No abstract

UVODPrave grede su najčešće korišćeni elementi konstrukcija, prije svega zbog dostupnosti, jednostavnosti i višestruke primjenljivosti. Shodno tome, najrazvijenije i najutemeljenije grane mehanike kontinuuma jesu upravo gredne teorije. Iako su mnogi aspekti ponašanja ovih elemenata dobro proučeni, analiza greda i dalje privlači pažnju istraživača čiji je cilj njihovo pojednostavljenje i unapređivanje. Jedna od najinteresantnijih oblasti istraživanja jeste nelinearna dinamička analiza grednih konstrukcija. Odgovarajuće modeliranje ovakvog ponašanja od presudnog je značaja u savremenom građevinarstvu, s obzirom na to što su moderne konstrukcije vitke i osjetljive na dinamičke uticaje. Prilikom analiza koje razmatraju slučajeve s velikim pomjeranjima i deformacijama, nelinearni efekti moraju se uzeti u obzir. Matrica krutosti više nije jednaka samo linearnoj, tj. materijalnoj, već se moraju uzeti u obzir i efekti početnih pomjeranja i početnih napona. Kao posljedica izmjene krutosti, mijenjaju se i svojstvene frekvencije i svojstveni oblici vibracija konstrukcije.

No abstract

No abstract

This paper deals with dynamic analysis of a steel structure, constructed by steel beams and pillars which are connected by bolts. This structure is designed to serve as an acoustic barrier to one rotating machine which generates an air borne and structure borne sound and vibrations on a certain frequencies. This excitation energy is transmitted to the steel structure and might cause the oscillations of the structure. Depending on the frequency of the source of excitation, oscillations of the structure may occur at one of its natural frequencies, which depends on the physical characteristics of the structure - shape, dimensions, materials, grounding conditions, as well as other structural parameters. If it happens that excitation frequencies and the natural frequencies of the structure coincide to each other, a resonant oscillation of the structure will occur. To avoid the resonant oscillation of the structure, it is necessary the structure be designed such a way that its natural frequencies are not in the operating frequency range of the source of vibration. The investigated steel structure is subjected to mass and stiffness changes due to inserting some additional elements. The change of these physical characteristics of the structure can lead to change of its natural frequencies. To investigate dynamic behaviour of overall structure, a numerical model was set by FEM analysis and experimental analysis was done using modal test and bump test.