Does AISC 341 replace AWS D1.1 for seismic structural welding, or do both apply?

Both apply — AISC 341-22 layers on top of AWS D1.1 (and requires AWS D1.8 for seismic connections). The hierarchy is: AISC 341-22 sets the seismic design and material requirements; AWS D1.8 is the welding supplement specifically for seismic applications (it modifies AWS D1.1 for seismic connections); AWS D1.1 is the base welding code. A structural fab shop building an SMRF must satisfy all three standards simultaneously, with 341 governing where conflicts arise.

What is a demand-critical weld under AISC 341 and how does it affect the WPS?

Demand-critical welds are those in seismic force-resisting systems where fracture could cause significant degradation of frame strength — typically complete joint penetration (CJP) groove welds in moment connections and column splices in high-seismic applications. Under AISC 341-22 Section I2.3 and AWS D1.8, demand-critical welds require: CVN-rated filler metal (20 ft-lbf at -20°F [27 J at -29°C] and 40 ft-lbf at 70°F [54 J at 21°C]), preheat per D1.8 Table 4.2 (often higher than D1.1 minimums), and a WPS that documents all CVN filler certifications.

Does AISC 341 require additional PQR testing beyond AWS D1.1?

Yes. AWS D1.8 (required by AISC 341 for seismic connections) requires CVN testing of the weld metal deposited with the actual filler metal and heat input used in the PQR. The weld metal Charpy tests must meet minimum values at the required temperature. This is additional to the standard mechanical tests (tensile, bend) required by AWS D1.1 Table 6.6 for process qualification. The CVN test results become part of the PQR and govern whether the qualified procedure may be used for demand-critical welds.

Which AISC 341 provisions apply only to special moment frames versus ordinary moment frames?

AISC 341-22 differentiates by seismic design category and system type. Special moment frames (SMF), intermediate moment frames (IMF), and ordinary moment frames (OMF) have different connection prequalification and WPS requirements. SMF connections must meet AISC 358 prequalified connection standards or be project-specific tested connections — both impose specific WPS requirements for CJP groove welds. OMF connections have fewer restrictions. The EOR's structural drawings should specify which frame type and seismic design category applies; the fabricator's WPS must match.

AISC 341 Seismic Provisions: WPS and PQR Requirements

AISC 341-22 imposes welding requirements beyond AWS D1.1 and D1.8 for seismic force-resisting systems. Know what changes for WPS, PQR, filler metal, and base metal.

A fab shop that builds ordinary structural steel and then takes on its first high-seismic moment frame project is in for a significant shift in welding program requirements. AISC 341-22 (Seismic Provisions for Structural Steel Buildings) is the design standard, but it reaches into fabrication through mandatory compliance with AWS D1.8, specific filler metal certification requirements, tighter material specifications, and additional PQR testing that does not appear in standard AWS D1.1 qualification.

This article focuses specifically on how AISC 341-22 changes what goes into the WPS, what the PQR must demonstrate, and how filler metal and base metal selection decisions differ from non-seismic structural work.

Rule library based on AWS D1.1:2025; verify against your governing edition.

The standard stack: how 341, D1.8, and D1.1 relate

Understanding which standard governs which decision is the first thing a WPS author must get right:

AISC 341-22 is the design standard. It specifies what types of connections are permitted, what material properties are required (yield-to-tensile ratio limits, notch toughness requirements for protected zones), and which seismic force-resisting systems (SFRS) are available at different seismic design categories. It references AWS D1.8 as the mandatory welding standard for seismic connections.

AWS D1.8 is the structural welding code supplement for seismic applications. It modifies AWS D1.1 specifically for welding in seismic force-resisting systems: CVN filler metal requirements, preheat rules for demand-critical welds, additional WPS content requirements, and provisions for weld access holes and backing removal. AWS D1.8 does not stand alone — it supplements D1.1 and explicitly states which D1.1 provisions are modified or replaced.

AWS D1.1 remains the base welding code. Prequalified WPS joint details (Annex B), essential variables for qualification (Table 6.6), and general workmanship requirements still apply unless D1.8 modifies them. The essential variable table number is AWS D1.1:2025 Table 6.6 — the 2020 edition called this Table 6.5.

The practical result: a WPS for a demand-critical CJP groove weld in an SMF beam-column connection must satisfy all three simultaneously.

What AISC 341 requires from base metal

AISC 341-22 Section A3 imposes material requirements beyond standard ASTM minimums:

Yield-to-tensile ratio. For members in the SFRS, AISC 341-22 Section A3.1 limits the yield-to-tensile strength ratio to a maximum of 0.85 (Ry/Rt ≤ 0.85). Standard A36 may not meet this in practice. ASTM A992 — the standard specification for wide-flange shapes used in moment frame columns — has built-in yield-to-tensile ratio limits and is generally the code-conforming choice for W-shapes in seismic applications.

Protected zone base metal. The protected zone (typically defined by the connection prequalification in AISC 358) must be free of attachments that create notch effects, and base metal in this zone must not have properties that compromise ductility. AWS D1.8 Clause 4.1 restricts welding in the protected zone to the connection welds themselves.

Supplemental CVN for protected zone material. AISC 341-22 Section I2.1 requires that steel in the protected zone have a minimum Charpy V-notch toughness of 20 ft-lbf at 40°F [27 J at 4°C] when required by the SFRS type. Not all standard steel specifications meet this without supplemental ordering requirements — the fabricator must order material to the supplemental requirement (e.g., ASTM A572 Gr. 50 ordered to Supplemental Requirement S5 for Charpy testing) and obtain a CMTR confirming compliance.

See CMTR verification for structural welding: CWI checklist for how the material test report review integrates with this requirement.

Demand-critical welds: designation and WPS implications

The designation of a weld as demand-critical comes from the EOR's drawings or specification — it is a design designation, not a fabricator's choice. AWS D1.8 Clause 3.3 defines demand-critical welds as those where fracture would be expected to result in significant degradation of the building's structural integrity.

In practice, demand-critical welds typically include:

CJP groove welds at beam flange-to-column flange connections in SMF and IMF
CJP groove welds in column splices in certain seismic design categories
Other welds designated by the EOR per AISC 341-22 or project specification

The WPS for a demand-critical weld must include and document:

1. CVN-rated filler metal. AWS D1.8 Clause 6.3 requires filler metals for demand-critical welds to meet minimum CVN toughness values: 20 ft-lbf at −20°F [27 J at −29°C] minimum, and 40 ft-lbf at 70°F [54 J at 21°C] minimum. These values must be certified by the filler metal manufacturer's mill certification — the fabricator's WPS must specify the filler metal classification and include or reference the CVN certification.

2. Preheat per D1.8 Table 4.2. Minimum preheat for demand-critical welds is specified in AWS D1.8 Table 4.2, which sets values based on base metal thickness and typically requires higher preheat than AWS D1.1 Table 5.3 minimums for the same material. The WPS preheat value must satisfy D1.8 Table 4.2 requirements, even if D1.1 alone would allow lower preheat.

3. Maximum interpass temperature. AWS D1.8 imposes a maximum interpass temperature for demand-critical welds — typically 550°F [290°C] unless otherwise established by qualification testing. This must appear on the WPS.

4. Filler metal heat input restrictions. AWS D1.8 limits heat input ranges to ensure that CVN properties demonstrated in the PQR are replicated in production. Heat input must remain within the range used during PQR testing. See arc energy heat input AWS D1.1 formula for the heat input calculation.

PQR testing: CVN weld metal requirements

The PQR for a demand-critical weld application must include Charpy V-Notch testing of the deposited weld metal, in addition to standard mechanical tests:

Weld metal CVN test specimens are taken from the PQR test coupon transversely to the weld axis, from the weld centerline. AWS D1.8 specifies the specimen location, orientation, test temperature, and minimum impact values. The same filler metal and heat input range used in the PQR govern production welding — a change in filler metal classification or a heat input that falls outside the PQR-qualified range is an essential variable change requiring a new PQR.

This is a significant increase in PQR cost and complexity compared to standard D1.1 qualification. A shop transitioning from non-seismic fabrication to seismic moment frame work should plan for additional testing — the existing PQRs for standard structural work will not satisfy D1.8 CVN weld metal requirements.

See when does a PQR require requalification for a general discussion of requalification triggers.

AISC 358 prequalified connections and WPS linkage

AISC 358 (Prequalified Connections for Special and Intermediate Steel Moment Frames Under Seismic Loading) provides pre-engineered connection designs that are permitted without project-specific connection testing — provided the WPS and fabrication comply with the specific requirements of the prequalified connection.

Common AISC 358 connections with specific WPS requirements:

WUF-W (Welded Unreinforced Flange-Welded Web): Requires CJP groove weld at beam flanges; WPS must use backing bars meeting D1.8 backing removal or replacement requirements
RBS (Reduced Beam Section / dog-bone): No CJP at beam flange; requires specific cut geometry and CJP weld at reduced section; WPS must cover the CJP weld after RBS cut
BSEP (Bolted Stiffened End Plate): No CJP beam flange weld; WPS covers stiffener-to-column welds only

When a shop fabricates an AISC 358 connection, the WPS must be written to the specific filler metal, preheat, and heat input requirements in the relevant AISC 358 chapter — not just generic D1.8 minimums. The connection type governs the WPS content.

Weld access holes under AISC 358 and AWS D1.8

A frequently cited source of rejections in seismic moment connections is the weld access hole (cope). AWS D1.8 Clause 4.1 sets dimensional and surface finish requirements for access holes in seismic connections that are more restrictive than AWS D1.1 Clause 4 alone. The access hole must be:

Sized per AISC 358 requirements for the specific connection type
Thermally cut to a smooth finish (grinding to remove burrs and notches is required)
Inspected by the CWI before connection welding begins

See weld access holes cope cuts AWS D1.1 for general cope requirements; for seismic connections, add D1.8 Clause 4.1 requirements on top.

CWI inspection program differences for seismic work

Quality control for AISC 341 seismic work is more structured than standard D1.1 fabrication. AISC 341-22 Section J requires:

Fabricator QC (quality control): The fabricator is responsible for quality of materials and workmanship, including CWI inspection of demand-critical welds.
Special inspector (quality assurance): Most building codes require a special inspector — typically an independent third-party CWI — to inspect demand-critical welds. The special inspector is the Owner's quality assurance agent, distinct from the fabricator's CWI.

The WPS and PQR documentation must be available to both the fabricator's CWI and the special inspector. Hold points, inspection records, and acceptance/rejection documentation for demand-critical welds must be maintained and available for the building department's review.

Practical steps for a shop entering seismic fabrication

Obtain AWS D1.8 and review the differences from D1.1 applicable to the seismic connections on the job. Do not attempt to run D1.8 work from D1.1 alone.
Order CVN-rated filler metal with manufacturer mill certifications showing compliance with D1.8 Clause 6.3 values. Confirm with your filler metal supplier which specific lots have compliant certifications.
Run new PQRs with CVN weld metal testing if existing PQRs do not include D1.8 Charpy data.
Write D1.8-compliant WPSs that include: D1.8 Table 4.2 preheat, maximum interpass temperature, heat input range, and filler metal CVN certification reference.
Obtain CMTRs with supplemental CVN certification for base metal in protected zones if required by the SFRS type and AISC 341-22 Section A3.
Coordinate with the special inspector before fabrication begins to confirm hold points, inspection frequency, and documentation requirements.

For managing the WPS library, PQR records, and filler metal certifications across seismic and non-seismic work simultaneously, purpose-built welding management software reduces the risk of applying a non-seismic WPS to a demand-critical joint. See welding procedure library — audit ready for what a compliant library looks like, and pricing for tooling options.

Summary

AISC 341-22 seismic provisions change structural welding in four primary ways: stricter base metal requirements (yield-to-tensile ratio, protected zone CVN), mandatory AWS D1.8 compliance for seismic connections, demand-critical weld designations that require CVN-certified filler metal and elevated preheat, and PQR testing that must include Charpy weld metal qualification. A shop that has never built high-seismic SFRS work should treat this as a new qualification category — not an incremental change to existing non-seismic procedures.