Ductility Behavior of Partially Concrete-filled Steel Box Piers with T-shaped Stiffeners

A simplified computation method is suggested to compute the ductility performance of partially concrete-filled steel box piers with T-shaped stiffeners. The 3D elastoplastic finite element model for the steel piers under vertical and lateral loadings is verified numerically. Subsequently, numerical studies are performed to understand the influence of normalized stiffener and pier slenderness ratios, normalized flange width-to-thickness ratio, and axial compression ratio on the ductility behavior and ultimate strength of the piers. To meet the need of actual bridge design, the 2D-beam model is employed to investigate the ductility behavior of the pier. The computational results show that the proposed 2D-beam model can predict the ductility capacity of the piers with T-shaped stiffeners more quickly than the 3D-shell model. Further, the 2D-beam model can predict the ductility behavior of the piers with an acceptable error when local buckling occurs in the hollow steel pipe above the infill concrete. However, when local buckling occurs on the flanges and webs near the pier bottom, a correction coefficient must be introduced to modify the ultimate strain criterion of the stub column. The modified ductility ratio obtained from the 2D-beam model after introducing a correction coefficient is consistent with the results of the 3D-shell model, and all data points fall within the ±10% error line. The proposed model is expected to provide a more efficient and convenient computational method for practical bridge design.