Mitigation of Weldment Cracking of Highway Steel Structures due to the Galvanizing Process
Structural supports for signs, luminaires, and traffic signals and other highway steel structures are generally galvanized to prevent corrosion and provide a long service life. However, recent investigations have revealed incidents of cracking in weldments of galvanized structures that appear to be induced during the galvanizing process. When placed in service, structures with such flaws will exhibit short service life and pose safety concerns. There is a need to identify the factors contributing to the occurrence of weldment cracking during the galvanizing process of steel highway structures and to propose improved design, materials, and construction specifications to help mitigate such cracking. This information will ensure that galvanized highway structures provide the intended service life and eliminate related safety concerns.
The objective of this research is to propose improved design, materials, and construction specifications of galvanized steel highway structures to mitigate weldment cracking caused by the galvanizing process. This research is concerned with structural supports for signs, luminaires, and traffic signals and bridge superstructures (other than decks).
Accomplishment of this objective will require at least the following tasks.
1. Collect and review relevant domestic and foreign literature; research findings; and information relative to cracking of weldments in highway and other steel structures that may be attributed to galvanizing. This information may be obtained from published and unpublished reports, and contacts with transportation agencies and other public and private organizations.
2. Evaluate the information collected in Task 1, and identify the factors contributing to cracking of weldment in galvanized steel structures (e.g., galvanizing process, material properties and chemistry, and design details).
3. Assess the relevance of the factors identified in Task 2 to cracking of weldments in galvanized highway structures and the adequacy of existing specifications to identify and mitigate such cracking.
4. Based on the findings of Task 3, propose a plan that includes an experimental investigation, to be executed in Phase II, to develop improved design, materials, and construction specifications to mitigate cracking of weldments in galvanized highway structures.
5. Prepare an interim report that documents the research performed in Tasks 1 through 4. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the project panel. Work on Phase II of the project will not begin until the interim report is approved and the Phase II work plan is authorized by the NCHRP. The decision on proceeding with Phase II will be based on the contractor’s documented justification of the updated work plan.
6. Execute the plan approved in Task 5. Based on this work propose improved design, material, and construction specifications for galvanized highway structures.
7. Prepare a final deliverable that documents the entire research effort. The proposed specifications shall be prepared as a stand-alone deliverable in a format suitable for consideration and adoption by AASHTO.
Research in progress.