Graduation Semester and Year
2023
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Civil Engineering
Department
Civil Engineering
First Advisor
Himan Jalali Hojat
Abstract
In the past decade, a new paradigm gained popularity among researchers aiming to protect structures from low-frequency seismic vibrations using metamaterials. However, developing a workable design for metamaterials is still challenging, given the various factors such as material availability, size, and shape of its components. This project proposes a new configuration that can widen the attenuation frequency of metamaterials and evaluates the attenuation ability of double-graded metamaterials. The project investigates unit cell parameters such as but not limited to size, density, and modulus of elasticity to finalize a unit cell with the broadest possible bandgap by using common construction material such as concrete, steel, Carbon Fiber Reinforced Polymer (CFRP), and rubber. Moreover, the project investigates multi-layered unit cells with two, three, and four-layered metamaterials and evaluates its effects on the bandgap bounds. Furthermore, the double-graded configuration is evaluated by modeling the real-world application of metamaterial, unit cells periodically embedded in soil medium and subjected to low-harmonic amplitude with low-frequency waves. The evaluation included both surface and body waves. Moreover, the configuration performance was evaluated for a Single Degrees of Freedom Structure (SDOF) by investigating the peak amplitude of the SDOF. Finally, the performance of double-graded metabarriers was assessed in the time domain in which the configuration is subjected to two artificial wavelets, Ormsby and Ricker, and a real-life seismic event from the records of El Centro earthquake, California 1940 (Peer Ground Motion). Moreover, a new double-graded configuration is presented to help reduce the SDOF peak frequency amplification. The result shows that a 4.5-15.3 Hz bandgap can be achieved using a 2 m two-layered unit cell made of rubber matrix and steel core. Moreover, the upper bound of the attenuation zone can be increased up to 29 Hz by using the proposed configuration (double-graded configuration), and the lower bound can be decreased to 3.5 Hz, where the double-graded metabarriers can block 85% of the most destructive seismic frequencies. Furthermore, the double-graded configuration is shown to reduce the amplification of SDOF at the peak frequency, which is not located in the attenuation zone of the unit cell. Finally, the configuration is evaluated using a triangle-like double-graded design with fewer unit cells and more wave absorption.
Keywords
Metamaterials, Seismic protection, Graded unit cell, Surface waves, Earthquake engineering, Seismic resistance, Seismic control, Vibration mitigation, Bandgap, Attenuation zone, Engineering metabarriers, Seismic metamaterials, Seismic wedge, Ground vibration mitigation, Dispersion analysis, Frequency response, Dynamics response, Frequency response function, FRF, equivalent mass spring mass model, Rayleigh waves, Single degree of freedom, SDOF, Transient analysis, Time domain, Finite element analysis, COMSOL multiphysics, FEM, Earthquake
Disciplines
Civil and Environmental Engineering | Civil Engineering | Engineering
License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Daradkeh, Ashraf Mohammed, "Wide Band-Gap Metamaterials as Seismic Shields" (2023). Civil Engineering Dissertations. 354.
https://mavmatrix.uta.edu/civilengineering_dissertations/354
Comments
Degree granted by The University of Texas at Arlington