REVIEW OF RESISTANCE PREDICTION METHODS FOR DOUBLE-SKIN COMPOSITE COLUMNS

Derived from CFST (Concrete-Filled Steel Tube) columns, CFDST (Concrete-Filled Double Skin Tubular) columns, or double-skin columns, are composite columns formed by two concentric steel tubular profiles – one inner and one outer – with concrete filled in the space between them. Typically, carbon steel is used for the inner tube, and either carbon or stainless steel is used for the outer tube. One of the main advantages of this type of column is the confinement of the infilled concrete, which contributes to excellent axial capacity, reduced self-weight, improved protection against local buckling, and greater ductility. Furthermore, the use of stainless steel in the outer tube ensures greater durability and resistance to external agents, in addition to offering aesthetic appeal and ease of execution. Due to these advantages, investigations into the behavior of these columns have been encouraged in recent years. Despite numerous experimental tests and numerical simulations based on the Finite Element Method, there is still no specific standardized method for designing CFDST columns with a stainless-steel outer tube, which motivates researchers to propose new equations. In this context, the present work presents a summary of the main methods used to predict the axial capacity of CFDST columns, highlighting the characteristics of each proposed equation. This includes the equations found in ACI 318, AISC 360, GB 50936 and Eurocode 4, as well as formulations proposed by Uenaka et al., Han et al., Hassanein et al. and Castanheira. A large number of experimental results available in the literature regarding the behavior of these columns is also reviewed. Based on this, comparisons are made between the experimental results and the strength predictions of the connectors according to the reference standards (ACI 318, AISC 360, GB 50936 and Eurocode 4), as well as other methods found in the literature (Uenaka et al., Han et al., Hassanein et al. and Castanheira). Therefore, this study aims to investigate the accuracy of the formulations in predicting the resistance of CFDST columns.