Finite element modeling of the seismic response of a bridge-like model with restrained rocking piers

This paper presents a three-dimensional finite element (FE) model to predict the seismic response of a bridge-like model with restrained rocking piers. The model comprises four slender cylindrical rocking piers capped with a concrete slab. The piers can uplift and are connected to the slab with tendons. The use of tendons increases the displacement capacity of the system. Depending on the stiffness of the tendons, the overall stiffness of the system may either be positive or negative. Uplifting acts as a form of seismic isolation, limiting the accelerations transmitted to the superstructure. The numerical model is statistically validated against experimental results, which involved testing of the system under 169 three-directional ground motions. The rocking columns, the slab, and the shake table are modeled using elastic elements. The tangential behavior of the contact surfaces is modeled with Coulomb friction. Energy dissipation is explicitly considered through friction. The tendon or tendon-spring system is modeled as an elastic spring. The numerical analysis accounts for the geometric non-linearity of the response. Because rocking motion is notoriously unpredictable and experiments are often non-repeatable, this study employs a statistical approach to validate the proposed numerical model. The main response parameters of interest were the maximum displacement at the center of the slab and the slab rotation. The experimental cumulative distribution function (CDF) is compared to the numerical one for the corresponding response parameter. The one-by-one comparison of the experimental and the numerical results shows a moderate correlation. However, the model can accurately predict the statistical response of the system under 169 ground motion excitations.