This glossary is drawn from the "Glossary of Terms," pp. 223-236, in Waddell, J. A. L.,The Designing of Ordinary Iron Highway Bridges. New York, J. Wiley, 1884.


A (top)
Adjustable Member
A member of a bridge the length of which can be increased or diminished at will.
Angle Iron
Iron rolled into the shape shown in section on Plate II., Fig. 3.
The intersection of a brace with a chord or flange; called also a panel point.
Axis of Symmetry
A line dividing an area into two parts equal and similar to each other, and similarly disposed to the line.
B (top)
A piece of iron flat or square in section.
Slope, or inclination, to the vertical; usually measured by the tangent of the angle, or so many inches to the foot.
Batter Brace
The inclined end post of a bridge. (Plate I.)
A member intended to resist bending.
Beam Hanger
A rod or square bar supporting a floor beam from a chord pin. (Plate I. and Plate II., Fig. 13.)
Beam-hanger Nuts
Nuts on the ends of beam hangers, serving to press the floor beam against the feet of the posts or against, the chord heads. (Plate IL, Fig. 13.)
Beam-hanger Plate
A plate placed beneath the end of a floor beam for the beam-hanger nuts to rest against (Plate II.,. Fig. I3.)
Beam-trussing Posts
Posts for trussing beams (P1ate II., Fig. 16.)
Beam-trussing Rods
Diagonal rods for trussing beams. (Plate II., Fig. 16.)
A resting-place, usually for a pin or rivet
The pressure on a bearing.
Bed Plate
A plate to distribute pressure upon masonry. (Plate III.)
The moment of a force or forces which bend or tend to bend a piece.
The stress produced in a piece by bending.
A frame of timber or iron, usually the former, as a bent of false-work.
Bent Eye
An eye on the end of a bar, the plane of which makes an angle with the direction of the 1ength of the bar.
The slope on the end of a piece.
Bill of Material
A list of various portions of material giving dimensions and weights, or other quantitative measurements.
A system of one or more pulleys or sheaves, so arranged in a frame or shell as to multiply the power of the rope passing around them, or to change its direction.
Board Measure
The measure of timber, the unit being a piece one foot square and one inch thick.. Timber is sold at so much per thousand feet board measure, usually written, per M. b. m.
An iron rod with a square head at one end, and a thread and nut at the other: the head may sometimes be wanting.
Generally a strut, but sometimes the term is applied to a tie.
A knee or knee brace to connect a post or batter brace to an overhead strut. (Plate I.'or Plate II., Fig. 12.)
A beam made up of plates and angles riveted together. (Plate IL, Fig. 13.)
A rough edge or ridge left by a tool in cutting metal. The term is sometimes used for a nut.
Button Sett
A tool for forming the heads of rivets.
C (top)
The upward curvature of a truss. It is measured by the height of the middle point of the centre line of the lower chord above the line joining the centres of end pins.
Camber Blocks
Blocks of wood used in erection, so placed as to be easily renioved (Plate VII.)
Cape Chisel
A tool for cutting iron. It consists of a rounded edge on the end of a short rod. The edge is very obtuse, so as not to break easily.
Centre of Gravity
That point of a body about which the weights of all the different portions balance.
Channel, or Channel Bar
Iron rolled into the shape shown in section on Plate II., Fig. 1.
Check Nut, or Lock Nut
A contrivance to prevent a nut from turning when subjected to shock.
The upper or lower part of a truss, usually horizontal, resisting compression or tension. (Plate I.)
Chord Bar
A member of the chord which is subjected to tension. (Plate I.)
Chord Head
The enlarged end of a chord bar, through which the pin passes.
Chord Packing
The arrangement of the bottom chord of a truss.
Clear Headway
The vertical distance from the upper surface of the floor to the lowest part of the overhead bracing. It is a measure of the height of the highest vehicle that could pass through the bridge.
Clear Roadway
The horizontal distance, measured perpendicular1y to the planes of the trusses, between the inner edges of the batter braces. It is a measure of the width of the widest vehicle that could pass through the bridge.
A narrow strip of wood nailed to something for the purpose of keeping a piece of work in its proper place.
Co-efficient of Friction
A numerical quantity, which, multiplied into the normal pressure, gives the frictional resistance. It is equal to the natural tangent of the angle of repose.
Cold Chisel
A tool for cutting iron.
A pillar or strut; a long member which resists compression.
One of the parts into which a stress may be resolved or divided.
A stress which tends to shorten the member which is subjected to it.
Concentrated Load
A load which is, or may be considered, collected at one or more points.
Continuous Spans
Consecutive spans connected over the points of support.
Connecting Chord Heads
Chord heads used to connect bottom chord channels to pins. (Plate II, Fig. 10.)
A plate used for connecting two pieces.
An adjustable diagona1 which is not subjected to stress by a uniformly distributed load covering the bridge. (Plate I.)
Countersunk Rivets
Rivets, the heads of which are let into one or both of the plates which they connect, so as to leave a flush surface or surfaces.
Two equal and parallel forces not acting in the same line.
Cover Plate
A plate used to cover a joint, or to connect two pieces of the top chord plate. (Plate II., Figs. 11 and 12.)
A slow-motion machine, worked by a crank for the purpose of winding a rope upon a drum, thereby raising a heavy weight.
D (top)
To notch timber on to its bearing.
Dead Load
The weight of all the parts of the bridge itself, and any thing that may remain upon it for any 1ength of time.
Deck Bridge
A bridge in which the passing loads come upon the upper chords or the upper ends of the posts.
Motion laterally, or at right ang1e to the length of the piece. It is also used for the amount of motion, and is generally expressed in inches.
Depth of Truss
The vertical distance between the centre lines of upper and lower chords.
A member running obliquely across a panel. In this work all the diagonals except the batter braces are tension members.
Diagram of Stresses
A skeleton drawing of a truss, upon which are written the stresses in the different members. (Plate V.)
Double Intersection
The style of truss where the diagonals cross the posts at the middle of their length, as in the bridge shown on Plate I.
Double-riveted Lacing
Lacing in which each bar is connected by two rivets at each end. (Plate II., Fig. 13.)
Drift Bolt
A round or square piece of iron, usually from one to three feet long, without head or nut, used to connect timbers
Drift Pin
A slightly tapering rod of hard steel, used for niaking rivet holes coincide. Its use is more convenient than advisable.
E (top)
Effective Area
The gross area of a section, less that lost by rivet or pin holes; the net area.
Elastic Limit
That intensity of stress at which the ratio of stress over strains commences to show a decided change. For wrought-iron it is from twelve to fifteen tons.
A bill of material for a bridge, so arranged as to facilitate the finding and placing of members during erection.
Expansion Joint
The connection of pedestal to bed-plate, shown on Plate III.
Expansion Rollers
A set of half a dozen or more turned rods of exactly the same diameter, placed under the shoe plate at one end of a truss to permit of expansion and contraction. (Plate II., Fig. 9.)
Extension Plate
A plate riveted to the end of a strut channel, and projecting beyond it, to permit of the passage of a pin. (Plate 11., Fig. 12.)
A hole in the end of a member to permit of the passage of a pin.
Eye Bar
A bar with an eye at each or one end.
F (top)
Factor, or Factor of Safety
The ratio of ultimate load to greatest allowable working-load. This term is getting out of favor among engineers, as its use has been somewhat 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 proportionate to the character and amount of work which it has to perform.
Fall Line
A rope used in erection for raising and lowering weights.
Temporary timber work to support a bridge during erection.
Felly Plank
A guard rail so placed as to catch the felly of a wheel, and thus prevent the vehicle from striking the truss. (Plate II., Fig. I3.) In wide bridges a felly plank is often placed midway between the trusses, to prevent vehicles passing from one side of the bridge to the other.
Field Riveting
Riveting done in the field, or during erection. It is the poorest and most expensive kind of riveting.
Fixed End
An end of a strut so firmly connected as to prevent all motion of the strut in the neighborhood of the end.
A plate the function of which is to make flush two surfaces (Plate II., Fig. 12.)
A small ring of iron or piece of pipe placed on a pin in order to keep in place the members coupled thereon.
Fixed Load
A load remaining permanently, or for a considerable length of time, upon a structure or portion of a structure.
The upper or lower chord of a beam. It is the principal part for resisting either compression or tension.
Floor, or Flooring
That part of the bridge which directly receives the travel. (Plate IL, Fig. 13.)
Floor Beam
A beam to support a portion of the floor and its load. (Plate I. and Plate II., Fig. 13.)
An apparatus for heating iron.
The carpenter work on timber.
G (top)
Giasticutus Rods
A term (perhaps unauthorized, but in common use among bridge builders) to denote a small horizontal rod connecting the middle points of two adjacent posts of the same truss, for the professed purpose of fixing or holding the posts at the middle in order that they may be figured for half-length. The benefit derived therefrom is more imaginary than real.
Any structure to cross a chasm or opening. The term is generally applied to short structures for places where it is not advisable to use trusses; for instance, a plate girder, or a rolled girder.
Guard Rail
See felly plank.
Guys, or Guy Lines
Lines for bracing the top of a pole, derrick, or any similar apparatus.
See radius of gyration.
H (top)
Hammered Head
A head formed on the end of a bar by haznmering.
Hand Lines
Small ropes used in erection.
Hand Rail, or Hand Railing
An iron or wooden frame placed on or near the outside of a bridge in order to prevent persons or animals from falling therefrom. (Plate IV., or Plate II., Fig. 13.)
Hand-rail Cap
The upper longitudinal timber or timbers of a wooden hand-railing. (Plate IL, Fig. 13.)
Hand-rail Post
Post for supporting a hand railing. (Plate II., Fig. i~; Plate IV.)
See clear headway.
Hinged End
An end of a strut connected only by a pin.
The place at which the top chord meets the batter brace.
Hip Joint
The joint of the top chord and batter brace.
Hip Vertical
A rod hung from the pin at the hip for the purpose of suspending the floor beam.
Holding-on Bar
A lever to hold against one end of a rivet while the head at the other end is being formed with a button sett.
Hub Plank
A plank to protect the iron-work of the truss from being struck by the hubs of passing wheels. (Plate II., Fig. 13.)
I (top)
A piece of rolled iron of the section shown on Plate II., Fig. 2.
Initial Tension
The tension caused in any adjustable member by screwing up the adjusting apparatus.
The intensity of a stress is the amount of stress upon a square inch of section.
Intermediate Strut
An overhead strut in high bridges, attached to the posts of opposite trusses, and lying between the upper lateral strut and the floor. In deck bridges, if used at all, it would lie between the upper and lower lateral struts. (Plate I.)
J (top)
A connection on the end of a strut similar to that shown on Plate IL, Fig. 13.
A place where two abutting or lapping pieces are connected.
A timber beam that supports part of the door and its load. (Plate I. and Plate IL, Fig. 13.)
K (top)
Knee, or Knee Brace
See bracket.
L (top)
A system of bars, not intersecting each other at the middle, used to connect the two channels of a strut in order to make them act as one member. (Plate II., Fig. 12.)
A bar belonging to a system of lacing.
Lateral Rod
A tension diagonal of a lateral system. (Plate I.)
Lateral Strut
A compression member of a lateral system. (Plate I.)
Lateral System
A system of tension and compression members forming the web of a horizontal truss connecting the opposite chords of a bridge. Its purposes are to transmit wind pressure to the piers or abutments, and to prevent undue vibration from passing loads.
A system of bars crossing each other at the middle of their lengths, used to connect the two channels of a strut in order to make them act as one member. (Plate II., Fig. 12.)
Lattice Bar
A bar belonging to a system of latticing.
One of the two portions of an angle iron separated from each other by the bend.
Lever Arm
The perpendicular from the centre of moments to the line of action of a force. The lever arm of a couple is the perpendicular distance between the lines of action of the two equal and parallel forces.
Live Load
The moving or passing load upon a stnicture.
Linville Truss (also called "Double Quadrangular," "Whipple," and "Double System Pratt" truss)
A truss with vertical posts and diagonal ties spanning two panels. It is the truss represented on Plate I.
Lock Nut
See check nut.
Loop Eye
An eye on the end of a rod or square bar, elongated into the form of a ioop, as shown on Plate II., Fig. 16.
Lower Falsework
The falsework below the level of the lower chords.
M (top)
Main Diagonal
A tension member of a truss, sloping upward towards the nearer end of the span. Main diagonals in iron bridges are not adjustable.
The product of a force by its lever arm.
Moment of Inertia
Represented by the equation, I = Apt = Zr2dA, whereA is the area of the section considered, p the radius of gyration, andr the distance of any point from an assumed line lying either in the surface or outside of it: in other words, the moment of inertia of a surface about any axis is the product of the area by the square of the radius of gyration; or it is the summation of the products of each differential of the area by the square of its distance from the axis. If the axis lie in the surface, the moment of inertia is called a surface moment of inertia; while, if the axis be perpendicular to the surface, the moment of inertia is called a polar moment of inertia.
Monkey Wrench
A wrench capable of being adjusted so as to fit nuts of different sizes.
Moving Load
See live load.
A timber, usually from 6" by 6" to 12" by 12", at the bottom of a bent. It is laid horizontally in a trench, and the posts of the bent rest upon it.
N (top)
Name Plate
A plate of iron placed in a conspicuous position on a bridge, containing the name of the maker or designer of the structure.
Negative Rotation
Rotation in a direction opposite to that of the hands of a watch.
Net Section
See effective area.
Neutral Surface
That part of a member subjected to bending, which is neither extended nor compressed. In symmetrical wrought-iron beams, with equal or nearly equal flanges, it is taken to be at the centre line of the web.
A small piece of iron with a threaded core to fit on the screw end of a bolt, rod, or bar. (Plate II., Fig. 6.)
O (top)
Order Dill
A form of bill used in ordering material from the mannfacturers.
Ornamental Work
Fancy work at the portals of a bridge to give it architectural effect (Plates I. and VI.)
Overhead Bracing
The upper lateral or sway bracing in through bridges. The term is usually applied to the sway bracing, if there be any; if not; to the upper lateral bracing.
P (top)
See chord packing;
That portion of a truss between adjacent posts or struts in Pratt truss bridges; called also a bay.
Panel Length
The distance between two adjacent panel points of the same chord.
Panel Point
See apex.
The foot of a batter brace or end post. (Plate II., Fig. 9.)
Permanent Set
The alteration in length of a piece of material which has been subjected to stress, remaining after the stress has been removed.
See column.
Pilot Nut, or Pin Pilot
A nut, one end of which is a truncated cone, used to protect the thread on the end of a pin when the latter is being driven into place. (Plate II., Fig. 5.)
A cylindrical piece of iron used to connect bridge members. (Plate II., Fig. 5.)
The distance between centres of consecutive rivets of the same row.
Plane of Symmetry
A plane dividing a body into two equal and symmetrical parts similarly disposed in reference to the plane.
Tools and apparatus used in construction.
A piece of fiat iron wider than a bar. The common distinction between the two is that a plate is attached to something else, and acts with it, while a bar is an independent member.
Plate Girder
A beam, built of plates and angles, used to span a small opening, generally less than forty feet.
Pony Truss
A truss so shallow as not to permit the use of overhead bracing.
The space between the batter braces at one end of a bridge. Sometimes the term is applied to the portal bracing, though incorrectly.
Portal Bracing
The combination of struts and ties in the plane of the batter braces at a portal, which transfers the wind pressure from the upper lateral system to the abutment or pier.
Portal Strut
A strut belonging to the portal bracing. (Plate I.)
Positive Rotation
Rotation in the direction of the hands of a watch.
A vertical strut. (Plate I.)
Pratt Truss (called also the "Murphy-Whipple," or "Quadrangular" truss)
A single-intersection truss with vertical struts and diagonal ties.
Q (top)
Quadrangudar Truss
See Pratt truss.
R (top)
Radius of Gyration
The radius of gyration of any surface in reference to an axis is the distance from the axis to that point of the surface in which, if the whole area were concentrated, the moment of inertia in reference to the axis would be unchanged. It is therefore equal to the square root of the ratio of the moment of inertia over the area.
To enlarge a rivet hole.
A tool for enlarging rivet holes.
Re-enforcing Plate
A plate used for the purpose of providing additional pin bearing, or strength, to compensate for material cut away. (Plate II., Figs. 11 and 13.)
To divide a force into component parts.
A short piece of round iron ticrhtly connecting two or more thicknesses of metal, and having, when in place, a head at each end.
The passage-way of a bridge for vehicles; usually means clear roadway,q. v.
A piece of round iron.
Rolled Beam
An I-beam. (Plate II., Fig. 2.)
See expansion roller.
Roller Frame
A light frame of iron for holding the rollers in position. (Plate II., Fig. 9.)
Roller Plate
The plate upon which the rollers rest, and which itself rests upon the masonry.
Rope Sling
See sling.
A line, or string; as, a run of joists.
S (top)
The extension or compression of a piece of material under stress.
Shear, or Shearing-Stress
The resistance which a body offers to the passage, or to the tendency to passage, of, one section along the next consecutive section.
A list of portions of a bridge, arranged in a manner to facilitate counting and checking when the material is received after shipment.
Another term for pedestal,q.v.
Shoe Plate
The plate on the under side of the shoe, resting on the rollers, bed-plate, or masonry.
Side Bracing
A bracing for pony trusses to attach the panels of the top chord to the floor beams prolonged, in order to fix the panel points of the top chord. (Plate III.)
Roadways at the sides of a bridge for foot-passengers only.
Single Intersection
That style of truss in which the diagonals do not cross the posts. It is represented in skeleton on Plate V.
Skeleton Drawing
A drawing which shows only the centre lines of members, such as a diagram of stresses. (Plate V.)
Skew Bridge
A bridge in which the horizontal lines joining corresponding panel points of the opposite trusses are oblique to the planes of the trusses.
A heavy hammer, or mallet.
Sleeve Nut
An elongated nut, the core at one end having a right-hand thread, and that at the other a left-hand thread. Its office is to lengthen or shorten a tension member. (Plate II., Fig. i6.)
A loop of rope, very useful in erection for making a hasty attachment.
Inclination to a horizontal plane.
Snatch Block
A block with one side capable of being opened for the insertion of the rope. Its office is to change the direction of the rope.
The length of a bridge from centre to centre of end pins or bearings.
Large nails for timber work. (Plate II., Fig. 13.)
To spread at one end the two main portions of a member.
A joint connected by means of plates.
Splice Plate
A connecting plate at a joint. (Plate II., Fig. 12.)
The distance apart laterally.
Staggered Rivets
Rivets are said to be staggered when each rivet of one row is opposite to the middle of the space between two rivets of the next row.
Static Load
Dead load,q.v.
Stay Plate
A plate always used at the end of a system of lacing or latticing. (Plate II., Fig. 12.)
An angle iron used to stiffen the web of a beam. (Plate II., Fig. 13.)
A piece of iron used to stiffen the web of a beam: it may be of angle or tee section. (Plate IL, Fig. 13.)
The extension or compression of a piece of material which is or has been under stress.
The internal resisting force of a piece of material which is strained.
A member which rasists compression.
The punching of rivet holes which have to be afterwards enlarged by reaming.
Sway Bracing
Bracing transverse to the planes of the trusses. Its objects are to resist wind pressure, and to prevent undue vibration from passing loads. (Plate I.)
T (top)
Table of Data
A list of the known circumstances that affect the designing of a structure.
A screw for cutting a thread in a nut.
Tee or T iron
A piece of rolled iron of the section shown on Plate II., Fig. 4.
A stress tending to elongate a body.
The spiral part of a screw or nut.
Through Bridge
A bridge with overhead bracing.
A tension member; generally refers to a main truss.
Timber Truck
A small, strong wooden frame, with an iron roller set entirely below the upper surface. It is used in bridge erection for moving large timbers and heavy weights along a runway.
Part of a riveting outfit; used for holding and carrying heated rivets.
Transverse Component
A component in a transverse direction; generally intended for a component perpendicular to the planes of the trusses.
An assemblage of tension and compression members so arranged as to transmit loads from intermediate points to the ends.
A poor substitute for lacing or latticing. (Plate II., Fig. 8, Plate VI.)
Turn Buckle
Similar to a sleeve nut, and for the same purpose. The sides are open, so that a crowbar may be inserted for the purpose of screwing up. Turn buckles are used for larger bars or rods than are sleeve nuts. (Plate IL, Fig. i6.)
U (top)
Ultimate Strength
The greatest load that a portion of material can bear.
Uniform Load
A load so distributed over an entire structure, that equal lengths everywhere receive equal portions.
A piece of iron, in the shape of the letter U, through which passes the threaded end of a rod, and which affords a bearing for the nut, with room to screw up the latter. Its use is not permissible in first-class bridge construction.
Upper Falsework
The falsework that lies above the level of the upper chords.
Upset End
An end of a rod or bar enlarged for the cutting thereon of a screw-thread.
V (top)
Vibration Rod
A tension member for vertical or portal sway bracing. (Plate I.)
W (top)
A piece of cast or wrought iron to distribute the pressure of a bolt-head or nut over timber. (Plate II., Fig. 6.)
The portion of a truss or beam between the flanges. Its office is principally to resist shear.
Welded Heads
Heads first worked into shape, then welded on the bars.
Whipple Truss
See Linville truss.
Wind Shakes
Cracks in timber caused by the wind while the free was living.
Drawings containing all the measurements necessary for construction.
The stress, usually the greatest stress, to which a piece of material is or should be subjected. Sometimes incorrectly employed for intensity of working-stress.
A tool for screwing up nuts.

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