A nonlinear poisson-based analytical procedure for predicting ultimate axial strength of short, compact circular concrete-filled steel tubes

This study proposes an analytical procedure for predicting the ultimate axial strength of short, compact circular concrete-filled steel tubes (CFTs) by explicitly considering the nonlinear Poisson’s ratio of concrete and the associated confinement interaction with the steel tube. The procedure incrementally evaluates axial strain, lateral expansion, and confinement pressure, enabling strain-dependent coupling between the concrete core and the steel tube. The confined concrete strength and strain are determined using established confined concrete models, while the steel tube response is evaluated using a von Mises yield criterion. The proposed method is validated against 99 experimental results collected from the literature. Comparisons with existing design codes and prediction models demonstrate improved accuracy within the applicable range of short, compact circular CFTs with conventional concrete and steel strength levels, particularly for cases where confinement effects are significant.