Effect of Influential Parameters on Lateral Cyclic Response of Posttensioned Base Rocking Steel Bridge Piers

This paper provides a detailed overview of an extensive parametric analysis involving more than 26,000 3D continuum finite element (FE) simulations of posttensioned base rocking steel bridge pier subjected to lateral cyclic loading. The FE model components included a circular tube, tendon, and foundation and base plates. Parameters such as the diameter-to-thickness ratio of tube, height-to-diameter ratio of tube, tendon-to-tube area ratio, prestressing ratio, axial force ratio due to dead load, and base plate thickness and extension were varied. The study measured response quantities such as residual drift, column shortening, and accumulated energy dissipation. It also assessed the impact of successive earthquakes through additional metrics of stiffness and strength degradations. The study was conducted in two primary phases, employing a displacement-based lateral cyclic loading protocol developed to simulate different types of earthquakes. Phase I comprised more than 18,000 static cyclic analyses of the 3D continuum FE model, whereas Phase II combined a 2D macro model (to establish rocking-induced axial force amplification) with a further 8,748 static continuum simulations that incorporated this variable axial load. Findings revealed that the residual drift, ratio of column shortening to height, and response degradations are closely associated with the occurrence of local buckling. The height-to-diameter ratio of tube and base plate dimensions had minimal impacts on these measures. The study confirmed that local buckling could be effectively curtailed by controlling the diameter-to-thickness and axial force ratios. Moreover, it was found that rocking steel piers with initial axial force ratios exceeding 20% had a higher susceptibility for local buckling.