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      Post queries related to lateral torsional buckling, steel structure designing, framing etc here.

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      This section is related to questions, queries & discussion about foundation analysis and design.

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    6. Software Issues

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  • 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
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    • 1. First of all, you need to understand how to design the slab on grade (SOG) through hand calculations. Later on, you may develop a spreadsheet or use some patent software to do it using a computer. 2. The references given above provide design methods (pca, WRI, COE etc), dealing with different types of SOG (e.g., unreinforced, reinforced concrete, post-tensioned etc.) subjected to various types of loads (uniform, line, wheel & post loads).  3. Before starting the design, you will need to go through the reference available with you (i.e., ACI 360), and a. Select the SOG type from the Section 7 onwards, applicable to your case. b. Study the design requirements from the relevant section c. Determine the type and intensity of various loads, the slab will be subjected to during service. d. Solve the relevant design examples, given in the appendices of ACI 360 to understand various design parameters, charts, equations & their application to the design. e. Using the design prameters applicable to your slab, design the SOG by following the procedure adopted in the reference design example. HTH Regards.
    • thanks sir, would you please to tell me how to put the load? i've modeling the slab in SAFE then i assign the area spring, and put the surface load, due to uniform load and i get 0 moment i think i'm wrong in assign the load, i wonder if someone would explain it how to analyse slab on grade using SAFE, i've read the ACI 360, but still not to understand. Thanks
    • I have not seen such a limit written anywhere. However, the lowest value of bearing capacity (BC) for the building sites I have come across during my professional practice, was mostly 0.5 tons per square foot (TSF). In only one case, the reported BC was 0.25 TSF. However, the client was advised to change the site, as such a low BC indicates a very weak soil, ordinarily requiring a very heavy & expensive footing design. As such, IMO 0.5 TSF may be considered a reasonable lower limit of BC for a building site. Regards.
    • You may use following sources for designing floor slabs resting on ground:- a. Designing Floor Slabs on Grade by Ringo & Anderson, 1996 ( Link ) b. ACI 360R-10 Guide to Design of Slabs-on-Ground Regards.
    • anyone please advice how to design slab rest on grade? anyone have a referen? i have analyse with SAFE, but i still not confirm with the value of k (subgrade modulus) and the load. that the load assign full on the slab or just partial load at the critical location? thanks
    • 2d analysis is never recommended with walls above. https://wiki.csiamerica.com/m/view-rendered-page.action?spaceKey=safe&title=Modeling+uplift+and+foundations+on+soil+supports  
    • Hey man, hold on. Your building isnt symmetrical. Also the theres difference between axial stiffness of cols vs walls. This will effect z direction deflections from bottom to top stories. 2nd thing..safe..in safe deflections will be different than in etabs. This has been discussed no of times here and you can search.
    • If I calculated for an example the total area of rebars in a beam and I got let's say 433 mm2 I can now choose let's say 4 - 12 diameter bars or 2 - 16 diameter bars in a 300 mm width beam both will satisfy the minimum reinforcement and the maximum and minimum spacing due to ACI code. Does it matter if I chose any of them ? I know that the lesser the spacing between rebars the better to resist internal cracks in concrete. What are your thoughts ?
    • Does code recommends any minimum limit for bearing capacity if the bearing capacity of actual soil is known?
    • Hey guys, I think I have found what's wrong but don't know how to fix it.

      I drew the slab on SAFE and I have obtained the beams moments and slab deflections and they were very far away from ETABS results. However, there is an option to check it for columns and walls in SAFE it's called : ''Automatic rigid-zone area over column''  When I uncheck it, it gives nearly the exact deflection and beams moment in ETABS This option means the following from CSI america's website : ''Rigid zones are used to model the physical overlap between columns/walls and slab, which prevents deformation of the slab at the column location. This also will have the effect of producing maximum design moments at face of columns/walls instead of center line of columns/walls.  This in turn will produce less reinforcement and hence a more economical design, and allowed by most codes(i.e ACI-318). Deformations also will be more realistic in this case.'' So I assume applying a rigid zone is more realistic but somehow it's not assigned in ETABS and I don't know how to assign it in ETABS.

      What are your thoughts ?
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