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Glossary of Bridge Terminology



Hack Saw: A small frame hand saw having a narrow blade with fine teeth set close together and well tempered. Used for sawing metals.

Hacked Bolt: A bolt which has been notched with a hatchet to use as a fox bolt.

Hacksaw: Same as "Hack Saw."

Haft: A handle for a cutting tool. To supply with a handle.

Half-and-half Joint, or Halving Joint: A joint having both parts dapped or gained in equally on their faces.

Half-latticed Girder or Half-plate Latticed Girder: A lattice girder the ends of which have web plates while the central portion of the web is latticed.

Half-plate Latticed Girder: Same as "Half-plate Lastticed Girder."

Half-round Bastard File: A medium cut file having a semi-circular cross section.

Half-round Rasp: A rasp having a semicircular cross-section.

Half Round Tie: A slabbed tie having greater width on the lower than on the top face.

Half-round Wood File: Similar to a half-round bastard file, excepting that it is coarser cut and is used exclusively on wood.

Half-through Girder: A loose expression for a girder of a "Half-through Girder Span."

Half-through Latticed Girder: A loose expression for a latticed girder of a "Half-through Span."

Half-through Plate Girder: A loose expression for a plate girder of a "Half-through Span."

Half-through Span: A span in which the deck is placed between the upper and the lower chords and where there is no overhead bracing.

Half-through Truss: A loose expression for the truss of a half-through span.

Halving: Notching together two timbers which cross each other, so deeply that the joint thickness shall equal only that of one whole timber.

Halving Joint: Same as "Half-and-half Joint."

Hammer: A hand tool consisting of a solid head of metal, wood, or stone set crosswise on a handle. Used for beating, breaking, or driving. The part of a pile driver or of a steam hammer which strikes the blow. To beat or to drive.

Hammer Axe: Same as "Axe Hammer." -- A mason's hand tool consisting of a combined hammer and axe on a short handle.

Hammer Beam: A short beam attached to the foot of a principal rafter to act in place of a tie-beam.

Hammer Dressing: Same as "Hammered Dressing."

Hammer Guides: The guides for holding in proper course the motion of a hammer.

Hammer-hardened: Hardened by a process of hammering.

Hammer-mark: A mark left by the blow of a hammer.

Hammer-pick: A hand tool having a hammer face at one end of the head, and a pointed pick at the other.

Hammer Tongs: A pair of tongs which is designed for picking up the handles of tools or hammer heads which are red hot.

Hammer-wrought: Anything which has been wrought with a hammer.

Hammered Dressing: A finish in stonework wrought with a mason's hammer.

Hammered Head: A head formed on the end of a bar by hammering.

Hand Axe: A small, short-handled axe.

Hand-book: A book containing structural shapes, tables, etc. A "Vade mecum."

Hand Brick: A scrubbing brick for hand operation.

Hand Car: A small flat-car mounted on four wheels suitable for railway track and operated by handpower, used for carrying men and equipment for small repairs.

Hand Drill: Any drill that is operated by hand. Usually one man operating both drill and hammer.

Hand Float: A wooden or metal trowel."

Hand Float Trowel: A form of trowel having squared ends and the handle between them.

Hand Frame: An iron barrow used in a foundry.

Hand Gauge: The ordinary wooden scratch gauge used by carpenters for marking off a line parallel to the edge of a board.

Hand Gear: A hand mechanism for opening the valves of a steam engine in starting it.

Hand Glass: A reading or magnifying glass; used in transit work.

Hand Gouge: A gouge that is operated by holding it in the hand.

Hand Hammer: Any hammer which is used by hand.

Hand-hole: A hole in a piece of metal, wood, etc., large enough for a hand to be inserted. Used in webs and diaphragms at times to facilitate bolting up and riveting in close spaces.

Hand Hook: A tool for twisting iron or steel bars.

Hand Level: A small leveling instrument held in the hand for approximating differences in elevation.

Hand Lever: A hand tool consisting of a small steel bar for prying. The handle by which an engine or a machine is started.

Hand Line: A small rope used in guiding moving, suspended objects.

Hand Pile Driver: A small pile driver operated by hand.

Hand Pump: A pump worked by man power.

Hand Rail: Same as "Handrail."

Hand-rail Cap: The upper horizontal member or members of a hand-rail.

Hand Reamer: A reaming machine operated by hand.

Hand Riveting: Driving rivets by hand.

Hand Saw: A saw consisting of a blade of steel with a serrated edge, and having a handle at one end adapted for use by one hand.

Hand Spike: A wooden lever for turning a capstan or windlass.

Hand Vise: A small vise to be held in the hand while gripping the object.

Hand Wheel: A small wheel fitted to the hand for operating valves, etc.

Hand Winch: A winch operated by hand power.

Hand-wrought: Worked or shaped by hand.

Handle: To direct or control by hand. That part of anything which is intended to be grasped by the hand.

Handle Gouge: A gouge in the form of a rivet-buster mounted on a handle and used to cut metal.

Handle Lock Sleeve: A threaded sleeve, or elongated nut, having a handle by which it is turned and locked at some desired position.

Handrail: A railing of concrete, stone, wood, or metal placed on top of posts or balusters to form an open-work construction. Used on the sides of bridges to prevent persons and animals from falling off.

Handrail Post: A post supporting the handrail and its attachments. The vertical member of a handrailing.

Hanger Plate: A gusset plate connecting the hip-vertical to either the top or the bottom chord.

Hangers: Fixtures projecting below a ceiling to support bearings for a line shaft. Also a hip-vertical or suspender of a truss. Also a tension member supporting a floor system in an arch or in a suspension bridge. A beam hanger.

Hanging Bridge: Same as "Suspension Bridge."

Hard-burned: Overburned, a term used in the manufacture of brick.

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

Hard Set of Cement: Same as "Hard Set."

Hard Steel: Steel that has undergone the process of hardening. Also same as "High Steel."

Hard Wood: A term arbitrarily applied by the lumber trade to woods of the broad-leaved trees.

Hardening of Steel: Bringing the metal to the condition in which it is best able to resist abrasion or scratching. This is accomplished by heating the steel to a high temperature and cooling quickly, or by mechanical working.

Hardie: A steel block having a wedge-shaped edge set in an anvil and used for cutting heated metals.

Hardpan: A very compact layer or bed of mingled clay and sand or pebbles, or one of shale.

Hardwood: Same as "Hard Wood."

Harmonic Curve: Same as "Sine Curve."

Harmonic Motion: A reciprocating, rectilinear motion in which the space described by the moving body or point varies as the sine of time angle. Also the motion described by the projection, on a diameter, of a point moving uniformly in the circumference of a circle.

Hasp: A clasp that passes over a staple and is fastened to it by a pin or a padlock.

Hatch: To shade drawings by equidistant parallel lines.

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

Haunch: That part of an arch between the crown and the skewback.

Hay Steel: Steel made by a process patented by a Mr. Hay. It was used in the construction of the bridge over the Missouri River at Glasgow, Mo. It is no longer manufactured.

Head: A top, upper, or higher part or place. An enlargement resembling the head of an animal.

Head-block: A timber at the top of a pile driver which connects the two leads.

Head Frame: Same as "Gallows Frame." -- The frame of a "Gallows" (A set of timbers consisting of two upright posts, or props, and a bar or cap, laid across their tops and cantilevered out from the posts.)

Head Sheaves: The sheaves mounted on the head block of a pile-driver.

Head Valve: The upper airp ump valve of a condensing steam engine.

Head Wall: The wall at the head or main part of an abutment.

Header: In timber construction, the large beam into which the common joists are framed in forming openings for stairs, chimneys, etc. A cross-beam between and supported by two longitudinal beams, furnishing a rest for one or more intermediate short longitudinal beams. A stone or brick which has its greatest dimension perpendicular to the face of the wall.

Header and Stretcher Bond: A form of masonry bond consisting of headers and stretchers alternating in the same row.

Heading Chisel: A mortise chisel.

Heading Joint: A joint between two planks at right angles to their fibres, or between two voussoirs in the same course.

Heading Tool: A tool for the swaging of bolt heads.

Headway: Same as "Clear-headway." -- The vertical distance from the upper surface of a floor to the lowest part of the overhead bracing. It is the measure of height of the tallest vehicle that could pass through the bridge. Also the vertical distance from the water surface or the ground to the lowest part of the superstructure.

Heart: The solid central part of a tree containing neither sap nor albumen.

Heart Bond: A masonry bond in which two headers in opposite faces of a wall meet in the middle of the wall, and have another header to cover the joint between them.

Heart Cam: A form of cam-wheel used for converting uniform rotary motion into uniform reciprocating motion.

Heart Check: A check in the heart of a timber.

Heart Shake: A fissure in the heart of a timber due to growth.

Heart Tie: A railroad tie showing sapwood on one or two corners only and which sapwood does not measure more than one inch on either corner, on lines drawn diagonally across the end of the tie.

Heart Wood: The older and central part of a log, usually darker than the sapwood.

Heat: A form of energy manifested by the motion of the molecules of a body.

Heat Test (of Cement): Same as "Boiling Test." -- A test for determining the constancy of the volume of cement. Pats of cement mortar are made, protected against drying for twenty-four hours, then put in hot water or steam for five hours, after which they are removed and observed for signs of cracking and disintegration. If no such signs appear, the cement has proved satisfactory in respect to soundness.

Heater: An apparatus for heating, a furnace, a forge, a feed water heater, etc.

Heel: The dip of a barge. A form of moulding in masonry. The lower end of a stud or rafter. Applied to almost anything in construction that resembles a heel.

Heel Dolly: A tee-headed dolly, having the far end rounded with a hole for a seven-eighths (7/8) inch bolt located one and seven-eighths (1 7/8) inches away from the centre of the tee head. Also a dolly with a long shaft and a short right-angled bend at one end, the cup being in the short end.

Helicoid: The surface generated by a straight line revolving about the axis of a helix and moving parallel to itself along such axis while following the curve of the helix.

Helix: A curve of double curvature generated by a point rotating about an axis with a constant radius which moves along the axis in proportion to its angular motion.

Helve: The handle of an axe.

Helve Hammer: A trip-hammer.

Hemp: A species of plant which has tough and strong fibres, used for twisting into ropes and cables.

Hemp Packing: Packing made of hemp fibres and put up in the form of a soft, loosely-woven rope.

Henequin Hemp: A kind of hemp which grows in Cuba and parts of Mexico.

Herring-bone: The diagonal struts fixed at intervals between the beams of a floor to distribute the load on one beam to adjacent beams and to increase the stiffness of the beams. Also applied to a course of stone laid at an angle so that the stones in each course are placed side by side, and obliquely to the right and to the left in alternate courses.

Herring Bone Dressing: A type of stone dressing made by cutting flutings in a diagonal direction on the face of the stone.

Herringbone Work: Masonry work done according to the Herringbone system. See also "Herring-bone."

Hewed Tie: A railroad tie which is hewed on at least two sides.

Hexagon: A regular six-sided figure.

Hexagonal Nut: A nut having six equal sides in the form of a regular hexagon.

Hick Joint: A flush joint in masonry.

Hicky: A purely field expression employed by bridgemen for almost any contrivance, or part of one, which lacks a specific name. Analogous to "thingumbob."

Hiding Power: The capacity of a paint or painting material to obscure a surface beneath it.

High Bridge: A, bridge over navigable water having ample clearance beneath it to permit the passage of all vessel traffic without moving a span or any portion of one.

High Carbon Steel: Same as "High Steel."

High Steel: Steel containing a comparatively large amount of carbon, from one-half to one per cent.

High Water: The condition of a stream when discharging a large amount of water.

High-Water-mark: A mark left by any high water.

Highway: Formerly restricted to a way or road reserved for the use of ordinary vehicles, pedestrians, or animals, but now it is often used to mean a way or road on which an electric railway also runs.

Highway Bridge: A bridge that carries highway traffic only.

Hinge: A device for connecting two pieces, so that one may turn about the other.

Hinge-end: The end of a piece or member that is provided with a hinge.

Hinge Lift Bridge: A lift bridge which has its ends hinged together when down.

Hinge Pin: A pin which fastens together the parts of a hinge or which connects members having a slight rotating movement about each other.

Hinged Arch: An arch which has one or more hinged joints.

Hinged End: The end of a member that is connected to the rest of the structure by a device that permits of a slight rotation. In contradistinction to a fixed end.

Hinged Joint: A joint in which the parts are connected by a pin, or a similar device, permitting a rotating motion to occur.

Hinged Plate: A plate containing a pinhole for hinging the end of a member.

Hinged Post: A post having one or both ends connected by pins to other parts of the structure.

Hip: The place at which the top chord meets the batter-brace or inclined end post.

Hip-joint: The junction. of the top chord and the batter post.

Hip-joint Hood: A bent tie plate or strap placed over the hip to keep water out of the joint.

Hip Knob: A finial on the hip of a roof or between the barge boards of a gable.

Hip Roof: A roof rising directly from the wall-plate on all four sides, and so having no gable.

Hip Vertical: The upright tension member attached to the pin or to the plates at the hip of a truss and carrying a floor beam at its lower end.

Hitch Plate: A plate having a hole or a ring attached for tying lines thereto.

Hitcher: Same as a "Boat Hook." -- A brass or iron hook and a spike fixed to a staff or pole, used for pushing or pulling a boat or barge.

Hoarding: A temporary, close fence of boards placed around work in progress, to exclude stragglers.

Hod: A form of V-shaped box fixed on the end of a pole, or handle, used on construction work for carrying bricks and mortar.

Hodgkinson's Formula: An early column formula, devised by Eaton Hodgkinson, based upon Euler's formula; but modified to conform with experiments made at the time.

whereP = the load
b = width of column
l = length of column

Hoe: A tool for digging, scraping, loosening, or mixing material, consisting of a thin blade set transversely to a long handle and at the end thereof.

Hog Chain: A chain cable or rod stretched over the straining posts in a "Hog-chain Truss." Same as the rod used for trussing a beam.

Hog-chain Truss: Properly a trussed beam. Same as an inverted "Queen Post Truss. (A type of trussed beam having two vertical posts.)"

Hoist: A machine for lifting weights or loads of various kinds. To elevate by means of block and tackle or by machinery of any kind.

Hoist Bridge: Same as "Lift Bridge." -- A type of movable bridge which travels in a vertical plane.

Hoisting Block: The lower pulley block of the block and falls, carrying the hoisting hook.

Hoisting-cable Rope: A wire rope roven through a suspended block or a fixed block in the top of a mast of a derrick and fastened to the drum of a hoisting engine. Used to raise weights.

Hoisting Crab: Any crab used for hoisting.

Hoisting Engine: An engine used to operate hoists, derricks, pile drivers, etc.

Hoisting Jack: A lifting device in which a screw-jack is employed.

Hoisting Machine: Any machine used for hoisting purposes.

Hoisting Shears, or Sheers: A support made of two timbers which cross each other near one end and are pivoted so that they may be spread more or less. Used in hoisting gin poles.

Holder-up: A dolly bar for bucking up rivets. Called, also, "Bucker-up."

Holding-on Bar: A lever which is used to hold one head of a rivet against the impact of the hammer while the other head is being formed with a snap.

Holding-up Hammer: A heavy engineer's hammer on a long handle, used in times past for bucking up rivets.

Hollow Pile: A shell driven into the ground to receive concrete.

Homogeneous: Having parts of only one kind. Composed of similar parts or congruous elements.

Homogeneous Steel: A steel solid and free from blow holes. A variety of crucible steel easily bent and worked.

Honey-comb: A condition of having cells like those of a honey-comb, occurring at times in concrete, castings, etc.

Hook: A piece of metal curved or bent so as to catch or grab something. To take hold with a hook.

Hook and Ring Chain: A chain with a hook at one end and a ring at the other. Called also a "Sling Chain."

Hook Block: A pulley block fitted with a hook at one end.

Hook Bolt: A bolt having one end in the form of a hook.

Hook Chain: A chain having a hook on one end or one at each end.

Hook-eye: The eye or loop of a hook.

Hooke's Joint: A contrivance by which a motion of rotation is communicated from one shaft to another not lying in the same plane.

Hooke's Law: This law states that the deformation of an elastic body is proportional to the force applied, or that the intensity of stress is proportional to the rate of strain.

wheredp = the differential intensity of stress
dl =the differential of the rate of strain
E = a constant

Hoops: Reinforcing bars, bent into a circular shape like hoops, which surround the longitudinal reinforcement of compression members.

Hopper: A trough, usually shaped like an inverted frustum of a cone or pyramid, through which materials pass.

Hopper Barge: A boat having a compartment with a movable bottom to receive the mud or gravel from a dredging machine and to discharge it by gravity.

Horizontal Bracing: Bracing lying in a horizontal plane.

Horizontal Clearance or Lateral Clearance: The horizontal space allowed for the passage of any vehicle or craft through or near a construction.

Horizontal Component: A component of an oblique force taken in a horizontal line.

Horizontal Line: Any line in a horizontal plane.

Horizontal Moment: A moment acting in a horizontal plane.

Horizontal Pump: A pump with its cylinders in a horizontal position.

Horizontal Pumping Machine: Same as "Horizontal Pump."

Horizontal Section: A section made by a horizontal secant plane.

Horizontal Strut: A compression member lying in a horizontal position.

Horizontal Sway Bracing: Sway bracing in a horizontal plane.

Horizontal Thrust: A thrust in a horizontal direction, as that of a braked train.

Horizontal Truss: A truss placed in a horizontal plane.

Horn: The big end or prong of the shoe on a pile. The round tapering end of an anvil.

Horns: The stationary arms on a gam press.

Horse: A wooden bar with legs for supporting a staging.

Horse Dolly: Same as a "Goose-neck Dolly." A dolly that has a quickly curved bend near one end, with both ends arranged for receiving rivet heads.

Horse Gin: A gin driven by one or more horses.

Horse Pile Driver: A driver in which the hammer is raised by horsepower.

Horsepower: A practical unit of power equal to the raising of five hundred and fifty pounds one foot high in one second. Also a machine by which the power of a horse can be made available for doing useful work.

Horseshoe Riveter: A form of yoke riveter hung from a travelling crane, so as to be readily moved about the shop to reach different parts of a job.

Hose: A flexible tube or pipe for conveying a liquid or gas to a point where it is required for use.

Hot-box: A heated journal box of an engine, a vehicle, or any other machinery.

Hot Chisel: A chisel used for cutting metals while hot.

Hot Cutter: A tool for cutting metal which has been softened by heating.

Hot-pressed Paper: A variety of drawing paper polished by pressure between heated plates.

Hot Saw, or Iron Saw: A circular saw for hot steel or iron shapes.

Hot Short: A condition of brittleness in iron or steel due to the presence of sulphur.

Hot-short Iron: Iron that is brittle above a temperature denoted by a medium orange color-due to sulphur.

Hot-short Steel: A steel that is very brittle when hot-usually due to an excessive amount of sulphur.

Housing: In carpentry, the space left in one piece for the insertion of the extremity of another in order to connect them. The uprights supporting the cross slide of a planer. A covering or roofing. A covering for machinery. That part of the framing which holds the journal box in place.

Housing Iron: An iron tool used for placing a strand of oakum in a crack.

Housing Joint: In carpentry, a joint formed between two pieces by removing a portion of one piece to allow the insertion of a part of the other piece.

Housing Maul: An iron maul heavier than a calking mallet.

Howe Truss: A form of truss in which the vertical members of the web take tension and the diagonal members compression. See Fig. 22p.

Fig. 22p

Hub: Any rough protuberance or projection. A block of wood for stopping carriage wheels. The central part of a wheel through which the axle passes, and from which the spokes radiate. A surveyor's stake with a tack in the top to denote line and position.

Hub Guard: An angle, plate, etc., on corners of concrete, masonry, and similar materials, where vehicular traffic passes, to protect them against injury by the rubbing of wheel hubs.

Hue: The predominating spectral color in a color mixture.

Humped-up: Raised in the centre, synonymous with the term "camel-hack."

Hurst: The ring of the helve of a trip-hammer which supports the trunnions. A sand bank near a river, also a shallow in a river.

Hutton's Formula: An empirical formula for determining wind-pressure on surfaces inclined to the direction of the wind.

wherePn = the normal component of wind pressure
P = the pressure per square foot on a plane perpendicular to the direction of the wind
andα = angle of inclination of the surface with the direction of the wind

Hydrant: An apparatus for drawing or discharging water directly from a main or pipe.

Hydrated Lime: Same as "Slaked Lime."

Hydration: The process of combining or impregnating with water, or the resulting condition.

Hydraulic Activity: Same as "Activity of Cement."

Hydraulic Buffer: An automatic device for checking recoil by means of water or other liquid forced under high pressure through a small aperture or apertures.

Hydraulic Cement: A cement which sets or hardens under water. There are three common kinds: Portland, natural, and Pozzuolana.

Hydraulic Condenser: A chamber in which gas from a retort is cooled.

Hydraulic Crane: An apparatus for raising and lowering loads acting on the principle of a hydraulic press.

Hydraulic Elevator: An elevator operated by some kind of hydraulic mechanism.

Hydraulic Energy: The energy of water in motion.

Hydraulic Gauge: Same as "Hydraulic Indicator."

Hydraulic Hoist: A hoist operated by hydraulic power.

Hydraulic Index: The ratio of the sum of the weight of silica and alumina to the weight of lime in any cement or cement material.

Hydraulic Indicator: A gauge for indicating the pressure of water.

Hydraulic Jack: A device for lifting heavy weights or exerting great force by means of liquid pressure from a hand-pump connected with a large-bore cylinder and a piston working therein.

Hydraulic Lime: A lime made from limestone containing clay or silica which, during calcination, enters into combination with a portion of the lime and thereby gives it the additional property of hardening under water.

Hydraulic Mortar: Mortar made of hydraulic cement, so that it will set under water.

Hydraulic Press: A press consisting of a water cylinder and movable plunger mounted in a frame. A small pump forces water into the cylinder and causes the plunger to move slowly, but with great pressure against the object held in the frame.

Hydraulic Quickness: Same as "Activity of Cement."

Hydraulic-radius: The ratio of the area of a cross-section of a stream to the length of the wetted perimeter.

Hydraulic Ram: An automatic device by which the fall of a comparatively large quantity of water is suddenly checked and a portion diverted to an air chamber. Owing to the momentum of the water, the air in the chamber is compressed, as the water enters, until the said momentum is absorbed. By the dropping of an outlet valve in the supply pipe a new flow is set up for a brief moment and again checked, causing an additional supply to enter the air chamber and renew or increase the previous pressure. This interior air pressure causes the water to pass out of the discharge pipe which ends at a higher elevation than the source of supply.

Hydraulic Riveter: A riveting machine operated by water under pressure.

Hydraulic Strength: The strength developed by cement, mortar, or concrete setting in water.

Hydraulic Valve: Any valve controlling the flow of water.

Hydraulics: A branch of the science of the mechanics of fluids which treats of water in motion.

Hydrographic Map: A map showing a watercourse or a portion thereof and indicating the depth of water at various points, the direction and velocity of the current, the character of bed and bank, and other information pertinent to any special stream.

Hygrometer: An instrument for measuring the amount of moisture in the atmosphere.

Hygrometric: Relating to the amount of moisture in the air.

Hyperbola: A curve such that the difference between the distance from two fixed points, called the foci, to any point on the curve is a constant.

Hyperbolic Curve: Same as "Hyperbola."

Hyperbolic Logarithm, or Naperian Logarithm, or Natural Logarithm: A system of logarithms in which the base is 2.71828+.