Date of Award
9-12-2024
Publication Type
Dissertation
Degree Name
Ph.D.
Department
Civil and Environmental Engineering
Keywords
Adaptive chracteristics;Fragility analysis;Full rollover;Impact model;Numerical modeling;Unbonded fiber-reinforced elastomeric isolator
Supervisor
Niel Van Engelen
Supervisor
Rajeev Ruparathna
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
Earthquakes pose a significant threat to buildings and infrastructure, resulting in various types of damage and potential loss of life. The severity of earthquake-induced damage is influenced by multiple factors, including the earthquake's magnitude and location, construction quality, and soil conditions. In light of the recent catastrophic earthquakes in Turkey and Syria in February 2023, and in Morocco in September 2023, which led to substantial casualties and extensive structural damage, the necessity for pioneering seismic mitigation techniques is abundantly clear. One promising approach to enhance the seismic resilience of buildings is the utilization of base isolation systems. These systems aim to decouple structures from ground motion, reducing the transmission of seismic energy to superstructures. This is achieved by increasing the fundamental period and energy dissipation capacity of the structure, thereby improving seismic performance and safety. However, excessive displacement under severe events may cause damage to the isolation bearings as well as the structure. The growth in seismic isolation technology has led to the development of innovative base isolation systems which exhibit adaptive behavior. The behavior is denoted adaptive when the properties of the device change substantially depending on the loading level. Thus, the response can be tailored to the hazard level based on the softening and subsequent stiffening response and/or changing damping ratio as displacement increases. Recently, the concept of adaptive behavior has gained significant attention within the research community. This thesis first presents the evolution of base isolation systems with adaptive characteristics. Such adaptability is crucial to address the limitations of conventional base isolation systems, which may not perform optimally for all earthquake events. The study subsequently concentrates on unbonded fiber-reinforced elastomeric isolators (UFREIs), a category of elastomeric isolators known for their adaptive characteristics. Their cost-effectiveness, coupled with their adaptive characteristics, makes them a suitable choice for widespread adoption, particularly in developing countries. UFREIs exhibit lateral softening and subsequent stiffening responses under different loading levels, making accurate numerical modeling essential, especially for larger displacement amplitudes. This research introduces novel model fitting techniques and objective functions to enhance the accuracy of UFREI simulations. Furthermore, an innovative impact model is proposed to refine existing numerical models for UFREIs, improving their ability to predict isolator behavior under dynamic loading conditions. The accuracy of the impact model is validated through comparisons with experimental tests, demonstrating its effectiveness in capturing UFREI responses. The study also investigates the seismic fragility of UFREIs, considering various limit states and ground motion conditions. It explores the influence of full rollover, a unique characteristic of UFREIs, on their seismic performance. The findings underscore the importance of accurate modeling to fully appreciate the adaptive potential of UFREIs, particularly during severe seismic events. To comprehensively evaluate the proposed impact model, the lateral cyclic and shake table test data of full-scale circular UFREIs were also utilized, addressing perceived limitations of previous validations primarily considered quarter-scaled UFREI specimens and rectangular/square shapes. The accuracy of the proposed model is validated, and the outcomes are compared with experimental data and with finite element analysis results.
Recommended Citation
Sheikh, Hediyeh, "Innovative Modeling and Exploration of Adaptive Characteristics in Unbonded Fiber-Reinforced Elastomeric Isolators" (2024). Electronic Theses and Dissertations. 9395.
https://scholar.uwindsor.ca/etd/9395