AWS D1.1 Explained: Steel Structural Welding Requirements

AWS D1.1 Structural Welding Code — Practical 2026 Guide

AWS D1.1 Structural Welding Code—Steel is the dominant structural-steel welding standard across the US, Middle East, Latin America, and Asia. It governs the design, fabrication, inspection, and qualification of welded steel structures — bridges, buildings, offshore platforms, pressure-vessel skirts, towers, cranes, Marine & offshore NDT, mining-haul-truck frames, and any cyclically-loaded weldment ≥ 1/8 in. (3 mm) thick. The current edition is AWS D1.1/D1.1M:2025, the 25th edition, which revised D1.1:2020.

The inspection side of the code, meaning what a weld must meet once it is examined, is covered in our guide to AWS D1.1 acceptance criteria.

Scope and Structure of D1.1

D1.1 is organised into 8 mandatory clauses plus 11 normative annexes:

• Clause 1 — General Requirements: base metals, design, fabrication and inspection roles, contract documents
• Clause 2 — Design of Welded Connections: joint types, weld symbols, allowable stresses, fatigue
• Clause 3 — Prequalification of WPS: 16 essential variables for prequalified status
• Clause 4 — Qualification (WPS, PQR, Welder): the test process when prequalification doesn't apply
• Clause 5 — Fabrication: preheat, interpass, heat input, welding consumables, position
• Clause 6 — Inspection: visual + NDT requirements, acceptance criteria, inspector qualifications
• Clause 7 — Stud Welding: shear connectors, qualification, inspection
• Clause 8 — Strengthening + Repair of Existing Structures

Annex M (NDT methods — PT, MT, UT, RT) is normative for any D1.1 contract that calls out NDT beyond visual.

Prequalified vs Qualified WPS — Clause 3 vs Clause 4

The single biggest cost-saver in D1.1 is the prequalified WPS (welding procedure specification). Clause 3 lists 16 essential variables — base metal grade, filler metal, joint type, position, preheat, etc. — and if your WPS meets ALL of them, no Procedure Qualification Record (PQR) test plate is required. Common prequalified examples: SMAW with E7018 on A36, A572 Gr 50, A992; FCAW with E71T-1 on similar; GMAW with ER70S-6 short-circuit on thin material.

If even one essential variable falls outside Clause 3 (e.g., reduced preheat, exotic base metal like ASTM A514, hybrid laser-arc process), the WPS must be qualified by Clause 4 — weld a test plate, NDT inspect it, mechanical-test specimens (tensile, bend, sometimes Charpy V-notch for fracture-critical), and produce a Procedure Qualification Record (PQR). The WPS / PQR set then governs production welding until an essential variable changes again.

Welder Qualification — Clause 4 Part C

D1.1 welder-qualification is by performance test on a coupon. Variables: process (SMAW vs FCAW vs GMAW vs SAW), position (1G flat, 2G horizontal, 3G vertical, 4G overhead, 6G inclined-fixed), thickness range, joint type (groove vs fillet), and electrode F-number. Pass = visual + bend test (face + root bends; or side bends for thicker material). Qualified welders are tracked in a continuity log: 6 months between welds of the qualified process triggers requalification.

For API 510 Pressure Vessel Inspector or API 570 Piping Inspector multi-cert work, the welder typically maintains BOTH AWS D1.1 (for structural attachments) AND ASME Section IX (for pressure-retaining welds). Atlantis NDT Atlantis NDT ERP tracks dual welder-continuity logs automatically.

Visual Inspection — Clause 6.9 + Table 6.1

Every D1.1 weld receives 100 % visual inspection by a Certified Welding Inspector (CWI per AWS QC1). Visual acceptance per Table 6.1 (statically loaded) and Table 6.2 (cyclically loaded):

• No cracks of any size in any direction
• Complete fusion at the root and between adjacent weld passes
• Undercut: ≤ 1/32 in. (1 mm) for material < 1 in.; ≤ 1/16 in. (1.5 mm) for ≥ 1 in.
• Convexity / reinforcement limits per Figure 6.5
• Underfill / overlap not permitted
• Slag, spatter, arc strikes ground out + retested per the cleanup procedure

NDT Acceptance — Annex M + Clause 6.13

NDT acceptance criteria for D1.1 welds (when called out by contract):

• magnetic particle testing (Annex M2): per SNT-TC-1A guide Level II MT; visible + fluorescent both accepted; no cracks; specific linear / rounded limits per Table 6.1 / 6.2
• liquid penetrant testing (Annex M3): Level II PT; no cracks; linear ≤ 1/16 in. on weld; visible OR fluorescent
• ultrasonic testing (Annex M4 — manual + Annex N for PAUT/TOFD): the most-used volumetric method on structural welds > 5/16 in. (8 mm). Acceptance per Table 6.3 (statically loaded — reflector amplitude + length-based) and Table 6.4 (cyclically loaded — much stricter, defect classes A/B/C/D)
• radiographic testing (Annex M5): ASME Section V Article 2 technique; acceptance per Table 6.5 (statically) and Annex G fatigue category for cyclic

For cyclic-loaded structures (bridges, offshore platforms, cranes), Annex G fatigue-category curves drive a much tighter NDT acceptance limit. Atlantis NDT NDT reporting software ships built-in D1.1 acceptance lookup tables for all four methods.

Prequalified Joint Geometries — Figures 3.3 / 3.4 / 3.5

Clause 3 lists prequalified joint geometries (joint angle, root opening, root face, included angle, backing). Use one of these and a prequalified WPS, and no PQR is required. Example: a single-V groove butt weld in 19 mm A36 plate with 60° included angle, 6 mm root face, 3 mm root opening, backing strip — all prequalified for E7018 SMAW in any position.

Cyclic Loading — Annex G + Clause 2.20

Structures subject to cyclic loads (bridges per AASHTO, offshore platforms per API RP 2A) follow AWS D1.1 + AASHTO LRFD / API RP 2A overlay. Fatigue categories A (smooth base metal) through E' (transverse stiffener weld) define allowable stress range vs cycle count. NDT acceptance is correspondingly tighter — Annex G specifies "fracture critical" inspection requiring 100 % UT or RT on Category D / E / E' details.

Inspector Qualifications — Clause 6.1 + AWS QC1

D1.1 inspections are performed by an AWS-Certified Welding Inspector (CWI) or Senior CWI per QC1. The CWI exam has three parts (Part A Fundamentals, 150 questions; Part B Practical, hands-on with 46 questions at AWS exam locations; Part C Code Book, 50-65 open-book questions) with a minimum of 72% on each, per aws.org. Atlantis NDT does not run CWI exam preparation; its training is ASNT SNT-TC-1A NDT training (see ASNT NDT training).

Frequently Asked Questions

Q1: When does D1.1 apply vs B31.3 vs ASME VIII?

A: D1.1 = structural steel (frames, supports, brackets, stiffeners, offshore-platform topsides, building frames). B31.3 = process piping carrying fluid. ASME VIII = pressure vessels. The same project often has all three — D1.1 for the vessel skirt, ASME VIII for the vessel shell, B31.3 for the connecting piping. Each has its own WPS / PQR / acceptance.

Q2: Is a prequalified WPS valid if my plate is ASTM A572 Gr 65 (above the prequalified range)?

A: No. Clause 3.5 lists prequalified base metals — A572 Gr 65 is outside the prequalified list (Gr 50 is prequalified, Gr 60 + 65 are not). You must qualify via Clause 4 — test plate, mechanical specimens, and PQR.

Q3: Does D1.1 require Charpy V-notch testing?

A: Only when called out by the contract owner. The base D1.1 PQR test (groove weld, tensile, bend) doesn't include Charpy. Fracture-critical and low-temperature applications add Charpy per supplementary essential variables — common on offshore platforms, Alaska / Arctic structures, LNG-service supports.

Q4: How does D1.1 differ from AWS D1.5 (Bridge Welding Code)?

A: D1.5 is bridge-specific (highway / railway bridges per AASHTO); includes stricter Charpy V-notch requirements, fracture-critical member rules, and tighter UT acceptance. D1.1 is the general-purpose code — accepted for buildings, offshore, mining, and most non-bridge structural work.

Q5: What NDT methods are most common for D1.1 inspection?

A: Visual + magnetic particle testing is the workhorse pair on carbon-steel welds; ultrasonic testing for groove welds > 5/16 in.; radiographic testing on critical full-penetration butt welds; liquid penetrant testing only on stainless or aluminum sub-fab. Atlantis NDT teams routinely run combined VT + MT + UT inspection per Annex M.

Q6: How long must D1.1 weld records be retained?

A: Per Clause 6.1.5 + Annex K — at least the period required by the building code or contract; many jurisdictions require life-of-structure for fracture-critical members. Atlantis NDT Atlantis NDT ERP maintains the WPS / PQR / welder-cert / inspection-record bundle in a PDF/A-3 audit trail.

Q7: Can I qualify a welder once and use them across multiple D1.1 jobs?

A: Yes — welder qualification is portable across employers in most cases (per Clause 4.10) and stays valid as long as the welder maintains 6-month continuity in the qualified process. The continuity log is your responsibility.

Q8: Does AWS D1.1 cover stainless steel?

A: No — D1.1 is carbon and low-alloy steel only. Stainless-steel structural welding falls under AWS D1.6 Structural Welding Code—Stainless Steel. The two codes share design philosophy but differ on consumables, preheat, and HAZ-control requirements.

Related Atlantis NDT Resources

• ASNT certification — Level I/II/III pathway, pass rates, employer recognition
• API 510 Pressure Vessel Inspector · API 570 Piping Inspector · API 653 Tank Inspector
• ASNT Level III consulting — outsourced Level III of record with SLA
• NDT reporting software — Marine NDT report format structured to IACS Rec. 20 content, auto-bundled
• Atlantis NDT ERP — affordable, accessible, fully customizable; 28 business apps included
• Atlantis Digital Twin platform — 3D inspection-data overlay, predictive maintenance
• magnetic particle testing
• ultrasonic testing
• Marine & offshore NDT

Atlantis NDT is led by Anoop Rayavarapu (ASNT NDT Level III in UT, RT, MT, PT and VT). Free consultation for NDT inspection companies, training providers, and asset owners worldwide. request a demo — pricing varies by region and scope, quote on request.