Web crippling behavior of grouted galvanized rectangular steel tube

To research the web crippling behavior of welded galvanized steel tubes with square and rectangular hollow sections under concentrated load, SHS and RHS carbon welded galvanized steel tubes under four different loading conditions were tested. This paper also examined an approach to enhance web crippling strength of the tubes, by infilling the mortar as composite section. Although very relevant, the understanding about the web crippling behavior in carbon welded galvanized composite section is still very limited, as attested by the lack of information available in design codes and guidelines. End-two-flange (ETF) and interior-two-flange (ITF) loading conditions were adopted, with specimens seated on a bearing plate. Specimens were also placed on the ground with end (EG) or interior (IG) bearing load to simulate the loading conditions of floor joist members. The effects of the loading positions (end loading or interior loading) as well as the supporting conditions (on a bearing plate or on the ground) on the web crippling behavior are discussed and the enhancements of infilling mortar are evaluated. It was found that infilling the mortar in galvanized rectangular steel tube is a very effective approach to enhance the web crippling strength of the tubes, especially for specimens with end bearing with solid ground. Based on the results of the parametric study, a number of design formulas proposed in this paper can be successfully employed as a design rule for predicting web crippling ultimate capacity of grouted galvanized steel tubes under four loading and boundary conditions.