Compressive performance of an innovative tall pier with composite box section

To improve the seismic performance of tall-pier bridges, an innovative tall pier with a composite box section, composed of four-limb concrete-filled steel tube (CFST) columns and low-yield-strength (LYS) steel plates, was proposed based on the principle of capacity design and the replaceable fuse concept. Both axial and eccentric compression tests were conducted on a series of specimens to study the compressive performance of the composite tall pier. Parametric analysis was performed to investigate the effects of load eccentricity, slenderness ratio, thickness, and yield strength of the LYS steel plates on the compressive capacity using validated finite element (FE) models. The main results indicate that the composite tall pier fails with global bending deformation and elastoplastic instability under axial or eccentric compression. The compressive capacity and initial stiffness of the composite tall pier decrease significantly with an increase in eccentricity or slenderness ratio, and the influences of eccentricity and slenderness ratio are essentially independent. Additionally, the increase in the thickness of the steel plates enhanced the flexural stiffness and compressive capacity, and reduced the uneven loading distribution for the pier. Under axial compression, the pier can be simplified as a CFST lattice column connected by steel beams and LYS steel plates. Finally, practical formulas for the compressive capacity are proposed considering the connection and restraint effects of the LYS steel plates on the CFST columns, which can be used to predict the compressive capacity of the novel composite tall pier.