Which standard is primarily used for structural welding of steel in the United States?

• A. OSHA 1910
• B. API 1104
• C. AWS D1.1
• D. ISO 9001

Answer: (C)

Welding of structural steel in the United States is governed primarily by the AWS D1.1 Structural Welding Code—Steel. This standard specifically outlines the requirements for welding materials, joint design, welding procedures, welder qualifications, fabrication, inspection, and acceptance criteria for structural-steel projects like buildings and bridges. It is the baseline reference that fabricators and inspectors rely on to ensure the strength and safety of welded structures.

Other standards aren’t focused on the welding specifics for structures: OSHA 1910 deals with safety regulations, API 1104 covers pipelines and related facilities, and ISO 9001 is a quality-management system standard rather than a welding code. While those may be relevant in broader contexts, they do not provide the primary, structure-specific welding requirements used in US practice.