Let’s Rock: A Numerical Analysis of the 3D Rocking Model in Applications to Performance-based Seismic Design

Abstract

Rocking isolation is a form of base isolation that relies on a structure’s ability to uplift and rock during ground excitations, dissipating energy via impact with the ground. In 2D, the planar rocking motion is easily understood and modeled. But in the 3D scheme, the system becomes more complex, requiring more intensive calculations and parameters to consider. This thesis will use Distinct Element Modeling to simulate the 3D rocking behavior of free-standing columns and their framed systems. A parametric approach is taken to examine how a column’s geometry and a frame’s orientation can impact its rocking behavior and overall stability under various ground accelerations modeled using a Single-Pulse Sine wave and time history velocities of recorded earthquakes. The analyses reveal that a column’s capacity to endure intense ground excitations can be predicted based on its column’s size and shape. Additionally, this thesis finds that when an array (2D) or matrix (3D) of solitary columns are capped by a freely supported, rigid beam or slab, its capacity to endure intense ground movements is enhanced. The rocking behavior will be ascertained through the numerical analysis of the vertical displacements and velocities of the column’s centroid, in tandem to the qualitative observations of the system’s overall displacements from its original position. Small-scale, physical experimentations are performed to provide qualitative observations of how the 3D rocking model behaves under real-time loading conditions and constraints. Discussion of results will be done in context of performance-based design criteria in hopes of informing applications to modern designs.