A 16.5 x 8.5 m slab is supported by 8 6m high concrete columns. 2 shredders are mounted on 4 columns each to take the brunt of the weight of the shredder. The shredder exerts a dynamic load of 314kN at a frequency of 12Hz.
Hi
As far as I see it - you cannot.
However, what you can do is the reverse. Take a N-degrees of freedom system, analyze it and turn it into a 1-dof system. This is called modal analysis and the sdof would then be one of the system modes.
/Claes
The columns that suport the platform work in parallel hence the stiffness of the generalised system is simply the summation of partial column stiffnesses while the mass is defined by the load on the platform. In the first instance ignore the dynamic action of the machinery and damping.
Once you define the natural frequency of the structure, then you can review its dynamic performance due to harmonic external loading. Again, that is a well-known problem whose solutions exist in general literature on structural dynamics.
Hello again - yes, parallel stiffness contributions basically come down to add up individual values. And the weight of the slab should add up to the total mass, for sure.
Hello. For frequency computing you need to sum of stiffness of columns and mass of the slab and the shakers. (N/m) unit of stiffness and (kg) unit of mass and using frequency formula.
314 kN is a lot of force. In a say 200mm concrete slab or beam tests a force like that acting on a sufficiently small area will crack the concrete. I am talking about drop tests with a contact point like a 180 mm diameter sphere and drop weights of about 250-500 kg dropped from 1,2m. The initial part of the shock is very steep and short, possibly the damaging force bit. A sine force might be less dangerous. However statics and dynamics like this is not my speciality. Drop tests is something i've been studying for a while, though.
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