000015811 001__ 15811
000015811 005__ 20161115135330.0
000015811 04107 $$aeng
000015811 046__ $$k2013-06-12
000015811 100__ $$aOlhoff, N.
000015811 24500 $$aOn Optimum Design and Periodicity of Band-Gap Structures

000015811 24630 $$n34.$$pComputational Methods in Structural Dynamics and Earhquake Engineering
000015811 260__ $$bNational Technical University of Athens, 2013
000015811 506__ $$arestricted
000015811 520__ $$2eng$$aA band-gap structure usually consists of a periodic distribution of elastic materials or segments, where the propagation of waves is impeded or significantly suppressed for a range of external excitation frequencies. Maximization of the band-gap is therefore an obvious objective for optimum design. This problem is sometimes formulated by optimizing a parameterized design model which assumes periodicity in the design. However, it is shown in the present paper that such an a priori assumption is not necessary since, except for regions adjacent to the structural boundaries, the maximization of the band-gap alone, generally leads to significant design periodicity. This paper extends earlier optimum shape design results for transversely vibrating Bernoulli-Euler beams by determining new optimum band-gap beam structures for (i) different combinations of classical boundary conditions, (ii) much larger values of the orders n (n>1) and n-1 of adjacent upper and lower eigenfrequencies of maximized band-gaps, and (iii) different values of a minimum beam cross-sectional area constraint. In the present paper, instead of maximizing band-gaps between frequencies of propagating waves or forced vibrations excited by external time-harmonic loads, the closely related problem of maximizing the gap between two adjacent eigenfrequencies ωn and ωn-1 of any given consecutive orders n (n>1) and n-1, is considered. This is justified by the fact that external time-harmonic dynamic loads cannot excite resonance with high vibration levels of standing waves, if the eigenfrequencies of the structure are moved outside the range of the external excitation frequencies by the optimization. Finally, the present study shows that if an infinite beam structure is constructed by repeated translation of an inner beam segment obtained by the aforementioned frequency gap optimization, then a band-gap of traveling waves in this infinite beam is found to correlate almost perfectly with the maximized frequency gap in the finite structure.

000015811 540__ $$aText je chráněný podle autorského zákona č. 121/2000 Sb.
000015811 653__ $$aBand-gap Structures, Optimum Eigenfrequency Gap, Periodic Structures.

000015811 7112_ $$aCOMPDYN 2013 - 4th International Thematic Conference$$cIsland of Kos (GR)$$d2013-06-12 / 2013-06-14$$gCOMPDYN2013
000015811 720__ $$aOlhoff, N.$$iNiu, B.$$iCheng, G.
000015811 8560_ $$ffischerc@itam.cas.cz
000015811 8564_ $$s1692141$$uhttps://invenio.itam.cas.cz/record/15811/files/1490.pdf$$yOriginal version of the author's contribution as presented on CD, section: CD-MS 28 PERIODICITY EFFECTS AND PERIODICITY-BASED METHODS IN VIBRO-ACOUSTICS AND STRUCTURAL DYNAMICS
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000015811 962__ $$r15525
000015811 980__ $$aPAPER