Compressive behavior of concrete-filled double skin steel tubular columns: An analytical approach

An analytical model is proposed to predict the confinement pressure exerted by steel tubes on sandwiched concrete in concrete-filled double skin steel tubular columns (CFDSTC) when subjected to uniaxial compression, based on which precise stress state within the concrete element is achieved. This model incorporates the steel tube -concrete interaction using force equilibrium and radial displacement compatibility appropriately. Additionally, it takes into consideration the stress state within the steel tube by accounting for buckling effects and the multiaxial 2D stress experienced by the steel tube. Utilizing this, an incremental iterative analysis-oriented model is proposed to capture the effect of void ratio, steel tube thickness and buckling on the global axial load-strain response of the columns. Unlike other existing models, this model effectively considers the non-uniform distribution of lateral stresses within sandwiched concrete in CFDSTC. The predictions from the proposed model are then compared with numerous experimental load-strain responses, and the results showed that the model effectively captures the experimental behavior compared to existing models available in the literature.