Pile Design For Machine Foundation

[UmarMakhzumi]

CSI has made an example which may help you understand how to apply loads and analyse rotatory equipment. Its attached with the post.

 

 

Thanks.

Vibrating machinery steel skid on piles.pdf

[Suarez]

After the application of Time History Function as per CSI-tutorial "Vibrating machinery steel skid on piles", the undesirable range of frequencies (20% above and below of machine operating speed):

 

Turbine         -  mode 11   to   mode 16,

Alternator      -  mode  35  to   mode 47.

 

The result of frequencies are almost the same as before. Please comment.

Book1.xls

[UmarMakhzumi]

Before going in modes, did you check what your maximum vibration is  due to both machines operating?

[Suarez]

Attached are vibration parameters. I appreciate your time & input.

Book2.xls

[UmarMakhzumi]

Your spreadsheet is showing acceleration. You need to look at either velocity or displacement. Have a look at the tutorial I posted the link to. It explains how you can check specific nodes for vibration limit. Once you do that, then you could run resonance runs and find your final amplitudes.

 

Thanks.

[Suarez]

Please have a look again. All three parameters are there in the spreadsheet, i.e., displacement, velocity & acc.

[UmarMakhzumi]

Okay, lets go step by step.

 

What are the points where you are checking the max vibrations? CGs?

 

Provide a table where you report maximum vibrations due to load case at cg locations only and also what machine caused these vibrations? Also, what are your maximum limits in microns? 

 

 

Thanks.

[Suarez]

Loads are applied at TOP DECK-points (TTF-zip-file attached in my earlier posts) provided by vendor with static loads (vertical direction only) & dynamic loads (Unbalanced forces in x,y & z directions) for respective machines. Top deck has common bottom level with different thicknesses. Left side of the deck is for TURBINE (different color in SAP2000 picture) & right side is for Alternator (TTF-zip-file attached in my earlier posts).

 

Maximum permissible amplitude of vibration on top of deck is 30 microns (Provided by Vendor). 

 

Lines from tutorial - "In many cases, the vendor will give separate CoM locations for major components (pump, gearbox, turbine, turbine rotor, generator, etc.), in which case you would add joints for each component of the equipment where you will assign force/weight which will be converted to mass." 

 

I'm assuming that LOAD POINTS provided by vendor are aforementioned CoM-locations. In that case, I have applied static & dynamic loads at these locations and have run TIME-HISTORY FUNCTION, which yielded into results posted earlier.

[UmarMakhzumi]

Suarez,

I have gone through all your attachments. Here are a few things that you should consider:

Time History Function & Load Case:

You have applied the loads but you have to associate your loads with some function that would make it a dynamic load. The loads that vendor provided are normally called machine unbalanced forces and they are function of machine speed. What you do is set-up a time history load case and specify load patterns which contain your dynamic load along with sine and cosine functions and link them to your TH load case. Read through tutorial to understand how to define a TH Load Case for machine operating. See attached Image from CSI Example .

COM Location:

I'm assuming that LOAD POINTS provided by vendor are aforementioned CoM-locations. In that case, I have applied static & dynamic loads at these locations and have run TIME-HISTORY FUNCTION, which yielded into results posted earlier

You should not assume and ask vendor to provide you the COM locations. COM locations are always higher than the supporting structure. Image that you provided above (TTF-zip-file ) there are no joints defined above the top platform, so I cann't say that you are applying your loads at the correct locations. See attached Image from CSI Example.

Results:

The results posted by you do not mean anything. You have posted 5634 lines of output. Before you proceed, ask your vendor, what is the location where the amplitude needs to be satisfied. Is it the COM locations? Is it the Top of Concrete Table Top? and then check your maximum vibration at that level. Tutorial shows you how to check amplitudes too.See attached image.

What is stopping you to complete your calc correctly?

The machines your are designing the concrete table top foundation operate at 2 different speeds. You need output for both machines independent at the points of interest and then you need to superimpose that output. Let it be displacement or velocity. Another reason why you need to do that is your pile impedance for both operating speeds is different.First you establish that at the machine speed your vibrations are less than 30 microns, then you proceed to check your resonance runs (for all modes between 0.8 to 1.2 * Operating Speed).

Going Forward:

You have to realize that you have a complete example with you, and if you go through all my replies, I have provided you with all general and some specific information that you would need to complete the analysis. You have to take your time and understand things that you are trying to design. I can't review or vet models because of my work load, but I can tell you what to do. I can't check anything.

[Suarez]

Dear Umar,

 

You have no idea how important & informative your replies has been. I have learned so much from these posts and they have been so forthcoming. I really appreciate and admire, and I really recognize and acknowledge your efforts.

 

Following replies are in good faith and utmost respect:

 

1. Time History Function & Load Case:
You have applied the loads but you have to associate...............
I had already done that [New Picture (4) & (5)].....
 
2. COM Location:
You should not assume and ask vendor to provide you...........
I shall ask vendor for CoM locations.
 
"Load Points" are load locations on top of deck for static loads & dynamic loads (unbalanced forces) which were provided by vendor with machine drawings along with machine dimensions etc. These locations are Foundation-Bolts-Locations which connects machine to foundation through base plate.
 
3. Results:
Before you proceed, ask your vendor, what is the location where the amplitude needs to be satisfied. Is it the COM locations? Is it the Top of Concrete Table Top?
In my last post, I mentioned what vendor had ask for, "Maximum permissible amplitude of vibration on top of deck is 30 microns." 

Attached is "Display Plot Function Traces" ..... [New Picture (6)].

 

Thx a bunch.

New Picture (4).bmp

New Picture (5).bmp

New Picture (6).bmp

[UmarMakhzumi]

I am glad that you have set up everything and results are with you. I am not sure if your Time History load case is correct since I don't use periodic Time History function. Also, your modal damping looks high. Anyways, you have completed your analysis. Good.

Now do your resonance runs and you are done. 

[kHURRAM ALI]

also try PDISP software