ANSI/AISC 360-22 - Specification for Structural Steel Buildings

What this standard covers

ANSI/AISC 360 (Specification for Structural Steel Buildings) is the American standard for structural steel design. It covers members in tension, compression, flexure, shear and combined forces, along with connections, stability and serviceability.

AISC 360 presents design in two formats side by side: LRFD, which applies a resistance factor to the nominal strength and compares it against factored loads, and ASD, which divides the same nominal strength by a safety factor and compares it against service loads. Both draw on the same nominal strength equations, so a chapter is read once and applied in either format.

The specification is organised by limit state rather than by member type. For a beam that means yielding, lateral-torsional buckling and local buckling of the flange and web are each evaluated and the lowest governs; for a column, flexural, torsional and flexural-torsional buckling. Stability of the structure as a whole is addressed through the direct analysis method, which accounts for second-order effects and imperfections within the analysis itself.

What you will find in it

LRFD and ASD

The two design formats, the resistance factors and safety factors that distinguish them, and the shared nominal strength equations behind both.

Tension members

Yielding on the gross section and rupture on the net section, with the shear lag factor for members not connected through all elements.

Compression members

Flexural, torsional and flexural-torsional buckling, and the treatment of slender elements that buckle locally first.

Flexural members

Yielding, lateral-torsional buckling and local buckling of compact, noncompact and slender sections, with the unbraced length central to the check.

Combined forces

Interaction of axial force and flexure in beam-columns, which usually governs a frame member.

Stability analysis

The direct analysis method, with reduced stiffness and notional loads that bring second-order effects and imperfections into the analysis.

Connections

Bolted and welded connection design, block shear, and the checks on connected elements and concentrated forces on members.

When to use this standard

Use AISC 360 for steel building design to American practice. It is the counterpart of EN 1993, and the two are not interchangeable: section classification, resistance factors and buckling formulations differ. Loads and load combinations come from ASCE 7, not from AISC 360.

How it fits with the other standards

Loads and combinations come from ASCE 7. Bolted joints using high-strength bolts also invoke the RCSC Specification; seismic design adds AISC 341 and, for qualified moment connections, AISC 358; fabrication and erection practice is defined by AISC 303.

What each chapter covers

Chapter A

Scope of the specification, the referenced standards and material specifications it relies on, and the structural design drawings and specifications it assumes.

Chapter B

Material and section property requirements, and the classification of sections for local buckling as compact, noncompact or slender - the classification every later chapter depends on.

Chapter C

The direct analysis method, in which reduced stiffness and notional loads bring second-order effects and initial imperfections into the analysis itself rather than into an effective length factor.

Chapter D

Yielding on the gross section and rupture on the net section, with the shear lag factor for members not connected through every element.

Chapter E

Flexural, torsional and flexural-torsional buckling, and the treatment of members with slender elements.

Chapter F

Yielding, lateral-torsional buckling and local buckling, organised by section type - the unbraced length is what usually decides the answer.

Chapter G

Web shear resistance with and without tension field action, and the shear of round and rectangular HSS.

Chapter H

The beam-column interaction equations, which govern most frame members, plus torsion on open and closed sections.

Chapter I

Concrete-filled and concrete-encased steel members, and composite beams with steel headed stud anchors.

Chapter J

Welds, bolts, and the limit states of the connected elements including block shear and concentrated forces on members.

Chapter K

The chord-face and punching limit states specific to hollow structural sections.

Chapter L

Deflection, drift, vibration and connection slip - conditions that affect use rather than safety.

Appendix 1

Inelastic and direct modelling alternatives to the standard chapter provisions.

Appendix 3

Stress categories and the assessment of members and connections under repeated loading.

Appendix 4

Design by analysis or by qualification testing, with steel properties at elevated temperature.

Related standards

Tools that implement this standard