A new edition of the American Association of State Highway and Transportation Officials (AASHTO)/American Welding Society (AWS) D1.5, Bridge Welding Code, was published last fall. The code changes were huge — most notably, the code features significant improvements to welding procedure qualification rules and a new nondestructive examination method. Years of experience under the code demonstrated the time was ripe to update a number of qualification rules. First, a groove weld qualification plate is no longer required for single-pass fillet weld procedures. This means it will no longer be necessary to dial fillet welding parameters away from optimal settings to settings intended for groove welds just to pass a test. Further, there will be more flexibility in use of filletweld designed consumables, such as active fluxes for submerged arc welding. Alloys in active fluxes react with voltage to improve weld metal strength; however, in multipass welds, the alloys build up and make the weld brittle, so the code’s groove weld test had the unintended consequence of precluding some of the best techniques available for fillet welding. Rules for the heat input and production procedure qualification methods have also been tuned. The intent of the heat input method is that an acceptable range of welding parameters based on heat input can be qualified by testing. The heat input window can be created by testing either the maximum and minimum heat input to be used, or just by testing the maximum to be used and then staying within 60% of the test value. Additional amperage and voltage constraint restrictions narrowed these windows, but experience demonstrated the additional restrictions were not warranted; these have been removed, thus returning the flexibility originally intended with the heat input method. In the production procedure method, the actual parameters to be used in the work are tested (as opposed to testing to create a heat-input based operating window). The premise of this method is that any settings could be used provided they could pass testing, except that the code imposed additional limits on amperage, electrode diameter, and layer thickness. Years ago, when they were adopted, these limits more closely reflected the state of the art at that time. But technology has changed; hence, the lifting of these code restrictions will facilitate innovation while procedure testing continues to ensure that weld strength, toughness, and soundness are maintained. Technology in nondestructive examination is also advancing, and by way of a new annex, the new code adopts optional phased array ultrasonic testing (PAUT) to keep up. This is a highly sophisticated and powerful form of ultrasonic testing. To use it, a scanning plan is developed for the joint to be tested, and a block tailored to the joint is used for calibration. This offers significant advantages over traditional methods — given it is much faster, more thorough, and more repeatable — plus with encoding, it provides a permanent digital record of the test that can be reevaluated at any time. Owners have already begun adopting this testing for general improvement or to address particularly challenging weld joints. Research sponsored by the National Cooperative Highway Research Program is underway to discover better ways to take advantage of it, possibly to include fit-for-service evaluation and acceptance. Hence, adoption of the new PAUT annex is just the first progressive step toward much-improved quality and value in nondestructive examination under D1.5. With the new code, our community takes great steps forward in welding procedure qualification and nondestructive examination, and further advances lie ahead. The code committee’s strategic plan envisions structural tube welding, digital radiography, new welding processes, and new materials in the code’s future. Further, the committee will continue to work diligently to improve the code’s accuracy and clarity, and to keep it up to speed with the state-of-the-art in fabrication technology. As vice chair of the committee, I invite you to come along: Use the code, provide feedback, and consider getting involved in committee activities. As welding revolutionized bridges, let’s work together to continue advancing state of the art processes, and achieve the best possible quality and value in steel bridges fabricated under the code. EDITORIAL How the New Bridge Welding Code = Great Steps Forward Ronnie Medlock Vice chair, AASHTO/AWS D1J Subcommittee on Bridge Welding “With the new code, our community takes great steps forward in welding procedure qualification and nondestructive examination, and further advances lie ahead.” 6 WELDING JOURNAL / MARCH 2016 WJ
Welding Journal | March 2016
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