| Abutment |
The ground end-support of a bridge,
especially to resist the horizontal thrust of an arch. |
| Aerodynamic stability |
The ability of a bridge deck to
withstand wind forces without damage from torsion, or oscillation: most
relevant to cablestayed and suspension bridges. |
| Aerodynamic deck |
A bridge-deck with a cross-section tapering
at each edge to provide aerodynamic stability. |
| Air-spinning |
A modern method of constructing suspension
bridge cables, in which wires are continuously unspooled back and forth across
a span and bound into strands. |
| Anchor arm |
The side-span, usually of a cantilever
bridge, from abutment to pier, balancing the cantilever. |
| Anchorage |
A secure fixing, usually in mass reinforced
concrete, at the extremity of a side-span or anchor arm. |
| Aqueduct |
A bridge or channel for conveying water,
often over long distances. |
| Aramid |
An artificial fibre whose exceptionally high
tensile strength makes it potentially suitable for very long
spans. |
| Arch |
A curved structural span. |
| Art Deco |
A decorative style of the 1920s and 1930s,
characterized by streamlined curves and geometrical forms. |
| Backspan |
See side-span. |
| Bar chain |
See eyebar. |
| Bascule |
A form of moving bridge in which a hinged
counterweight at one end of a span falls, causing the deck to
rise. |
| Batter |
An inclination from the vertical, as in the
sloping side of a bridge pier. |
| Beam |
A rigid, usually horizontal, structural
element which may itself form an entire bridge. |
| Bed joint |
The joint between the radiating elements of
an arch. |
| Bedrock |
The solid rock layer beneath sand or silt,
especially in a river-bed. |
| Bellman truss |
A patent design of overlapping wrought-iron
king-post trusses plus further diagonal suspension ties. |
| Bowstring arch |
An arch whose ends are linked to resist
outward thrust. |
| Box-girder |
A beam with a hollow square or rectangular
section |
| Brittle fracture |
The fracture of steel elements at low
temperatures. |
| Burr truss |
A timber design, combining king-post and
arch. |
| Cable-stayed bridge |
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
formed 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 su
rface. |
| Cantilever |
A horizontal member fixed 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. |
| Capital |
The head of a column in Classical
architecture. |
| 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. |
| Catenary |
The curve into which a uniform rope or cable
falls when suspended from two points, as in a suspension
bridge. |
| Cellular construction |
In early 20th century American suspension
bridges, the method of constructing towers from relatively small welded steel
box units. |
| Cement mortar |
The mixture of sand, cement, water and lime
that binds masonry and brick. |
| Centering |
A temporary framework over which arch
elements are assembled until they are self-supporting. |
| Chain |
The principal supporting element of a now
obsolete type of suspension bridge. |
| Chord |
The top or bottom horizontal part of a
truss. |
| Cladding |
The outer, usually nonloadbearing, surface of
a structure. |
| Clapper |
A prehistoric type of stone slab
bridge. |
| Cofferdam |
A watertight structure allowing underwater
foundations to be built in the dry. |
| Colonnade |
A series of regularly spaced
columns. |
| Composite construction |
The use of different materials together in a
single structu re. |
| 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 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. |
| Corbelling |
Successive layers of masonry or brick
projecting beyond each other. |
| Corinthian |
A Classical architectural style, with leafy
decoration at column-heads. |
| Corne de vache |
A decorative feature in masonry bridge
design, involving shaving the lower curving edge near the springing of an
arch. |
| Counterweight |
See bascule. |
| Creep |
The slow permanent deformation of material
under stress, as in shrinkage of concrete. |
| Creeper crane |
The cranes used for building a steel
cantilever bridge, moving slowly along the upper chord. |
| Crown |
The highest part of an arch. |
| Cutout |
The non-structural material removed from a
spandrel, as in Maillart's bridges. |
| Cutwater |
The end of a pier-base, pointed to cleave the
water. |
| Dead
load |
A structure's own weight. |
| Deflection theory |
An early 20th-century theory that very long
suspension bridges would remain stable without deep stiffening trusses through
a balance between flexibility and self-weight. |
| Doric |
A Classical architectural siyle, with no
decoration at column-heads. |
| Dovetail |
A splayed piece of timber (or iron or stone)
fitting tightly into a similarly shaped cutout. |
| Drawbridge |
See bascule. |
| Dressing |
The cutting of stone units to the required
shape. |
| Dry-stone |
Masonry laid without
mortar. |
| Elliptical
arch |
An arch with a curve that becomes tighter
towards the crown. |
| Entablature |
In Classical architecture, the element that
rests upon the capitals of the columns. |
| Environmental load |
The external forces on a structure, such as
wind and water. Extrados The outer surface of the curve of an
arch. |
| Eyebar |
The unit from which the chain of early
suspension bridges was constructed, with a flattened ring at each end for
linkage. |
| Falsework |
Temporary scaffolding during
construction. |
| Fan configuration |
A cable-stayed bridge design in which the
cables fan outwards as if from the handle of a fan. |
| Fender |
A protective enclosure round a pier
structure. |
| Fill |
The material, usually rubble or earth, used
to fill the space behind the outer surface of a masonry bridge
structure. |
| Fin-back bridge |
A very modern bridge type in which a vertical
solid plane of prestressed concrete supports the spans above the
deck. |
| Fink truss |
A patent design of overlapping wrought-iron
king-post trusses with additional diagonal bracing. |
| Flange |
The flat top and bottom plates of a
box-girder. |
| Formwork |
Temporary boarding to hold concrete in shape
while it hardens. |
| Galvanizing |
The coating of metal with zinc for
waterproofing. |
| Girder |
A large beam, usually steel or
concrete. |
| Glass fibre |
A reinforcing material with high tensile
strength. |
| Gradient of stress |
The theoretically uniform change from purely
compressive forces along the top of a beam to purely tensile along the
bottom. |
| Granite |
A hard crystalline rock, suitable for masonry
bridges. |
| Hanger |
See suspender. |
| Harp configuration |
A cable-stayed bridge design in which cables
radiate at a uniform distance from each other throughout their
length. |
| Haunch |
The part of an arch between the springing and
the crown. |
| Horizontal thrust |
The tendency of an arch to push
outwards, |
| Howe truss |
A patent design with vertical iron tension
rods. |
| I-beam |
A beam or girder with an 1-shaped
cross-section. |
| Intrados |
The inner surface of an arch ring. lonic A
Classical architectural style with scroll decoration at the
column-heads. |
| Jack-knife
bridge |
A form of moving bridge with a deck that
hinges upwards at the centre. |
| Keystone |
The voussoir at the crown of an
arch. |
| King-post truss |
A truss consisting of a vertical post,
connected to a horizontal beam by inclined tie-beams. |
| Laminated
timber |
Layers of timber clamped or glued
face-to-face. |
| Lift bridge |
See bascule. |
| Lime mortar |
A non-waterproof binding material for
masonry, consisting of lime, water and sand. |
| Limiting span |
The maximum span possible for each particular
type of bridge. |
| Live load |
The weight of traffic passing over a
bridge. |
| Long truss |
A patent timber design based on overlapping
king-post trusses. |
| Mortar |
See lime mortar and cement
mortar. |
| Mortice |
A slot in a member, into which a projecting
tenon is fixed to form a joint. |
| Navigation
span |
The part of a bridge with maximum clearance
for shipping. |
| Ogival
arch |
A pointed arch |
| Orthotropic deck |
A bridge deck which i stiffer in the
direction of the span th it is laterally. |
| Oscillation |
The movement, usually vertically, of a
suspended bridge deck in the wind. |
| Pier |
The support between two bridge spans, usually
arches. |
| Pinned arch |
An arch with hinges at the abutments and
sometimes also at the crown. |
| Plate girder |
A flat bridge deck with a shallow rectangular
section. |
| Pointed arch |
An arch with an angle at it~
crown. |
| Pneumatic caisson |
A caisson with a compressed-air
chamber. |
| Pontoon bridge |
A bridge formed from floating units,
sometimes boats, tied together in a series. |
| Portal |
Aframe with side uprights connected by a
horizontal member at the top. |
| Post-tensioning |
The method of making prestressed concrete
with steel strands tightened after the concrete has hardened. |
| Pozzolana |
The volcanic dust first found at Pozzuoli,
with which the Romans made waterproof concrete. |
| Pratt truss |
A patent truss design with iron diagonals in
tension. |
| Pre-tensioning |
The method of making prestressed concrete
with steel strands under tension as the concrete sets. |
| Prefabrication |
The manufacture of structural units in an
off-site factory. |
| Prestressed concrete |
A modern type of concrete with stretched
steel strands embedded in it to impart additional tensile
strength. |
| Pylon |
The vertical structural element from which
stays radiate in a cable-stayed bridge. |
| Reinforced
concrete |
Concrete with steel bars or mesh embedded in
it for increased tensile strength. |
| Ripple |
The undulating motion of a suspended deck
caused by wind. |
| Scour |
The destructive effect on submerged piers
from fast-flowing water. |
| Segmental arch |
An arch formed from a segment of a
circle. |
| Semi-circular arch |
An arch forming a complete
half-circle. |
| Semi-fan configuration |
A style of cablestayed bridge midway between
the fan and harp. |
| Shear |
The force acting across any beam or
structural unit. |
| Side-span |
The outer suspended section of a suspension
bridge from the tower to the anchorage, balancing the central
suspendedspan. |
| Side-sway |
The movement of a suspended bridge deck from
side to side in wind. |
| Soffit |
The under-surface of any piece of
structure. |
| Spandrel |
The area of an arch bridge above the extrados
and below deck level. |
| Springing |
The point where the end of an arch meets the
abutment. |
| Starling |
The usually boat-shaped foundation for a
masonry pier. |
| 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. |
| Stiffening truss |
A truss usually beneath the entire deck of a
suspension bridge. |
| Strand |
A unit within a suspension bridge cable,
itself formed from many individual wires. |
| Striking |
The action of removing formwork, particularly
centering, from beneath a completed arch. |
| Suspender |
The vertical or zig-zag element on suspension
b~idges that links a cable with a deck. |
| Suspension bridge |
A bridge with its deck supported from above
by large cables or chains hanging from towers. |
| Swing bridge |
A type of moving bridge in which the deck
pivots sideways. |
| T-beam |
A beam or girder with a T-shaped
cross-section. |
| Tenon |
A projecting piece of a member that fits into
a mortise cut in another to form a joint. |
| Tensile strength |
The ability of a material to withstand
tension. |
| Tension |
The pulling force that tends to lengthen a
member. |
| Tied arch |
See bowstring arch. |
| Torsion |
The strain produced by
twisting. |
| Tower |
The vertical element in suspension bridges
from which cables are hung. |
| Town truss |
A patent truss design forming a wooden
lattice. |
| Transporter bridge |
A type of moving bridge in which a travelling
gondola is suspended from an overhead frame. |
| Trapezoid |
A four-sided figure with one pair of parallel
sides. |
| Travertine |
A pale form of limestone. |
| Truss |
A frame of members in tension and
compression. |
| Tuned mass damper |
A counterweight to subdue a bridge deck's
tendency to vibrate. |
| Voussoir |
The wedge-shaped units, usually stone, from
which an arch is formed. |
| Web |
The side-plates of a box-gird
r. |
| Whipple truss |
Several patent designs by Squire Whipple: the
most characteristic was a bowstring, with a curved cast-iron upper chord and
lower members of wrought iron. |
| Wire cable |
See cable. |
| Wrought iron |
Soft and malleable alloy with very low carbon
content; low compressive strength, high tensile strength. |
| Zig-zag
bridge |
Traditional Chinese bridge type, with deck
elements at right angles to each other. |
| Zig-zag suspension |
The arrangement of suspension bridge cables
first introduced on the Severn Bridge, as differing from vertical
suspenders. |
