Available at: https://digitalcommons.calpoly.edu/theses/3151
Date of Award
6-2025
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Giovanni De Francesco
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Engineering
Abstract
Earthquakes can cause considerable damage to buildings, and their unpredictability means engineers must often design for worst-case scenarios. The current goal of building design codes is to prevent collapse and loss of life during a seismic event. However, after a seismic event, even if the building did not collapse, enough damage can leave the building uninhabitable and need of extensive and costly repairs. Therefore, seismic mitigation techniques like base isolation systems have been widely implemented as a seismic design solution. An isolation system works to decouple the structure from the ground and laterally displaces it with a longer fundamental period compared to a traditional non-isolated building. This thesis explores placing the seismic isolation system at an intermediate height along the structure, known as inter-story seismic isolation. A case study where a building with inter-story seismic isolation is modeled and analyzed using a Nonlinear Time History Analysis (NTHA). A preliminary design, initial modal analysis, ground motion selection procedure, and a performance-based approach to designing the lead-rubber bearings (LRBs) are included. Furthermore, the building itself has a lower podium structure below the seismic isolation layer and an upper tower structure above the isolation layer. Results showed that the decoupling dynamic behavior of the tower from the podium resulted in displacements increasing from the bottom of the podium to the top of the podium but held constant throughout the tower. In addition, the force distributions showed that the force experienced decreased from the base of the podium to the top of the podium, and the same result was seen with the tower structure. The acceleration time histories revealed that the accelerations transmitted decreased from the top of the podium to the joint above the isolators. These results suggest that the isolation layer at an intermediate height is absorbing seismic energy, or dissipating energy, which is reducing the forces and accelerations transmitted through the building. The goal of this thesis is to create a guideline for the modeling, design, and analysis of a building with inter-story seismic isolation and to be used for further analysis in the dynamic behavior of these kinds of structures.