Structural steel fabrication in the United States sits at the intersection of two major specifications: AISC 360 (Specification for Structural Steel Buildings) and AWS D1.1 (Structural Welding Code — Steel). If you're a CWI or QC manager on a building project, understanding how these two documents divide responsibilities is the difference between a clean audit and a stack of nonconformance reports.
How AISC 360 hands off to AWS D1.1
AISC 360 Chapter J covers the design of welded connections — weld types, effective throat, required strength. For the actual execution of welding — procedures, qualifications, inspection — the specification delegates to AWS D1.1. Once the engineer of record (EOR) designs a connection using AISC 360 provisions, every weld in that connection must be performed in accordance with a valid WPS that meets AWS D1.1 requirements.
The delegation is clean: AISC 360 tells you what the weld must do structurally. AWS D1.1 tells you how to make that weld and how to verify it. Don't conflate them. An EOR who specifies a CJP butt weld in a primary member under AISC 360 is telling you the joint type and required strength; they are not substituting for your WPS program.
WPS responsibility: who provides it and when
AWS D1.1 places WPS responsibility on the fabricator or contractor performing the welding. Before any production weld is laid down, a WPS — either prequalified under Clause 5 or PQR-qualified under Clause 6 — must exist, be available to the welder, and be followed.
On AISC 360 projects, the EOR specifies the weld type and quality level; the fabricator supplies the WPS. A common audit finding is production welding underway before WPS documents are approved or distributed to the welding stations. That is a nonconformance under both AWS D1.1 and most fabricator QC programs regardless of how good the welds look.
For more on the cost tradeoff between the prequalified route and full PQR qualification, see PQR vs. prequalified WPS cost comparison and prequalified WPS under AWS D1.1 Clause 5.
QC vs. QA: the inspector split in AISC 360 Chapter N
One of the most practically important distinctions in AISC 360 Chapter N is the split between Quality Control (QC) and Quality Assurance (QA):
QC is the fabricator's own internal inspection program. The CWI on the fab shop floor checking fit-up, preheat, and completed welds is performing QC. The fabricator is contractually responsible for this work. QC inspection tasks include verifying the correct WPS is in use, checking preheat and interpass temperatures, and performing visual inspection of completed welds.
QA is an independent inspection and testing program, typically specified by the EOR and paid for by the owner. A third-party CWI or inspection firm performs QA. They review the fabricator's QC records, conduct independent visual inspection, and specify or witness NDE.
The two programs are not redundant — they have defined, complementary roles. The QA inspector does not replace the fabricator's QC inspector. When a third-party audit finds deficiencies in QC records, the fabricator must respond. See common WPS deficiencies found in third-party audits for what typically goes wrong when QC documentation lags production.
Prequalified vs. PQR-qualified on AISC 360 projects
Most fabricators running standard structural steel (A36, A572 Gr50, A992 wide flanges) default to prequalified WPS under AWS D1.1 Clause 5. The prequalified route is faster and less expensive — no test plates, no mechanical testing. The tradeoff is that you must stay strictly within the Clause 5 limits: prequalified base metals, prequalified joint geometries, filler metals from the prequalified list, and process/parameter limits defined in the code.
When you fall outside Clause 5 limits — higher-strength steels like A514 or A913, non-prequalified joint geometries, or processes like ESW/EGW — you need a PQR (Procedure Qualification Record) under Clause 6. The PQR requires test plates welded under the proposed conditions and mechanical testing to verify the WPS range works.
The AISC 360 framework does not itself dictate which path you take — that is an AWS D1.1 decision based on your materials and joint geometry. The EOR may specify requirements that effectively force the PQR route (e.g., requiring CVN impact testing on the PQR), but the path selection is the fabricator's engineering call.
Base metal and filler conformance
AISC 360 specifies structural steel materials (ASTM A36, A572, A992, A913, etc.). AWS D1.1 establishes prequalified base metal groups. When an EOR specifies a steel grade, confirm:
- The base metal is on the AWS D1.1 prequalified list, or the PQR covers that base metal group.
- The filler metal strength matches the specified steel group — prequalified fillers are listed in Clause 5; PQR-qualified fillers are supported by mechanical test results.
- Mill test reports (MTRs) are on file with heat numbers traceable to the joints being welded.
Material traceability is a consistent finding in AISC shop audits. Missing or incomplete MTRs are enough to put a job on hold during a third-party review.
Weld inspection hold points under the combined framework
AWS D1.1 drives inspection requirements; AISC 360 Chapter N specifies when QA needs to witness or review. Typical hold points in a fabrication sequence:
- Fit-up inspection (before welding): joint geometry, root opening, bevel angle, cleanliness, and tack weld quality. The WPS must match the joint detail on the drawing.
- Preheat verification (before first pass): measured with a contact pyrometer or Tempilstick at the correct standoff distance from the joint per AWS D1.1.
- In-process inspection (during welding): interpass temperature, pass sequence per WPS, electrode handling (low-hydrogen control if required by the WPS).
- Final visual inspection (after welding): AWS D1.1 visual acceptance criteria for the weld category.
- NDE (after visual): RT, UT, MT, or PT per contract documents and weld category.
QA inspector hold points should be agreed on in writing during the pre-construction meeting. Unannounced hold points mid-production create friction; good upfront coordination avoids it.
When AISC 341 adds requirements
On seismic force-resisting systems — moment frames, concentrically braced frames, eccentrically braced frames — AISC 341 applies alongside AISC 360. AISC 341 imposes:
Demand-critical weld designation for welds in specific connections. Demand-critical fillers must meet CVN toughness requirements specified in AISC 341, and they must be deposited with a procedure qualified to those toughness levels.
Supplementary essential variables under AWS D1.1:2025 Table 6.8. Any change to heat input, preheat, or filler classification on a demand-critical WPS triggers requalification with new CVN impact specimens. This is separate from and additional to the Table 6.6 essential variables that govern all PQR-qualified procedures.
Filler metal restrictions: certain classifications are not permitted for demand-critical applications. Check AISC 341 and the AWS D1.8 Seismic Supplement before specifying fillers on seismic projects.
The intersection of AWS D1.8 and AISC 341 makes seismic project WPS packages significantly more complex than standard AISC 360 work. Budget the time and testing cost accordingly.
Audit-readiness checklist for AISC 360 projects
A quick self-audit for QC managers before a third-party review or AISC certification audit:
- WPS documents exist for every weld process and joint type in production
- WPS documents are prequalified (Clause 5) or backed by a signed PQR (Clause 6)
- Welders are qualified and WPQs are current (no 6-month continuity lapse per AWS D1.1 Clause 6.4.1)
- MTRs on file, heat numbers traceable to joints
- Preheat and interpass temperature records maintained
- QC inspector is a CWI or equivalent; credentials current
- NDE records, acceptance criteria, rejections, and repairs tracked and signed
If any of these are missing, AISC certification audit readiness covers the full scope of what AISC auditors look for in your welding documentation program.
Ready to track all of this in one place — WPS, PQR, WPQ, and NDE records — for your next AISC 360 project? See how WPS Welding is built for structural fabricators.
Rule library based on AWS D1.1:2025; verify against your governing edition (the AHJ or contract may specify 2020 or earlier).