AWS D1.1

Covers — welding of statically and cyclically loaded structural steel connections in carbon and low-alloy steels: weld design, prequalified and qualified WPSs, welder qualification, workmanship, and visual/NDE inspection acceptance for structures.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Pressure piping and vessel welds → ASME Section IX + the construction code.
• Sheet steel (thin gauge) → AWS D1.3; reinforcing bar → AWS D1.4; aluminum structures → AWS D1.2.
• Pipeline welding → API 1104.

D1.1 owns structural steelwork (supports, racks, structures); pressure-boundary welds belong to Section IX.

D1.1 sets minimum requirements for structural welding:

• Weld Design — joint details, allowable weld sizes, and effective throats for structural connections.
• Procedure Qualification — prequalified WPSs (avoiding a PQR) or qualification by test.
• Welder Qualification — performance tests by process, position, and joint type.
• Inspection & Acceptance — visual inspection plus NDE (UT/RT) with structural acceptance criteria for statically vs cyclically loaded members.

AWS D1.1 is the flagship structural welding code for carbon and low-alloy steel — the standard behind welded pipe supports, pipe racks, and steel structures. It combines weld design rules, procedure and welder qualification (including prequalified WPSs), workmanship, and inspection acceptance in one code.

Its acceptance criteria differ for statically and cyclically (fatigue) loaded connections. Because it is a structural (non-pressure) code, structural welds are qualified to D1.1 while pressure-boundary welds stay under ASME Section IX.

Engineering Note: Use D1.1's prequalified WPS provisions to avoid a separate PQR for common structural joints — but confirm the joint, process, and steel grade actually fall within the prequalified limits.