Theory, Numerical Simulation and Experiment on Periodically Engineered Metamaterials for Enclosed Regional Protection against Seismic Destruction

Description

Earthquake is a natural catastrophic phenomenon which causes large amount of damage to human life and properties. Mortality caused by this natural hazard affects the social, economic and environmental life of humans. Every year a large number of earthquakes occur and damages caused account for nearly 60% of natural disasters. Different conventional seismic isolation design techniques aim at vibration damping and/or isolation but these systems are unable to protect the structures against large earthquakes and it results in the collapse mechanism of building. Also there is no proper seismic design methodology for protecting the social overhead capitals like dams, power plants, museums, nuclear reactor, oil refineries, long span bridges, express rail roads, airports and historical structures. The costly and important contributions of these structures necessitate a novel seismic design methodology for protecting them from natural and artificial hazards such as earthquakes. Metamaterials are artificially engineered materials with certain properties which are not found in nature. The properties include negative refraction, negative passion ratio, negative bulk and shear modulus, negative mass density and frequency bang gap (BG) at certain excitation frequencies. Seismic waves are elastic inhomogeneous acoustic waves with frequency range of 030 Hz. The anisotropic ground and soil condition makes the propagation of seismic waves more complex. In order to mitigate the damages caused by earthquake, a novel seismic metamaterial is proposed in this project. The metamaterial will be embedded around the structure in the form of unit cell arrays to attenuate seismic waves. Embedded metamaterials attenuate the central frequencies of earthquake because of their intrinsic frequency BG property. The seismic frequencies corresponding to BG of metamaterials is absorbed and attenuated. The width and position of BG depends upon shape, size, geometry of metamaterial and property of host medium. In this proposal, different shapes, geometries and types of metamaterials will be investigated to determine their frequency BG by theoretical, computational and experimental approaches. A finite element computational approach will be used to perform numerical simulation while the Fouquet Bloch theories will be applied to verify the computational results. To investigate practically the effect of soil type, ground condition on width and position of BG of metamaterials and to validate theoretical and computational results, scaled seismic tests will be performed in the laboratory on selective shapes of metamaterials. Based on the overall results, potential applications of seismic metamaterials will be analyzed and recommended in the form of new seismic design techniques.