Author(s): Godinho Luís, Albino Carlos, Alves-Costa Pedro, Amado-Mendes Paulo, Soares Jr. Delfim
Well-known classical strategies to mitigate vibrations induced by vehicles include buried trenches and inertia blocks. Besides these strategies, innovative methods are being devised by researchers using novel physical concepts. Periodic structures and metamaterials are one such concept, which seem to be very promising for real engineering applications. These devices interfere with wave propagation in a controlled and tuned manner, and can be used for specific frequency bands. Some of these concepts are well-developed for acoustic protection (noise barriers), as it is the case of “sonic” or “phononic” crystals, but the protection of vibrations by such structures is still in an earlier development stage. The present paper presents a preliminary study on the concept of using a periodic buried structure, made of repeated solid elements, disposed with a geometrical arrangement that allows maximization of the shielding effect in the dominant vibration frequencies. The 3D finite element model, formulated using tetrahedral elements, is used to perform a set of numerical simulations, assessing the effectiveness of the proposed shielding device. The model simulates a set of elastic inclusions, buried in a homogeneous host soil, under the incidence of a propagating wave generated by a line source. In order to improve computational efficiency, a time-marching algorithm is used, and the time domain signals are then transformed to the frequency domain by means of a FFT, allowing calculation of insertion loss results at receivers placed behind the shielding device. The presented results reveal a good efficiency of these devices, and evidence the existence of a band gap where large attenuation occurs. Comparison with results obtained for a standard buried wall also allowed to observe that the use of the proposed strategy can lead to better attenuation results.
Name: Prof Paulo Amado-Mendes