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Glossary of Bridge Terminology



Fabrication: The act or process of framing and fitting rolled steel shapes for structures. The putting together of parts of a structural steel construction and riveting them.

Facade: An elevation or exterior face of a building, usually the front or chief face.

Face: A plane, exterior face of a solid. The front view or exposed part. The working or cutting portion of a grinding-wheel, or the edge of any cutting tool. To prepare or polish a face.

Face of Gear Tooth: The part of the rolling surface of a gear tooth outside the pitch circle.

Face Wall: An exposed wall, a front wall.

Faced Joint: A joint in which the adjacent faces have been planed. Also a voussoir joint that shows on the face of an arch.

Facing: A layer of earth, turf, or stone laid upon the sloping sides of a railroad embankment or other inclined earthwork in order to protect the exposed surface and to give it a steeper slope than generally is natural.

Facing Brick: Brick suitable for the exterior of constructions where a neat finish is required.

Factor: One of the two or more numbers, expressions, or quantities which multiplied together form a given product.

Factor of Safety: Same as "Safety Factor." -- The ratio of ultimate load to the greatest allowable working load. This term is losing favor with engineers, as its use has been abused. There is no such thing as a factor of safety for a well proportioned bridge, for each member should have an intensity of working stress proportional to the character and amount of work which it has to perform. This is best accomplished by adding to the live load stress a certain varying proportion thereof to allow for the effect of impact.

Fall Blocks: Pulley-blocks used with ropes or "fall-lines."

Fall Line: A rope or steel cable used with pulley-blocks in hoisting.

Fall Line Ball: A heavy iron ball with two projecting staples for attaching to the movable block of a hoisting tackle to overhaul the lines when no load is carried.

Falls: The ropes used with pulley blocks in hoisting.

False-bottom: A movable, horizontal partition inserted in the lower part of a box, shell, bucket, etc.

False Cap: A cap on a column below the true cap. Also a construction to make an intermediate portion of a structure look like the top.

Falsework: The scaffold or temporary supports employed for erecting a structure. Usually a temporary timber trestle sustaining a bridge during erection.

Falsework Bolts: Any bolts used in tying wooden bracing to posts or piles.

Falsework Cap: Any cap used in falsework.

Falsework Pile: A pile driven temporarily as a part of the falsework used during the erection of a span.

Fan-tail Joint: Same as "Dovetail." -- A manner of making joints by having a series of projections in one piece fitting into corresponding recesses in another piece. A joint in carpenter work. It is a poor joint in timber where much stress has to be provided for. The shape of the tongue of the joint is like that of the spread tail of a dove.

Fascia: Any flat member or moulding with but little projection, usually the outermost portion.

Fascia Girder: A longitudinal girder at the extreme edge of a structure so finished as to present a neat appearance.

Fascine: A bundle of brush wired together and used in the construction of river protection work to prevent the washing away of the banks. Similar to "Babies."

Fast Joint: Any joint held fast by means of the addition of one or more bolts.

Fast Pulley: A pulley which is fastened to its shaft.

Fastening Angle: Same as "Connecting Angle." -- An angle-iron used for connecting two pieces.

Fat Lime: A lime rich in protoxide of calcium.

Fatigue of Metals: The doctrine which states that repetitions or reversals of stress, when excessive, cause a deterioration of the metal. Strictly speaking, it does not apply at all to bridgework.

Faucet: A device fixed in a receptacle or pipe to control the flow of liquid.

Feather: A longitudinal, projecting guide on a shaft. One of the two tapered pieces of metal placed in a hole in conjunction with a plug, used for splitting rock.

Feather and Wedge: A single feather combined with a wedge, used in quarries for splitting rock.

Feather-edge: Any edge that is thin and sharp like a feather. The edge of a board that is thinner than the other.

Feather-edge Brick: Same as "Compass Brick." -- A brick having one edge shorter than the other. Used in lining shafts, etc.; also called "Voussoir brick."

Featherstone Dredge: One of the many types of dipper dredges.

Feed Water Pump: Same as "Donkey Pump." -- A feed pump for boilers.

Felloe: The circular rim of a wheel into which the outer ends of the spokes fit.

Felloe Plank, or Felly Plank: A guard rail on a roadway, so placed as to catch the felloe of a wheel and thus prevent the vehicle from striking the truss. In wide bridges, a felloe plank is often placed midway between the trusses, to prevent vehicles passing from one side to the other.

Felly: Same as "Felloe."

Felly Plank: Same as "Felloe Plank."

Felt: An unwoven fabric of short hair or wool matted together by rolling. Used for waterproofing by applying pitch.

Female Joint: The socket of a spigot and faucet joint.

Female Screw: A hollow cylinder having an interior thread. A nut.

Fender: A guard for protection. Vertical timbers, piles, etc., to protect vessels from striking, rubbing, and scarring piers.

Fender Pile: A pile which is driven at wharfs, or in front of large masonry structures or other important works, to protect them from sudden blows by vessels.

Fiber or Fibre: The longitudinal filament of a body.

Fibre Stress: The stress on an elementary fibre, strip, or element of a member.

Fibrous: Containing or consisting of fibres.

Fibrous Fracture: A fracture that shows the broken ends of fibres.

Fibrous Iron: An iron having a fibrous texture.

Fibrous Stroked Dressing: A stroked dressing in masonry in which the flutings are made wavy and like fibres in appearance.

Field Rivet: A rivet driven in the field during the erection of a steel structure.

Field Work: Surveying and kindred operations in the field.

Field-book: A book containing any field records.

Fiery: The character or quality of steel as exhibited by its fracture when the grains are very coarse and bright.

Fiery Steel: Burnt steel showing very coarse, bright grains when fractured.

File: A collection of papers arranged in order. A receptacle for holding papers. A rough steel hand-tool used for reducing or smoothing metals, wood, and other resistant materials. To cut or wear away a portion of an object by the application of a filing tool.

Fill: To occupy with material so as to leave no space empty. An embankment behind an abutment. Any railroad embankment.

Filler: A plate the sole function of which is to fill up space. Anything that serves to fill up a vacancy.

Filler Plate: A plate used to fill open spaces under members or parts thereof

Fillet: A plain, narrow, flat moulding in a cornice or a corner. The rounding of a sharp corner.

Filling: The material in an embankment or that put back into an excavation.

Filling Pile: A form of concrete pile made by first forming a hole in the ground with a mandrel and, after withdrawing it, filling the hole with concrete.

Fin: A thin projection on a surface of a casting caused by the imperfect contact of the two moulding flasks each containing a part of the mould. A small, thin projection on the rolled surface of any metal, especially at the edges thereof.

Final Set, or Hard Set: The degree, of hardening of cement mortar as determined by the non-penetration of the Vicat needle.

Fine Pointed Dressing: A type of stone dressing in which the surface left by rough pointing is reduced to a degree of smoothness such that no part projects more than a quarter of an inch beyond the pitch face.

Fine Sand: A sand containing more than thirty per cent of particles that will pass a No 40 sieve. Usually undesirable for concrete.

Fineness: The relative size of the particles of cement, sand, or other materials.

Finish: The condition of a surface after the final work upon it has been performed. To complete anything.

Finishing Stakes: Final stakes set for the completion of the work.

Fink Truss: Properly, a trussed beam. See Fig. 22n.

Fig. 22n

Fire Brick: A brick made of pure clay (or pure clay with a clean sand) to resist high temperatures.

Fireless Locomotive: A locomotive driven by steam generated from highly heated water carried in strongly constructed tanks.

First-class Masonry: A term applied to quarry-faced ashlar, laid in regular horizontal courses, having parallel beds and vertical joints, of not less than ten inches in thickness nor more than thirty, and decreasing in thickness regularly from the bottom to the top of the wall. For complete specifications, see "Baker's Masonry."

First Cost: The sum of all the expenditures made for investigation, promotion, engineering, and construction of a structure, plant, etc.

Fish: To join two beams by fastening long splice-pieces to their sides.

Fish Bellied Girder: A girder having the top flange horizontal and the bottom flange curved in the shape of a fish's belly.

Fish-belly: The form taken by some girders or trusses where the bottom flange or chord is convex downward. To swell downward.

Fish Bolt: A bolt for securing a fish joint.

Fish Joint: A joint between two rails connected by fishplates bolted thereto.

Fish Plate: Same as "Splice Bar." -- The short bar used for making the joints in railroad rails.

Fishbolt: Same as "Fish Bolt."

Fishing: The act of uniting two parts by clamping them between two short pieces which cover the joint.

Fitting-up: Assembling the different members of a structure and connecting them with bolts preparatory to riveting.

Fitting-up Bolt: An ordinary bolt used to hold steel members together while the same are being riveted.

Fitting-up Clamp: An ordinary screw clamp, used for fitting up instead of bolts.

Fitting-up Gang: A gang which does the bolting up of the metal in a bridge shop.

Fixed Bridge: One that does not move except for expansion and contraction

Fixed Charges: The annual expenditure, in connection with a structure, which remains the same, or nearly so, regardless of operation. Generally refers to the interest on the bonded indebtedness.

Fixed End: The anchored end. An end of a girder or strut so firmly connected as to prevent all motion in the vicinity of the end.

Fixed Load: Any determined load.

Fixed Point: Any point that is stationary or assumed to remain fixed throughout the entire discussion. The common centre of gravity of a system of bodies.

Fixed Post: A post having fixed ends.

Fixed Span: A span that is not movable, in contradistinction to a draw span.

Flange: One of the principal longitudinal members of a girder which resist tension or compression, also sometimes called the upper and lower chords of a beam. A projecting edge, rim, or rib on anything.

Flange Angle: One of the upper or lower chord angles in a girder.

Flange Coupling: A coupling made up of two parts, each firmly attached to the end of its shaft, bolted together to form a permanent connection.

Flange Joint: A joint between two pieces or members terminating in flat disks or flanges which are usually held together by bolts. Used for shafting and pipes.

Flange Plate: Same as "Cover Plate." -- A plate fastened on the flanges of a girder to give additional cross-section thereto; a top or bottom plate of a chord member.

Flange Rail: A rail having on one side an elevated edge or flange to keep the wheels from running off.

Flange Splice: A splice made in the flange of a beam or girder.

Flange Stress: The stress developed in the flange or flanges of a member.

Flange Union: A type of pipe connection consisting of two circular plates with hubs bored and tapped to screw on the ends of the pipes, and held together with bolts.

Flank of Gear Tooth: The part of the rolling surface of a gear tooth inside the pitch circle.

Flap Valve: Same as "Check Valve." -- A valve arranged to permit a flow in one direction only, thereby preventing the return of the fluid.

Flashing Angle: An angle to which flashing is attached.

Flashing Point: The temperature at which escaping gas will ignite momentarily.

Flashings: Broad strips of sheet metal used at the joints of a wall so as to lap over gutters, chimneys, etc. Also strips worked in under the slates or shingles around dormers, chimneys, and any rising part, to prevent leaking.

Flasks: The upper 'and lower parts of a box which contain the mould into which molten metal is poured.

Flat: The broad side of anything. Any rectangular iron or steel bar having a greater width than thickness. A level stretch of ground near a stream.

Flat Arch: An arch in which the intrados is straight; an arch of low rise.

Flat Dolly: A hammer headed dolly, flat on both faces for flattening rivet-heads.

Flat File: A thin file flat on the two opposite faces.

Flat-head: A rivet or bolt head that has been flattened.

Flat-head Rivet: A rivet which has the point hammered flat instead of rounding.

Flat Rasp: A rasp having a narrow, rectangular cross-section.

Flat Reamer: A tapered, flat bit with chisel cutting edges.

Flat-rope Pulley: A pulley having a flat face, but with flanges at the edges, over which passes a flat rope.

Flat Scale: A scale made on a flat stick, strip of metal, or cardboard. Hammer Scale: A scale of oxide which forms on bars when heated.

Flat Wood File: A coarse-cut, flat file for using on wood.

Flattening: Causing painting to have a dead or dull finish instead of a glossy one by using turpentine instead of oil in the last coat.

Fleet: To swing into place by means of a horizontal, subsidiary tackle, a bridge member when it has to be picked up by the main tackle from a position not directly under the support of the main tackle.

Fleeting Tackle: A horizontal subsidiary tackle used in connection with the main hoisting tackle to fleet members into place.

Flemish Bond: A bond consisting of a header alternating with a stretcher in each course, but so placed that the outer end of each header lies on the middle of a stretcher in the course below.

Flemish Brick: A species of hard yellow brick used for paving.

Flexible Joint: A joint permitting motion between the parts.

Flexure: Bending.

Fliers: A straight flight of steps in a stairway.

Flight: A continuous series of steps connecting two different levels.

Flitch: A plank or slab, especially one of several planks fastened side by side to form a compound beam. To join planks in order to make such a beam.

Flitch Beam: A compound wooden beam strengthened with a "flitch plate."

Flitch Plate: A plate in a compound wood and steel beam.

Flitched Beam: Same as "Flitch Beam."

Flitched Girder: Same as "Sandwich Girder." -- A girder or beam having an iron or steel plate inserted between two wooden beams and rigidly bolted thereto.

Float Finish: A finish on cement work made by floating grout over the surface with a straight edge.

Floated Surface: A surface made on cement or concrete work while wet by rubbing with a smooth board.

Floater: A term used for a bridgeman who works a few days on one job and then moves to another.

Floating Bridge: Same as a "Boat Bridge" or a "Pontoon Bridge."

Floating Derrick: A movable derrick erected on a special boat, barge, or vessel.

Floating Pier: A term applied to a pier sunk to a great depth in a soft, yielding, or semi-fluid soil and depending for stability on the principle of flotation.

Floating Pile Driver: A pile driver mounted and operated on a scow or barge.

Flogging Hammer: A very large hammer used with a flogging chisel for chipping iron castings.

Floor or Flooring: That part of a bridge which directly receives the travel.

Floor-beam: A transverse beam or girder placed at the panel points of a span to support the stringers which carry the floor.

Floor-beam Concentration: The load transferred from one line of stringers to a floor-beam.

Floor Bolt: A bolt used in the construction of a floor.

Floor Girder: Any girder which supports a portion of the floor and its load.

Floor Plank: A plank used in the flooring of a highway bridge.

Floor Space: The area of a floor.

Floor Spike: Any spike used in putting on flooring.

Floor System: The system of members in a bridge that carries the floor and its load.

Flooring: Same as "Floor." Also planks used in floors.

Flour of Lime: Air-slaked lime reduced to the consistency of flour.

Flow (of liquids): A continuous passing of a liquid. A current.

Flow (of solids): The permanent change in relative position of the elements of a solid subjected to great pressure.

Flume: A moderate-size ditch or channel for conducting water.

Flush: To make one part even or level with another. To wash by turning on a sudden dash of water.

Flush (with mortar): Same as to float Also to throw rich grout onto old concrete before pouring new concrete on.

Flush Joint: A masonry joint filled with mortar and pointed. Also a butt joint not projecting beyond the general level.

Fluted: Grooved or furrowed.

Fluted Drill: A drill having two longitudinal grooves or flutes on opposing sides.

Fluted Reamer: Same as "Common Reamer."

Fluting: The system of longitudinal grooves in a pilaster or column.

Flux: To convert to a liquid state by means of heat; to melt. A substance that promotes the fusion of minerals or metals. The process of melting. Fusion.

Fly Wheel: A heavy, revolving wheel for equalizing motion in machinery.

Flying Buttress: A support in the form of a segment of an arch springing from a solid mass of masonry.

Flying Falsework: A type of falsework used in the erection of large cantilever bridges. It consists of a horizontal truss, lying in the plane of the lower chord, with a set of heavy girders under each of its own chords in order to furnish a bearing for the jacks to work against. Each side of its flying end is hung by two ties, consisting of eye-bars, which are in turn attached to the last subpanel point erected. The rear end of this flying falsework is supported by the pier for the first panel erected and then by the last bottom chord panel point for succeeding panels.

Flying Level: A hasty, preliminary leveling over a proposed route.

Folding Bridge: Same as "Jack-knife Bridge."

Foliated Granite: Same as "Gneiss."

Follower: Any cog that is driven by another. A temporary piece of pile or timber set above a pile that is to be driven below the leads of the pile-driver.

Foot Block: A heavy casting which supports the mast in a derrick, and permits of its turning.

Foot Bridge: A bridge for foot passengers only.

Foot Hammer: A machine hammer operated by a treadle.

Foot-pound: A unit of work equal to that involved by the raising of a weight of one pound one foot high. Also used as a unit of bending moment in which case it is equal to a force of one pound multiplied by a lever arm of one foot. This latter unit is called by some authorities "pound-foot,".

Foot-pound Second: A unit of power, or rate of doing work, equal to raising one pound one foot high in one second.

Foot-ton: A unit of work equal to that involved in overcoming one ton of resistance through the space of one foot, or in raising one ton one foot high.

Foot-walk: A sidewalk for pedestrians.

Foot Wall: A low wall at the foot of an embankment.

Footing: The spreading course at the base of a foundation.

Footing Beam: The tie-beam of a roof.

Footing Course: The bottom course of masonry at the base of a foundation.

Force: That which moves or tends to move matter. The action between two bodies either causing or tending to cause change in their relative rest or motion.

Force Diagram: A diagram in which the amounts and directions of forces are represented by lines for the purpose of finding their resultant.

Force Polygon: A polygon used in graphic statics to determine the magnitude and direction of the resultant of a system of forces. The sides of the polygon are made parallel to and equal in length to the forces. The closing line represents the magnitude and direction of the resultant.

Force Triangle: A system of three forces in equilibrium represented by three sides of a triangle drawn parallel and with lengths proportional to the respective forces.

Foreman: A man who directs the work either in person or through his sub-foremen.

Foresight: A forward observation made with a surveyor's instrument. A fixed object in the front which is sighted upon from time to time to cheek the orientation of the instrument.

Forge: To work wrought iron into shape by first softening by heat and then hammering into required form. The apparatus or furnace in which the iron is heated before being worked.

Forge Hammer: A hammer used for breaking and trimming rocks.

Forge Iron: An inferior grade of iron used for puddling.

Forge Pig: An inferior grade of iron used for puddling and for some classes of foundry work.

Forge Shop: A shop in which forgings are made.

Forging: The process of welding metal or that of bringing it to shape when hot by hammering. Also the article made by a forging process.

Forked Drill: A Slotted tool with a forked point used in a slot drilling machine.

Forked-end: The end of a bar, wrench, truss member, etc. which is separated into two or more projecting parts like the tines of a fork.

Forked Wrench: A wrench having a pair of jaws at one end of a bar, while the other end tapers to a point.

Form: A shape or mould. A figure described by lines and surfaces. A temporary wooden or metallic structure for giving concrete a desired shape.

Former: A device for giving a particular shape to an article.

Forming Iron: A blacksmith's swage block.

Formula: Any general equation; a rule or principle expressed in algebraic symbols.

Foundation: That portion of a structure, usually below the surface of the ground, which distributes the pressure upon its support. Also applied to the supporting material itself.

Foundation Bed: The earth or rock surface on which a construction rests.

Foundation Pile: A pile used permanently in the foundation of a pier.

Foundation Pit: An excavation in which a foundation is placed.

Foundry: An establishment or plant where metals are cast.

Foundry Iron: An iron used in foundry work.

Foundry Pig: Pig iron used in foundry castings.

Four-cylinder Locomotive: A locomotive having four cylinders and two systems of driving wheels.

Fox Bolt: A masonry bolt having either a head or a thread and nut at one end and a split with inserted wedge at the other. After the bolt, with the wedge inserted in the split, is placed in the hole it is driven down so as to spread the end; then it is grouted in.

Foxtail: A thin wedge inserted into a slit at the lower end of a pin so that when the pin is driven down the wedge enters it and causes it to spread and thus hold more firmly.

Fracture: To break or split. A partial or total separation of parts of a continuous solid body under the action of force.

Fracture Section: The section at which failure occurs.

Frame: The sustaining parts of a structure.

Frame Bridge: A bridge constructed of sticks of timber framed together.

Frame Diagram: A diagram of a frame in which the positions of the axes of the joints are shown by points, while the rigid connections are shown by lines between them.

Frame Pulley: A type of pulley-block having an iron frame in which the sheaves or grooved pulleys turn.

Framed Bent: A bent composed of framed timbers.

Framed Bridge: Same as "Frame Bridge."

Framed Girder: A girder constructed of timbers framed together.

Framed Trestle: A trestle having framed bents.

Framework: An instrument for holding or supporting things, as the frame of a hack-saw. An open structure supporting anything.

Framing: The cutting and shaping of timbers which fit together to form a framework.

Framing Chisel: A heavy carpenter's chisel, used in mortising timbers.

Free-body Method: A method that consists in conceiving a body or a portion thereof as isolated from all others which act in any way upon it, those actions being introduced as so many forces, known or unknown, in amount and position.

Free-end: Tire expansion end, or the end that is free to move or to rotate.

Free Haul: The distance within a given limit, set by the specifications, that material is hauled in construction work.

Free Lime: In cement, lime that has not combined with the silica and alumina.

Freezing Process: A process for freezing earth that is thoroughly saturated with water, by means of a freezing mixture forced into tubes by an ice-making machine. When the wall of earth is frozen sufficiently to withstand the external pressure, the excavation then can proceed as in dry ground.

Freight Locomotive: Any heavy locomotive which draws freight cars. Usually one with heavy wheel concentrations and small drivers.

Friction: The resistance to the relative motion sliding or rolling, of surfaces of bodies in contact.

Friction Brake: Same as "Prony Friction Brake."

Friction Clutch: A device for conveying motion from one line of shafting to another by the frictional resistance between plates in contact.

Friction Coupling: An adjustable connection consisting of a cone keyed rigidly to one shaft against which a movable part, having an interior conical surface, sliding on a feather on the other shaft can be pressed.

Friction Drum: Any drum operated by the action of friction.

Friction Gear: A toothless gear wheel transmitting power by means of friction between its periphery and that of the wheel in contact.

Friction Hammer: A drop-hammer raised by the friction of rollers.

Friction Pulley: A pulley which transmits its motion to another by friction of the rolling surfaces instead of by teeth.

Friction Rollers: Rollers placed between moving bodies or around a revolving shaft to reduce the friction.

Friction Washer: A thin ring of metal or other material inserted between two adjoining pieces, one or both of which rotate, in order to reduce the friction between them.

Friction Wheel: A form of slip coupling applied in cases where the variations in load are sudden and great, as in dredges.

Frictional Gearing: Wheels which make rolling contact and transmit motion by the friction set up between their faces.

Frieze: The middle division of an entablature; that part above the architrave, and below the cornice.

Frog: A contrivance built of four pieces of rails mounted on a common base and used for passing the flanges of car-wheels across a rail of an intersecting track.

Frost Batter: A forward inclination of the back face near the top of a wall, the object being to allow the earth to lift upward under the action of frost, and thus prevent an additional horizontal pressure at the top of the wall.

Frustum: That which is left of a solid, usually a cone or pyramid, after cutting off the upper part, including the vertex, by a plane that is generally parallel to the base.

Fulcrum: A pivot point or support. The point about which a lever turns.

Full Splice: A splice capable of developing the full strength of a member.

Fuller: A special block with a rounding edge set into an anvil for bending heated metals.

Function: A mathematical quantity which has a value depending upon the values of other quantities that are called the arguments, or independent variables, of the function.

Funicular Polygon: Same as "Equilibrium Polygon." -- A term used in graphic statics to designate the polygon drawn through a system of non-concurrent forces in order to determine the position of the resultant thereof. The sides of the polygon are made parallel to the rays of an accompanying force polygon.

Furnace: A structure in which a fire is maintained to heat materials or to melt metals or ores.

Furring: A piece placed upon another that is too low, merely to bring its upper surface to a required level.

Fuse: To melt. A slow burning match used to ignite an explosive, such as powder or dynamite. By burning some time it enables the man lighting the fuse to get out of the way before the explosion occurs.

Fuze: Same as "Fuse."