill the space above or
behind the outer surface of bridge structure.
Flange
The flat
top and bottom plates of a rolled section or of a plate or
box-girder.
Formwork
Temporary
boarding, plywood
or steel forms to hold concrete in shape while it hardens.
Application by hot dipping or
electroplating of a protective layer of zinc to a metal, chiefly
steel, to prevent or inhibit corrosion.
Girder
A large
beam, usually steel or concrete which generally supports other
beams.
Glass fibre
A reinforcing material with high
tensile strength.
Granite
A hard
crystalline rock, suitable for masonry bridges.
A beam or
girder with an I-shaped cross-section.
A truss
consisting of a vertical post, connected to a horizontal beam by
inclined tie-beams or members.
Layers of
timber clamped or glued face-to-face.
Lift bridge
A form of
moving bridge in which a hinged counterweight at one end of a span
falls, causing the deck to rise.
Live load
The weight
of traffic passing over a bridge.
A bridge
superstructure that is moved to provide clearance for large ships to
pass, like a drawbridge.
The part of
a bridge with maximum clearance for shipping.
A bridge
deck which is stiffer in the direction of the span than it is
laterally. A steel orthotropic deck has a steel deck plate stiffened
with ribs or troughs.
Oscillation
The
movement, usually due to wind, of bridge deck or bridge component in
the wind.
An
intermediate support or the adjacent ends of two bridge spans.
Pneumatic caisson
A caisson
with a compressed-air chamber.
Portal
A frame
with side uprights connected by a horizontal member at the top.
Post-tensioning
The method
of making prestressed concrete elements with steel strands tightened
after the concrete has hardened.
Pratt truss
A patent
truss design with diagonals in tension.
Pretensioning
The method
of making prestressed concrete elements with steel strands under
tension as the concrete sets.
Prefabrication
The
manufacture of structural units in a factory, usually off-site.
Prestressed concrete
A more
efficient type of concrete with stretched steel strands embedded in
it to precompress the concrete allowing it to carry higher load.
Concrete
with steel bars or mesh embedded in it for increased tensile
strength.
The
destructive effect on submerged piers from fast-flowing water.
Shear forces
Any force
that tries to cut or slice structural parts of the bridge. A sheet
of paper undergoes a shear force when it is cut with a pair of
scissors.
Side-sway
The
movement of a structure from side to side in wind.
Soffit – Underside?
The
under-surface of any piece of structure.
Steel
An alloy of
iron with more carbon than wrought iron but less than cast iron,
combining the tensile strength of the former with the compressive
strength of the latter.
Suspender
The
vertical elements on a suspension bridge that links a cable with a
deck.
Suspension bridge
Has a
roadway supported by a deck that hangs from two main cables which
are attached to supportive towers. Although similar to a cable
stayed bridge, suspension bridges are different because their
roadbeds are suspended by two sets of cables (the two main cables
and the suspender cables which attach the road to the main cables).
This type of bridge can extend for well over 1 220 m (4 000 feet).
A beam or girder with a T-shaped
cross-section.
Tensile strength
The ability
of a material to withstand tension.
Tension
The pulling
force that tends to lengthen a member.
Torsion
The strain
produced by twisting.
Trusses
Highly
stable beams which form a network of triangles.
The
vertical plates of a girder.
Wrought iron
Soft and
malleable alloy with very low carbon content; low compressive
strength, high tensile strength.
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