Performance of New Sandwich Tube under Axial Loading: Experiment

The strength of steel tubes used in offshore construction is often limited by local and global stability considerations. We propose a new composite tube, which consists of two concentric steel tubes with polymer concrete sandwiched in between them. The increase in section modulus will enhance the global stability in long tube applications. The interaction of the three components of the composite tube will have a positive impact on the local stability of the tube. This study concentrates on the local stability issue and quantifies the strength and ductility enhancement due to the interaction. Twenty-six small-scale models of short composite tubes were tested under uniaxial compression and six were tested under cyclic semireversal axial loading. Test results showed that the new composite tubes generally had a compressive strength 10–30% higher than the sum of the individual components. The ductility of the composite tube was also much improved. The prediction of strength by an analytical model and an empirical formula is reported in a companion paper.