Finite element analysis of the axial compression performance of short T-shaped reinforced concrete columns strengthened with encased concrete-filled steel tubes

This study examines the axial compressive behavior of the short T-shaped reinforced concrete columns strengthened with externally encased concrete-filled steel tubes (CFST). A finite element model (FEM) was developed and validated to simulate the mechanical response of the strengthened columns under axial loading. Key parameters considered include the thickness and yield strength of the steel tube, along with the compressive strength of the cast-in-place concrete. The results indicate that the proposed strengthening technique significantly improves the deformation capacity, confinement effect, and stress distribution in the original columns. A new analytical method based on the superposition principle was introduced to predict the axial bearing capacity of the strengthened columns, and its accuracy was verified against numerical results, showing very good agreement. The findings offer a practical and reliable basis for designing and optimizing the strengthening of irregular-shaped columns in structural engineering applications.