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WR1

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Everything posted by WR1

  1. WR1
    Check your structure and foundations on all applied loads. You can't skip earthquake if you are designing for it.
  2. WR1
    We use REVIT structure everyday for structural drafting and structural information. We don't however use ROBOT structural analysis or REVIT to export because making analytical model personally for me in REVIT is useless.
  3. WR1
    1. Because ETABS modifier of 0.25 is different than cracking analysis of SAFE. Are you sure the cracking analysis in SAFE corresponds to 75% cracked section? 2. If you are not performing cracked analysis in SAFE. still results would differ.
  4. WR1
    Good question/observation. That is the reason codes changed the foundation design from service to ultimate. 1. For your case; make sure there is no tension under service load combinations. Or remove it. 2. Make sure the compression is less than bearing capacity under service load combinations. 3. Once above two steps are done, and before proceeding to ultimate design of reinforcement, make sure that there is zero tension under ultimate load combinations, otherwise the ultimate design will be under-estimated.
  5. WR1
    Educate the client.
  6. WR1

    CULVERT

    WR1 replied to Hira Malik's topic in Concrete Design

    For any retained wall, always use all applicable cases e.g. for a water tank; case1: full tank, no backfill tension on external side of wall at mid span (if top slab exists) check crack width for 0.27mm tension on inside of wall at base and at top (if top slab exists) check crack width of 0.15mm case2: tank empty (e.g. for cleaning); backfill exists this is opposite of case1
  7. WR1
    Self weight is automatically calculated in ETABS if self weight multiplier in load patterns is set equal to 1.0. Yes, load is distributed by tributary area. It's a starting point, so start from here and then see how the load path gets affected by using different type of shell elements.
  8. WR1
    I am not sure why you doing it in a software. A simple hand made analysis would suffice. Also I am not sure what do you mean by load combinations? I mean, there should be just one wind load combination 1.6W for ultimate moment. Dead would not produce moments in the wall/supporting structure. Then you add 0.6D of overall assembly with 1.0W for checking service tension and footing design.
  9. WR1
    Stiffness of this beam is 2EI/L. See here; http://classes.mst.edu/civeng217/concept/12/03/index.html
  10. WR1
    I did mine from Heriot Watt, UK. Distance Learning. But I would not recommend it. Its a pain in the back. Plus the fee is almost the same.
  11. WR1
    The analysis is Linear. Automatic redistribution would have been possible if analysis were Non-Linear. In order to approximate redistribution (during cracking), the USER has to put some kind of stiffness modification. This applies to shear, torsion, moments, axial...everything.
  12. WR1
    Forget check Ax on dynamic. If you need to check, then check as on ETABS online wikki. If so, you have to combine all modes manually. That's time taking and complex. Check Ax on all static load combinations and whatever is the value, apply this in response spectrum.
  13. WR1
    The paper says that upon cracking the internal redistribution occurs. However like for moments, ETABS does not redistribute Torsion automatically. If you want it, then release (or apply modifiers) to redistribute forces. That is why I said, after this, you need to check for increased forces in slab. Its that simple.
  14. WR1
    It was short 2 day trip. Came back already. Next time.
  15. WR1
    I will be in Islamabad for a weekend from 12th april 9PM to 13th full day. Let's meet?
  16. WR1
    Checking torsional irregularity from dynamic analysis is complex. Do as follows; 1. Make all static load combinations with static E. 2. Check Ax 3. Apply the required amplification in response spectrum cases. Don't check Ax on dynamic (unreasonable results, wrong results). Also, don't include all static seismic directions in single load case (e.g. in newer versions of ETABS like 13 onwards). Make each static load case separately like in older ETABS 9. Combined case will give you wrong Ax. Also, if amplification is too high, check manually that joint, which might be unrestrained or at the corner. You might need to change it's framing etc.
  17. WR1
    Foundation should be designed for response spectrum cases too if they are used for super structure design also.
  18. WR1
    Moments should not differ by that much amount (10x in your case). Yes you can calculate punching directly based on 450kn.m like in RCM Builder. We use it daily, its my company software. Or you can calculate manually or by any sheet. I dont know why you are getting huge moment in SAFE. Probably because of the loading from raft? check your model again or try checking only on self weight...
  19. WR1
    Yes the program still divides it. Thats why I say ETABS is not a true FEA tool. They have made it damn easy for majority of the engineers. It is not for FEA analysts.
  20. WR1
    There is no seismic design category in UBC. Its simply zone 2B in UBC. What you probably meant is the equivalent seismic design category of ASCE 7 related to zone 2B of UBC. If so, then you have to convert your zone 2b spectra to ASCE 7 spectra and to find out S1 and Ss. After that you can find out the sdc from ASCE tables based on this S1, Ss and Fa and Fv.
  21. WR1
    Who said so? For majority of the buildings (low rise) dynamic time period is way lesser than 1.4Ta. Read code to understand about these limits. It should have been; if Tmode>1.4Ta then T=1.4Ta. Just a typo mistake i think, but inside ETABS it takes it correctly for both UBC and IBC/ASCE codes. Don't worry.
  22. WR1
    pretty simple check stresses in walls, if they are more than modulus of rupture they are cracked, use 0.35 otherwise they are un-cracked so use 0.7. Then iterate. Cracked walls will be in high rise with more seismic loads. See above.
  23. WR1
    What are the restraints to circular walls? Is it open from top? The circular shape is it self restraining (hoop stresses). Outward and inward? Yes, if bowing action but you need to apply gradient temperature then in softwares. Sign will determine if it bows outwards or inwards. Which software you are talking about? Yes application of any load in any software and even in papers depends on the direction in which you want to apply. Yes 1.2 factor for T, but not all combinations. You need to find out logically where you will need to use 1.2T. I mean effects should not be counteracting.
  24. WR1
    I can connect you with some on this if you like...
  25. WR1
    Make one and post for us please!
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