Hybrid laser arc welding (HLAW) is a hybrid welding process developed in the 1980s.  The technology has been used in nuclear, pipeline, shipbuilding, and other heavy manufacturing/fabrication industries. Over time, it has become a quick and reliable welding process option that can be applied using standard commercially available welding equipment. However, HLAW is not currently used in bridge welding and does not align with the current essential variables, weld design guidelines, and inspection criteria in the current AASHTO/American Welding Society (AWS) D1.5 Bridge Welding Code and AWS D1.1 Structural Welding Code. HLAW is not foreign to AWS; there is a dedicated AWS HLAW welding standard (C7.6) that can be referenced for the modification of the current bridge-related welding codes. 

The objective of this research is to develop design procedures and acceptance criteria for HLAW of American Petroleum Institute (API) 5L X52 Product Specification Level (PSL) 2, ASTM A252 grade 3, and ASTM A709 bridge girder and pipe-pile steels. Through welding development and material testing, this project will demonstrate whether HLAW is an acceptable process for bridge steels and provide guidance on procedures to validate how acceptable welds have been produced. The primary material for this development and testing would be various thicknesses of ASTM A709 grades 50, 50W, and HPS 70W for girders, and ASTM A709 grade 50, API 5L PSL 2, and ASTM A252 grade 3 steels for pipe piles.

Specific research tasks to accomplish the main objective include:

• Identify and summarize the current applicable HLAW literature;
• Develop an experimental program with laboratory tests of the weld joint to determine material properties, such as strength, ductility, and fracture resistance; 
• Determine whether weld defects will occur and how to mitigate them;
• Develop recommendations for design, workmanship, practice recommendations, qualification, inspection, and acceptance criteria for HLAW welds; and
• Prepare a final research report presenting the complete results of the research with recommendations to the joint AASHTO/AWS Bridge Welding Code Committee and the AASHTO Committee on Bridges for implementation and future research.

The final products of this project will be:

• Guidelines for all aspects of HLAW production on bridge steel,
• Guidelines for acceptance criteria, and
• Language for AASHTO to consider incorporating into the AASHTO/AWS D1.5 Bridge Welding Code and to recommend for the AWS D1.1 Structural Welding Code.