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Abstrakt
Periodic structures are known to produce passbands and stopbands for propagation of vibration energy within the frequency domain. Sources vibrating harmonically at a frequency within a passband can lead to propagation of energy through propagating modes over long distances. However, sources vibrating at a frequency within a stopband excite only nearfields in the form of attenuating and evanescent modes, and the energy decays with distance. The decay phenomena are due to destructive interference of waves reflected and scattered by interfaces or obstacles placed periodically within or between the repeated cells of the structure. For a truly periodic structure, the vibration level within a stopband goes toward zero after infinitely many repetitions of the cell. For example, employing a twodimensional model, Andersen [1] found that stopbands for ground vibration in the lowfrequency range can be introduced by periodic inclusions or changes to the ground surface geometry.
However, for vibration mitigation in the context of real civilengineering problems related to groundborne noise from railways, for example, the excitation is not strictly harmonic and a steady state of the response is usually not achieved. Further, only a limited number of repetitions of wave impedance blocks or barriers can be made in practice, and in three dimensions, the inclusions have finite extent in the direction orthogonal to the array. Similarly to the work by Andersen et al. [2], this paper addresses the question whether repeated structures of nearly periodic nature can be used to mitigate vibrations caused by nonstationary sources. For this purpose, wave impedance blocks with finite numbers of repetitions are compared to their truly periodic counterparts. Firstly, a twodimensional study is conducted with focus on studying the nature of wave modes in a periodic array of wave impeding blocks. Secondly, threedimensional analysis is performed in the frequency domain, focusing on the insertion loss provided by increasing numbers of repetitions of blocks with different height and embedment. Finally, the insertion loss provided by nearly periodic structures is examined, and the mitigation efficiency of waveimpedingblock arrays is quantified in the case of transient loads.
However, for vibration mitigation in the context of real civilengineering problems related to groundborne noise from railways, for example, the excitation is not strictly harmonic and a steady state of the response is usually not achieved. Further, only a limited number of repetitions of wave impedance blocks or barriers can be made in practice, and in three dimensions, the inclusions have finite extent in the direction orthogonal to the array. Similarly to the work by Andersen et al. [2], this paper addresses the question whether repeated structures of nearly periodic nature can be used to mitigate vibrations caused by nonstationary sources. For this purpose, wave impedance blocks with finite numbers of repetitions are compared to their truly periodic counterparts. Firstly, a twodimensional study is conducted with focus on studying the nature of wave modes in a periodic array of wave impeding blocks. Secondly, threedimensional analysis is performed in the frequency domain, focusing on the insertion loss provided by increasing numbers of repetitions of blocks with different height and embedment. Finally, the insertion loss provided by nearly periodic structures is examined, and the mitigation efficiency of waveimpedingblock arrays is quantified in the case of transient loads.
Originalsprog  Engelsk 

Titel  COMPDYN 2017  6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering : Compdyn 2017 Proceedings 
Redaktører  M. Papadrakakis, M. Fragiadakis 
Antal sider  22 
Udgivelsessted  Athens 
Forlag  Computational Methods in Structural Dynamics & Earthquake Engineering 
Publikationsdato  2017 
Artikelnummer  C 18112 
Status  Udgivet  2017 
Begivenhed  COMPDYN 2017  6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering  Rhodes Island, Rhodes Island, Grækenland Varighed: 15 jun. 2017 → 17 jun. 2017 Konferencens nummer: 6 
Konference
Konference  COMPDYN 2017  6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering 

Nummer  6 
Lokation  Rhodes Island 
Land/Område  Grækenland 
By  Rhodes Island 
Periode  15/06/2017 → 17/06/2017 
Emneord
 Wave propagation
 Waveimpeding block
 WIB
 Layered soil
 Insertion loss
Fingeraftryk
Dyk ned i forskningsemnerne om 'Efficiency of Nearly Periodic Structures for Mitigation of Ground Vibration'. Sammen danner de et unikt fingeraftryk.Projekter
 1 Afsluttet

Urban Tranquility
Andersen, L. V., Bucinskas, P., Damkilde, L., Frier, C., Jensen, R. L., Madsen, S., Parigi, D., Pedersen, L., Svidt, K., Ulriksen, M. D., Gerdt, T. L. & Wyke, S. C. S.
01/01/2016 → 31/12/2018
Projekter: Projekt › Forskning