Frequency resonances of a machine structure
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Hi everyone,
I'am working with the frequency analysis of a structure supporting a rotary machine resting on its fundation (attached in figure 1), and i am having some problems with the fundation response. My goal is decrease the frecuency of the sistem with structure modifications.
Parameters of the problem:
The first frequency of the fundation (alone) starts at 68 [hz], but when i attached the rest of the structure the first frequency decrease to 23 [hz]. The operating frequency of the machine are 31, 35 and 41.8 [hz].
With some modifications to the machine structure (attached in fugure 2, in red), i achieved up the firts frequency to 34 [hz] but this still low for me. This frequency are rocking in x global axis and the second at 39 [hz] is rocking in y global axis. I'm thinking seriously to make the fundation a rigid body, but this is no the real response.
So, i please need your help. First to check the whole model and why if i stiffened the machine support structure, the fundations still drop my frequencies.
The elastic fundation coefficient (Kz) is 9130 [ton/m3] and no perpendicular reaction (Kx and Ky =0), the geometry of the slab is 8x8x0,2 [m].
