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WR1

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Everything posted by WR1

  1. WR1
    In addition to what Umar said, your errors are not negligible. They are the order of E+15. You must look at those joints. Usually it happens when you have rectangular grid system for circular buildings
  2. WR1
    Uzair I know the clause you are talking about. But it is for special moment frames whereas I have ordinary. Umar, these large rectangular columns attract 70% of base shear when modelled as frames and 95% when shells. What would you do when you have 10mx20m large bulky column? Still model it as frame? Whereas in reality it has continuous support like compression tension couple making the base fixed? I know we can model 200x200mm column as frame and then longer things as shells and then a mass by 3d brick elements. So whats close to reality? 1200mmx600mm vertical element as shell?
  3. WR1
    What would be the proper choice between shell and frame for modelling 1.2m x 0.6m vertical element? In a building I am studying expansion joints. All columns are 600mm dia circular. Except some vertical elements 1200x600mm. 1) The question is what system for seismic behaviour you would consider as per ASCE? shear wall or frame? 2) How would you model 1200x600 as frame or as shell?
  4. WR1
    Well I am taking Ground Engineering course in this semester. Havent studied anything yet. Will update if find some examples on that
  5. WR1
    It is normal. and loss of accuracy happens due to many reasons. For example, areas overlapping etc. Unless you see ***WARNING*** Structural is ill conditioned in last analysis run log, keep going. But just check how can you improve the model. Check if you meshed membranes or applied modifiers to them. Things like that generate these type of errors
  6. WR1
    Spring stiffness is provided in geotechnical report. If you don't have that, you can see other relations; such as in Bowel's book. Here, in middle east, we take modulus of subgrade reaction = SBC x 100 for isolated foundations and SBC x 120 for rafts. SBC is in units of kN/m². SBC=Soil Bearing Capacity
  7. WR1
    Dont mesh membranes or you will get errors...Just leave them as it is (default mesh option for membranes). And do meshing only for shell elements. and makes sure you have maximum of four edges for either membrane or shell
  8. WR1
    Sir Umar, why partially fixed is not the right word to say? If we model a very flexible member to a member of infinite stiffness, that infinite stiff member will provide enough stiffness as close to that of a fixed connection.
  9. WR1
    You do not need to model 2 columns at one grid. You can use a built up or tapered custom section to model the equivalent stiffness. That would work!
  10. WR1
    Thats very lengthy and detailed discussion. I appreciate and thanks you for this. Anyway, What I got, I put it in simple words... 1. Inter-storey drift is okay now as you all said (we have reduced the system R and Cd values, anyway). 2. I was not talking about basement wall out-of-plane bending or displacement. I was talking about frame drift (but not only on EQ, rather on H too). So this was my question, how do I combine H & E. Sir baz and Umair mentioned how to combine it in their replies.
  11. WR1
    In addition to what Umar said about bolds inside or outside flanges...I would add that... you can model 8 feet high concrete column just as you modelled the steel column. Add another line element made up of concrete (that is 8 feet high) directly connected to steel column. It will be a continuous (fixed) connection between 2 columns as mentioned in post#6. Then at the base of concrete column you dont really need to model pedestal in SAP. just apply a suitable support according to post #7.
  12. WR1
    1) Yes! I am combining inelastic seismic drift with elastic earth pressure deflection at beam column joint. 2) I still did not get why there would not be any problem in basement for drift. I have multi-basements. Do you mean there would not be excessive drift between basement stories? I am getting it and it is more than allowable seismic drifts....guidance needed pls!
  13. WR1
    This depends on what type of material you use. See ASTM material specifications. For example you need to see ASTM 615/615M for yield stress of grade 60 reinforcement and it will be 60ksi or 420mPA. You will put this value in ETABS. For shear reinforcement again it depends upon you what type of material or grade you want to use e.g. Grade 40 or Grade 60. For all this see ASTM standards
  14. WR1
    WAIT! I dont understand why you are transferring your reactions from top of footing to bototm of footing? second thing is why you said the reactions on top of footing will produce moment at the bottom of footing? Now I tell you what you do! 1-Apply pin supports to steel columns in SAP. 2-Note down the reactions for manual design or export to SAFE..(upto you). 3-If you do manual design then just design an isolated footing on this reaction. Bearing pressure = reaction/area of footing check shear and design for reinforcement simple!
  15. WR1
    i dont have walls all around. I am designing a big building separated by lot of expansions joints. And so the wall is one just one side of the building part.
  16. WR1
    Moving with the ground? So what is the maximum limit on that?
  17. WR1
    What you want to know?
  18. WR1
    What are the code requirements for drift of a basement wall in seismic zone? Lateral earth pressure produces elastic deflections whereas seismic generate inelastic sway (after multiplying elastic by Cd/I in ASCE/IBC). Now how to combine both? and by what combination?
  19. WR1
    You have not mentioned units. Anyway Weight per unit volume of concrete is: 24 kN/m³ which is 2.4E-05 mPa or (N/mm²). To get mass per unit volume divide the weight by 9.82; we get: 2.450E-09 mPA. It looks like above numbers in your post are wrong due to wrong units.
  20. WR1
    Give him the video lectures by SK GOSH DVDs easier to watch than to read a book!
  21. WR1
    See examples in PCA Notes for ACI
  22. WR1
    thats good! read good books and use internet forums!
  23. WR1
    This is very weird way of seniors to teach their juniors. Well D+L is a service combo but not the only combinations. There a lot of other combinations like 1.0D+0.6W etc. Goto ASCE 2005 pdf page 34, chapter 2 for example. You must first read basics before using prokon and other softwares; for example read Nilson's 14th edition book on Reinforced Concrete Design. Chapter 17 i think on foundations. I am very upset to say that if that is the behaviour of your seniors in office, tomorrow they gonna say "well you have done so much your self so you are now an expert. Come on, take this building and design everything because you did it before. Right?" Talk to your seniors boss and dont worry, otherwise QUIT THIS JOB! A sincere but strange suggestion from my side!
  24. WR1
    Well you must use service combinations for bearing pressure of foundations! 13 load combinations you mentioned are ultimate combinations for design of reinforcement! You should really check with seniors as these are basic things which you must learn asap!
  25. WR1
    You should check sign convention used in Prokon! and sign convention of your system ------- From the above discussion it looks like that in prokon P = Fy (check + or - sign convention in Prokon) Hx = Fx Hy = Fz Mx = 0 My = 0 Mz = 0
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