Enhancing the Seismic Performances of Concrete Filled Steel Box Columns by Improving Confinement Effect: A Numerical Approach

Highway piers are essential in elevated roadways, and they are widely used in industrialized nations. Therefore, designing piers that can withstand severe seismic loadings is critical, especially in regions where earthquakes are common. Because of their remarkable seismic resilience, concrete-filled steel tubular (CFST) columns have become more popular. Numerous investigations have been carried out to enhance the seismic performance of CFST columns. The goal of this study is to alter the stiffener arrangements of concrete-filled steel box columns in order to increase their strength, ductility, energy absorption capacity and hence enhance their overall performance by enhancing the confinement effect. A comprehensive finite element model of CFST column with stiffeners was developed and validated using past experimental data. By adopting the same modelling procedure, ten models of CFST columns with modified cross sections by changing the stiffener length, stiffener arrangement and flange to web ratio of stiffeners were numerically tested under lateral cyclic loads with constant axial loads to understand the effective cross section for the confinement effect. Results revealed that the T arrangement of stiffeners shows an increment in confinement effect which results in enhancement of lateral performance of the column. Further enhancement of the confinement was obtained by changing the flange to web ratio (L_f/L_w) of the stiffeners. Finally, the obtained force-displacement curves were compared to investigate the effect of confinement and it was revealed that the cross-section having the ratio of L_f / L_w = 2.0 performs better than the other cross-sectional arrangements in strength and for the energy absorption capacity, while L_f / L_w = 1.0 is the best arrangement for the ductility.