New Millennium Building Systems

Glossary of Terms

Steel Joist Institute, ANSI, Steel Deck Institute Steel Joist Institute ANSI Steel Deck Institute

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

Terms in BLUE and their definitions come from the AISC AND AISI STANDARD Standard Definitions for Use in the Design of Steel Structures, 2004 Edition, First Printing April 2005.

* These terms are usually qualified by the type of load effect, e.g., nominal tensile strength, available compressive strength, design flexural strength.

** Term usually qualified by the type of component, e.g. local web buckling, local flange buckling, etc.


Strips of lumber attached to the top chord of a steel joist (bar joist) so plywood or other flooring can be nailed directly to the joist.


Description applied to data that is "allowed to be changed" after it has been transferred.

NBC (National Building Code)

A minimum model regulatory code for the protection of public health, safety, welfare and property by regulating and controlling the design, construction, quality of materials, use, occupancy, location and maintenance of all buildings and structures within a jurisdiction.


National BIM Standard – US effort in IFC.

NBS (National Bureau of Standards)


NCEES (National Council of Examiners for Engineering and Surveying)

Provides leadership in professional licensure of engineers and land surveyors.

NCS (National Cad Standard)

Developed through the cooperation of the American Institute of Architects (AIA), the Construction Specifications Institute (CSI), and NIBS.

NEA (National Erectors Association)



For steel joists and joist girders, when looking at the member with the tagged end to the right, it is the side you see first and is closest to you.

Neutral Axis

The surface in a member where the stresses change from compression to tension, i.e., represents zero strain and therefore zero stress. The neutral axis is perpendicular to the line of applied force.


The SI unit of measure for force (N).

NFPA (National Fire Protection Association)

An international nonprofit organization to reduce the burden of fire on the quality of life by proposing codes and standards, research, and education on fire related issues.

NIBS (National Institute of Building Sciences)

Federal agency, has downloads.


Abbreviation for 'Not in Contract'.

NIST (National Institute of Standards and Technololgy)

An organization that works with industry and government to advance measurement science and develop standards.

Nominal Load

Magnitude of the load specified by the applicable building code.

Nominal Strength*

Strength of a structure or component (without the resistance factor or safety factor applied) to resist the load effects, as determined in accordance with these Standard Specifications.

Non-Bearing Wall

A wall that supports no vertical load, other than its own weight.

Noncompact Section

A steel section, which does not qualify as a compact section, and the width-thickness ratios of its compression elements do not exceed the values designated in the AISC Manual.

Nonrigid Structure

A structure that cannot maintain its shape and may undergo large displacements and would collapse under its own weight when not supported externally.

NRCA (National Roofing Contractors Association)


NSPE (National Society of Professional Engineers)



Abbreviation for 'Not to Scale'.



Offset Bowstring Joist

A non-standard type of steel joist where the top chord is curved and the bottom chord is straight or level.

Offset Ridge

When the ridge of a steel joist that has the top chord pitched two ways is not in the center of the member or bay.

On The Flat

A measurement of distance horizontally on a plan, no slopes involved.

One-third Increase

When designing steel members for forces produced by wind or seismic conditions, the allowable stresses in the design formulas may be increased 1/3 above the values otherwise provided.

OSHA (Occupational Safety and Health Administration)

A federal organization whose purpose is to save lives, prevent injuries, and protect the health of the workers of America.


A structural member that is usually perpendicular to a steel joist and attaches under the outstanding leg of one of the steel joist top chord angles. It then bears on a beam or wall and cantilevers across, similar to a top chord extension.

Outstanding Leg

The leg of a structural angle which is projecting toward or away from you when viewing.


The extension of the top chord of a steel joist beyond the outside of the bearing support. See Top Chord Extension.


The entity that is identified as such in the Contract Documents.



P-Delta Effect

The secondary effect of column axial loads and lateral deflection on the moments in structural members.

Pack Out

When steel joists are erected in multiple bays, they begin to hit each other end to end (or pack out) because the center to center of beam is not true or the steel joists are too long.

Panel or Panel Length

1) The distance between two adjacent panel points of a steel joist or joist girder 2) A sheet of steel deck for a roof or floor.

Panel Point

The point where one or more web members intersect the top or bottom chords of a steel joist or joist girder. See Joint.

Parallel Chord

Type of steel joist or joist girder, which has its top and bottom chords parallel to each other. The member can be sloped and still have parallel chords.


Describes objects or components characteristics and relationships.


The portion of a vertical wall of a building, which extends above the roofline at the intersection of the wall and roof.

Part Number

See Mark and Piece Mark.

Partially Restrained

A type of connection that displays a moment rotation behavior that can neither be described as pinned nor fixed.


A wall that is one story or less in height used to subdivide the interior space in a building and can be a bearing wall or a non-bearing wall.


The SI unit of measure for stress or force per unit area (N/m^2).


Abbreviation for 'Professional Engineer'.


The highest point of a gable or also the highest point on a steel joist or joist girder where the sloped chords meet. See also Apex.


A small enclosed structure above the roof of a building.

Permanent Load

Load in which variations over time are rare or of small magnitude. All other loads are variable loads.


An official document or certificate by a governmental agency or building official authorizing performance of a building process or other specified activity.

Piece Mark

See Mark and Part Number.


A reinforced or enlarged portion of a masonry wall to provide support for vertical roof loads or lateral loads on the wall.

Pin Connection or Support

A connection where no moment is transferred from one member to another, only axial and shear forces. This type of support has one degree of freedom, it can freely rotate about its axis but it cannot displace in any direction. Two mutually perpendicular reactive forces exist at the pin and their lines of action pass through the center of the pin. See Hinge Support.


A hollow cylinder of metal used for the conveyance of water or gas or used as a structural column, which comes in sizes of standard, extra strong and double-extra strong.

Pipe Bridge

A structural system where two steel joists are used to carry loads such as piping or ducts. The two steel joists have to have diagonal bridging and their top and bottom chords have to be laced together with structural members to provide stability for the whole structure.


Is the slope or inclination of a member. It is defined as the ratio of the total rise to the total width. It also is defined as the angle that the top chord makes with the lower chord. There can be single or double-pitched members.

Placement Plans

Drawings that are prepared depicting the interpretation of the Contract Documents requirements for the material to be supplied by the Seller. These floor and/or roof plans are approved by the Specifying Professional, Buyer or Owner for conformance with the design requirements. The Seller uses the information contained on these drawings for final material design. A unique piece mark number is typically shown for the individual placement of steel joists (bar joists), Joist Girders and accessories along with sections that describe the end bearing conditions and minimum attachment required so that material is placed in the proper location in the field.

Placing Plan

See Erection Plan and Framing Plan.

Plan North

The North arrow symbol on a contract drawing, usually 90 degrees to the longitudinal axis of the plan so that communication will be easier for the elevations of the building, sections, etc.

Plane Frame

A two-dimensional structural framework.

Plastic Design

A design concept based on multiplying the actual design loads by a suitable load factor and then using the yield stress as the maximum stress in any member.


A thin, flat piece of metal of uniform thickness usually over 8 inches to 48 inches in width.

Plate Girder

A built-up structural beam.

PLF (Pounds per Linear Foot)

A unit of load obtained by multiplying pounds per square foot times the tributary width on a joist.


A rod, plate, or angle welded between a two-angle web member or between a top or bottom chord panel to tie them together usually located at the middle of the member. See Tie or Filler.

Plug Weld

A weld in a slot in a piece of steel, which overlaps another piece. A principle use for a plug weld is to transmit shear in a lap joint. See Slot Weld and Puddle Weld.


Project Management Contract

Poisson's Ratio

Defined as the ratio of the unit lateral strain to the unit longitudinal strain. It is constant for a material within the elastic range. For structural steel, the value is usually taken as 0.3. It gradually increases beyond the proportional limit, approaching 0.5.

Polar Moment of Inertia (J)

Is the sum of any two moments of inertia about axes at right angles to each other. It is taken about an axis, which is perpendicular to the plane of the other two axes.


Retention of water at low or irregular areas on a roof due solely to the deflection of flat roof framing.

Portal Frame

A rigid frame structure that is designed to resist longitudinal loads, where diagonal bracing is not permitted. It has rigidity and stability in its plane.

Pounds (LB or #)

A unit of weight.

Pour Stop

An angle used around the sides of a floor to contain the concrete when it is being poured.

Powder Actuated

A fastening method that uses a powdered charge to imbed the fastener into the member.


To manufacture or construct parts or sections of structural assemblies beforehand, ready for quick assembly and erection at a jobsite.

Press Brake

A machine used in cold-forming metal sheet or strip into a desired cross section or structural shape.

Primary Members

This is the main load carrying members of a structure such as a beam or joist girder.

Principle of Superposition

States that the resultant is the algebraic sum of the effects when applied separately.

Primer or Paint

The initial coating of a member applied in the shop, which is not a finish coat and only protects from rust for a limited time.

Prismatic Beam

A beam with uniform cross section.

Profile Drawing

A drawing or diagram, which shows the outline of a steel joist with dimensions and also maybe the web system configuration and bridging rows. See Side-View Diagram

Proportional Limit

The point on a stress-strain curve where the linear relationship between stress and strain ends, and usually coincides with the material yield point.

PSI (Pounds per Square Inch)

A unit of stress or pressure.

PSF (Pounds per Square Foot)

A unit of stress on a steel joist.

Puddle Weld

See Plug Weld.


Horizontal structural member that supports roof deck and is primarily subjected to bending under vertical loads such as dead, snow or wind loads.



Quality Assurance

System of shop and field activities and controls implemented by the owner or his/her designated representative to provide confidence to the owner and the building authority that quality requirements are implemented.

Quality Control

System of shop and field controls implemented by the seller and erector to ensure that contract and company fabrication and erection requirements are met.



Radius of Gyration (r)

Is the distance from the neutral axis of a section to an imaginary point at which the whole area of the section could be concentrated and still have the same moment of inertia. Formula: The square root of (the moment of inertia in inches^4 divided by the area of the section in inches^2) expressed in inches.


The main beam supporting a roof system or a sloping roof framing member.


The edge of a roof that intersects the gable part of a roof.

RCSC (Research Council on Structural Connections)



The force or moment developed at the points of a support.


The reactions that are not necessary for static equilibrium.


An additional member added to a structural member to provide additional strength.


The process of strengthening a member with an additional piece of material.


Is a decrease in load or stress of a member under a sustained constant deformation.


The reconstruction or renewal of any part of an existing structure or building for the purpose of its maintenance.

Required Strength*

Forces, stress, and deformations produced in a structural component, determined by either structural analysis, for the LRFD or ASD load combinations, as appropriate, or as specified by these Standard Specifications.

Residual Stress

Pre-induced stresses within a structural member due to uneven cooling of the shape after hot-rolling.


The capacity of a structure or structural member to resist the effects of loads or forces imposed on it.

Resistance Factor

Factor that accounts for unavoidable deviations of the nominal strength from the actual strength and for the manner and consequences of failure.

Retaining Wall

A wall designed to resist the lateral displacement of soil, water, or any other type of material.


Request For Information. The RFI procedure is used in the construction industry when it is necessary to confirm the interpretation of a detail, specification or note on the construction drawings or to secure a documented directive or clarification from the architect or client that is needed to continue work.


A fabricated fold or bend in a sheet of steel deck which projects up from a horizontal plane.


The highest point on the roof of a building formed by two intersecting slopes or the horizontal line made by the top surfaces of the two intersecting sloping roof surfaces.

Rigid Connection

A connection where moment is transferred from one member to another. See also Fixed-End Support.

Rigid Frame or Structure

A structural framing system consisting of members joined together with moment or rigid connections, which maintain their original angular relationship under load without the need for bracing in its plane. See Frame and Stability.


The vertical distance from the bottom to the top of an entity.

RMI (Rack Manufacturers Institute)

An institute organized in 1958 by industry leaders as a not-for-profit trade association. Its mission is to advance standards, quality, safety, and general fitness for intended use of industrial steel storage rack systems.


A smooth solid round bar used for the web system of a steel bar joist.

Roof Covering

The exposed exterior roof skin of a building, which can be sheets, panels or other materials.

Roof Overhang

A roof extension that projects beyond the ends or sides of a building.

Roller Support

This type of support has two degrees of freedom, it can freely rotate about its axis or displace in one direction in the plane. Only one reactive force exists at a roller, which acts perpendicular to the path of the displacement and its line of action passes through the center of the roller.



S Shapes

A hot rolled shape called an American Standard Beam with symbol S.

Saddle Angle

The angle connection or seat on the end of a header or frame, which bears from the side on the top chord of a steel joist. This angle should be designed to carry the reaction of the header or frame to the center of the steel joist and must rest on and weld to both top chord angles.

Safety Factor

Factor that accounts for deviations of the actual strength from the nominal strength, deviations of the actual load from the nominal load, uncertainties in the analysis that transforms the load into a load effect and for the manner and consequences of failure.

Sag Rod

A tension member used to limit the deflection of a girt or purlin in the direction of the weak axis.

SBC (Standard Building Code)

A minimum model regulatory code for the protection of public health, safety, welfare and property by regulating and controlling the design, construction, quality of materials, use, occupancy, location and maintenance of all buildings and structures within a jurisdiction.

Scab On

A member fastened or welded to another member for reinforcement.

Scissor Joist

A non-standard type of steel joist where both the top chord and bottom chord are double pitched and parallel with each other.


Any opening or drain in the side of a structure, flat roof, or downspout for the drainage of rainwater.


A framed opening in a roof used for access to the roof from inside a building.

SDI (Steel Deck Institute)

An institute that brings uniformity to the design, manufacture, quality control, and construction practices applicable to cold-formed steel deck.

SEAA (Steel Erectors Association of America)

An organization that sets uniform standards among the many steel erectors and helps promote safety in the erection industry.

Seat Depth

The out-to-out depth of the end bearing shoe or seat of a steel joist or joist girder which is the distance from the top of the top chord to the bottom of the bearing seat angle or plate.

Section Modulus (S)

A physical property of strength of a structural member. It relates bending moment and maximum bending stress within the elastic range. Formula: S=I/c where 'I' is the moment of inertia of the cross-section about the neutral axis in inches^4 and 'c' is the distance from the neutal axis to the outermost fibers.

Seismic Load

Are assumed lateral forces acting in any horizontal direction that produce stresses or deformations in a structural member due to the dynamic action of an earthquake.

Self Tapping Screw

A mechanical fastener for attaching metal deck, panels, or other materials to a structure, which taps its own threads in a predrilled hole.


A company certified by the Joist Institute engaged in the manufacture and distribution of steel joists (bar joists), Joist Girders and accessories.

Semper Gumbie

Marine-speak for "always flexible", a principle requirement of BIM based collaboration among all participants in a construction project.


A breakdown of when materials are to be made or delivered for a project with one following after the other.

Service Load

Load under which serviceability limit states are evaluated.

Serviceability Limit State

Limiting condition affecting the ability of a structure to preserve its appearance, maintainability, durability, or the comfort of its occupants or function of machinery, under normal usage.

Set Back

The distance from the outside edge of an angle or other member to the edge of a gusset plate or angle welded near the end.


An interior space, enclosed by walls, which extends through one or more stories or basement which connects successive floors and/or roof for elevators, dumbwaiters, mechanical equipment, etc.

Shape Factor

The ratio of the plastic section modulus Z to the elastic section modulus S or the ratio of the plastic moment Mp to the yield moment My.


A condition or force causing two contacting parts of a material to slide past each other in opposite directions parallel to their plane of contact.

Shear Center

The point in a cross section of a structural member to which a load may be applied and not induce any torsional stress in the cross section.

Shear Diagram

A diagram that represents graphically the shear at every point along the length of a member.

Shear Release

A boundary condition that constrains a member end from axial displacement and rotation but allows movement in a direction perpendicular to the members longitudinal axis.

Shear Stud Connector

A steel device used in composite design which is welded to the top flange of a beam or top chord of a steel joist which transfers shear from a concrete slab to the supporting member.

Shear Wall

A wall that resists horizontal shear forces applied in the plane of the wall.


A piece of steel used to level a steel joist seat. It can be a bent plate, flat plate or rod.

Shipping List

A list that gives each part or mark number, quantity, length of material, total weight, or other description of each piece of material to be shipped to a jobsite. See also Bill of Lading.

Shop Drawings

1) Can also be called the erection plans or framing plans 2) The actual drawings used by a shop to fabricate a product which includes all dimensions, materials, tolerances, etc.


The process of temporarily supporting a structure or structural member with auxiliary members.

SI (Le Systeme International d'Unites)

The international abbreviation for the International System of Units or metric system.

Side Lap

The lap at the sides of a sheet of steel deck and is attached by side lap screws or welds between supports.

Side Lap Screws

A screw used to connect the sides of two adjacent sheets of metal decking together, #10 being the standard size.

Side-View Diagram

A drawing or diagram which shows the outline of a steel joist with dimensions and also maybe the web system configuration and bridging rows. See Profile Drawing.

Side Wall

An exterior wall which is parallel to the ridge of the building.


The lateral movement of a structure, when subjected to lateral loads or unsymmetrical vertical loads.

Simple or Single Span

A span with supports at each end, no intermediate support, that restrain only against vertical displacement with the ends of the member being free to rotate.

Single Curvature

When moments produce a deformed or bent shape of a structural member having a smooth continuous curve or arc.

Single Slope

A sloping roof in one plane which slopes from one wall to the opposite wall.

Single-Ply Roof

A type of roofing system using thermoplastic membranes, which are seamed by either hot air or solvent welding of one sheet to the next, or using thermoset membranes that are seamed with an adhesive.

SJI (Steel Joist Institute)

The institute is a non-profit organization of active steel joist manufacturers that maintains sound engineering practice throughout the steel joist industry. The institute cooperates with business and government agencies to establish steel joist standards and does continuing research of their products to maintain the integrity of their products.


The condition when two entities come together at an angle, which is not 90 degrees or perpendicular to each other.


An opening or roof accessory in a roof or ceiling for admitting light. If it bears across a steel joist, the top chord angles may be unbraced for design considerations.


A non-metallic byproduct of the welding process forming a hard crust over the molten steel, which should be chipped away for inspection of a weld.

Slender Element Section

A steel section whose width-thickness ratios of any compression element exceeds the values of a noncompact section.

Slenderness Ratio

The ratio of the effective length of a column to the radius of gyration of the column about the same axis of bending.

Slip-Critical Joint

A bolted joint in which the slip resistance of the connection is required.


The angle or inclination a structural member makes with reference to a horizontal position expressed in inches of vertical rise per 12 inches of horizontal run, i.e. 3/12.

Slot Length

The length of a slotted hole in a steel joist bearing seat or other structural connection.

Slot Weld

See Plug Weld.

Snow Drift

The triangular accumulation of snow at high/low areas of structures expressed in PSF or PLF.

Snow Load

Are forces applied to a member by snow accumulation on the roof of a structure.


A panel that covers the underside of an overhang, cantilever end, or mansard.

Soil Pressure

The load per unit area that a structure exerts through its foundation on the underlying soil.


The centerline-to-centerline distance between structural steel supports such as a beam, column or Joist Girder or the clear span distance plus four inches onto a masonry or concrete wall.

Spandrel Joist or Beam

A structural member at the outside wall of a building, supporting part of the floor or roof and possibly the wall above.

Special Design

A design required by a loading diagram or other special notes, because a standard steel joist or joist girder cannot be specified from a load table.

Special Profile Steel Joists

Open Web Steel Joist (OWSJ), a lightweight steel truss consisting of chords and a triangulated web system, proportioned to span between bearing points, similar to standard steel joist, but with unique architectural profiles. See Specialty Joists.

Specialty Joists

Open Web Steel Joist (OWSJ), a lightweight steel truss consisting of chords and a triangulated web system, proportioned to span between bearing points, similar to standard steel joist, but with unique architectural profiles. See Special Profile Joists.


The detailed description of requirements, materials, dimensions, etc. of a proposed building or project.

Specified Minimum Yield Stress

Lower limit of yield stress specified for a material as defined by ASTM.

Specifying Professional

The licensed professional who is responsible for sealing the building Contract Documents, which indicates that he or she has performed or supervised the analysis, design and document preparation for the structure and has knowledge of the load-carrying structural system.


Connection between two structural members joined at their ends by either bolting or welding to form a single, longer member.

Sprinkler System

A system for fire protection usually consisting of overhead piping connected to a water supply to which automatic sprinklers are attached that discharges water in a specific pattern for extinguishment or control of a fire.


In deck terminology, it is the term for 100 square feet of metal deck or roofing surface. Formula: number of squares = sum of(length of deck sheet in feet * width of steel deck sheet in feet * number of pieces)divided by 100.

Square Cut

A cut to a structural member made at 90 degrees to the length of the member.

SRI (Steel Recycling Institute)


SSPC (Steel Structures Painting Council)

A professional technical society whose primary objective is to improve the technology and practice of prolonging the life of steel and concrete structures through the use of protective coatings.

SSR (Standing Seam Roof)

A type of roof system where the metal decking is attached to clips which are then attached to the beam or steel joist. Usually this type of roof system cannot be counted on to provide lateral stability or support to the steel joist top chord.

SSRC (Structural Stability Research Council)



A hot rolled structural tee shape with symbol ST, which is cut or split from S Shapes.


Condition reached in the loading of a structural component, frame or structure in which a slight disturbance in the loads or geometry does not produce large displacements.

Stabilizer Plate

A steel plate at a column or wall inserted between the end of a bottom chord of a steel joist (bar joist) or Joist Girder to weld the bottom chord to or to restrain the bottom chord from lateral movement.

Standard Specifications

Documents developed and maintained by the Steel Joist Institute for the design and manufacture of open web steel joists and Joist Girders. The term "SJI Standard Specifications" encompass by reference the following: ANSI/SJI-K-1.1 Standard Specifications for Open Web Steel Joists, K-Series; ANSI/SJI-LH/DLH-1.1 Standard Specifications for Longspan Steel Joists, LH-Series and Deep Longspan Steel Joists, DLH-Series; and ANSI/SJI-JG-1.1 Standard Specifications for Joist Girders.

Standard Steel Joists

Open Web Steel Joist (OWSJ), a lightweight steel truss consisting of parallel chords and a triangulated web system, proportioned to span between bearing points. Also known as metal joists or bar joists.

Starter Joist

A steel joist (bar joist) that is spaced close to a wall for deck support, usually 6 inches.

Static Equilibrium

A member or body that is initially at rest and remains at rest, when acted upon by a system of forces.

Static Load

A load applied slowly and then remains nearly constant.

Statically Determinate

A member or structure that can be analyzed and the reactions and forces determined from the equations of equilibrium.

Statically Indeterminate

A member or structure that cannot be analyzed solely by the equations of statics. It contains unknowns in excess of the number of equilibrium equations available. Additional equations must be written based on a knowledge of elastic deformations.

Steel Decking

Also known as metal decking, a structural corrugated steel component used as the material layer between the primary structural components.

Steel Joists

Open Web Steel Joist (OWSJ), a lightweight steel truss consisting, in the standard form, of parallel chords and a triangulated web system, proportioned to span between bearing points. Also known as metal joists or bar joists.


A member used to strengthen another member against buckling or to distribute load or to transfer shear. Usually a flat bar, plate, or angle welded perpendicular to the longitudinal axis of the member.


The resistance to deformation of a structural member, which can be measured by the ratio of the applied force to the corresponding displacement.


That portion of a building that is between the upper surface of any floor and the upper surface of the floor next above.

Story Drift

The difference in horizontal deflection at the top and bottom of a story.

Strain Hardening

The condition when ductile steel exhibits the capacity to resist additional load than that which caused initial yielding after undergoing deformation at or just above the yield point.

Strength Limit State

Limiting condition affecting the safety of the structure, in which the ultimate load-carrying capacity is reached.


An internal force that resists a load. It is the intensity of force per unit of area, i.e., psi (pounds per square inch).

Stress Concentration

A localized stress which is considerably higher than average due to sudden changes in loading or sudden changes in geometry.


In buildings, a structural member supporting stair steps.

Strong Axis

The cross section that has the major principal axis.

Structural Analysis

Determination of load effects on members and connections based on principles of structural mechanics.

Structural Drawings

The graphic or pictorial portions of the Contract Documents showing the design, location and dimensions of the work. These documents generally include plans, elevations, sections, details, connections, all loads, schedules, diagrams and notes.


A mechanism designed and built or constructed of various parts jointed together in some definite manner to carry loads and resist forces.

Structural Steels

A large number of steels suitable for load-carrying members in a variety of structures because of strength, economy, ductility, and other properties. Strength levels are obtained by varying the chemical composition and by heat treatment.


A structural member used as a brace to resist axial forces.


A wood or metal vertical wall member, to which exterior or interior covering material may be attached. It can be either load bearing or non-load bearing.


A partial vacuum due to wind loads on a building, which cause a load in the outward direction.

Sump Pan

A metal decking accessory used at drain locations to close the opening where holes are cut in the metal deck.

Superimposed Load

Usually means a load that is in addition to the dead weight of the steel bar joists and bridging.


The curvature of a structural member in the perpendicular transverse direction of its vertical axis.



Tagged End (T.E.)

The end of a steel joist (bar joist) or Joist Girder where an identification or piece mark is shown by a metal tag. The member must be erected with this tagged end in the same position as the tagged end noted on the placement plan.

Tangent Modulus

The slope of the stress-strain curve of a material in the inelastic range at any given stress level.


A hot rolled shape with symbol T and is shaped like a “T”.

Temporary Structure

Anything not a part of the permanent structural system, to be removed before or after the completion of the structure.

Tensile Strength (of material)

Maximum tensile stress that a material is capable of sustaining as defined by ASTM.


A condition caused by the action of stretching or pulling of a component.

Thermal Block

A spacer that has a low thermal conductance.


The horizontal component of a reaction, or an outward horizontal force.


A rod, plate, or angle welded between a two angle web member or between a top or bottom chord panel to tie them together usually located at the middle of the member. See Filler or Plug.

Tie Joist

A steel joist (bar joist) that is bolted at a column.

Tilted Joist

A steel joist supported in a manner such that the vertical axes of the steel joist is not perpendicular with respect to the ground.


The outside points of each leg of a structural angle.

Toe of Fillet

1) The end or termination edge of a fillet weld; or 2)The end or termination edge of a rolled section fillet.

Toe of Weld

The junction between the face of a weld and the base metal.


A unit of weight equal to 2000 pounds.

Top Chord

The top member of a steel joist (bar joist) or joist girder.

Top Chord Bearing

The bearing condition of a steel joist (bar joist) or joist girder that bears on its top chord seat.

Top Chord Extension (TCX)

The extended part of a steel joist (bar joist) top chord. This type of extension only has the two top chord angles extended past the joist seat.

Torque Wrench

A wrench containing an adjustable mechanism for measuring and controlling the amount of turning force exerted when used to tighten nuts and bolts.

Torsional Buckling

Buckling mode in which a compression member twists about its shear center axis.

Torsion Loads

A load that causes a member to twist about its longitudinal axis. Simple torsion is produced by a couple or moment in a plane, perpendicular to the axis.


Abbreviation for 'Top of Steel'.

Total Project Cost Accountability

New Millennium's unique combination of digital design and engineering expertise that can lead to a wide range of project benefits, from enhanced architectural achievement, to cost reductions and owner-developer revenue gains.


The ability of steel to absorb large amounts of energy without being readily damaged.


Crossing from side to side or placed crosswise.

Tributary Width or Area

The design area that contributes load to a structural member. It is one half the distance between members on either side of the member.

Trimmer Joist

One of the steel joists supporting a header. The header applies a concentrated load at that point on the trimmer joist.


In general, a structural load-carrying member with an open web system designed as a simple span with each member designed to carry a tension or compression force. The entire structure act will act like a beam.


A hollow structural steel member shaped like a square or rectangle used as a beam, column, or for bracing. Usually the nominal outside corner radius is equal to two times the wall thickness.


A rotating sleeve or link with internal screw threads at each end and used to tighten or connect the ends of a rod.


A method for pre-tensioning high-strength bolts by the rotation of the wrench a predetermined amount after the nut has been tightened to a snug fit.



UBC (Uniform Building Code)

A minimum model regulatory code for the protection of public health, safety, welfare and property by regulating and controlling the design, construction, quality of materials, use, occupancy, location and maintenance of all buildings and structures within a jurisdiction.

UL (Underwriters Laboratories, Inc.)

A non-profit product safety testing and certification organization.

Ultimate Load

The force necessary to cause rupture.

Ultimate Strength

The maximum stress attained by a structural member prior to rupture which is the ultimate load divided by the original cross-sectional area of the member.

Ultimate Strength Design


Unbraced Frame

A frame providing resistance to lateral load by the bending resistance of the frame members and their connections.

Unbraced Length

Distance between braced points of a member, measured between the centers of gravity of the bracing members.

Unbraced Top Chord

The specific length where the top chord of a steel joist has no lateral bracing by steel deck, bridging, or any other means.


A notch or groove melted into the base metal next to the toe or root of a weld and left unfilled by weld metal.


Description of a joist that is suspended from upper support points where most of the mass of steel is below the actual support points.

Uniformly Distributed Load

A load or force, for practical purposes, that may be considered constant over the entire length or partial length of the member.


Abbreviation for 'Unless Noted Otherwise'.


The wind load on a member that causes a load in the upward direction. The gross uplift is determined from various codes and is generally a horizontal wind pressure multiplied by a factor to establish the uplift pressure. The net uplift is the gross uplift minus the allowable portion of dead load including the weight of the steel joist and is the load that the specifying professional shall indicate to the joist manufacturer.

Uplift Bridging

The bridging required by uplift design. Usually always required at the first bottom chord panel point of a K-Series, LH- or DLH-Series steel joist and at other locations along the bottom chord as required by design.

Upstanding Leg

The leg of a structural angle, which is projecting up from you when viewing.




The angle formed by two sloping sides of a roof.

Value Engineering

The application of the Scientific Method to the study of selecting the optimum or best system that meets the need of the customer.

Vapor Barrier

A physical membrane that prevents moisture or water vapor from penetrating to the other side.

Variable Load

Load not classified as permanent load.

Varying Distributed Load

A load or force, for practical purposes, that may be considered varying over the surface of the member, for example a snow drift.

VG-Type Joist Girder

A type of Joist Girder where steel joists are located at panel points where vertical webs intersect the top chord only. This type of girder is used for ducts to pass thru since the steel joists do not interfere with their passage.


The oscillating, reciprocating, or other periodic motion of a rigid or elastic body or medium, such as a floor when its position or state of equilibrium has been changed.



W Shapes

A hot rolled shape called a Wide Flange Shape with symbol W, which has essentially parallel flange surfaces.


A vertical or near vertical structure that encloses or separates spaces and may be used to resist horizontal or vertical forces or bending forces.

Wall Anchor

A small piece of angle or other structural material that is usually bolted to a wall, to which a starter steel joist or bridging angle is welded or bolted to.

Wall Covering

The exterior wall skin consisting of sheets or panels.


A flat ring of metal with a hole in the middle used to give thickness to a joint or to distribute pressure under the head of a nut or bolt.

Weak Axis

The cross section that has the minor principal axis.

Weathering Steel

A type of high-strength steel which can be used in normal outdoor environments, without being painted. Should not be used in corrosive or marine environments.


The vertical or diagonal members joined at the top and bottom chords of a steel joist (bar joist) or Joist Girder to form triangular patterns.

Web Buckling

The buckling of a web plate.

Web Configuration

The arrangement of the actual web system of a steel joist or joist girder, which can be shown with a profile view of the member.

Web Crippling

The local failure of a web plate in the region of a concentrated load or reaction.

Welded Splice

A splice between two materials, which has the joint made continuous by the process of welding.


The process of joining materials together, usually by heating the materials to a suitable temperature.


Is the ability of steel to be welded without its basic mechanical properties being changed.

Welding Washer

A metal device with a hole through it, to allow for plug welding of deck to structural steel.

Wind Column

A vertical member supporting a wall system designed to withstand horizontal wind loads. Usually between two main vertical load carrying columns.

Wind Load

A force or lateral pressure in pounds per square foot that is applied to a member due to wind blowing in any direction.


The direction or side toward the wind. Opposite of leeward.

Working Drawings

The complete set of architectural drawings prepared by a registered architect.

Working Load

Also called service load, is the actual load that is acting on the structure.

Working Point

The point where two or more centroid lines of structural members intersect.

WRC (Welding Research Council)

This organization conducts cooperative research in welding with interested scientific societies, government departments, and any company using welded products.

WSD (Working Stress Design)

A structural design method whereby a structural element is designed so that the unit stresses computed under the action of working or service loads do not exceed the specified allowable values. See Allowable Stress Design and Elastic Design.


A hot rolled structural tee shape with symbol WT, which is cut or split from W Shapes.




Structural bracing that resembles the letter “X”.



Yield Point

First stress in a material at which an increase in strain occurs without an increase in stress as defined by ASTM.

Yield Strength

Stress at which a material exhibits a specified limiting deviation from the proportionality of stress to strain as defined by ASTM.

Yield Stress

Generic term to denote either yield point or yield strength, as appropriate for the material.

Young's Modulus

See Modulus of Elasticity.



"Z" Section

A structural section in the shape of a "Z" cold formed from a steel sheet.


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New Millennium Building Systems is a wholly owned subsidiary of Steel Dynamics Inc.