Hot-dip galvanized hollow structural sections - crack prevention and mechanical behaviour

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The application of hot-dip galvanized cold-formed Hollow Structural Sections (HSS) in exposed steelstructures (e.g. bridges, transmission towers and sign supporting structures) is extremely popular due to theirsuperior strength-to-weight ratio, low initial cost, sustainability and aesthetics. Both HSS manufacturing andhot-dip galvanizing techniques have evolved over the years. However, the use of newly developed zinc bathmixtures together with thick-walled HSS resulting in significant damage in the latter in the form of crackingduring the galvanizing process, especially at comer regions of Rectangular Hollow Sections (RHS), has beenreported to be a widespread problem lately. In an even worse case, if such cracks do not cause visible damage to the section and remain undetected before the final product leaves the galvanizing shop, they can result in serious consequences on the performance of the structure. This research aims to investigate: (1) the prerequisites of cracking; (2) if hot-dip galvanizing-induced embrittlement is a concern for RHS with different cross-sectional dimensions and produced to different specifications; (3) the thresholds of wall thickness above which different levels of pre-galvanizing countermeasures for brittle cracking are needed; and (4) the detrimental/beneficial effects of hot-dip galvanizing on the mechanical behaviours of RHS.The long-term goals of this project are to: (1) provide guidelines to engineers, fabricators and galvanizers to minimize the risk of cracking in RHS during hot-dip galvanizing; (2) generate supplemental rules to HSS manufacturing specifications and crack control guidelines; and (3) provide a better understanding of the characteristics and structural performance of hot-dip galvanized RHS to facilitate its application.