These definitions are provided from the AISI 2016 Edition of North American Specification for the Design of Cold-Formed Steel Structural Members (S100-16).
Applicable Building Code. Building code under which the structure is designed.
Bearing. In a connection, limit state of shear forces transmitted by the mechanical fastener to the connection elements.
Bearing (Local Compressive Yielding). Limit state of local compressive yielding due to the action of a member bearing against another member or surface.
Block Shear Rupture. In a connection, limit state of tension rupture along one path and shear yielding or shear rupture along another path.
Braced Frame. Essentially vertical truss system that provides resistance to lateral loads and provides stability for the structural system.
Buckling. Limit state of sudden change in the geometry of a structure or any of its elements under a critical loading condition.
Buckling Strength. Nominal strength [resistance] for instability limit states.
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.
Confirmatory Test. Test made, when desired, on members, connections, and assemblies designed in accordance with this Specification or its specific references, or rational engineering analysis, in order to compare actual to calculated performance.
Connection. Combination of structural elements and joints used to transmit forces between two or more members.
Cross-Sectional Area:
Effective Area. Cross-sectional area calculated using the effective widths of component elements in accordance with Appendix 1. If the effective widths of all component elements, determined in accordance with Appendix 1, are equal to the actual flat widths, it equals the gross or net area, as applicable.
Full, Unreduced Area. Cross-sectional area calculated without considering local buckling in the component elements, which equals either the gross area or net area, as applicable.
Gross Area. Cross-sectional area without deductions for holes, openings, and cutouts.
Net Area. Net area, An, equal to gross area less the area of holes, openings, and cutouts.
Curtain Wall Stud. A member in a steel framed exterior wall system that transfers transverse (out-of-plane) loads and is limited to a superimposed axial load, exclusive of sheathing materials, of not more than 100 lb/ft (1460 N/m or 1.49 kg/cm), or a superimposed axial load of not more than 200 lbs (890 N or 90.7 kg) per stud.
Diaphragm. Roof, floor, or other membrane or bracing system that transfers in-plane forces to the lateral force resisting system.
Direct Analysis Method. Design method for stability that captures the effects of residual stresses and initial out-of-plumbness of members by reducing stiffness and applying notional loads in a second-order analysis.
Direct Strength Method. A design method that provides predictions of member strengths without the use of effective widths.
Distortional Buckling. A mode of buckling involving change in cross-sectional shape, excluding local buckling.
Doubly-Symmetric Section. A section symmetric about two orthogonal axes through its centroid.
Effective Design Width (Effective Width). Flat width of an element reduced for design purposes, also known simply as the effective width.
Effective Length. Length of an otherwise identical column of the same strength when analyzed with pinned end conditions.
Effective Length Factor, K. Ratio between the effective length and the unbraced length of the member.
Effective Length Method. A method of design that addresses stability through calculation of available strength [factored resistance] using the effective length factor.
Effective Width Method. A method that considers the local buckling of cold-formed steel members by reducing the gross cross-section under a non-linear stress distribution to an effective cross-section under a simplified linear stress distribution.
Factored Load. Product of a load factor and the nominal load [specified load].
Fatigue. Limit state of crack initiation and growth resulting from repeated application of live loads.
First-Order Analysis. Structural analysis in which equilibrium conditions are formulated on the undeformed structure; second-order effects are neglected.
Flange of a Section in Bending (Flange). Flat width of flange including any intermediate stiffeners plus adjoining corners.
Flat Width. Width of an element exclusive of corners measured along its plane.
Flat-Width-to-Thickness Ratio (Flat Width Ratio). Flat width of an element measured along its plane, divided by its thickness.
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.
Girt. Horizontal structural member that supports wall panels and is primarily subjected to bending under horizontal loads, such as wind load.
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.
Joint. Area where two or more ends, surfaces, or edges are attached. Categorized by type of fastener or weld used and the method of force transfer.
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.
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 [resistance] 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. A factor defined by the applicable building code to take into account the variability in loads and the analysis of their effects.
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 where the line junctions between elements remain straight and angles between elements do not change.
Local Yielding. Yielding that occurs in a local area of an element.
Master Coil. One continuous, weld-free coil as produced by a hot mill, cold mill, metallic coating line, or paint line and identifiable by a unique coil number. In some cases, this coil is cut into smaller coils or slit into narrower coils; however, all of these smaller and/or narrower finished coils are said to have come from the same master coil if they are traceable to the original master coil number.
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.
Multiple-Stiffened Element. Element stiffened between webs, or between a web and a stiffened edge, by means of intermediate stiffeners parallel to the direction of stress.
Non-symmetric Section. Section not symmetric about either an axis or a point.
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.
Patterned hole. Repeated pattern of holes along the longitudinal axis of a member, excluding those holes in the corners of a cross-section.
Performance Test. Test made on structural members, connections, and assemblies whose performance cannot be determined in accordance with Chapters A through J and L through M of this Specification or its specific references.
Permanent Load. Load in which variations over time are rare or of small magnitude. All other loads are variable loads.
Point-Symmetric Section. Section symmetrical about a point (centroid) such as a Z-section having equal flanges.
Power-Actuated Fastener (PAF). Hardened steel fastener driven through steel members into embedment material using either powder cartridges or compressed gas as the energydriving source.
Power-Actuated Fastener Point. Portion of pointed end of PAF shank with varying diameter.
Published Specification. Requirements for a steel listed by a manufacturer, processor, producer, purchaser, or other body, which (a) are generally available in the public domain or are available to the public upon request, (b) are established before the steel is ordered, and (c) as a minimum, specify minimum mechanical properties, chemical composition limits, and, if coated sheet, coating properties.
Purlin. Horizontal structural member that supports roof deck and is primarily subjected to bending under vertical loads such as snow, wind, or dead loads.
P-d Effect. Effect of loads acting on the deflected shape of a member between joints or nodes.
P-D 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.
Rational Engineering Analysis. Analysis based on theory that is appropriate for the situation, any relevant test data, if available, and sound engineering judgment.
Resistance Factor, f. Factor that accounts for unavoidable deviations of the nominal strength [resistance] from the actual strength and for the manner and consequences of failure.
Rupture Strength. Strength limited by breaking or tearing of members or connecting elements.
Second-Order Analysis. Structural analysis in which equilibrium conditions are formulated on the deformed structure; second-order effects (both P-d and P-D effects, unless specified otherwise) are included.
Second-Order Effect. Effect of loads acting on the deformed configuration of a structure; includes P-d effect and P-D effect.
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.
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 Wall. Wall that provides resistance to lateral loads in the plane of the wall and provides stability for the structural system.
Singly-Symmetric Section. Section symmetric about only one axis through its centroid.
Specified Minimum Yield Stress. Lower limit of yield stress specified for a material as defined by ASTM.
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.
Stiffened or Partially Stiffened Compression Elements. Flat compression element (i.e., a plane compression flange of a flexural member or a plane web or flange of a compression member) of which both edges parallel to the direction of stress are stiffened either by a web, flange, stiffening lip, intermediate stiffener, or the like.
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).
Stress. Stress as used in this Specification means force per unit area.
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 Members. See the definition of Cold-Formed Steel Structural Member.
Sub-Element of a Multiple Stiffened Element. Portion of a multiple stiffened element between adjacent intermediate stiffeners, between web and intermediate stiffener, or between edge and intermediate stiffener.
Tensile Strength (of Material). Maximum tensile stress that a material is capable of sustaining as defined by ASTM.
Tension and Shear Rupture. In a bolt or other type of mechanical fastener, limit state of rupture due to simultaneous tension and shear force.
Thickness. The thickness, t, of any element or section is the base steel thickness, exclusive of coatings.
Top Arc Seam Sidelap Weld. Arc seam weld applied to the top sidelap connection.
Top Sidelap Connection. A connection formed by a vertical sheet leg (edge stiffener of deck) inside an overlapping sheet hem, or by vertical sheet legs back-to-back.
Torsional Buckling. Buckling mode in which a compression member twists about its shear center axis.
Unbraced length. Distance between braced points of a member, measured between the centers of gravity of the bracing members.
Unstiffened Compression Elements. Flat compression element stiffened at only one edge parallel to the direction of stress.
Variable Load. Load not classified as permanent load.
Virgin Steel. Steel as received from the steel producer or warehouse before being cold worked as a result of fabricating operations.
Virgin Steel Properties. Mechanical properties of virgin steel such as yield stress, tensile strength, and elongation.
Wall Diaphragm. A wall, load-bearing or non-load-bearing, designed to resist forces acting in the plane of the wall (commonly referred to as a “vertical diaphragm” or “shear wall”).
Web. In a member subjected to flexure, the portion of the section that is joined to two flanges, or that is joined to only one flange provided it crosses the neutral axis.
Web Crippling. Limit state of local failure of web plate in the immediate vicinity of a concentrated load or reaction.
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 appropriate 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 bending moment reaches the plastic moment.
Yielding (Yield Moment). Yielding at the extreme fiber on the cross-section of a member when the bending moment reaches the yield moment.
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).
Allowable Strength. Nominal strength divided by the safety factor, Rn/W.
Available Strength. Design strength or allowable strength as appropriate.
Design Earthquake. The ground motion represented by the design response spectrum as specified in the applicable building code.
Design Load. Applied load determined in accordance with either LRFD load combinations or ASD load combinations, whichever is applicable.
Design Strength. Resistance factor multiplied by the nominal strength, fRn.
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).
Nominal Load. The magnitudes 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 this Specification.
Required Strength. Forces, stresses, and deformations acting on a structural component, determined by either structural analysis, for the LRFD or ASD load combinations, as appropriate, or as specified by this Specification.
Resistance. See the definition of Nominal Strength.
Risk Category. A categorization of buildings and other structures for determination of flood, wind, snow, ice, and earthquake loads based on the risk associated with unacceptable performance.
Safety Factor, W. 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.
Seismic Design Category (SDC). A classification assigned by the applicable building code to a structure based on its risk category and the severity of the design earthquake ground motion at the site.
Span Continuity. Ability of a member to develop moment over a support.
Strength Limit State. Limiting condition, in which the maximum strength of a structure or its components is reached.
Factored Resistance. Product of nominal resistance and appropriate resistance factor.
Limit States Design (LSD). A method of proportioning structural components (members, connectors, connecting elements, and assemblages) such that no applicable limit state is exceeded when the structure is subjected to all appropriate load combinations.
Nominal Resistance (Resistance). The capacity of a structure or component to resist the effects of loads, determined in accordance with this Specification using specified material strengths and dimensions.
Specified Loads. The magnitudes of the loads specified by the applicable building code, not including load factors.