Concrete-filled steel tubular (CFTS) columns subjected to eccentric compressive load

Concrete-steel composite structures are very efficient in carrying high loads as they combine benefits of both materials concrete and steel. The combination of them can significantly improve the strength of the composite structure by taking advantage of high compression resistance of concrete and high strength of steel in tension. Recently, there has been renewed interest in the composite structures used in different forms, as beams, slabs, sandwich structures and columns and many methods of structural analyses were utilised. However, none of them was able to eliminate concrete material when it fractured. The presented work concerns circular composite columns CFST under eccentric compression. The principal objective of the project was to investigate a straightforward method based on a finite element analysis employed to estimate the load carrying capacity of columns. This study has also been set out to determine whether the Drucker-Prager material model of concrete without a crack capability could be used for analyses of the CFST columns with the additional elimination of the concrete material when concrete is damaged. The elaborated finite element model was verified with existing test data from the literature. The findings show that the correlation between the test results and the numerical analysis was excellent confirming the feasibility of usage of the proposed method for the assessment of complex cases of the CFST columns. A new part of the work is the employment of a death element feature to eliminate concrete material, which theoretically is not taking any load after reaching its tensile strength. A criterion to eliminate elements from the model is the maximum principal stress greater than tensile strength. The obtained results are excellent; the established goal was met entirely.