bascule bridge
base metal
base plate
battered pile
bearing capacity
bearing failure
bearing pile
bearing pressure
bearing seat
bearing stiffener
bearing stress
bed rock
bench mark
bending moment
bevelled washer
bond stress
bowstring truss
box beam
box culvert
bridge deficiency
bridge pad
bridge site
brush curb
built-up member
buried pipe
buttressed wall
butt weld

back - see EXTRADOS

backfill - material, usually soil used to fill the unoccupied portion of a substructure excavation

backstay - cable or chain attached at the top of a tower and extending to and secured upon the anchorage to resist overturning stresses exerted upon the tower by a suspended span 

backwall - the topmost portion of an abutment above the elevation of the bridge seat, functioning primarily as a retaining wall with a live load surcharge; it may serve also as a support for the extreme end of the bridge deck and the approach slab backwater - the water upstream from an obstruction in which the free surface is elevated above the normal water surface profile

bank - sloped sides of a waterway channel or approach roadway, short for embankment

bascule bridge - a bridge over a waterway with one or two leaves which rotate from a horizontal to a near-vertical position, providing unlimited clear headway

base metal - the surface metal of a steel element to be incorporated in a welded joint; also known as structure metal, parent metal

base plate - a rectangular slab of steel, whether cast, rolled or forged, connected to a column, bearing or other member to transmit and distribute its load to the substructure

batten plate - a plate used in lieu of lacing to tie together the shapes comprising a built-up member

batter - the inclination of a surface in relation to a horizontal or a vertical plane; commonly designated on bridge detail plans as so many feet to one foot; see RAKE

battered pile - a pile driven in an inclined position to resist horizontal forces as well as vertical forces 

bay - the area of a bridge floor system between adjacent multibeams or between adjacent floor beams

beam - a linear structural member designed to span from one support to another

bearing - a support element transferring loads from superstructure to substructure while permitting limited movement capability

bearing capacity - the load per unit area which a structural material, rock, or soil can safely carry

bearing failure - a crushing of material under extreme compressive load

bearing pile - a pile which provides support through the tip (or lower end) of the pile

bearing pressure - the bearing load divided by the area to which it is applied

bearing seat - a prepared horizontal surface at or near the top of a substructure unit upon which the bearings are placed

bearing stiffener - a vertical web stiffener at the bearing location

bearing stress - see BEARING PRESSURE

bedding - the soil or backfill material used to support pipe culverts

bed rock - the undisturbed hard rock layer below the surface of the soil

bench mark - an established reference point used to document dimensions, elevations and movement

bending moment - the internal force within a beam which causes a bending effect

bent - a substructure unit made up of two or more column or column-like members connected at their top-most ends by a cap, strut, or other member holding them in their correct positions

berm - the line which defines the location where the top surface of an approach embankment or causeway is intersected by the surface of the side slope

bevelled washer - a wedge-shaped washer used in connections involving members with sloped flange legs, e.g. channels and S-beams

bituminous - a black sticky mixture of hydrocarbons obtained from natural deposits or from distilling petroleum

blanket - a stream bed protection against scour placed adjacent to abutments and piers

bolt - a mechanical fastener with machine threads at one end to receive a nut, and a hexagonal head at the other end

bolster - a block-like member used to support a bearing on top of a pier cap or abutment bridge seat; see PEDESTAL

bond - in reinforced concrete, the grip of the concrete on the reinforcing bars, thereby preventing slippage of the bars

bond stress - a term commonly applied in reinforced concrete construction to the stress developed by the force tending to produce movement or slippage at the interface between the concrete and the reinforcement bars

bowstring truss - a general term applied to a truss of any type having a polygonal arrangement of its top chord members conforming to or nearly conforming to the arrangement required for a parabolic truss

box beam - a hollow structural beam with a square, rectangular, or trapezoidal cross-section 

box culvert - a culvert of rectangular or square cross-section

bracing - a system of secondary members that maintain the geometric configuration of primary members

bracket - a projecting support fixed upon two intersecting members to strengthen and provide rigidity to the connection

breastwall - the portion of an abutment between the wings and beneath the bridge seat; the breast wall supports the superstructure loads, and retains the approach fill; see STEM

bridge - a structure spanning and providing passage over a river, chasm, road, or the like 

bridge deficiency - a defect in a bridge component or member that makes the bridge less capable or less desirable for use

bridge pad - the raised, leveled area upon which the pedestal, masonry plate or other corresponding element of the superstructure takes bearing by contact; also called bridge seat bearing area
bridge seat - the top surface of an abutment or pier upon which the superstructure span is placed and supported; for an abutment it is the surface forming the support for the superstructure and from which the backwall rises; for a pier it is the entire top surface

bridge site - the selected position or location of a bridge and its surrounding area

bridging - a carpentry term applied to the cross-bracing fastened between timber beams to increase the rigidity of the floor construction, distribute more uniformly the live load and minimize the effects of impact and vibration

brush curb - a narrow curb, 9 inches or less in width, which prevents a vehicle from brushing against the railing or parapet

buckle - to fail by an inelastic change in alignment as a result of compression

built-up member - a column or beam composed of plates and angles or other structural shapes united by bolting, riveting or welding

bulkhead - a retaining wall-like structure commonly composed of driven piles supporting a wall or a barrier of wooden timbers or reinforced concrete members

buoyancy - upward pressure exerted by the fluid in which an object is immersed

buried pipe - a subsurface structure that incorporates both the strength properties of the pipe and the support properties of the soil surrounding the pipe

buttress - a bracket-like wall, of full or partial height, projecting from another wall; the buttress strengthens and stiffens the wall against overturning forces; all parts of a buttress act in compression

buttressed wall - a retaining wall designed with projecting buttresses to provide strength and stability

butt weld - a weld joining two abutting surfaces by combining weld metal and base metal within an intervening space