# Seismic Isolation via I-Shaped and T-Shaped Large-Scale Phononic Metamaterials
## 1 Introduction
presented a spectral approach, accompanied by an asymptotic model and numerical simulations for slender elastic systems such as long bridges or tall buildings [20]. [PERSON] et al. introduced a seismic metamaterial composed by a chain of mass-in-mass systems that could be realized by a continuous structure within a 3D matrix of isochronous oscillators based on a sphere rolling over a cycloidal trajectory. This seismic metamaterial was able to filter the S-waves of an earthquake [21]. [PERSON] et al. proposed a novel approach to the problem of seismic wave mitigation and discussed the feasibility of a passive isolation strategy for seismic waves based on large-scale mechanical metamaterials [22]. [PERSON] et al. showed the experimental results of a seismic test carried out using seismic waves generated by a monochromatic vibrocompaction mode [23]. Recently, [PERSON] et al. realized a geophysical experiment that demonstrates that a Rayleigh wave, propagating in soft sedimentary soil at frequencies lower than 150 Hz, experiences strong attenuation when interacting with a forest [24]. In the field of seismic metamaterials, [PERSON] et al. studied numerically and experimentally the use of metastructures to shield sensitive buildings from waves generated by an earthquake [25]. Seismic metamaterials embedded at the ground surface of granular media were also studied by using small-scale physical models with laser measurement techniques [26; 27]. Moreover, artificial landforms such as terraced slopes were recently studied as potential seismic metasurfaces for the attenuation of seismic waves [28; 29]. Recently, several studies have been conducted, which include a plethora of proposed seismic metamaterials of several shapes that are either considered embedded in the ground surface or stand at the ground surface as pillars. [PERSON] et al. proposed a seismic metamaterial that consisted of curved boundaries on a square cross-section that resulted in the reduction in the contact area between adjacent cells and achieved a wide band gap at a very low frequency range [30]. [PERSON] and [PERSON] studied numerically vertical resonators, which are composed of a periodic array of square structures that are buried vertically along the depth and can attenuate Love waves [31]. Similar seismic metamaterials of rectangular geometriesthat implement the negative Poisson's ratio of the auxetic foam have also been numerically investigated for their effectiveness on the attenuation of surface seismic waves [32; 33]. V-shaped and N-shaped pillars were studied for their performance as seismic metamaterials by [PERSON] and [PERSON] and provided wide band gaps for surface waves [34]. [PERSON] et al. studied wide band gaps in seismic metamaterials, which were composed of H-shaped steel columns covered with rubber [35]. [PERSON] et al. numerically studied the use of I-shaped pillars as seismic metamaterials that provided low frequency band gaps [36]. Inverted T-shaped pillars were also studied by [PERSON] et al., both numerically and experimentally, as seismic metamaterials with wide frequency band gaps in the low frequency range [37]. [PERSON] et al. proposed a radial periodic arrangement of steel rings of rectangular, I-shaped, and T-shaped cross-sections that were embedded in soil for the attenuation of Lamb and surface seismic waves [38]. As PCs and AMs are a constantly evolving scientific area, new ideas that are now being implemented for sound waves [39] in combination with machine learning techniques [40] could provide the community with novel and more effective structures suitable for seismic isolation applications. It is evident from the relevant research progress that the manipulation of the propagation of seismic waves with seismic metamaterials triggered the academic interest. It is also important to mention that each proposed seismic metamaterial provides specific limitations to its potential applicable field, which is related to several parameters such as its geometry, the combination of used materials, and its geometric dimensions [11].