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Bridge Welding Code Updated for 2008
Posted by Geoff Weisenberger on March 14, 2008 at 3:00 PM.

The American Association of State Highway and Transportation Officials (AASHTO) and the American Welding Society (AWS) jointly develop the AASHTO/AWS D1.5M-D1.5 Bridge Welding Code. The Code has been adopted by most states and transportation authorities (cities, tollways, etc.) to assure weld longevity in structures carrying millions of vehicles. The first edition was published in 1988, with revised editions in 1995, 1996, and 2002. AWS policy does not authorize interim changes, except for errata published in the Welding Journal, so there were no official changes between editions. The latest edition, 2008, is now available. Changes include:

 

  • Providing welding guidance for two grades of high-performance steel—ASTM A709 (AASHTO M270) HPS 50W/HPS 345W and HPS 70W/HPS 485W—and deleting Gr. 70W/485W, a quenched and tempered Gr. 50W/345W. The HPS steels have higher toughness and better weldability and weathering characteristics, but their chemistry requires different welding consumables than Gr. 50W/345W or Gr. 70W/485W.
  • Tables 4.1, 4.2 have been revised, including moving the increasingly popular metal-cored GMAW electrodes to Table 4.1, thereby reducing the need for procedure qualification testing under Section 5.13. In addition, minor changes have been made to Tables 4.3 (unpainted steel), 4.4 (preheat), and 4.5 (stress relief holding time).
  • The suggested Weld Procedure Specification (WPS) and Procedure Qualification Test Record (PQR) forms provided in Annex III have been amended, based on input from fabricators, owners, and consumable producers. The PQR form now provides areas to document test parameters, witnesses, and results, reducing the potential for later questions or disputes. The WPS form now provides an area for listing all significant variables, clarifying expectations for welders and inspectors. Shops working for multiple owners may improve common acceptance with these updated forms.
  • Illustrations for specifying and measuring intended camber have been included. These images better define the desired camber and how to assess post-welding acceptance tolerances.
  • Machining and testing tolerances for performance test specimens are now included. These do not entail significant changes to test equipment or specimens; rather, they better define the geometry and finishing needed to ensure consistent test conditions and accurate results.
  • Storage requirements for fracture-critical welding consumables have been amended. The absence of hydrogen is critical for weld soundness, and even small hydrogen-induced cracks can propagate under cyclic loading. Fracture-critical consumables must be certified “low-hydrogen” by the producer, and they must be handled and stored to remain that way. Requirements include GMAW and FCAW reels, and clarify drying SMAW electrodes.
  • RT film type and scanning patterns for UT are now addressed in Section 6, and NDT qualifications have been correlated between Sections 6.1 and 12.8. Also, additional welder qualification requirements have been clarified between 12.8 and Section 5, Part B.
  • A commentary was added for Section 4, and extensive changes were made for other sections, including moving notes and italicized items from the Code to commentary sections, and replacing mandatory language (”shall” and “must”) with permissive (”may”).
  • Other clarifications and modifications include: welder grinding deficiencies during a PQR that also proves qualification; correcting weld-induced distortion; dimensional tolerances; plasma cutting joint faces; undermatching weld strength; and clarifying fillet soundness tests.

 

Some future expected changes include the following:

 

  • AWS has adopted a policy permitting interim code changes before a subsequent edition. This will not be common practice, but may allow new technology or avoid problem details.
  • Narrow gap improved electro-slag welding (NGIESW) is expected to be included in the next edition.
  • Combining Tables 4.1 and 4.2, and merging the qualification test requirements of 5.12 (max or min-max heat input) and 5.13 (production) are also expected in the next edition.
  • The use of partial joint penetration (PJP) welds perpendicular to tensile stress.
  • Gr.50S/345S will be included to cover rolled beams.

 

The Bridge Welding Code has evolved over the past twenty years and will continue to change, reflecting owners’ needs for confidence, fabricators’ needs for consistency, and the ever-changing technology of welding.

 

—By Jon Edwards, former fabrication engineer with the Illinois Department of Transportation and advisor to the AWS D1.5M-D1.5 Subcommittee.

 

A Separate Standard

 

Bridge welding didn’t always have its own code. It was originally covered in Section 9 in the AWS D1.1 Structure Welding Code – Steel. However, as AASHTO and individual states added requirements, fabricators found that they had to undergo separate, expensive qualification tests for different owners. So, in the early 1980s, AASHTO and AWS formed a joint committee to establish a document for all owners to adopt, resulting in AWS D1.5M-D1.5.

 

After the initial publication, subsequent editions incorporated changes in technology, clarified areas of confusion or contention, improved efficiency for fabricators, and ensured that owners were satisfied with results. Significant changes included the addition of metric to the U.S. Customary units, Section 12 for Fracture Critical Welding (replacing the AASHTO Fracture Critical Guide Specification—which became the Fracture Control Plan for non-redundant structures)—and commentaries for Sections 1, 2, 3, 5, 6, 7, and 12.


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