BACKGROUND: AASHTO M 270 (ASTM A709), Standard Specification for Structural Steel for Bridges, covers the chemical, mechanical, and toughness properties of structural steel intended for use in bridges. The AASHTO/AWS D1.5 Bridge Welding Code covers the welding processes and requirements for welded highway bridges, but it does not address the toughness requirements for heat-affected zones (HAZs) of welded structural steels. Also, toughness requirements for HAZs of welded structural steels are not covered in AASHTO LRFD Bridge Design Specifications. There is a need to identify the factors affecting the toughness for HAZs of welded structural steels used in highway bridges and determine what toughness requirements are necessary for incorporation in the AASHTO/AWS Bridge Welding Code and the AASHTO LRFD Bridge Design Specifications. This information will ensure that the HAZs will exhibit the toughness properties that are necessary for the intended performance and service life. Recent work completed under NCHRP Project 10-95 provided a review of some of the issues related to the toughness of HAZs of welded structural steels and proposed a preliminary research plan for identifying toughness requirements of welded structural steels used in highway bridges (see Special Note A). However, additional research is needed to further define and address the issues associated with toughness of HAZs, and to develop the proposed toughness requirements.
OBJECTIVE : The objective of this research is to develop proposed toughness requirements for the heat-affected zones (HAZs) of welded structural steels for highway bridges. The research shall deal with steels intended for use in bridges as identified in AASHTO M 270, Standard Specification for Structural Steel for Bridges.
RESEARCH PLAN: Accomplishment of the project objective will require at least the following phases.
Phase I—Planning: Prepare and submit, no later than 4 months after the contract award, an interim report that documents (1) the factors that affect the toughness of HAZs of welded structural steels, (2) the acceptance criteria for the HAZs of welded steel applications, (3) an assessment of the relevance of the identified factors and acceptance criteria to the toughness of HAZs to identify those most relevant to welded structural steels used in highway bridges for further consideration in this project, and (4) a proposed research plan that includes an experimental investigation of the most relevant factors and acceptance criteria, to be executed in Phase II, to develop toughness requirements of HAZs of welded structural steels for highway bridges.
Phase II—Development of Toughness Requirements: Execute the plan approved in Phase I. Based on the findings of this work, propose toughness requirements of HAZs of welded structural steels for highway bridges.
Phase III—Final Deliverables: Prepare and submit final deliverables. The deliverables shall include (1) a research report documenting the work performed in the project and used to develop the toughness requirements and (2) a stand-alone document delineating the proposed toughness requirements for HAZs prepared in a format suitable for incorporation in the AASHTO/AWS D1.5 Bridge Welding Code and AASHTO LRFD Bridge Design Specifications.
STATUS: Research in progress. Draft final report under review.