Document Type : Research Paper


Civil Engineering Dept., University of Technology-Iraq, Alsina’a street, 10066 Baghdad, Iraq.


The foundation plays a significant role in safe and efficient turbo machinery operation. Turbomachinery generates harmonic load on the foundation due to its high-speed rotating motion, which causes vibration in the machinery foundation. Any increase in machine vibration reduces the machine's performance. In studying engineering problems, using numerical programs helps get a well-designed foundation. Before conducting a parametric study, the program used shall be validated and/or verified by conducting a series of analyses to ensure that the program output represents the reference studied cases well. In many cases, the real problem is simplified by assuming that the machine's loads are applied at the upper slab of the frame foundation. The present work included the effect of the machine's mass elevation on the response of a high-speed turbo machine's frame foundation. The mass elevations of (12.6, 13.0, 13.3, 13.6, 13.9, and 14.2) m are selected for the dynamic analyses. A verification process is carried out to calculate the three-dimensional frame foundation's natural frequencies and mode shapes using Ansys software. The results show that the machine's masses must be included and applied at its specific elevation to reflect the true dynamic vertical response of the system as far as the mass height to top slab elevation ratio exceeds 5%. The results show a good agreement in calculating static and modal analysis with the study case. When neglecting the machine mass, the difference between the calculated natural frequencies for any mode shape is less than 10%.

Graphical Abstract


  • Ansys software was utilized to verify and compute the natural frequencies of a frame foundation
  • The effect of machine's mass on the frame’s calculated natural frequencies is studied.
  • The effect of the machine’s mass elevation on dynamic response and calculated natural frequencies is investigated


Main Subjects

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