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.