Abstract:At present, the experimental studies, theoretical models, and calculation methods on the shear bearing capacity of concrete-encased concrete-filled steel tube (CFST) composite columns are insufficient. Therefore, the shear behavior tests were conducted to figure out whether the truss-arch field theory can be used to calculate the shear capacity of concrete-encased CFST composite columns. The results were compared with that of the Chinese standard T/CECS 188, the American standard AISC and the European standard EC4. Based on the different restraint conditions of the outer and core concretes, the modified truss-arch model used a steel tube as the boundary to divide the cross-sectional area of the members. which can consider the effect of steel tube restraint on concrete shear strength under axial compression. The results showed that the calculated values of the proposed calculation methods were in good agreement with 36 groups of the test data, which reflected the shear mechanism of the concrete-encased CFST columns, and the model calculation sensitivity was not greatly affected by the different design parameters. The ratio of the calculated value to the test value of most specimen was between 0.85 and 1.15. The calculated values using Chinese standard T/CECS 188 were generally lower than the test values, which cannot be accurately estimated to the actual bearing capacity of the columns. The dispersion of the calculated values using the American standard AISC or the European standard EC4 was large.