AISC 360-22: Specification for Structural Steel Buildings
AISC 360 is the governing specification for the design, fabrication, and erection of structural steel buildings in the United States. Published by the American Institute of Steel Construction, the current edition -- AISC 360-22 (16th Edition) -- took effect in 2022 and is referenced by the International Building Code (IBC) and ASCE/SEI 7-22. This page covers the specification's scope, chapter organization, resistance factors, key changes from the prior edition, and links to every calculator on this site that implements AISC 360 provisions.
Overview of AISC 360-22
AISC 360 provides requirements for the design of members, connections, and systems in structural steel buildings and other structures. The specification covers hot-rolled shapes, hollow structural sections (HSS), built-up members, plates, and connection elements.
Scope and applicability
The specification applies to structural steel buildings and non-building structures using steel members and connections. It does not cover cold-formed steel (governed by AISI S100), steel storage racks (RMI), steel joists (SJI), or transmission towers (ASCE 10). For composite construction with reinforced concrete, AISC 360 Chapter I works in conjunction with ACI 318.
LRFD vs ASD
AISC 360 provides two parallel design methods:
- LRFD (Load and Resistance Factor Design) -- Factored loads from ASCE 7 are compared against design strengths that apply a resistance factor (phi) to the nominal strength. The general form is: Required Strength (R_u) <= Design Strength (phi * R_n).
- ASD (Allowable Strength Design) -- Service-level loads are compared against allowable strengths that divide the nominal strength by a safety factor (Omega). The general form is: Required Strength (R_a) <= Allowable Strength (R_n / Omega).
Both methods produce structures with equivalent reliability when loads are derived from the same load combinations. Our calculators implement LRFD only. Engineers using ASD should convert results or verify independently.
Referenced standards
AISC 360 is not standalone. A complete design typically requires:
- ASCE/SEI 7-22 -- Minimum design loads and associated criteria
- AISC 341 -- Seismic provisions for structural steel buildings
- AISC 358 -- Prequalified connections for special and intermediate moment frames
- AISC Design Guide 1 -- Base plate and anchor rod design
- ACI 318-19 -- Concrete anchorage (Chapter 17)
- RCSC Specification -- Structural joints using high-strength bolts
Key Chapters
Chapter B: Design Requirements
Establishes the design basis including required strength, available strength, design for stability (Direct Analysis Method as the primary approach), member properties, and classification of sections as compact, noncompact, or slender. The Direct Analysis Method (B1 and Chapter C) replaced the older effective length method as the primary stability approach.
Chapter D: Design of Members for Tension
Covers tensile yielding of the gross section (phi = 0.90) and tensile rupture of the net section (phi = 0.75). The effective net area (A_e = U * A_n) uses shear lag factor U per Table D3.1, which depends on connection geometry. This chapter is straightforward but the shear lag factor is a frequent source of errors.
Chapter E: Design of Members for Compression
Governs column design. Section E3 addresses flexural buckling using the critical stress F_cr, which depends on the slenderness ratio KL/r relative to the limiting slenderness 4.71*sqrt(E/F_y). Section E4 covers torsional and flexural-torsional buckling for singly symmetric and unsymmetric sections. Section E7 addresses members with slender elements where local buckling reduces column capacity.
Chapter F: Design of Members for Flexure
Covers beams. The limit states include yielding (F2.1), lateral-torsional buckling (F2.2), flange local buckling (F3), and web local buckling. Lateral-torsional buckling depends on unbraced length L_b relative to L_p (plastic) and L_r (inelastic limit). Compact I-shapes use Section F2; noncompact and slender flanges use F3; channels, angles, tees, and HSS each have dedicated sections (F6-F11).
Chapter G: Design of Members for Shear
Section G2 covers I-shaped members. For most rolled W-shapes with h/t_w <= 2.24*sqrt(E/F_y), the web shear coefficient C_v1 = 1.0 and phi = 1.00 (LRFD) -- a simplification introduced in AISC 360-16. For all other cases, phi = 0.90 and C_v2 is computed based on web slenderness. Tension field action (G3) can increase shear capacity in stiffened web panels.
Chapter H: Combined Forces
Section H1 handles combined axial force and flexure using the interaction equations H1-1a (P_r/P_c >= 0.2) and H1-1b (P_r/P_c < 0.2). These bilinear interaction equations apply to doubly symmetric members and cover the majority of beam-column checks in practice.
Chapter I: Design of Composite Members
Covers composite columns (encased and filled), composite beams with steel headed stud anchors, and composite floor systems. Composite beam design requires determination of the degree of composite action and the shear stud demand per Table I3.2a.
Chapter J: Design of Connections
The most clause-dense chapter, governing bolts, welds, affected elements, and bearing. Key sections include:
- J2 -- Welds: Fillet welds (J2.4), groove welds (J2.3), effective area, and strength per unit length. The weld metal nominal strength is 0.60 * F_EXX.
- J3 -- Bolts and Threaded Parts: Shear (J3.6), tension (J3.6), combined shear-tension interaction (J3.7), bearing and tearout at bolt holes (J3.10), slip-critical connections (J3.8).
- J4 -- Affected Elements: Block shear rupture (J4.3) using the unified equation with U_bs = 1.0 (uniform stress) or 0.5 (non-uniform stress). Whitmore section checks.
- J8 -- Column Bases and Bearing on Concrete: Bearing strength on concrete per ACI 318, linked to Design Guide 1 for base plate bending.
- J10 -- Flanges and Webs with Concentrated Forces: Web yielding, web crippling, sidesway web buckling, and flange bending.
Resistance Factors (Phi) -- LRFD
The following table summarizes the resistance factors used in AISC 360-22 LRFD design. These are the exact values implemented in our calculation engine.
| Limit State | Phi (LRFD) | Omega (ASD) | Clause |
|---|---|---|---|
| Tensile yielding (gross section) | 0.90 | 1.67 | D2(a) |
| Tensile rupture (net section) | 0.75 | 2.00 | D2(b) |
| Compression (flexural buckling) | 0.90 | 1.67 | E1 |
| Flexure (yielding, LTB) | 0.90 | 1.67 | F1 |
| Shear (most rolled W-shapes) | 1.00 | 1.50 | G1 |
| Shear (other cases) | 0.90 | 1.67 | G1 |
| Bolt shear | 0.75 | 2.00 | J3.6 |
| Bolt bearing / tearout | 0.75 | 2.00 | J3.10 |
| Slip-critical (serviceability) | 1.00 | 1.50 | J3.8 |
| Slip-critical (strength-level) | 0.85 | 1.76 | J3.8 |
| Block shear rupture | 0.75 | 2.00 | J4.3 |
| Weld capacity (fillet, PJP, CJP) | 0.75 | 2.00 | J2.4 |
| Concrete bearing | 0.65 | 2.31 | J8 |
| Plate bending (base plates) | 0.90 | 1.67 | DG1 |
| Anchor rod tension | 0.75 | 2.00 | ACI 318 17.5.1.2 |
| Anchor rod shear | 0.65 | 2.00 | ACI 318 17.5.1.2 |
Note on phi = 1.00 for shear: AISC 360-16 introduced phi = 1.00 for shear in rolled I-shapes with h/t_w <= 2.24*sqrt(E/F_y), which covers essentially all standard W-shapes. This is retained in AISC 360-22.
Key Changes from AISC 360-16 to AISC 360-22
AISC 360-22 is an incremental update. The structural reliability framework and resistance factors are unchanged. Key modifications include:
Connection design (Chapter J)
- Bolt bearing and tearout (J3.10): The bearing/tearout provisions were reorganized for clarity. The clear distance (l_c) equations for tearout remain, but the presentation separates inner and end bolt behavior more clearly.
- Fillet weld directional strength enhancement: The 1.0 + 0.50*sin^1.5(theta) amplification for transverse fillet welds continues. No change in the formula but improved commentary guidance on weld group eccentricity.
Stability (Chapter C)
- Direct Analysis Method: Further editorial refinements. The 360-22 Commentary provides expanded guidance on notional loads and tau_b stiffness reduction. The method remains the primary stability approach; the effective length method is an alternative only for braced frames meeting specific conditions.
Member design
- HSS connections: Expanded provisions for round and rectangular HSS connection design, coordinated with AISC Design Guide 24.
- Single angle members: Updated L_b provisions for single angle beams and columns, including cases with unequal legs.
- Web slenderness limits: Minor editorial adjustments to the classification thresholds for web slenderness in built-up sections.
General
- Metric companion: The 360M-22 metric companion was published simultaneously, with hard metric conversions throughout.
- Commentary: Significantly expanded with worked examples and discussion of Direct Analysis Method applications.
- Coordination with ASCE 7-22: Load combinations and drift limits are now consistent with the updated load standard.
Cross-References to Other Standards
Engineers working across jurisdictions should note how AISC 360 maps to international equivalents:
| AISC 360 Concept | AS 4100 Equivalent | EN 1993 Equivalent | CSA S16 Equivalent |
|---|---|---|---|
| Phi factor (resistance) | Phi (capacity factor) | 1/gamma_M (partial factor) | Phi (resistance factor) |
| LRFD load combos (ASCE 7) | AS/NZS 1170 combos | EN 1990 combos | NBCC load combos |
| Chapter J (Connections) | Section 9 (Connections) | EN 1993-1-8 | Clause 13 (Connections) |
| Chapter F (Flexure) | Section 5 (Bending) | EN 1993-1-1 Cl. 6.3.2 | Clause 13.5-13.6 |
| Chapter E (Compression) | Section 6 (Compression) | EN 1993-1-1 Cl. 6.3.1 | Clause 13.3 |
| Block shear (J4.3) | Cl. 9.1.9 | EN 1993-1-8 Cl. 3.10 | Cl. 13.11 |
Available Calculators
Every calculator below implements AISC 360-22 LRFD provisions with full clause-by-clause derivation output. Select AISC 360 as the design code in the calculator interface.
Connection design
- Bolted Connection Calculator -- Bolt shear (J3.6), bearing and tearout (J3.10), block shear (J4.3), slip-critical checks (J3.8). Supports A325/A490/A307 bolt grades with threads included or excluded.
- Welded Connection Calculator -- Fillet weld capacity per J2.4 with directional strength enhancement. E60/E70/E80 electrodes supported.
- Base Plate & Anchors Calculator -- Concrete bearing per J8/ACI 318, plate bending per Design Guide 1, anchor rod tension and shear per ACI 318-19 Chapter 17.
- Gusset Plate Calculator -- Whitmore section, block shear, and buckling checks for gusset plate connections.
- Splice Connection Calculator -- Bolted and welded splice design with force transfer calculations.
Member design
- Beam Capacity Calculator -- Flexural yielding (F2.1), lateral-torsional buckling (F2.2), flange local buckling (F3), and shear (G2) for W-shapes and channels.
- Column Capacity Calculator -- Flexural buckling (E3), torsional buckling (E4), and slender element effects (E7) with K-factor or Direct Analysis inputs.
- Beam Deflection Calculator -- Serviceability checks against L/240, L/360, and custom limits per IBC Table 1604.3.
Utilities
- Load Combinations (ASCE 7-16) -- LRFD and ASD load combination generator per ASCE/SEI 7-22.
- Steel Grades Reference -- F_y and F_u for ASTM A36, A572 Gr. 50, A992, A500, A53, and more.
- Bolt Hole Sizes -- Standard, oversize, short-slot, and long-slot hole dimensions per AISC Table J3.3.
- Weld Electrode Reference -- F_EXX values and matching electrodes for common processes.
Frequently Asked Questions
Does this site support ASD? No. All calculators implement LRFD only. For ASD equivalence, multiply the LRFD phi factor by the corresponding Omega to verify: phi * Omega is approximately 1.5 for most limit states.
Which edition does the calculator use? AISC 360-22 (16th Edition). The resistance factors and design equations are identical to 360-16 for connection and member checks. If you are working to 360-16, the calculator results are directly applicable.
How are bolt shear strengths determined? Nominal shear stress Fnv is taken from AISC Table J3.2 based on bolt grade and thread condition (threads included or excluded from the shear plane). The design shear strength is phi * Fnv * A_b * n_s, where phi = 0.75.
Can I use these results for seismic design? The calculators provide strength-level checks per AISC 360. For seismic applications, you must also satisfy AISC 341 requirements (expected yield stress R_y*F_y, overstrength factors, connection prequalification per AISC 358, and special detailing).
Related Pages
- Design Codes Overview
- AS 4100 Design Guide
- EN 1993 (Eurocode 3) Design Guide
- CSA S16 Design Guide
- Tools Directory
- Reference Tables
- How to Verify Calculator Results
- AISC Bolted Shear Tab Worked Example
- Disclaimer (educational use only)
Copyright and Standards Notice
This page is a high-level educational guide to help engineers navigate AISC 360 provisions and use our calculators effectively. It does not reproduce copyrighted code text, proprietary tables, or design examples from the published specification. For authoritative requirements, purchase the official AISC 360-22 specification from aisc.org.
Disclaimer
This page is provided for general technical information and educational use only. It does not constitute professional engineering advice or a substitute for review by a qualified structural engineer. All structural design depends on project-specific loads, combinations, stability requirements, detailing, fabrication tolerances, and the governing code edition. You are responsible for verifying inputs, validating results independently, and obtaining professional sign-off. The site operator provides this content "as is" without warranties of any kind.