Modelling and lock-seam effects on compressive behaviour of concrete-filled helical corrugated steel tubes

Concrete-filled galvanized helical corrugated steel tube, abbreviated as CFCST, is a new type of composite member that has great potential to be used in seismically active regions or highly corrosive environments. However, the unique lock-seam connections of helical corrugated steel tube (CST) result in high difficulty in precise simulation analysis, and the effects of such connections on the mechanical properties are not clear, so further investigations are needed. This paper attempts to present a detailed finite element (FE) model of CFCST with the real dimension of lock-seam connections, and then investigate the effects of lock-seam connections on the basic compressive behaviour of CFCST stub columns. The FE models are developed with the consideration of the real shape of helical CST, the non-linearity of each constituent material, and the interfacial properties at lock-seam regions. The simulated results are verified carefully through comparisons against experimental results of 41 stub columns under axial compression in terms of failure modes, load–displacement histories, and local stress developments. The influence of lock-seams on the working mechanisms has been particularly investigated and discussed. Parametric studies have also been conducted to investigate the compressive behaviour of the CFCST. Finally, simplified design methods for axial compressive bearing capacity are proposed.