Jump to content
  • Welcome to SEFP!

    Welcome!

    Welcome to our community forums, full of great discussions about Structural Engineering. Please register to become a part of our thriving group or login if you are already registered.

Recommended Posts

I am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons. 

I ll appreciate your help in terms of guidance & provision of notes...  

 

Thank you..

Edited by Umar Makhzumi
Changed Thread Title so it is more relevant to discussion.

Share this post


Link to post
Share on other sites

100 tons is the operational load including weight of the machine? or it will be 100+50=150 tons? Whatever is the case, select a pre-cast pile having capacity more than that. For example select a pile of 200 tons. Regarding pile cap you can model it or design yourself manually. Other members are encouraged to continue and discuss!

Share this post


Link to post
Share on other sites

Vertical resistance of piles will depend on soil conditions; insure enough skin friction, or bearing capacity at bottom of pile according to external vertical forces. In case of machine loading, you will also need to provide for ability to shear and bending stresses. Check for punching shear in pile cap.

 

Check out this book for guidance.

https://www.dropbox.com/s/v5ffxjcq4jyqcpt/Pile%20Foundation%20Analysis%20and%20Design_H%5B1%5D.%20G.%20Poulos%20%26%20E.%20H.%20Davis_1980.pdf

Share this post


Link to post
Share on other sites

I am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons. 

I ll appreciate your help in terms of guidance & provision of notes...  

Thank you..

 

What kind of machine is that ? Would the operation of machine induce any dynamic forces in the foundation ? If yes, then pile design is a total different story. The static design of pile is easy. Depending upon what kind of pile you select (friction, end bearing) Consider your pile cap as rigid plate and find reactions at pile locations and design.

 

Thanks.

Share this post


Link to post
Share on other sites

It’s a circular Boiler required to be installed at a Pharmaceutical factory... Yes, the referred operational loading is the dynamic load which will be exerted on the pile cap & subsequently on the Piles. With regards to the type of pile, the soil investigation report based on two bore holes drilled upto 40 feet, state that the strata consists of Silty clay up till 25 feet and from 25 to 40 feet, the strata consists of sand and silt. Based on the results obtained from these bores, the Geotech experts have recommended 26 feet deep piles (without indicating the type of Pile). Based on my site experience, I will certainly recommend combine (skin friction & end bearing piles for this case with more concentration towards end bearing)

 

Please share your experience and recommendations.

Share this post


Link to post
Share on other sites

Attached are two docs I got from Google; they are lucid and easy to understand and cover examples. Pile Groups (Literature).pdf, Pile_Foundation_Design.pdf

 

With Dynamic loading, the question is not about piles designing only, but in fact, you need to design a foundation system and satisfy vibration limits for the machine. I can share with you typical rule of thumbs for dynamic design of machine foundations. Keep me posted on this as this is my specialty in structures.

 

1) Your utilization for piles should not exceed 45 - 55 % of capacity under static loading. This is to ensure that soil remains fairly elastic and expected behavior is achieved.

 

2) Is the boiler centrifugal or reciprocating machine ? You can check ACI - 351 that talks about minimum ratios of foundation weights to machine operating and their CG Locations for both centrifugal and reciprocating machines.

 

3) Your center of resistance for pile group should be with in 6-7% of machine C.G.

 

4) What is the max vibration limit for the boiler on the foundation level and at the machine CG level ? You normally get this information from the vendor and you proportion your foundation to satisfy those limits.

 

5) I am interested in knowing that how would you do a dynamic analysis for the system ?

 

6) You need to have complete soil investigation report with SCPT test providing shear wave velocities in each soil layer.

 

7) Is the foundation system an elevated one or is at ground level ? It is important to know this as table top machine design needs more engineering input and caution ?

 

8) What is your acceptable Human Perception Limit for the system ?

 

9) Is the foundation system being shared by super structure too. Please provide foundation plan. I want to see what is around your boiler.

 

10) You response of foundation should be outside the operating range of the machine to avoid resonance. (V.Imp) 

 

11) Please reply asap :).

 

Thanks.

Edited by Umar Makhzumi
Modified 10, added 11

Share this post


Link to post
Share on other sites

It’s a circular Boiler required to be installed at a Pharmaceutical factory... Yes, the referred operational loading is the dynamic load which will be exerted on the pile cap & subsequently on the Piles. With regards to the type of pile, the soil investigation report based on two bore holes drilled upto 40 feet, state that the strata consists of Silty clay up till 25 feet and from 25 to 40 feet, the strata consists of sand and silt. Based on the results obtained from these bores, the Geotech experts have recommended 26 feet deep piles (without indicating the type of Pile). Based on my site experience, I will certainly recommend combine (skin friction & end bearing piles for this case with more concentration towards end bearing)

 

Please share your experience and recommendations.

When you say end bearing, do you mean "belled piles" ? or "end bearing" with straight shaft piles ?

What pile diameters are you expecting ?

Share this post


Link to post
Share on other sites

Pls. contact at info@rockwellgrp.com for comprehensive civil/structural engineering, geo-technical and foundation engineering solutions, Regards, Asif Saeed, Director-ROCKWELL Group (Pakistan)

Share this post


Link to post
Share on other sites

Pls. contact at info@rockwellgrp.com for comprehensive civil/structural engineering, geo-technical and foundation engineering solutions, Regards, Asif Saeed, Director-ROCKWELL Group (Pakistan)

 

Asif, this is a free forum for educational purpose only. We don't allow any advertisements. Any post not related to topic falls under spam and therefore is not allowed.

 

Please review Forum Posting Rules at http://www.sepakistan.com/topic/1344-forum-posting-rules/#entry2660

 

Thanks.

Share this post


Link to post
Share on other sites

If vendor drawing for a particular machine shows values of Static Load & Dynamic Load, is static load "weight of machine"?

Share this post


Link to post
Share on other sites

If vendor drawing for a particular machine shows values of Static Load & Dynamic Load, is static load "weight of machine"?

Generally that is correct. However, Torque is considered as a static load too and is reported with other static loads.

Share this post


Link to post
Share on other sites

Dear Umar Bhai,

 

I have to design Tabletop Elevated Foundation for Turbo-Alternator. I have vendor drawings with static and dynamic loads identified to be applied on various points. Now my question: What is static and dynamic load, and how am I to convert them into masses/weights so that I can find to frequencies [fn = 2*pi*(k/m)^0.50].

Share this post


Link to post
Share on other sites

Dear Umar Bhai,

 

I have to design Tabletop Elevated Foundation for Turbo-Alternator. I have vendor drawings with static and dynamic loads identified to be applied on various points. Now my question: What is static and dynamic load, and how am I to convert them into masses/weights so that I can find to frequencies [fn = 2*pi*(k/m)^0.50].

 

You need to calculate the unbalance load and apply that as a dynamic force based on the speed of machine. What kind of company you work for and what software are you using ?

 

Thanks.

Share this post


Link to post
Share on other sites

I am working for a consultant in Karachi and we use SAP2000.

 

If I calculate the unbalanced load, then should I add it with dynamic load provided by vendor/supplier? or only apply the vendor's dynamic load?

Share this post


Link to post
Share on other sites

I am working for a consultant in Karachi and we use SAP2000.

 

If I calculate the unbalanced load, then should I add it with dynamic load provided by vendor/supplier? or only apply the vendor's dynamic load?

Use the vendor provided unbalanced load and perform a Modal Time History Analysis in SAP2000 to see what your vibrations are.

Share this post


Link to post
Share on other sites

Can I have DYNA5 software to download. I need to calculate the stiffness constants and damping constants.

Share this post


Link to post
Share on other sites

Can I have DYNA5 software to download. I need to calculate the stiffness constants and damping constants.

You need DYNA5 to get pile impedance(stiffness + damping) values. DYNA5 would calculate these values for your pile group considering group effects. You should convert the group values to single pile, and use them in SAP2000 as a One Node/Joint link and do the Modal Time History Analysis. Find your critical modes and check structure for resonance. If your amplitudes are lower than vendor allowable, you are good.

Tell you company to buy DYNA5.

Share this post


Link to post
Share on other sites

Dear Umar Bhai,

 

Modal analysis of a Table-top foundation has been done on SAP2000, with following result:

 

Frequency of foundation in mode-12 (last mode)  =  25.72 Cyc/sec. (Mode-12 has maximum frequency value)

 

Turbine's Frequency      =  117 Cyc/sec.

Generator's Frequency  =    25 Cyc/sec.

 

Plz comments

Share this post


Link to post
Share on other sites

12 Modes are very few and I believe is the default number in settings. You should run your modal analysis for at least 300 modes or 95% of Static Dead.

 

Check your magnitudes for cases of Turbine Operating and Generator Operating and superimpose them to see if the total doesn't exceed vendor limit at points specified by vendor. Since your operating frequencies are different for both turbine and generator, you should have two files for each case operating with pile impedances referring to the speed of forcing function.

 

Regarding Modal Analysis,

You have to see two bandwidths. First one is from 0.8-1.2 of your Generator Operating Speed; which would be 20 Hz to 30Hz and the second bandwidth will be from 0.8-1.2 of Turbine Operating Speed. For each case, note all the modes that fall into the bandwidth. Then run Modal Time History Function by equating your forcing function to the frequency of the mode(that's how you check resonance). Superimpose the results for each operating case and if they are below the vendor allowable limit at the points vendor has specified. you are good.

 

Thanks.

Share this post


Link to post
Share on other sites

Do u ve manual (or can u refer to a manual or book) for this procedure?


Also, I have designed mat foundation (not piles) for this table-top.


Please elaborate this point "Then run Modal Time History Function by equating your forcing function to the frequency of the mode(that's how you check resonance)".

Attached is modal analysis result for frequencies of Turbine & generator. I am confused as to what should I do with analysis. Should I apply turbine loads & generator loads separately in two SAP2000 files? Or as I have done here by combining both in same single file?

I would appreciate any and all kinds of inputs.

Tabletop foundation - Modal Analysis Result.pdf

Share this post


Link to post
Share on other sites

I would like to see the definition of your Time History Function? Explain to me how are you applying your loads in SAP2000 for the given frequency of operation and that would contain answer to 

"Please elaborate this point "Then run Modal Time History Function by equating your forcing function to the frequency of the mode(that's how you check resonance)"."

 

 

Moreover, attach snapshots of your SAP200 file so that I can see if you are modelling it correctly.

 

Thanks.

Share this post


Link to post
Share on other sites

Attached is zip file containing info of loads and model picture. I do not have "Time-history Function Data" of my project.

 

Thank you anyways for the input.

TTF.zip

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Our picks

    • I am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons. 
      I ll appreciate your help in terms of guidance & provision of notes...  
       
      Thank you..
      • 36 replies
    • Material behavior can be idealized as consisting of an 'elastic' domain and a 'plastic' domain. For almost 200 years, structural design has been
      based on an elastic theory which assumes that structures display a linear response throughout their loading history, ignoring the post-yielding
      stage of behavior. Current design practice for reinforced concrete structures is a curious blend of elastic analysis to compute forces and moments, plasticity theory to proportion cross-sections for the moment and axial, load, and empirical mumbo-jumbo to proportion members for shear.

       

      From the book "Design of Concrete Structures with Stress Fields" by A. Muttoni,  J. Schwartz and  B.Thurliman.

       
      • 0 replies
    • Dear Fellow Researchers, Academicians, and research students,

       

      NED University of Engineering & Technology in collaboration with Institution of Engineers Pakistan (IEP) is organizing 9th International Civil Engineering Conference (ICEC 2017) on December 22-23, 2017 at Karachi, Pakistan.

       The congress details are available at its website www.neduet.edu.pk/icec

       Also attached is congress flyer for information and dissemination among your peers.

       Abstracts submission deadline has been extended till October 31, 2017.

      Please click on the link to see the full description.
      • 0 replies
    • AoA all,

      Is it mandatory to do column concreting upto the soffit of the beam in a single pour ?

      What code says about the construction/cold joint location in column ?

      Majority of the contractors are pouring the column concrete upto the soffit of the beam (full height of the column), some contractors leave the column height about 9" to 12" below the beam level and then fill this 9" to 12" column height with the beams & slab concreting. On one site column concreting was stopped at the mid height and the remaining half was filled on the next day.

      Thanks

       

       
      • 5 replies
    • AOA 

      i am facing problems in shear wall design .what are the pier and spandral ?what will be the difference when we assign pier or spandral? without assigning these the shear wall design is incomplete .

      i am taking about etabsv16

      someone have document about shear wall design plz provide it 

      thank you

       
      • 9 replies
    • Salam Members,

      Congratulations to Engineers, PEC has become full signatory of Washington Accord, what are the benefits to Pakistani engineers for this agreement. 

       

      Regards   

       

       
      • 3 replies
    • Please clarify the following confusions one by one:-

       

      1. If we run P-delta analysis in ETABS, then should we ignore stiffness property modifiers for beams and columns? I have heard that if we perform P-delta analysis and apply stiffness modifiers at the same time then the moment magnification process is doubled...?

       

      2. ETABS considers selenderness of a column by applying moment magnification factors. If we run P-delta analysis also, does it mean that the selenderness of column is being over-estimated? I mean once the moments are magnified in P-delta analysis process and again through moment magnification process?

       

      Please help me understand the software myth and clarify above confusions.
      • 1 reply
    • Assalam o alaikum.
      According to ACI 12.5.2,
      development length for fc' = 3000, fy=60000, for normal weight concrete and epoxy less reinforcement, The required development length comes out to be
      for #3 = 8.2 inch
      for #4 = 10.95 inch
      for #6 = 16.42 inch
      for #8 = 21.9 inch
       
      And if in my case, ACI 12.5.3 is not fulfilled, it means now i have to provide ldh as mentioned above. ldh is STRAIGHT EMBEDMENT LENGTH + RADIUS OF BEND + ONE BAR DIAMETER as shown in figure attached. Now my question is, if in my case, main reinforcement of beam is of #6 and #4, minimum column size required will be 18 inch and 12 inch respectively. Lets say by any means, i can not select #4, #3 bars and size of column where bars are to be terminated is 12 inch, how to fullfil this development length???
      • 11 replies
    • Dear all,

      I am trying to design shearwalls through ETABS with temperature load applied over shell. At various location, spandral section fails in Shear due to temperature and piers (sometime in shear, mostly in flexure).  (See Attached Image)

      Certainly all the problem in Shearwalls are due to temperature. I don't want to increase cross section of spandral or pier at some location just due to temperature load case as it will appears non-uniform with rest of the wall. 

      I have seen stiffness modifier affect distribution of forces and also rigid/semi rigid daiphragm assumption. 

       

      Can anybody guide how to properly design the shear wall with temperature load applied in ETABS or share any similar experience. Thanks in Advance.    
      • 15 replies
    • ENGINEERS;
      I WILL LOOSE MY BRAIN FROM ETABS. 
      I DECIDED TO MAKE MANUAL MESHING FROM AREA ELEMENTS BESIDE EACH OTHER AND EVERY HING WAS FINE .
      BUT AFTER DEVISION SAY 7*7 ELEMNTS FOR EVERY BIG ELEMENT AND MAKING ETABS CHECH..................THEN 500 ERROR MESSAGE THAT ALL ELEMNTS ARE CLOSE TO EACH OTHER.  WHAT ARE GOING...... SOMEONE TELL ME PLEASE...... I WILL LOST MY WORK
      • 6 replies
  • Recently Browsing   0 members

    No registered users viewing this page.

×

Important Information

By using this site, you agree to our Terms of Use and Guidelines.