UC Irvine

Prior research has illuminated the significance of the column base connections on the seismic performance of structural systems. Among the various configurations adopted worldwide, this dissertation predominantly focuses on stiffened column base (SCB) connections. The SCBs are the common practice in countries where the fabrication of thick plates for exposed column base (ECB) connections and the execution procedure of embedded column bases are challenging. The SCB configuration is characterized by integrating stiffeners atop an exposed base plate. The formed stiffened panels effectively reduce the required base plate thickness to resist the desired flexural strength compared to that demanded by comparable ECB configurations. Despite their application in low- to high-rise structures, empirical investigation on their hysteretic behavior is scarce, and their design methodologies either stem from theoretical principles or adaptations of existing ECB design approaches. Nonetheless, their distinctive features — the combination of rigid nature and thin base plate, alongside the incorporation of multi-row arrangement — notably diverge from those of ECBs. To bridge the gap between theory and practice, this dissertation investigates the hysteretic characteristics of SCB connections, both experimentally and analytically. The research effort presented herein first conducts an experimental testing campaign on SCBs to document the qualitative observations and quantitative outcomes of their responses to cyclic loadings. Four large-scale tests explore the impact of the inclusion of inner rods, construction features, and base plate thickness. The collected database provides the foundation to validate a virtual finite element (FE) framework. This robust simulation environment tackles the deficiency of mechanical evidence for the complex interactions between connection components. This study sheds light on the disregarded significance of the friction between anchor rods and concrete on the internal characteristics of hysteretic curves. The activated friction is attributed to the developed compressive forces in the anchor rods leading to their expansion. The observation of a punched foundation after experiments motivated an FE study to quantify the impact of the incorporation and location of leveling nuts on the behavior and hysteretic energy dissipation of column bases. Following this, SCB specimens featuring diverse anchor rod arrangements, axial loading levels, and stiffener layouts are simulated to generate a comprehensive dataset for subsequent evaluations. Through these sophisticated simulations, this work elucidates the hysteretic characteristics of SCBs, evaluates the efficiency of current design approaches in predicting yield strength, identifies potential unconservative design practices, and proposes a numerical method for predicting SCB connection behavior. The limitations of the project are outlined. The perspective derived will contribute to developing system-level analytical models to explore SCB's impact on structural performance.