Axial compression tests on seawater and sea sand concrete-filled double-skin stainless steel circular tubes

Seawater and sea sand concrete (SWSSC) filled double-skin stainless steel (SS) tubes consist of two concentric circular SS tubes, sandwiching SWSSC between them. This paper presents an experimental study on SWSSC-filled double-skin SS tubes (CFDSTs) under axial compression. Unfilled circular hollow sectional (CHS) specimens, fully-filled tubes (CFSTs) and double-skin tubes without inner tube (CFHT) were also tested for comparison purpose. Load-axial strain curves, stress in concrete, post-peak behaviour and energy absorption are investigated in this study. The effects of some key parameters, including confinement factor, void ratio and tube slenderness ratio, on the structural behaviour of SWSSC-filled SS tubes are discussed. It is found that the ultimate stress in concrete is mainly affected by confinement factor and the post-peak behaviour depends on both confinement factor and inner tube slenderness. Formulas are proposed to estimate the load carrying capacity of SWSSC-filled SS circular tubes in compression.