ANSI/AISC 341-22 - Seismic Provisions for Structural Steel Buildings

What this standard covers

ANSI/AISC 341 (Seismic Provisions for Structural Steel Buildings) covers the design of steel and composite structures in seismic regions, defining the seismic force-resisting systems and the detailing that makes them ductile.

AISC 341 applies on top of AISC 360 rather than replacing it. It defines the recognised seismic force-resisting systems - special and intermediate and ordinary moment frames, concentrically and eccentrically braced frames, buckling-restrained braced frames and special plate shear walls - and gives each one the member, connection and detailing requirements needed to deliver the ductility that its design coefficients assume.

The provisions work through capacity design: members and connections expected to remain elastic are proportioned for the forces developed when the designated yielding elements reach their expected strength, not for the code-level design forces. Expected strength is higher than nominal, so the standard defines the Ry and Rt factors that scale it, and demand-critical welds and protected zones receive additional requirements.

What you will find in it

Seismic systems

The recognised moment-frame, braced-frame and shear-wall systems, each with its own ductility expectations and detailing rules.

Expected strength

The Ry and Rt factors that convert specified minimum strengths into the expected strengths used in capacity-design calculations.

Capacity design

Proportioning non-yielding elements for the forces delivered when the designated fuse yields and strain hardens.

Member ductility

Width-to-thickness limits for highly and moderately ductile members, stricter than the compactness limits of AISC 360.

Protected zones

Regions where inelastic behaviour is expected and where attachments and discontinuities are prohibited.

Demand-critical welds

Welds whose failure would compromise the system, with additional toughness and quality requirements.

Quality assurance

Inspection and testing requirements for seismic systems, including nondestructive testing of critical welds.

When to use this standard

Use AISC 341 when a steel building in a region of significant seismicity relies on a ductile seismic force-resisting system. For structures where seismic demands are low enough that the governing building code permits design without seismic detailing, AISC 360 alone may suffice.

How it fits with the other standards

AISC 341 supplements AISC 360, with loads and seismic design categories from ASCE 7. Prequalified moment connections that satisfy its requirements are given in AISC 358, bolting follows the RCSC Specification, and AISC 303 governs fabrication and erection.

What each chapter covers

Chapter A

Scope, applicable specifications and the definitions that the rest of the provisions depend on.

Chapter B

The loads, load combinations and the system requirements that apply before any individual system is detailed.

Chapter C

The requirements for determining seismic demands, including the amplified seismic load where capacity-limited forces are needed.

Chapter D

Highly and moderately ductile member classification, protected zones, and demand-critical weld requirements.

Chapter E

Ordinary, intermediate and special moment frames, plus special truss moment frames - their connection qualification and detailing.

Chapter F

Ordinary and special concentrically braced frames, eccentrically braced frames, buckling-restrained braced frames and special plate shear walls.

Chapter G

Moment frames combining structural steel and reinforced concrete.

Chapter H

Braced frames and shear walls in composite construction.

Chapter I

The requirements that carry the seismic detailing intent through into the built structure.

Chapter J

Inspection tasks and nondestructive testing, weighted towards demand-critical welds.

Related standards