Glossary · AISC 360-22

Notes:

(1) Terms designated with † are common AISI-AISC terms that are coordinated between the two standards development organizations.
(2) Terms designated with * are usually qualified by the type of load effect, for example, nominal tensile strength, available compressive strength, and design flexural strength.
(3) Terms designated with ** are usually qualified by the type of component, for example, web local buckling and flange local bending.
Active fire protection. Building materials and systems that are activated by a fire to mitigate adverse effects or to notify people to take action to mitigate adverse effects.

Allowable strength*†. Nominal strength divided by the safety factor, $R_{n} / \Omega$ .

Allowable stress*. Allowable strength divided by the applicable section property, such as section modulus or cross-sectional area.

Anchor bolt. See Anchor rod.

Anchor rod. A mechanical device that is either cast in concrete or drilled and chemically adhered, grouted, or wedged into concrete and/or masonry for the purpose of the subsequent attachment of structural steel.
Applicable building code†. Building code under which the structure is designed.
Approval documents. The structural steel shop drawings, erection drawings, and embedment drawings, or where the parties have agreed in the contract documents to provide digital model(s), the fabrication and erection models. Approval documents may include a combination of drawings and digital models.
ASD (allowable strength design)†. Method of proportioning structural components such that the allowable strength equals or exceeds the required strength of the component under the action of the ASD load combinations.
ASD load combination†. Load combination in the applicable building code intended for allowable strength design (allowable stress design).
Authority having jurisdiction (AHJ). Organization, political subdivision, office, or individual charged with the responsibility of administering and enforcing the provisions of this Specification.
Available strength*†. Design strength or allowable strength, as applicable.
Available stress*. Design stress or allowable stress, as applicable.
Average rib width. In a formed steel deck, average width of the rib of a corrugation.
Beam. Nominally horizontal structural member that has the primary function of resisting bending moments.
Beam-column. Structural member that resists both axial force and bending moment.
Bearing (local compressive yielding)†. Limit state of local compressive yielding due to the action of a member bearing against another member or surface.
Bearing-type connection. Bolted connection where shear forces are transmitted by the bolt bearing against the connection elements.
Block shear rupture†. In a connection, limit state of tension rupture along one path and shear yielding or shear rupture along another path.

Bolting assembly. An assembly of bolting components that is installed as a unit.

Bolting component. Bolt, nut, washer, direct tension indicator, or other element used as a part of a bolting assembly.
Box section. Square or rectangular doubly symmetric member made with four plates welded together at the corners such that it behaves as a single member.
Braced frame†. Essentially vertical truss system that provides resistance to lateral forces and provides stability for the structural system.
Bracing. Member or system that provides stiffness and strength to limit the out-of-plane movement of another member at a brace point.
Branch member. In an HSS connection, member that terminates at a chord member or main member.
Buckling†. Limit state of sudden change in the geometry of a structure or any of its elements under a critical loading condition.
Buckling strength. Strength for instability limit states.
Built-up member, cross section, section, shape. Member, cross section, section, or shape fabricated from structural steel elements that are welded or bolted together.
Camber. Curvature fabricated into a beam or truss so as to compensate for deflection in- duced by loads.
Charpy V-notch impact test. Standard dynamic test measuring notch toughness of a specimen.
Chord member. In an HSS connection, primary member that extends through a truss connection.

Cladding. Exterior covering of structure.

Cold-formed steel structural member†. Shape manufactured by press-braking blanks sheared from sheets, cut lengths of coils or plates, or by roll forming cold- or hot-rolled coils or sheets; both forming operations being performed at ambient room temperature, that is, without manifest addition of heat such as would be required for hot forming.
Collector. Also known as drag strut; member that serves to transfer loads between floor diaphragms and the members of the lateral force-resisting system.
Column. Nominally vertical structural member that has the primary function of resisting axial compressive force.
Column base. Assemblage of structural shapes, plates, connectors, bolts, and rods at the base of a column used to transmit forces between the steel superstructure and the foundation.
Combined method. Pretensioning procedure incorporating the application of a prescribed initial torque or tension, followed by the application of a prescribed relative rotation between the bolt and nut.
Compact composite section. Filled composite section that can reach the plastic axial compressive strength or plastic moment before local buckling of the steel elements occurs as defined by the steel element width-to-thickness ratios less than or equal to $\lambda_{p}$ .

Compact section. Section that can reach the plastic moment before local buckling occurs as defined by the element width-to-thickness ratio less than or equal to $\lambda_{p}$ .

Compartmentation. Enclosure of a building space with elements that have a specific fire endurance.
Complete-joint-penetration (CJP) groove weld. Groove weld in which weld metal extends through the joint thickness, except as permitted for HSS connections.
Composite. Condition in which steel and concrete elements and members work as a unit in the distribution of internal forces.
Composite beam. Structural steel beam in contact with and acting compositely with a reinforced concrete slab.
Composite component. Member, connecting element, or assemblage in which steel and concrete elements work as a unit in the distribution of internal forces, with the exception of the special case of composite beams where steel anchors are embedded in a solid concrete slab or in a slab cast on formed steel deck.
Composite plate shear wall. Composite wall composed of structural steel plates, ties, steel anchors, and structural concrete acting together.
Concrete breakout surface. The surface delineating a volume of concrete surrounding a steel headed stud anchor that separates from the remaining concrete.
Concrete crushing. Limit state of compressive failure in concrete having reached the ultimate strain.
Concrete-encased beam. Beam totally encased in concrete cast integrally with the slab.
Concrete haunch. In a composite floor system constructed using a formed steel deck, the section of solid concrete that results from stopping the deck on each side of the girder.
Connection†. Combination of structural elements and joints used to transmit forces between two or more members.
Construction documents. Written, graphic, and pictorial documents prepared or assembled for describing the design (including the structural system), location, and physical characteristics of the elements of a building necessary to obtain a building permit and construct a building.
Contract documents. The documents that define the responsibilities of the parties that are involved in bidding, fabricating, and erecting structural steel. Contract documents include the design documents, the specifications, and the contract.
Cope. Cutout made in a structural member to remove a flange and conform to the shape of an intersecting member.
Cover plate. Plate welded or bolted to the flange of a member to increase cross-sectional area, section modulus, or moment of inertia.
Cross-connection. HSS connection in which forces in branch members or connecting elements transverse to the main member are primarily equilibrated by forces in other branch members or connecting elements on the opposite side of the main member.
Cyclic loading. Repeated transient loading of sufficient frequency and magnitude of stress which could result in fatigue crack initiation and propagation.
Design. The process of establishing the physical and other properties of a structure for the purpose of achieving the desired strength, serviceability, durability, constructability, economy, and other desired characteristics. Design for strength, as used in this Specification, includes analysis to determine required strength and proportioning to have adequate available strength.
Design-basis fire. Set of conditions that define the development of a fire and the spread of combustion products throughout a building or portion thereof.
Design documents. Design drawings, design model, or a combination of drawings and models. In this Specification, reference to these design documents indicates design documents that are issued for construction as defined in Section A4.
Design drawings. Graphic and pictorial portions of the design documents showing the design, location, and dimensions of the work. Design drawings generally include, but are not necessarily limited to, plans, elevations, sections, details, schedules, diagrams, and notes.
Design load†. Applied load determined in accordance with either LRFD load combinations or ASD load combinations, as applicable.
Design model. Three-dimensional digital model of the structure that conveys the structural steel requirements as specified in Section A4.
Design strength*†. Resistance factor multiplied by the nominal strength, $\phi R_{n}$ .
Design wall thickness. HSS wall thickness assumed in the determination of section properties.
Diagonal stiffener. Web stiffener at column panel zone oriented diagonally to the flanges, on one or both sides of the web.
Diaphragm†. Roof, floor, or other membrane or bracing system that transfers in-plane forces to the lateral force-resisting system.
Direct bond interaction. In a composite section, mechanism by which force is transferred between steel and concrete by bond stress.
Distortional failure. Limit state of an HSS truss connection based on distortion of a rectangular HSS chord member into a rhomboidal shape.
Distortional stiffness. Out-of-plane flexural stiffness of web.
Double-concentrated forces. Two equal and opposite forces applied normal to the same flange, forming a couple.
Double curvature. Deformed shape of a beam with one or more inflection points within the span.
Doubler. Plate added to, and parallel with, a beam or column web to increase strength at locations of concentrated forces.
Drift. Lateral deflection of structure.
Effective length. Length of an otherwise identical compression member with the same strength when analyzed with simple end conditions.
Effective length factor, K. Ratio between the effective length and the unbraced length of the member.
Effective net area. Net area modified to account for the effect of shear lag.

Effective section modulus. Section modulus reduced to account for buckling of slender compression elements.

Effective width. Reduced width of a plate or slab with an assumed uniform stress distribution which produces the same effect on the behavior of a structural member as the actual plate or slab width with its nonuniform stress distribution.
Elastic analysis. Structural analysis based on the assumption that the structure returns to its original geometry on removal of the load.
Elevated temperatures. Heating conditions experienced by building elements or structures as a result of fire which are in excess of the anticipated ambient conditions.
Encased composite member. Composite member consisting of a structural concrete member and one or more embedded steel shapes.

End panel. Web panel with an adjacent panel on one side only.

End return. Length of fillet weld that continues around a corner in the same plane.

Engineer of record. Licensed professional responsible for sealing the design documents and specifications.
Erection documents. The field-installation or member-placement drawings that are prepared by the fabricator to show the location and attachment of the individual structural steel shipping pieces. Where the parties have agreed in the contract documents to provide digital model(s), a dimensionally accurate 3D digital model produced to convey the information necessary to erect the structural steel, which may be the same digital model as the fabrication model. Erection documents may include a combination of drawings and digital models.
Expansion rocker. Support with curved surface on which a member bears that is able to tilt to accommodate expansion.
Expansion roller. Round steel bar on which a member bears that is able to roll to accomodate expansion.
Eyebar. Pin-connected tension member of uniform thickness, with forged or thermally cut head of greater width than the body, proportioned to provide approximately equal strength in the head and body.
Fabrication documents. The shop drawings of the individual structural steel shipping pieces that are to be produced in the fabrication shop. Where the parties have agreed in the contract documents to provide digital model(s), a dimensionally accurate 3D digital model produced to convey the information necessary to fabricate the structural steel, which may be the same digital model as the erection model. Fabrication documents may include a combination of drawings and digital models.

Factored load†. Product of a load factor and the nominal load.

Fastener. Generic term for bolts, rivets, or other connecting devices.

Fatigue†. Limit state of crack initiation and growth resulting from repeated application of live loads.

Faying surface. Contact surface of connection elements transmitting a shear force.

Filled composite member. Composite member consisting of an HSS or box section filled with structural concrete.

Filler. Plate used to build up the thickness of one component.

Filler metal. Metal or alloy added in making a welded joint.

Fillet weld. Weld of generally triangular cross section made between intersecting surfaces of elements.

Fillet weld reinforcement. Fillet welds added to groove welds.

Finished surface. Surfaces fabricated with a roughness height value measured in accordance with ANSI/ASME B46.1 that is equal to or less than 500 µin. (13 µm).
Fire. Destructive burning, as manifested by any or all of the following: light, flame, heat, or smoke.
Fire barrier. Element of construction formed of fire-resisting materials and tested in accordance with an approved standard fire-resistance test, to demonstrate compliance with the applicable building code.
Fire resistance. Property of assemblies that prevents or retards the passage of excessive heat, hot gases, or flames under conditions of use and enables the assemblies to continue to perform a stipulated function.
First-order analysis. Structural analysis in which equilibrium conditions are formulated on the undeformed structure; second-order effects are neglected.
Fitted bearing stiffener. Stiffener used at a support or concentrated load that fits tightly against one or both flanges of a beam so as to transmit load through bearing.
Flare-bevel-groove weld. Weld in a groove formed by a member with a curved surface in contact with a planar member.
Flare-V-groove weld. Weld in a groove formed by two members with curved surfaces.
Flashover. Transition to a state of total surface involvement in a fire of combustible materials within an enclosure.
Flat width. Nominal width of rectangular HSS minus twice the outside corner radius. In the absence of knowledge of the corner radius, the flat width is permitted to be taken as the total section width minus three times the thickness.
Flexibility. The ratio of the displacement (or rotation) to the corresponding applied force (or moment); the inverse of the stiffness.
Flexural buckling†. Buckling mode in which a compression member deflects laterally without twist or change in cross-sectional shape.
Flexural-torsional buckling†. Buckling mode in which a compression member bends and twists simultaneously without change in cross-sectional shape.
Force. Resultant of distribution of stress over a prescribed area.
Formed steel deck. In composite construction, steel cold formed into a decking profile used as a permanent concrete form.
Fully restrained moment connection. Connection capable of transferring moment with negligible rotation between connected members.
Gage. Transverse center-to-center spacing of fasteners.
Gapped connection. HSS truss connection with a gap or space on the chord face between intersecting branch members.

Geometric axis. Axis parallel to web, flange, or angle leg.

Girder. See Beam.

Girder filler. In a composite floor system constructed using a formed steel deck, narrow piece of sheet steel used as a fill between the edge of a deck sheet and the flange of a girder.
Gouge. Relatively smooth surface groove or cavity resulting from plastic deformation or removal of material.

Gravity load. Load acting in the downward direction, such as dead and live loads.

Grip (of bolt). Thickness of material through which a bolt passes.

Groove weld. Weld in a groove between connection elements. See also AWS D1.1/D1.1M.

Gusset plate. Plate element connecting truss members or a strut or brace to a beam or column.

Heat flux. Radiant energy per unit surface area.

Heat release rate. Rate at which thermal energy is generated by a burning material.

High-strength bolt. An ASTM F3125/F3125M or ASTM F3148 bolt, or an alternative design bolt that meets the requirements in RCSC Specification Section 2.12.
Horizontal shear. In a composite beam, force at the interface between steel and concrete surfaces.
HSS (hollow structural section). Square, rectangular, or round hollow structural steel section produced in accordance with one of the product specifications in Section A3.1a(b).
Inelastic analysis. Structural analysis that takes into account inelastic material behavior, including plastic analysis.
Initial tension. Minimum bolt tension attained before application of the required rotation when using the combined method to pretension bolting assemblies.
In-plane instability†. Limit state involving buckling in the plane of the frame or the member.
Instability†. Limit state reached in the loading of a structural component, frame, or structure in which a slight disturbance in the loads or geometry produces large displacements.
Introduction length. The length along which the required longitudinal shear force is assumed to be transferred into or out of the steel shape in an encased or filled composite column.
Issued for construction. The engineer of record’s designation that the design documents and specifications are authorized to be used to construct the steel structure depicted in the design documents and specifications and that these design documents and specifications incorporate the information that is to be provided per the requirements of Section A4.
Joint†. Area where two or more ends, surfaces, or edges are attached. Categorized by type of fastener or weld used and method of force transfer.
Joint eccentricity. In an HSS truss connection, perpendicular distance from chord member center-of-gravity to intersection of branch member work points.
$k$ -area. The region of the web that extends from the tangent point of the web and the flange- web fillet (AISC $k$ dimension) a distance $1 \frac{1}{2}$ in. (38 mm) into the web beyond the $k$ -dimension.
K-connection. HSS connection in which forces in branch members or connecting elements transverse to the main member are primarily equilibrated by forces in other branch members or connecting elements on the same side of the main member.
Lacing. Plate, angle, or other steel shape, in a lattice configuration, that connects two steel shapes together.
Lap joint. Joint between two overlapping connection elements in parallel planes.
Lateral bracing. Member or system that is designed to inhibit lateral buckling or lateral-torsional buckling of structural members.
Lateral force-resisting system. Structural system designed to resist lateral loads and provide stability for the structure as a whole.
Lateral load. Load acting in a lateral direction, such as wind or earthquake effects.
Lateral-torsional buckling†. Buckling mode of a flexural member involving deflection out of the plane of bending occurring simultaneously with twist about the shear center of the cross section.
Leaning column. Column designed to carry gravity loads only, with connections that are not intended to provide resistance to lateral loads.
Length effects. Consideration of the reduction in strength of a member based on its unbraced length.
Lightweight concrete. Structural concrete with an equilibrium density of 115 lb/ft³ (1 840 kg/m³) or less, as determined by ASTM C567/C567M.
Limit state†. Condition in which a structure or component becomes unfit for service and is judged either to be no longer useful for its intended function (serviceability limit state) or to have reached its ultimate load-carrying capacity (strength limit state).
Load†. Force or other action that results from the weight of building materials, occupants and their possessions, environmental effects, differential movement, or restrained dimensional changes.
Load effect†. Forces, stresses, and deformations produced in a structural component by the applied loads.
Load factor. Factor that accounts for deviations of the nominal load from the actual load, for uncertainties in the analysis that transforms the load into a load effect and for the probability that more than one extreme load will occur simultaneously.
Load transfer region. Region of a composite member over which force is directly applied to the member, such as the depth of a connection plate.
Local bending**†. Limit state of large deformation of a flange under a concentrated transverse force.
Local buckling**. Limit state of buckling of a compression element within a cross section.

Local yielding**†. Yielding that occurs in a local area of an element.

LRFD (load and resistance factor design)†. Method of proportioning structural components such that the design strength equals or exceeds the required strength of the component under the action of the LRFD load combinations.
LRFD load combination†. Load combination in the applicable building code intended for strength design (load and resistance factor design).
Member imperfection. Initial displacement of points along the length of individual members (between points of intersection of members) from their nominal locations, such as the out-of-straightness of members due to manufacturing and fabrication.

Mill scale. Oxide surface coating on steel formed by the hot rolling process.

Moment connection. Connection that transmits bending moment between connected members.

Moment frame†. Framing system that provides resistance to lateral loads and provides stability to the structural system, primarily by shear and flexure of the framing members and their connections.

Negative flexural strength. Flexural strength of a composite beam in regions with tension due to flexure on the top surface.

Net area. Gross area reduced to account for removed material.

Nominal dimension. Designated or theoretical dimension, as in tables of section properties.

Nominal load†. Magnitude of the load specified by the applicable building code.

Nominal rib height. In a formed steel deck, height of deck measured from the underside of the lowest point to the top of the highest point.
Nominal strength*†. Strength of a structure or component (without the resistance factor or safety factor applied) to resist load effects, as determined in accordance with this Specification.
Noncompact composite section. Filled composite section that is not able to reach the plastic axial compressive strength or plastic moment due to insufficient confinement of the infill concrete, as defined by the steel element width-to-thickness ratio greater than $\lambda_{p}$ and less than or equal to $\lambda_{r}$ .
Noncompact section. Section that is not able to reach the plastic moment before inelastic local buckling occurs as defined by the element width-to-thickness ratio greater than $\lambda_{p}$ and less than or equal to $\lambda_{r}$ .
Nondestructive testing. Inspection procedure wherein no material is destroyed and the integrity of the material or component is not affected.
Notch toughness. Energy absorbed at a specified temperature as measured in the Charpy V-notch impact test.
Notional load. Virtual load applied in a structural analysis to account for destabilizing effects that are not otherwise accounted for in the design provisions.
Out-of-plane buckling†. Limit state of a beam, column, or beam-column involving lateral or lateral-torsional buckling.
Overlapped connection. HSS truss connection in which intersecting branch members overlap.
Panel brace. Brace that limits the relative movement of two adjacent brace points along the length of a beam or column or the relative lateral displacement of two stories in a frame.
Panel zone. Web area of beam-to-column connection delineated by the extension of beam and column flanges through the connection, transmitting moment through a shear panel.
Partial-joint-penetration (PJP) groove weld. Groove weld in which the penetration is intentionally less than the complete thickness of the connected element.
Partially restrained moment connection. Connection capable of transferring moment with rotation between connected members that is not negligible.
Percent elongation. Measure of ductility, determined in a tensile test as the maximum elongation of the gage length divided by the original gage length expressed as a percentage.

Pipe. See HSS.

Pitch. Longitudinal center-to-center spacing of fasteners. Center-to-center spacing of bolt threads along axis of bolt.
Plastic analysis. Structural analysis based on the assumption of rigid-plastic behavior, that is, that equilibrium is satisfied and the stress is at or below the yield stress throughout the structure.
Plastic hinge. Fully yielded zone that forms in a structural member when the plastic moment is attained.
Plastic moment. Theoretical resisting moment developed within a fully yielded cross section.
Plastic stress distribution method. In a composite member, method for determining stresses assuming that the steel section and the concrete in the cross section are fully plastic.
Plastification. In an HSS connection, limit state based on an out-of-plane flexural yield line mechanism in the chord at a branch member connection.
Plug weld. Weld made in a circular hole in one element of a joint fusing that element to another element.
Point brace. Brace that limits lateral movement or twist independently of other braces at adjacent brace points.
Ponding. Retention of water due solely to the deflection of flat roof framing.
Positive flexural strength. Flexural strength of a composite beam in regions with compression due to flexure on the top surface.

Pretensioned bolt. Bolt tightened to the specified minimum pretension.

Pretensioned joint. Joint with high-strength bolts tightened to the specified minimum pretension.
Properly developed. Reinforcing bars detailed to yield in a ductile manner before crushing of the concrete occurs. Bars meeting the provisions of ACI 318, insofar as development length, spacing, and cover are deemed to be properly developed.
Prying action. Amplification of the tension force in a bolt caused by leverage between the point of applied load, the bolt, and the reaction of the connected elements.
Punching load. In an HSS connection, component of branch member force perpendicular to a chord.
P-δ effect. Effect of loads acting on the deflected shape of a member between joints or nodes.
P-Δ effect. Effect of loads acting on the displaced location of joints or nodes in a structure. In tiered building structures, this is the effect of loads acting on the laterally displaced location of floors and roofs.
Quality assurance. Monitoring and inspection tasks to ensure that the material provided and work performed by the fabricator and erector meet the requirements of the approved construction documents and referenced standards. Quality assurance includes those tasks designated “special inspection” by the applicable building code.
Quality assurance inspector (QAI). Individual designated to provide quality assurance inspection for the work being performed.
Quality assurance plan (QAP). Program in which the agency or firm responsible for quality assurance maintains detailed monitoring and inspection procedures to ensure conformance with the approved construction documents and referenced standards.
Quality control. Controls and inspections implemented by the fabricator or erector, as applicable, to ensure that the material provided and work performed meet the requirements of the approved construction documents and referenced standards.
Quality control inspector (QCI). Individual designated to perform quality control inspection tasks for the work being performed.
Quality control program (QCP). Program in which the fabricator or erector, as applicable, maintains detailed fabrication or erection and inspection procedures to ensure conformance with the approved design documents, specifications, and referenced standards.
Reentrant. In a cope or weld access hole, a cut at an abrupt change in direction in which the exposed surface is concave.
Registered design professional in responsible charge. A registered design professional engaged by the owner or the owner’s authorized agent to review and coordinate certain aspects of the project, as determined by the authority having jurisdiction, for compatibility with the design of the building or structure, including submittal documents prepared by others, deferred submittal documents, and phased submittal documents.
Required strength*†. Forces, stresses, and deformations acting on a structural component, determined by either structural analysis, for the LRFD or ASD load combinations, as applicable, or as specified by this Specification or Standard.
Resistance factor, $\phi_{\mathrm{i}}^{+}$ . Factor that accounts for unavoidable deviations of the nominal strength from the actual strength and for the manner and consequences of failure.
Restrained construction. Floor and roof assemblies and individual beams in buildings where the surrounding or supporting structure is capable of resisting significant thermal expansion throughout the range of anticipated elevated temperatures.

Reverse curvature. See Double curvature.

Root of joint. Portion of a joint to be welded where the members are closest to each other.

Rupture strength†. Strength limited by breaking or tearing of members or connecting elements.

Safety factor, $\Omega_{\mathrm{i}}^{+}$ . 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.

Second-order effect. Effect of loads acting on the deformed configuration of a structure; includes $P-\delta$ effect and $P-\Delta$ effect.
Seismic force-resisting system. That part of the structural system that has been considered in the design to provide the required resistance to the seismic forces prescribed in ASCE/ SEI 7.
Seismic response modification factor. Factor that reduces seismic load effects to strength level.
Serviceability limit state†. Limiting condition affecting the ability of a structure to preserve its appearance, maintainability, durability, comfort of its occupants, or function of machinery, under typical usage.

Service load†. Load under which serviceability limit states are evaluated.

Service load combination. Load combination under which serviceability limit states are evaluated.

Shear buckling†. Buckling mode in which a plate element, such as the web of a beam, deforms under pure shear applied in the plane of the plate.
Shear lag. Nonuniform tensile stress distribution in a member or connecting element in the vicinity of a connection.
Shear wall†. Wall that provides resistance to lateral loads in the plane of the wall and provides stability for the structural system.
Shear yielding (punching). In an HSS connection, limit state based on out-of-plane shear strength of the chord wall to which branch members are attached.
Sheet steel. In a composite floor system, steel used for closure plates or miscellaneous trimming in a formed steel deck.
Shim. Thin layer of material used to fill a space between faying or bearing surfaces.
Shop drawings. Drawings of the individual structural steel pieces that are to be produced in the fabrication shop.
Sidesway buckling (frame). Stability limit state involving lateral sidesway instability of a frame.
Simple connection. Connection that transmits negligible bending moment between connected members.
Single-concentrated force. Tensile or compressive force applied normal to the flange of a member.
Single curvature. Deformed shape of a beam with no inflection point within the span.
Slender-element composite section. Filled composite section that is able to only reach an axial or flexural strength limited by local buckling of a steel element, and by not adequately confining the infill concrete to reach the confined compressive strength, as defined by the steel element width-to-thickness ratio greater than $\lambda_{r}$ .
Slender-element section. Section that is able to only reach a strength limited by local buckling of an element defined by element width-to-thickness ratio greater than $\lambda_{r}$ .
Slip. In a bolted connection, limit state of relative motion of connected parts prior to the attainment of the available strength of the connection.
Slip-critical connection. Bolted connection designed to resist movement by friction on the faying surface of the connection under the clamping force of the bolts.

Slot weld. Weld made in an elongated hole fusing an element to another element.

Specifications. The portion of the construction documents and the contract documents that consist of the written requirements for materials, standards, and workmanship.
Specified minimum tensile strength. Lower limit of tensile strength specified for a material as defined by ASTM.
Specified minimum yield stress†. Lower limit of yield stress specified for a material as defined by ASTM.
Splice. Connection between two structural elements joined at their ends to form a single, longer element.
Stability. Condition 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.
Steel anchor. Headed stud or hot rolled channel welded to a steel member and embedded in the concrete of a composite member to transmit shear, tension, or a combination of shear and tension, at the interface of the two materials.
Stiffened element. Flat compression element with adjoining out-of-plane elements along both edges parallel to the direction of loading.
Stiffener. Structural element, typically an angle or plate, attached to a member to distribute load, transfer shear, or prevent buckling.
Stiffness. Resistance to deformation of a member or structure, measured by the ratio of the applied force (or moment) to the corresponding displacement (or rotation).

Story drift. Horizontal deflection at the top of the story relative to the bottom of the story.

Story drift ratio. Story drift divided by the story height.

Strain compatibility method. In a composite member, method for determining the stresses considering the stress-strain relationships of each material and its location with respect to the neutral axis of the cross section.
Strength limit state†. Limiting condition in which the maximum strength of a structure or its components is reached.
Stress. Force per unit area caused by axial force, moment, shear, or torsion.
Stress concentration. Localized stress considerably higher than average due to abrupt changes in geometry or localized loading.
Stress range. The magnitude of the change in stress due to the application, reversal, or removal of the applied cyclic load.
Strong axis. Major principal centroidal axis of a cross section.
Structural analysis†. Determination of load effects on members and connections based on principles of structural mechanics.
Structural component†. Member, connector, connecting element, or assemblage.
Structural integrity. Performance characteristic of a structure indicating resistance to catastrophic failure.
Structural steel. Steel elements as defined in the AISC Code of Standard Practice for Steel Buildings and Bridges Section 2.1.
Structural system. An assemblage of load-carrying components that are joined together to provide interaction or interdependence.
Substantiating connection information. Information submitted by the fabricator in support of connections either selected by the steel detailer or designed by the licensed engineer working for the fabricator.
System imperfection. Initial displacement of points of intersection of members from their nominal locations, such as the out-of-plumbness of columns due to erection tolerances.
T-connection. HSS connection in which the branch member or connecting element is perpendicular to the main member and in which forces transverse to the main member are primarily equilibrated by shear in the main member.
Tensile strength (of material)†. Maximum tensile stress that a material is capable of sustain- ing as defined by ASTM.

Tensile strength (of member). Maximum tension force that a member is capable of sustaining.

Tension and shear rupture†. In a bolt or other type of mechanical fastener, limit state of rupture due to simultaneous tension and shear force.

Tension field action. Behavior of a panel under shear in which diagonal tensile forces develop in the web and compressive forces develop in the transverse stiffeners in a manner similar to a Pratt truss.

Thermally cut. Cut with gas, plasma, or laser.

Tie plate. Plate element used to join two parallel components of a built-up column, girder, or strut rigidly connected to the parallel components and designed to transmit shear between them.

Toe of fillet. Junction of a fillet weld face and base metal. Tangent point of a fillet in a rolled shape.

Torsional bracing. Bracing resisting twist of a beam or column.

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

Transverse reinforcement. In an encased composite column, steel reinforcement in the form of closed ties or welded wire fabric providing confinement for the concrete surrounding the steel shape.

Transverse stiffener. Web stiffener oriented perpendicular to the flanges, attached to the web. Tubing. See HSS.

Turn-of-nut method. Procedure whereby the specified pretension in high-strength bolts is controlled by rotating the fastener component a predetermined amount after the bolt has been snug tightened.
Unbraced length. Distance between braced points of a member, measured between the centers of gravity of the bracing members.
Uneven load distribution. In an HSS connection, condition in which the stress is not distributed uniformly through the cross section of connected elements.
Unframed end. The end of a member not restrained against rotation by stiffeners or connection elements.
Unrestrained construction. Floor and roof assemblies and individual beams in buildings that are assumed to be free to rotate and expand throughout the range of anticipated elevated temperatures.
Unstiffened element. Flat compression element with an adjoining out-of-plane element along one edge parallel to the direction of loading.

Weak axis. Minor principal centroidal axis of a cross section.

Weathering steel. High-strength, low-alloy steel that, with sufficient precautions, is able to be used in typical atmospheric exposures (not marine) without protective paint coating.
Web local crippling†. Limit state of local failure of web plate in the immediate vicinity of a concentrated load or reaction.
Web sidesway buckling. Limit state of lateral buckling of the tension flange opposite the location of a concentrated compression force.
Weld access hole. An opening that permits access for welding, backgouging, or for insertion of backing.
Weld metal. Portion of a fusion weld that has been completely melted during welding. Weld metal has elements of filler metal and base metal melted in the weld thermal cycle.

Weld root. See Root of joint.

Y-connection. HSS connection in which the branch member or connecting element is not perpendicular to the main member and in which forces transverse to the main member are primarily equilibrated by shear in the main member.
Yield moment†. In a member subjected to bending, the moment at which the extreme outer fiber first attains the yield stress.
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 applicable for the material.

Yielding†. Limit state of inelastic deformation that occurs when the yield stress is reached.

Yielding (plastic moment)†. Yielding throughout the cross section of a member as the moment reaches the plastic moment.

Yielding (yield moment)†. Yielding at the extreme fiber on the cross section of a member when the moment reaches the yield moment.