Search Results (23)

Seismic metamaterials (SMs) have emerged as a novel wave-control strategy for earthquake-resistant engineering, offering the potential to manipulate seismic waves via artificially designed periodic/resonant structures. Field and laboratory experiments are critical to bridge theoretical predictions and engineering practice, yet a systematic synthesis focusing on experimental progress remains lacking. This review systematically classifies SMs into buried (BSMs), above-surface (ASMs), and partially embedded (PESMs) configurations, summarizing their structural designs, attenuation mechanisms, experimental performance, and key limitations. Results show that SMs can achieve >70% attenuation in the 0–50 Hz seismic band, with buried periodic barriers reaching 99.7% energy blocking and forest-like ASMs achieving 93–99% Rayleigh wave reduction. PESMs exhibit superior adaptability to shallow soils, with bandgaps concentrated in 1.5–14.5 Hz (building-sensitive range). Current experiments have advanced from single mechanisms to multi-mechanism synergy and from specialized materials to conventional concrete/steel. However, critical gaps remain: scaling-induced deviations, poor complex-geology adaptability, lack of long-term durability, and insufficient multi-waveform control. Finally, we propose a 3–10-year engineering roadmap and outline future directions: multi-waveform regulation, soil–metamaterial dynamic matching, durability design, and full-scale intelligent upgrades. This work aims to provide a critical experimental reference for the practical deployment of SMs. Full article

Buried mass-resonator systems, including metafoundations, have attracted increasing attention as an effective approach for mitigating vibrations induced by seismic waves in structural systems. In this study, a series of shaking table tests are conducted on a small-scale metafoundation to experimentally evaluate its vibration reduction performance under seismic excitation. The metafoundation model was fabricated using acrylic plastic and ethylene propylene diene monomer (EPDM) rubber foam, and its dynamic characteristics were examined through white noise and sine sweep tests. The attenuation zones identified from the experiments were validated through comparison with the frequency band gaps (FBGs) of the metamaterial obtained from numerical simulations. A simple small-scale structure was subsequently installed on the metafoundation, and the dynamic behavior of the combined system was investigated using white noise and sine sweep signals. The effectiveness of the metafoundation in reducing the seismic response of the structural system was further evaluated using earthquake ground motions. The experimental results demonstrate that the metafoundation significantly reduces the seismic response of the structural system at frequencies corresponding to the attenuation zone of the structural system with metamaterial. Full article

Controlling seismic wave propagation to protect critical infrastructure through metamaterials has emerged as a frontier research topic. The narrow bandgap and heavy weight of a resonant seismic metamaterial (SM) limit its application for securing buildings. In this research, we first develop a two-dimensional (2D) seismic metamaterial with gammadion-shaped chiral inclusions, achieving a high relative bandgap width of 77.34%. Its effective mass density is investigated to clarify the generation mechanism of the bandgap due to negative mass density between 12.53 and 28.33 Hz. Then, the gammadion-shaped pillars are introduced on a half-space to design a three-dimensional (3D) chiral SM to attenuate Rayleigh waves within a wider low-frequency range. Further, time-frequency analyses for real seismic waves and scaled experimental tests confirm the practical feasibility of the 3D SM. Compared with common resonant SMs, our chiral configurations offer a wider attenuation zone and lighter weight. Full article

Despite recent numerical simulations and limited laboratory studies highlighting the potential of semi-embedded seismic metamaterials (SEM) in attenuating Rayleigh waves, their real-world effectiveness remains unverified, particularly for Love waves. Love waves pose significant destructive risks to slender structures but have rarely been the focus of research. To address this gap, we present the first full-scale 2D field experiment on an SEM composed of an array of semi-embedded rubber column resonators. The experimental results reveal a global bandgap spanning 25–37 Hz and a localized bandgap at 37–42 Hz. At the central frequency of the global bandgap (f₀ = 31 Hz), the attenuation reaches −9.3 dB for Love waves and −5.3 dB for Rayleigh waves, with the mitigation of Love waves being notably pronounced. Furthermore, our theoretical and experimental analyses provide novel mechanistic insights: the primary energy dissipation in flexible rubber resonators arises from the resonance of their exposed above-ground sections, while the underground buried parts introduce damping that moderately reduces the efficiency of surface wave attenuation. This pioneering full-scale on-site validation bridges the critical gap between simulation-based predictions and practical seismic protection systems, providing valuable reference for the engineering application of SEM, especially for mitigating destructive waves. Full article

Seismic metamaterial-inspired periodic foundations have emerged as promising vibration-mitigation concepts capable of attenuating seismic wave propagation within specific frequency bands. This study presents an experimental investigation on the dynamic response of periodic foundation configurations, with and without embedded piezoelectric layers, to evaluate their vibration-attenuation characteristics. The experimental program employed a shake table driven by a 0.75 kW servo motor and included excitation step counts of 3000, 4000, and 5000. Accelerometers mounted on the specimen surfaces recorded vibration data at 80 ms intervals. Three foundation configurations were tested: (i) a conventional reinforced concrete block, (ii) a one-dimensional periodic foundation composed of alternating concrete and rubber layers, and (iii) a periodic foundation incorporating piezoelectric modules. Time-domain and frequency-domain analyses showed that the periodic foundations achieved notable reductions in both peak and RMS accelerations, especially near resonance frequencies. The configuration, including piezoelectric layers, exhibited similar attenuation performance while also generating measurable instantaneous voltage outputs under vibration. However, these voltage peaks—reaching a maximum of 1.64 V—represent only a laboratory-scale, proof-of-concept demonstration of electromechanical coupling rather than a practical or continuous form of energy harvesting, given the inherently sporadic nature of seismic excitation. Overall, the results confirm that the tested system is not a full metamaterial in the classical sense but rather a metamaterial-inspired periodic arrangement capable of inducing band-gap-based vibration attenuation. The inclusion of piezoelectric elements provides auxiliary sensing and micro-energy-generation capabilities, offering a preliminary foundation for future multifunctional seismic-protection concepts. Full article

This study investigates the mechanical behavior and energy absorption capacity of a novel metamortar composite, developed by embedding re-entrant auxetic cellular structures into a cementitious mortar matrix. Auxetic materials, which exhibit a negative Poisson’s ratio, offer distinct advantages in impact resistance and stress dissipation. Despite their promising properties, their integration into cement-based systems remains limited. In this work, auxetic cells were fabricated using different 3D printing filaments and combined with mortar to form hybrid composites. The specimens were subjected to quasi-static compression tests to evaluate their Young’s modulus, yield strength, and energy absorption capacity. Results indicate that the auxetic inclusions substantially improved the mechanical performance of the mortar, particularly in the case of PLA-based cells, which achieved the highest values across all tested parameters. The enhancements are attributed to the synergistic deformation mechanisms of the auxetic geometry and the surrounding matrix, promoting efficient load distribution and delayed crack propagation. These findings contribute to the advancement of cementitious metamaterials and establish a foundation for scaling toward metaconcrete systems with improved energy dissipation for use in protective, seismic, and infrastructure applications. Full article

Due to their long wavelengths and low attenuation characteristics, seismic waves pose serious threats to engineering structures, resulting in an urgent need to develop effective vibration mitigation strategies. Locally resonant phononic crystals provide a novel approach to controlling seismic wave propagation, while auxetic materials have attracted considerable attention for their excellent energy absorption capabilities. To achieve broadband low-frequency seismic isolation, this study proposes a seismic metamaterial composed of embedded dual resonators combined with auxetic materials. The bandgap characteristics of the structure are calculated using the finite element method, and the mechanism of bandgap formation is elucidated through vibrational mode analysis. A parametric study is conducted to investigate the influence of mass block substitution on bandgap tunability, and complex band analysis is employed to evaluate seismic wave attenuation within the bandgap range. Furthermore, a graded composite structure is designed, and its seismic isolation performance is validated through frequency- and time-domain simulations. The results show that the proposed composite structure exhibits significant isolation effects within the 2.7–5 Hz bandgap range. Even under excitation with the Chi-Chi earthquake, whose dominant frequency lies outside the bandgap, the peak ground acceleration is reduced by approximately 42%, and the overall acceleration response is effectively suppressed. These findings provide a promising new design strategy for achieving broadband and low-frequency seismic protection in engineering applications. Full article

Metamaterials, characterized by engineered microstructures rather than chemical composition, are transforming civil infrastructure through their unique ability to achieve frequency-selective wave attenuation and programmable mechanical responses. This review provides a comprehensive overview of the applications of acoustic and mechanical metamaterials within civil engineering contexts. Acoustic metamaterials demonstrate significant potential for mitigating noise pollution in environments such as high-rise buildings, urban public areas, and transportation infrastructure by substantially enhancing sound insulation and noise reduction capabilities. Meanwhile, mechanical metamaterials, exhibiting advanced properties including shape memory, exceptional stiffness, and programmable functionality, offer novel strategies for improving structural resilience and seismic performance. Additionally, this article explores emerging opportunities in energy harvesting and adaptive infrastructure integration. Despite these advancements, critical challenges related to scalability, durability, and seamless integration with the existing infrastructure persist. Addressing these issues in future research will facilitate the advancement of sustainable, adaptive, and high-performance metamaterial solutions for modern civil infrastructure. Full article

We draw connections between eight different theories used to describe microscopic (atomic) and macroscopic (seismological) scales. In particular, we show that all these different theories belong to a particular case of a single partial differential equation, allowing us to gain new physical insights and draw connection among them. With this general understanding, we apply the micropolar theory to the description of shear-wave dispersion in marine sediments, showing how we can reproduce observations by only using two micropolar parameters in contrast to the seventeen parameters required by modifications of Biot’s theory. We next establish direct connections between the micro (laboratory) and macro (seismological) scales, allowing us to predict (and confirm) the presence of post-perovskite in the lowermost mantle based on laboratory experiments and to predict the characteristic length $L_c$ at which shear deformation becomes significant at seismological scales in the lowermost mantle. Full article

Seismic metamaterials have gained significant attention for their ability to reduce seismic wave energy. However, numerical simulations have dominated the majority of research on seismic metamaterials, with relatively few field experiments validating their effectiveness. Additionally, the focus has primarily been on attenuating Rayleigh waves, with less attention given to Love waves. In this study, we first designed a seismic metamaterial featuring a periodic and symmetric array of square holes using numerical simulations as our research platform. We then explored its attenuation effects on Rayleigh waves, particularly Love waves, through field experiments. The results revealed not only differences in energy attenuation between these wave types but, more importantly, uncovered a phenomenon that we termed Bandgap-Induced Attenuation Mode Inversion within the ultra-broadband gap that was generated by the seismic metamaterials, where Love waves exhibited greater attenuation than Rayleigh waves below 50 Hz, while Rayleigh waves exhibited greater attenuation above 50 Hz. These findings highlight the necessity of considering both wave types when designing cost-effective seismic metamaterials, providing valuable insights for the development and application of metamaterials that can effectively mitigate the energy of different seismic wave modes. Full article

This paper focuses on the theoretical and analytical modeling of a novel seismic isolator termed the Passive Friction Mechanical Metamaterial Seismic Isolator (PFSMBI) system, which is designed for seismic hazard mitigation in multi-story buildings. The PFSMBI system consists of a lattice structure composed of a series of identical small cells interconnected by layers made of viscoelastic materials. The main function of the lattice is to shift the fundamental natural frequency of the building away from the dominant frequency of earthquake excitations by creating low-frequency bandgaps (FBGs) below 20 Hz. In this configuration, each unit cell contains an inner resonator that slides over a friction surface while it is tuned to vibrate at the fundamental natural frequency of the building. This resonance enhances the energy dissipation capacity of the PFSMBI system. After deriving the governing equations for four selected lattice configurations (i.e., Cases 1–4), a parametric study is performed to optimize the PFSMBI system for a wide range of harmonic ground motion frequencies. In this study, we examine how key parameters, such as the mass ratios of the cells and resonators, tuning frequency ratios, the number of cells, and the coefficient of friction, affect the system’s performance. The PFSMBI system is then incorporated into the dynamic model of a six-story base-isolated building to evaluate its effectiveness in reducing the floor acceleration and inter-story drift under actual earthquake ground motion records. This dynamic model is used to investigate the effect of stick–slip motion (SSM) on the energy dissipation performance of a PFSMBI system by employing the LuGre friction model. The numerical results show that the optimized PFSMBI system, through its lattice structure and frictional resonators, effectively reduces floor acceleration and inter-story drift by leveraging FBGs and frictional energy dissipation, particularly when SSM effects are properly accounted for. Finally, a small-scale prototype of the PFSMBI system with two cells is developed to verify the effect of SSM. This experimental validation highlights that neglecting SSM can lead to an overestimation of the energy dissipation performance of PFSMBI systems. Full article

Seismic metamaterials are an emerging vibration-damping technology, yet concentrating the bandgap in the low-frequency range remains challenging due to the constraints imposed by lattice size. In this study, we numerically investigated seismic metamaterials connected by auxetic (negative Poisson’s ratio) slender strips, which exhibit an exceptionally wide low-frequency band gap for vibration isolation. Using a finite element method, we first performed a comparative analysis of several representative seismic metamaterial configurations. The results showed that the auxetic thin strip-connected steel column structure demonstrated outstanding performance, with the first complete band gap starting at 1.61 Hz, ending at 80.40 Hz, spanning a width of 78.79 Hz, and achieving a relative bandwidth of 192.15%. Notably, while most existing designs feature lattice constants in the ten-meter range (with the smallest around two meters), our proposed structure achieves these results with a lattice constant of only one meter. We further analyzed the transmission characteristics of the steel column structure, both with and without concrete filling. Interestingly, significant vibration attenuation, approaching 70 dB, was observed below the first complete band gap (approximately 0.22–1.17 Hz), even without the use of concrete. By comparing the flexural wave band gap with the transmission spectrum, we attributed this attenuation primarily to the presence of the band gap, a phenomenon often overlooked in previous studies. This attenuation at lower frequencies highlights the potential for effectively reducing low-frequency vibration energy. To further enhance the attenuation, the number of periods in the propagation direction can be increased. Additionally, we systematically explored the influence of geometric parameters on the first complete band gap. We found that optimal results were achieved with a slender strip length of 0.05 m, its width between 0.05 and 0.1 m, and a steel structure width of 0.1 m. Our findings underscore the critical role of auxetic thin strips in achieving broadband low-frequency vibration isolation. The approach presented in this study, along with the discovery of low-frequency flexural wave band gaps, provides valuable insights for seismic engineering and other applications requiring effective vibration reduction strategies. Full article

In this work, the attenuation of surface seismic waves from large-scale phononic metamaterials is numerically studied. The proposed metamaterials consist of rectangular trenches that form either I-shaped or T-shaped cavities embedded at the ground surface. The numerical investigation includes the study of the response of the proposed structures for different values of their geometric parameters. In addition, modifications of the proposed structures where heavy cores coated with a soft material were considered in the cavities were also numerically studied. For a more realistic numerical approach, the transmission spectrum of a selected large-scale phononic metamaterial was also investigated in a suitable half-space numerical scheme. The results of the present research showed that the studied large-scale metastructures could be a very promising potential candidate for seismic shielding applications for the protection of existing urban or countryside structures. The proposed metamaterials are low in cost and easy to construct for the protection of existing buildings, critical infrastructures, or even entire urban areas without need for any kind of intervention at them, therefore providing an effective solution in the field of seismic isolation. Full article

Rayleigh waves are vertically elliptical surface waves traveling along the ground surface, which have been demonstrated to pose potential damage to buildings. However, traditional seismic barriers have limitations of high-frequency narrow bandgap or larger volume, which have constraints on the application in practical infrastructures. Thus, a new type seismic metamaterial needs to be further investigated to generate wide low-frequency bandgaps. Firstly, a resonator with a three-vibrator is proposed to effectively attenuate the Rayleigh waves. The attenuation characteristics of the resonator are investigated through theoretical and finite element methods, respectively. The theoretical formulas of the three-vibrator resonator are established based on the local resonance and mass-spring theories, which can generate wide low-frequency bandgaps. Subsequently, the frequency bandgaps of the resonator are calculated by the finite element software COMSOL5.6 based on the theoretical model and Floquet–Bloch theory with a wide ultra-low-frequency bandgap in 4.68–22.01 Hz. Finally, the transmission spectrum and time history analysis are used to analyze the influences of soil and material damping on the attenuation effect of resonators. The results indicate that the resonator can generate wide low-frequency bandgaps from 4.68 Hz to 22.01 Hz and the 10-cycle resonators could effectively attenuate Raleigh waves. Furthermore, the soil damping can effectively attenuate seismic waves in a band from 1.96 Hz to 20 Hz, whereas the material of the resonator has little effect on the propagation of the seismic waves. These results show that this resonator can be used to mitigate Rayleigh waves and provide a reference for the design of surface waves barrier structures. Full article

In this paper, a radial gradient seismic metamaterial (RGSM) is proposed. The structural unit cell is composed of an external square soil embedded with a triangular-cross-sectioned steel ring, which is filled at different angles of multiple steel rings to form a supercell. The dispersion curve and attenuation spectrum of the unit cell are calculated by the finite element method, and the opening mechanism of the band gap is explained by analyzing the modes at the band gap boundary. The influence of geometric parameters and material parameters on the band gap is further studied, and the optimized supercell radial gradient seismic metamaterial (OS-RGSM) structure is designed through structure and parameter optimization. The ultra-low broadband excellent band gap in the range of 2.35–20 Hz for seismic Lamb waves is realized, and its three-dimensional frequency response and displacement field diagram are calculated. In addition, the attenuation characteristics of the optimized supercell seismic metamaterial on the seismic surface wave are calculated and analyzed. It is found that the attenuation can reach more than 50% in the ultra-low frequency range of 3.5–9 Hz. The seismic wave barrier is verified by the vibration transmission characteristics of RGSM under finite period and dynamic time history analysis. The results show that RGSM can effectively shield from seismic Lamb waves in the ultra-wideband with the starting frequency of 2.35 Hz and can also effectively attenuate the seismic surface wave in semi-infinite space. Full article