Dear All:
Good day. I have a study case where I want to investigate the response (displacement and velocity) of a Block Foundation with machine (compressor) installed on top of it. I'm aware that I'm going to perform Harmonic Analysis to achieve a graph of 1) displacement amplitude vs...
Good day to ALL:
I would like to ask for advise on INPUT in Time History Analysis using STAAD.
I have a vendor data which which states PRIMARY and SECONDARY unbalanced loads/couples for the given Compressor. I'm familiar with Time History Analysis for ROTATING MACHINES (which has 1 Unbalanced...
SantoZoo:
Good day.
I hope my response is not yet late.
Amplitude for machine vibration problem can be computed by:
F=mew^2
F=amplitude
m=mass of rotating element of your machine (rotor), you can have this value from vendor data
e= eccentricity (can be given or provided by vendor)
w=machine...
Pouchel:
Good day.
Your case might be an example of Singularity problem.
Does your loading applied on a single node only? Have you tried distributing it on a set of nodes, say distribute the point load to 6 or 8 nodes (just an example).
Maybe it can help you to eliminate non-convergence...
Kannanr03:
Good day.
Your posted problem is a common mistake which I happen to encounter often when I'm starting to study ANSYS.
As a general rule, when you are trying to apply a property to an ANSYS entity (like keypoints, lines, areas, volumes, elements, nodes), "BE SURE TO SELECT CORRECT THE...
Dear Terio:
Thank you for your response.
For ANSYS model, I've used the following units:
Loads/Weight = N
Length = mm
Density = kg/mm^3 (for material property)--- Is this correct? or do I need to use N/mm^?
Mass21 Loading = kg --- Is this correct also? or do I need to use N?
Regards.
Good day Terio:
Thank you for your response.
Meanwhile about equivalence of N and Kg, my understanding is like this:
1 kg x 9.81m/s^2 = 9.81kg-m/s^2, hence 1kg = 9.81 kg-m/s^2 or simply 9.81N....
If this is wrong, did I overlooked something?
Thanks
Dear All:
Also, If I used basic Mechanics formula for Single DOF, we have frequency = sgrt(stiffness/mass).
Applying this to my problem, we have:
1st frequency = sqrt {[5.0e6kN / 9810kg-m/s^2] / [(11500kN / 9810kg-m/s^2]}
This yields f= 21 rad/s or approximate 3.3Hz... This value is somewhat...
Good day Terio.
Thanks for the reply. Meanwhile, for clarity of the problem, let me redefine the problem:
ANSYS Model:
Block Foundation with base are dimension L=12.285m and W=8.900m (Used SOLID185)
Total Mass (Selfweight) = 10,000 kN (Used ACEL command)
Total Machine Weight = 1500 kN (Used...
Dear All:
Good day.
I've performed a Modal Analysis in ANSYS APDL simulating the Concrete Foundation Embedded in the ground (around 1.0 meter).
I made my foundation model using Solid185 and used MASS21 for machine dead loads (these dead load + the selfweight will comprise my MASS for frequency...
Bluebulb,
Good day, here are my suggestions about your case:
1) If you have the resources, I recommend you consider Quad-core to 8-Core CPU's
2) If you're limited to your current equipment specification, try manipulating ANSYS Customization/Preferences (use Graphics Device Name other than "3D")...
Im so thankful of you guys for your great replies... I'll sum it up and made a generalization...
Thanks Ron, 786392, MiketheEngineer, cvg, bimr, rmw and kslee1000 for all your efforts... Keep doing these Sirs, you help a lot... Thank you...
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Hanxi
