AWS D1.5 Bridge Welding

Exam blueprint

Sourced from AWS D1.5/D1.5M:2020 — Bridge Welding Code (jointly with AASHTO)

• Scope + key differences from D1.110%
• Charpy V-Notch (CVN) impact testing of qualification20%
• Fracture-Critical Members (FCM) — Clause 1220%
• NDT — RT/UT requirements for bridge welds20%
• Preheat, interpass, and hydrogen control10%
• AWS QC1 inspection requirements + CWI role10%
• ANSI/AASHTO/AWS welder qualification chain10%

1. 01D1.5 vs D1.1 — what changes for bridge work

   ~60min

   D1.5 inherits much of D1.1 but adds bridge-specific provisions because bridges experience cyclic loading, are often non-redundant, and carry public traffic. Knowing where the codes diverge is the test (and the field) discriminator.

   • Who has jurisdiction — AASHTO + state DOT

     D1.5 is invoked by reference in AASHTO's LRFD Bridge Construction Specifications. Every state Department of Transportation (DOT) adopts D1.5 (or a modified version) for state-highway bridges, federal-aid bridges, and most municipal arterial bridges. Private structures (a parking-deck pedestrian bridge in a private development) may default to D1.1 instead. The first question on any bridge job is: "Whose code applies?" The answer is usually D1.5 PLUS a state DOT supplement (a "Special Provisions" document) that adds even tighter requirements specific to that DOT.

     Reference: AASHTO LRFD Bridge Construction Specifications Article 11 (Welded Construction)

   • Where D1.5 diverges from D1.1

     Major differences worth memorizing: (1) D1.5 requires CHARPY V-NOTCH (CVN) testing of weld qualification specimens; D1.1 generally does not. (2) D1.5 has a separate FRACTURE-CRITICAL MEMBER (FCM) plan in Clause 12 with its own additional requirements; D1.1 does not address FCM at all. (3) D1.5 requires 100% NDT (typically UT or RT) on tension members and CJP butt welds; D1.1 leaves NDT to the engineer. (4) D1.5 mandates AWS QC1-certified inspection (CWI required); D1.1 only RECOMMENDS it. (5) D1.5 has tighter preheat tables and stricter hydrogen-control requirements (low-hydrogen electrodes only, often with reconditioning protocols).

   Practice questions (1)

   1. 1. A fabricator is welding plate girders for a state-highway bridge. Which code primarily governs the welding?

      • A.AWS D1.1 (Structural Steel)
      • B.AWS D1.5 (Bridge Welding) plus state DOT special provisions✓ correct
      • C.AISC 360 only
      • D.ASME Section IX

      State-highway bridges are governed by D1.5, invoked through AASHTO LRFD Construction Specifications. Most state DOTs add their own Special Provisions on top. D1.1 covers steel buildings and non-bridge structures. AISC 360 is the design code, not the welding code. ASME Section IX governs pressure-vessel welding, not bridges.

2. 02Charpy V-Notch (CVN) impact testing

   ~75min

   Bridges experience low-temperature, dynamic loading. CVN testing measures the toughness of weld and HAZ — the resistance to brittle fracture at service temperature. D1.5 requires CVN tests of qualification specimens; D1.1 does not.

   • What CVN testing measures

     A Charpy V-Notch test takes a small machined specimen (10 × 10 × 55 mm with a precise notch) and breaks it with a calibrated pendulum at a specified test temperature. The energy absorbed during fracture (in foot-pounds or joules) is the CVN value. High value = ductile, tough material. Low value = brittle. Bridge steels are tested at the COLDEST service temperature the bridge will see. Three temperature zones in D1.5: Zone 1 (warmer states, 0°F minimum service temp), Zone 2 (moderate, -30°F), Zone 3 (cold, -60°F). The required CVN energy is given in tables that vary by zone, member type, and yield strength.

     Reference: AWS D1.5 Clause 5 + Annex IV (CVN procedures)

   • Where CVN specimens are taken

     D1.5 prescribes specific specimen locations within a procedure-qualification weld: in the WELD METAL itself, in the HEAT-AFFECTED ZONE (HAZ) at varying distances from the fusion line, and (for some applications) in the BASE METAL. Three specimens at each location, all tested at the same temperature, with both individual minimum and average minimum values required. A single specimen below the individual minimum can fail the entire WPS qualification. This is why bridge fabricators run multiple-specimen qualification panels and bank "test buttons" so a failed specimen does not cost weeks of re-qualification.

   • CVN values for FCM members

     Fracture-critical member (FCM) welds have HIGHER CVN requirements than non-FCM members in the same zone. A typical example from D1.5 Table 12.x: a non-FCM member in Zone 2 may require 20 ft-lb at -30°F, while the same member designated FCM might require 25 ft-lb at -30°F. The numbers vary by edition and steel grade — never quote from memory; always read the current table. The point: FCM toughness requirements are tighter precisely because failure of an FCM is, by definition, catastrophic.

   Practice questions (2)

   1. 1. A welder qualified under AWS D1.1 (no CVN testing performed) is asked to weld a tension flange on a state highway bridge plate girder. Action?

      • A.Existing D1.1 qualification covers bridge work
      • B.Welder must be re-qualified under D1.5, including CVN testing of the qualification specimens✓ correct
      • C.Welder may proceed if a CWI signs off
      • D.Existing qualification is accepted only if the steel grade matches

      D1.1 procedure qualifications generally do NOT include CVN impact testing, which is a D1.5 requirement. The WPS and welder must be re-qualified under D1.5 with CVN tests at the appropriate Zone temperature. A CWI signature does not waive code-required testing. Steel-grade match is necessary but not sufficient — toughness testing is the gating requirement.

   2. 2. During CVN testing of a D1.5 procedure-qualification weld, one of the three weld-metal specimens fails the individual minimum at -30°F. The other two pass, and the average exceeds the required average. Outcome?

      • A.WPS qualifies — the average passes
      • B.WPS fails — D1.5 requires both individual minimum AND average minimum✓ correct
      • C.Re-test only the failing specimen
      • D.WPS qualifies if the failure is in the HAZ rather than weld metal

      D1.5 requires BOTH the individual specimen minimum AND the average minimum to be met. A single below-individual-minimum result fails the qualification regardless of how high the other two scored. You cannot retest just the failed specimen — the entire qualification panel must be reworked or a new test plate run. Location (weld metal vs HAZ) does not exempt the requirement.

3. 03Fracture-Critical Members (FCM) — Clause 12

   ~90min

   Clause 12 is the heart of D1.5's bridge-specific work. FCM members require dedicated quality, planning, and inspection. Fabricators need an AISC Sophisticated Paint Endorsement-tier QA program plus an additional FCM endorsement to fabricate FCMs.

   • What makes a member fracture-critical

     A FRACTURE-CRITICAL MEMBER (FCM) is a tension member or tension component of a member whose failure would result in COLLAPSE of the bridge — there is no load-redistribution path. Classic examples: tension flanges and tension diagonals on a two-girder bridge, eyebars on a pin-and-hanger truss, tension chords on a tied-arch tie. Bridge engineers identify FCMs on the design drawings and label them explicitly. Non-FCM members in the same bridge get standard D1.5 treatment; FCMs get Clause 12 treatment, which is materially more demanding.

     Reference: AWS D1.5 Clause 12.1 (FCM definitions)

   • The FCM Quality Plan

     A fabricator producing FCM components must maintain a written FCM Quality Plan covering: material control (CVN-tested plate, mill certs traced), welding procedures (FCM-specific WPSs with dedicated CVN-tested qualifications), welder qualifications (welders specifically qualified for FCM work and tracked individually), NDT (100% UT/RT, with technicians qualified per ASNT), and traceability of every weld back to a welder, electrode lot, and procedure. Most state DOTs require fabricators to hold an AISC certification with the SBR/FCM endorsement (Major Steel Bridge Fabricator, Fracture-Critical) to fabricate FCM components.

     Reference: AWS D1.5 Clause 12.4 (FCM fabrication plan)

   • FCM-specific welding restrictions

     Clause 12 imposes additional restrictions on FCM welding: (1) Tack welds must be made by qualified welders and inspected — not just by helpers. (2) Run-on / run-off tabs must be used on all CJP groove welds and removed by grinding (not torch-cut close to the joint). (3) Backing bars on T-joints are typically removed and the back gouged + back-welded. (4) Repair welding is restricted — multiple repairs at the same location may require engineer approval. (5) Stamping or hard-stamping of FCM material is generally prohibited (stress concentrators); identification uses paint or vibroetched marks.

   Practice questions (2)

   1. 1. A fabricator is welding the bottom-flange tension splice on a two-girder bridge designated as FCM by the engineer. Run-off tabs are torch-cut flush with the joint. Acceptable?

      • A.Yes — torch cutting is allowed
      • B.No — D1.5 Clause 12 requires run-off tabs to be removed by grinding✓ correct
      • C.Yes if the cuts are made within 1/8 inch of the joint
      • D.Acceptable only if a CWI signs the cut

      D1.5 Clause 12 requires that run-off tabs on FCM welds be REMOVED BY GRINDING to avoid leaving notches or thermal damage at the weld termination — these are stress raisers that promote brittle fracture. Torch cutting flush to the joint leaves a heat-affected band and rough surface that can initiate cracks. CWI sign-off does not change the requirement.

   2. 2. On a tied-arch bridge, the tie plate carrying the horizontal thrust from the arch is identified by the engineer as fracture-critical. Compared to non-FCM welds on the same bridge, FCM welds require:

      • A.Identical procedures — the FCM label is documentation only
      • B.A separate FCM Quality Plan including FCM-specific WPS qualification with CVN testing, qualified welders tracked individually, and 100% NDT✓ correct
      • C.Lower preheat to avoid HAZ embrittlement
      • D.Field welding only — shop welds are not allowed

      Clause 12 imposes a layered set of additional requirements: FCM-specific WPSs with their own CVN-tested qualifications, FCM-qualified welders tracked individually, 100% NDT (UT/RT) on all CJP welds, and a documented FCM Quality Plan. The FCM label is NOT documentation only. Preheat is INCREASED for FCM (not decreased). Field-only welding is the opposite of best practice — shop welds under controlled conditions are preferred for FCMs whenever feasible.

4. 04NDT + AWS QC1 inspection

   ~75min

   D1.5 mandates the volume of NDT D1.1 only recommends. Tension-member CJP butt welds typically get 100% RT or UT. All inspection must be performed under an AWS QC1-certified Quality Control program, with visual inspection by a CWI.

   • 100% NDT for tension members and CJP butts

     D1.5 requires 100% RADIOGRAPHIC TESTING (RT) or ULTRASONIC TESTING (UT) on all complete-joint-penetration (CJP) groove welds in tension members. Compression-member CJP welds typically get sample NDT (often 25% spot UT or RT). Fillet welds get 100% MAGNETIC PARTICLE (MT) on bridge work — much higher than D1.1's typical 10% sampling. The choice between RT and UT depends on access and material — UT is preferred for thick sections (>1.5 in) where RT becomes impractical, and for cracks (which UT detects more reliably than RT).

     Reference: AWS D1.5 Clause 6 (Inspection) + Table 6.x

   • NDT personnel qualification — ASNT SNT-TC-1A

     NDT technicians performing UT, RT, MT, or PT under D1.5 must be qualified to ASNT (American Society for Nondestructive Testing) SNT-TC-1A or CP-189, typically at LEVEL II (capable of performing testing and interpreting results independently). The NDT contractor maintains a written practice describing how they qualify and certify their technicians. This is more rigorous than D1.1 typically requires. Most state DOTs additionally require NDT contractors to be AISC NDT-certified or pre-approved on a state DOT roster.

   • AWS QC1 + the CWI requirement

     D1.5 mandates that VISUAL INSPECTION be performed by a Certified Welding Inspector (CWI) qualified per AWS QC1. D1.1 RECOMMENDS this; D1.5 REQUIRES it. The CWI inspects fit-up, before-welding conditions, in-process welding parameters, and final visual acceptance per Clause 6. A CWI signature is the gateway to NDT — failed visual inspections do not proceed to UT/RT. This is also why bridge contractors must factor CWI staffing into their bid: a fabrication shop turning out bridge girders typically needs a full-time on-staff CWI plus a third-party Quality Assurance (QA) inspector hired by the owner/engineer.

     Reference: AWS QC1 Standard for AWS Certification of Welding Inspectors

   Practice questions (2)

   1. 1. A 1-inch tension flange CJP butt weld on a state highway bridge girder must be NDT-tested per D1.5. Required coverage?

      • A.10% spot RT
      • B.25% spot UT
      • C.100% RT or UT✓ correct
      • D.Visual inspection only

      D1.5 requires 100% volumetric NDT (RT or UT) on tension-member CJP butt welds — there is no spot-sampling allowance for tension CJPs. 10% / 25% spot rates apply to lower-criticality welds (some compression CJPs, sample fillets). Visual inspection by the CWI is required FIRST but does not substitute for volumetric NDT.

   2. 2. Per AWS D1.5, who is required to perform the in-process visual inspection of bridge welds?

      • A.A welder trained to inspect their own work
      • B.An engineer of record
      • C.An AWS QC1 Certified Welding Inspector (CWI)✓ correct
      • D.Any third-party agent the contractor designates

      D1.5 explicitly requires visual inspection by an AWS QC1 Certified Welding Inspector. The CWI credential is governed by AWS QC1 and is mandatory under D1.5 (whereas D1.1 only RECOMMENDS it). An engineer of record may approve repairs but does not perform routine inspection. A welder cannot inspect their own work for code purposes. "Any third-party agent" misses the QC1 credential requirement.

5. 05Welder qualification chain — ANSI/AASHTO/AWS

   ~60min

   Bridge welder qualification is a paper trail spanning three jurisdictions. Each layer adds requirements; missing any layer can void the welder's ability to deposit production weld on a state-DOT bridge job.

   • The three layers of qualification

     Layer 1 — D1.5 (AWS): the welder passes a procedure test (typically a 3G or 4G plate, or 6G pipe for pipe work) under a qualified WPS. CVN testing is performed on the procedure-qualification panels (not the welder-qualification panels). Layer 2 — AASHTO/AWS additional requirements: state DOTs frequently impose extra welder-qualification provisions (annual re-qualification, tracked welder logs, electrode-lot traceability). Layer 3 — Project-specific requirements: many DOTs maintain a list of pre-approved fabricators and individual welders. Even a properly qualified D1.5 welder may not be allowed on a particular state's bridge jobs without separate state-DOT pre-approval.

   • Maintaining qualification — the 6-month rule

     Once qualified, a welder must maintain CONTINUITY by depositing weld in the qualified process at least once every 6 months. Failure to weld for 6+ months requires re-qualification (in some cases, a re-test in just one position is sufficient; in others, a full re-test is required). Bridge fabricators track each welder's last weld date in the qualified process — usually with a barcode or stamp on each weld traced back to a daily log. Apprentice welders are often DOUBLE-tracked because their qualifications can be tied to a journeyman supervisor.

     Reference: AWS D1.5 Clause 5.27 (Period of Effectiveness)

   Practice questions (1)

   1. 1. A welder is qualified under AWS D1.5 in 3G plate position with FCAW process. They have not welded for 8 months. Are they qualified to start production welding tomorrow?

      • A.Yes — D1.5 qualifications never expire
      • B.No — qualification continuity requires welding in the qualified process at least every 6 months✓ correct
      • C.Yes, after a CWI re-issues the qualification card
      • D.Yes if they have been welding in a different process during the 8 months

      D1.5 (Clause 5.27) requires welders to maintain continuity by depositing weld in the qualified process at least every 6 months. After 8 months without FCAW, re-qualification is required. A CWI cannot waive the time-out requirement. Welding in a DIFFERENT process keeps that other process current but does not maintain FCAW continuity — process is an essential variable.

External resources

• Official
  AWS D1.5/D1.5M Bridge Welding Code ↗

  The actual code, jointly published by AWS and AASHTO. State DOTs adopt either the current edition or one a few cycles back — confirm which edition your project specifies BEFORE you study. Some clauses (especially Clause 12 FCM) have been substantially revised between editions.

• Official
  AASHTO LRFD Bridge Construction Specifications ↗

  AASHTO's construction-side specification, which references D1.5 by section. Article 11 (Welded Construction) lays out where bridge construction sits in the broader AASHTO framework — useful context for inspectors and fabricators.

• Third-party
  FHWA Manual on Inspection of Fracture-Critical Bridge Members ↗

  Federal Highway Administration guidance on FCM identification, inspection, and reporting. Particularly useful for understanding WHY D1.5 Clause 12 exists — failure modes and historical incidents that drove the FCM provisions are documented here.