Jump to content
Structural Engineering Forum Of Pakistan

WR1

Administrator
 View Profile  See their activity

  • Posts

    985

  • Joined

  • Last visited

  • Days Won

    286

 Content Type 

Everything posted by WR1

  1. WR1
    Without looking into the models, this depends on the construction. If you are casting columns independently of walls without continuing bars then obviously design them separately. if they are integrated with walls then yes model them with wall.
  2. WR1
    first of all you have to take area as transformed area. I mean A will be (Ac-As) + n As where n = Es/Ec and As is the total area of steel bars. now calculate strain by PL/AE where A is the above area and E is the E of concrete because you have already transformed steel area into concrete above. now this strain is assumed to be same in bars and concrete. and you can back calculate to check how much P steel and concrete is carrying. because it will be different for both. You cannot take the same P for both steel and concrete as you are doing in your post.
  3. WR1
    I am facing a similar situation again. What exactly is the difference between multi-storey frame with columns modelled as line element, and the same frame with same sizes with columns modelled as shell elements.
  4. WR1
    judgement comes from experience. dont worry! just try to make your own rules in each project....you will need to refine them in next projects then....finally to arrive at suitable close approximations...thats called engineering judgement...it takes time...for this just do what your senior said...use 5 bars...and then compare the patterns in next project and build on this
  5. WR1
    Yes 5 bars might be perfect! it depends on length of additional reinforcement shown in SAFE. Never go for "the values" in a structural program. Always use engineering judgement.
  6. WR1
    Good information, But I have not tried non-linear analysis for slenderness! By the way are you interested to do this; 1. For research work either for educational or personal purposes or 2. For a tall/important building where the effect is more pronounced If yes on both counts then go for non-linear analysis, but in usual practice for normal buildings, we do it by magnifying moments, but it was good to know the inconsistencies between two methods to calculate column stiffnesses. Btw, how do you perform elastic 2nd order analysis?
  7. WR1
    It depends on engineering judgement, for example i will quote the example my professional (Col. Iqbal) gave me; If there is a barber shop and adjacent to that is the heavy storage area, then this is load pattern problem. The factor will come from the understanding and feel of the problem.
  8. WR1
    Which version is this 13.1 or 13.2 Please use the latest one, as initial versions of ETABS 13 had lot of bugs which is normal for any new mega release of any software!
  9. WR1
    You have to take all the forces for design of walls, axial, shear, lateral earth/water pressure. But usually walls are quite strong in compression and you can assume pinned connection of basement wall with floor. That way you design only for lateral earth/water pressure with propped-cantilever condition (fixed at base, pinned at top). Model a line element in a structural software and check the moments. a. For a triangular load (earth pressure) maximum moment at base will be -2WL/15 and positive moment somewhere above base will be 0.0596WL with 1/4th reaction on pinned support. where W is the total load in KN. b. For a uniform load (surcharge) max mom at base is WL²/8 and max positive moment is 9/128 WL² with 3/8th reaction going to pinned base. where W is the load per m in Kn/m. Then just add a and b together (superposition for linear analysis).
  10. WR1
    Once I looked for these softwares but dont remember it now. Would you please share what is the topic of your thesis and why exactly you need this information?
  11. WR1
    If I understood your question correctly, then NO you have to also think about structural integrity. Follow the standard rules given in ACI detailing manual or in BS standards. See how the bars are developed in PCA notes.
  12. WR1

    Framing System

    WR1 replied to dccar's topic in Seismic Design

    The type of structural framing system depend on many factors such as; energy dissipation characteristics interaction of rigid frame with shear walls and compatibility of deformations of slab and walls loss of stiffness and amount of cracking, softening, yielding self weight, concentration of shear forces, torsional resistance coupling of gravity and lateral loads etc It would be unwise to say anything without checking architectural features and constraints and the behavior/scope of structural design
  13. WR1
    They really helped me and I have included their recommendations in analysis and acknowledged it properly by attaching our correspondence with thesis. They suggested 7 to 10% damping for seismic and about 4% for wind. Although any value can be achieved but might not be practical.
  14. WR1
    okay guys i finished my dissertation. If any body is interested on this topic, I would be more than happy to discuss. Thanks all.
  15. WR1
    1) I dont think there is such an issue 2) Not sure about that but getting registered with PEC is obviously the first thing. Lets wait for other members to reply. I am also interested in this information.
  16. WR1
    Well this is against copyrights
  17. WR1
    I dont know if they are called integration nodes, but sure they are called "Gauss Points". these are the points in FEA where stresses are or displacements are calculated and are then interpolated or extrapolated to nodes or within the areas. Stress at nodes will be extrapolated from Gauss points. But at nodes, there will be many values different values from each corner of adjacent area. You should not average results at this intersection which will help you understanding the quality of mesh. Its an art where and what to check in FEA. You should consult FEA book by Robert D. Cook. Its very easy and well written plus the author is well known in this field.
  18. WR1
    Thats an interesting document although I already read it but I think I am not gonna scale the records as I am not studying or doing a comparison between code based equivalent static and actual time history records. Neither I am designing the structure for seismic forces. I am studying the effects of long-period components in time history records on tall buildings. So I should be concerned with that. But about the damping ratio, yes I have written the company in second link you mentioned above (First one is not working). Still I have not got a reply from any firm/expert about this. I just need a recommended rough "FEEL" value that can be used for my study.
  19. WR1
    I am studying about controlling building motions in long-period ground motions. These dampers are different than normal dampers because in long-period ground motion sway is much much more than in normal conditions. I just need the equivalent approximate increased damping ratios for these specialized dampers to use in linear time history analysis for all the modes. I need to cite this in my dissertation preferably from a book, from a manufacturer or from an expert.
  20. WR1
    As Muneeb pointed out, the lateral load transfer depends on stiffness of vertical elements. A concrete shell element of the same size of a line frame element has about 4% higher stiffness because of posions ratio. Thats not a big difference but a shell element when meshed has more supports at base adds up to the stiffness as compared to single support frame element.
  21. WR1
    Dear all, 1. Do we need to scale Time History Records for Linear analysis? Like we do in RSA? 2. How can we model a damper staying in linear analysis domain? as I am working a tall building for which I am not interested to go Non-Linear domain as this is part of my masters dissertation.
  22. WR1
    I think there is no absolute max requirement for overall building drift for strength seismic zone. All you have to check is inter-story drift. For wind yes, there is this usual H/400 requirement where H is the overall building height. And in your case it is 202x12/400 = 6.06" = 6" (Use 0.7W to check drift here). You can also check human comfort criteria and acceleration at top floors. Yes 20" seems excessive, and you must put more strength and stiffness to your building. The building is very flexible.
  23. WR1
    To select sway option before analysis, select all elements by Ctrl+A, then goto Concrete Design Preferences from Design menu, and select VIEW/REVIEW overwrites and then select the second checkbox and change the sway option. Remember that, you have to do this each time you add or change your model. All new members will be set to default and you have to change them too like this. What is the height of building, around 220 feet? This 20 inches sway is on wind or seismic? Add more stiffness to building to reduce it, add more shear walls, increase length of shear walls, etc.
  24. WR1
    Syed Umair, has nailed it down perfectly. We ignore torsional resistance of beams as mentioned in Nilson book.
  25. WR1
    1. You can check in ETABS analysis manual pdf about these things. These options enforce reinforcement limits according to the selected category. For example if you select sway intermediate/special, ETABS will check for reinf limitations given in ACI chapter 21. 2. Codes explicitly state that, please read again UBC or ASCE. You will find the limits of 0.020/0.025 for seismic. For Wind read commentary of wind chapter at the end of ASCE 7-05/10. Usually the limit is H/400 but you must know on which W to check this limit. Is W service or ultimate. Read about it in the same commentary chapter. Otherwise, you can check this article. Always search the topics before posting a new one. It helps us.
×
×
  • Create New...

Important Information

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

  I accept