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4 Problem Statement Structural supports for signs, luminaires, traffic signals, and other steel highway structures are generally galvanized to prevent corrosion and provide a long service life. Recent investiga- tions 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 lives and pose safety concerns. There was a need to identify the factors contributing to the occurrence of weldment cracking during the galvanizing process in steel highway structures and to propose changes to current design, materials, and construction speci- fications to help mitigate such cracking. This information will ensure that galvanized highway structures provide the intended service life and eliminate related safety concerns. Research Objective and Scope The objective of this research was to propose improved design, materials, and construction specifications of galvanized steel highway structures to mitigate weldment cracking caused by the galvanizing process. This research was concerned with structural supports for signs, lumi- naires, traffic signals, and bridge superstructures (other than decks). The work included a review of relevant literature from across the world, design specifications from all 50 states, national and international technical specifications and guidance documents, and previously unpublished data on incidences of cracking during galvanizing. Information obtained through this review was carefully organized and evaluated, resulting in the identifi- cation of factors shown to contribute to cracking of weldments in galvanized steel structures. The relevance of these factors to weldment cracking in steel highway structures was evaluated to provide the basis for an experimental investigation and a computational study conducted in the project. Report Organization This report presents the findings of the research. Chapter 2 presents a summary of back- ground information on cracking that occurs during the galvanizing process, and it introduces the phenomenon of liquid metal assisted cracking (LMAC). Chapter 3 includes a description of the various factors that have shown to contribute to cracking of steel structures during galvaniz- ing, embedded within an organizational framework to assist in categorization of cracks associ- ated with galvanizing. Chapter 4 presents the experimental study, and Chapter 5 presents the computational study performed on high mast illumination pole (HMIP) structures undergoing C H A P T E R  1 Introduction and Research Scope
Introduction and Research Scope 5  the full galvanizing process. Chapter 6 presents a summary of findings and recommendations for research. The attachment includes proposed changes to the AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, first edition (2015) and the AASHTO LRFD Bridge Design Specifications, eighth edition (2017). The report includes four appendices that provide details of the work performed in the project. The appendices are not provided herein but can be found on the TRB website at www.trb.org by searching for NCHRP Research Report 965.