Analytical and Numerical Study of Fire-Damaged Circular Concrete Columns Repaired Using Composite Confinement Techniques

This paper presents numerical and regression modeling of 21 undamaged, fire-damaged, and repaired fire-damaged reinforced circular concrete (RC) columns. The columns were exposed to three different temperatures of 300°C, 500°C, and 900°C and tested for axial residual capacity. It was found that concrete loses its strength after exposure to a temperature of 300°C or above. Fire-damaged columns were then repaired using various composite confinement techniques. Strength was regained when CFRP confinement was applied to fire-damaged columns but it increased the deformation as well and thus reduced the stiffness which is not desirable. To overcome this challenge, steel wire mesh, filled with cement sand mortar and wrapped with CFRP was employed. Further, a numerical model was developed that could precisely predict the residual capacity of these columns. The paper briefly reviewed and summarised the development of numerical techniques, including material properties, geometry, elements, loading, boundary conditions, and contact algorithm for undamaged, fire-damaged, and repaired fire-damaged columns. Moreover, analytical equations were developed using linear, multiple, and quadratic regression modeling. The results obtained using the proposed model and regression equations showed that these models offered a better alternative to the experimental testing for the prediction of the post-fire performance of damaged and repaired RC columns.