Abstract
The newly developed multi-CFT column piers, equipped with shear dampers, have been experimentally proven to exhibit excellent seismic robustness against ground motions surpassing Level 2 earthquakes. Consequently, utilizing these multi-CFT column piers appropriately is expected to enhance the resilience of elevated-girder bridges during ultra mega earthquakes. To achieve this, it is crucial to develop a practical model capable of assessing the hysteretic behavior of CFT columns, including significant local buckling deformations, and incorporating it into the seismic analysis of the entire elevated-girder bridge system. However, the multi-CFT column pier model based on shell-solid elements encounters challenges in obtaining convergent solutions due to the complex interaction among multiple CFT columns. The objective of the present research is to propose a practical and numerically stable segment model that can be inserted into the lower part of each fiber-based CFT column model to accurately depict its local buckling behavior. This segment model comprises computationally stable elements such as nonlinear beam elements, elastic solid elements, and contact spring elements. Numerical calibration of the numerous internal parameters of the elements within the segment model is performed using an optimization technique. The aim is to ensure that the segment model effectively represents the cyclic in-plane local buckling behavior of a single CFT column segment, as calculated through shell-solid element model analysis. The accuracy and computational efficiency of the fiber-based multi-CFT column pier model, with segment models inserted at the local buckling section of the CFT columns, were extensively evaluated using results from one-directional cyclic loading tests and spiral loading tests conducted on 1/10 scale models of multi-CFT column piers.
