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.

Abstract. Shafts of electric locomotives are exposed to complex normal and tangential stresses during its exploitation. These stresses could have extremely high level producing the breakage of the shaft. It is well known that shafts have much longer service life than wheels. However, since the stresses in shaft's material are high, it is possible to micro-cracks appear and propagate until the shaft's breakage. The breakage of the shaft may cause the great human and material losses. Because of that, during manufacturing these assemblies it must be taken into account all parameters which can initiate shaft crack. Geometric measure of seating and shaft are recommended by UIC regulations having great influence to quality and safety of realized assembly. The influence of contact surfaces and their lubrication during manufacturing the shaft -wheel assembly is shown in this paper.