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Everything posted by Rana


    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
  2. Slab deflection in ETABS

    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.
  3. Slab deflection in ETABS

    If the building is regular as you said with same column sizes, axial shortening should be same provided loading and gemoetry all are same and symmetrical. Gravity deflection on same combination should be same at each level. And by deflection i mean z deflection not x.
  4. Thickness of footing

    10 under the root factored load in kN is the thickness required in mm (tried & tested here).
  5. Reduce lateral displacement

    Decrease the distance between CR & CM. It will not eliminate 100% due to inherent torsion.
  6. Signup with IStructE and start your road toward chartership.
  7. Effective width of Point Load

    In addition to above, to get an idea how point load is distributed, see PCI Handbook.
  8. B/C ratio output in Etabs

    Answer is simple. Top columns have less axial load and more moment. That means more in the tension region of interaction diagram.

    It does. Simply use 3d.
  10. Expansion joints

    Expansion joints in superstructure are provided for lateral movements e.g. from wind/earthquake/temperature/geometry. No need in foundations as soil has sink down effect for temperature and earthquake and winds and geometry effects are above ground.
  11. Minimum thickness Equation

    You need to size the slabs for long term deflections. Forget these tables.
  12. Column Design In Etabs

    It will still design for minimum eccentricity. Refer to ACI chapter 10 I think. You can turn it off (not recommended) if you want in ETABS design overwrites.

    It depends on the ratio of local area vs total area. It also depends on the location and importance of localized stress area among other factors. This is engineering judgement beyond the number crunching drudgery. I cant provide this as I am not aware of the project details. You could refer to your seniors for this. And remember do not stop at this. There is always a solution no matter how hard the problem is. For example may be your geotech engineer might suggest a lesser soil stiffness value at this location which will help reduce the stresses. You might increase the local thickness to better distribute the pressure. You could optimize the load combinations or even the load path of superstructure not to have the concentration here. An important point here is if this is localized compression at corner then is it due to lateral loads? If yes then watchout for the reverse that is tension (blue color contours). This will be another whole new problem.

    1. Depending on how much the value is exceeding you could increase thickness of the footing. 2. Soil improvement. 3. Reduce loads/stories.
  15. Need Help Regarding Raft Design

    33% pressure increase is not allowed regardless of the soil type for example according to UBC-97 service combinations. If there is an allowance it should be clearly mentioned by the geo tech engineer/report.

    Why are you still using SAFE 8. The latest is SAFE 2016. In ver 8, negative means (tension) and positive means (compression). After ver 8, it is opposite.
  17. UBC 97, ASCE 7-O5

    Dear Tufail, Please read the forum rules regarding copyrighted material. We at SEFP do not recommend, promote or give away copyrighted material. Thanks.
  18. Shear Wall vs Column

    My point here is different. Walls are also designed as flexural members like columns. Aspect ratio is a guide line. Cols and walls however are reinforced differently but my main point is different regarding modelling. You can do an example in a 3d model try replacing a line element with shell element of same size and check how much latetal force both are resisting (compare their base reactions).
  19. Negative Reinf One Way Slab

    Provide L/3 that would be conservative. There is no moment in longer direction, there is no deflection, for suspended slab, it is not exposed to temperature difference, and nothing is restraining the slab opposite faces (if for example on brick walls), so nothing is required in my opinion. L/3 will be conservative. If the slab is monolithic with beams and beams are much stiffer, then that little degree of restraint (like point restraint) should also be okay by providing L/3.
  20. Plinth Beam

    Can't say. It depends on design, if it is required, it is required. Some times site people are not happy to see such numbers from a design engineer. It is a good observation but you need to consult the design engineer for further guidance.
  21. Flexural Analysis

    and for long term deflection and for increasing inertia and for moment reversal and in short spans.
  22. Structural Engineering Books

    You guys scared the hell out of him. No one can read that many books. Dear Hassan, just pick one book and get the max out of it.
  23. Shear Wall vs Column

    what about 200x600 column? This is just the geometrical constraint as in UBC or other codes. Usually I do it as wall; 1. if it is more than 1500mm + the above geometrical constraint. 2. if analysis is for lateral loads. If you have huge number of such elements, it will make huge difference for lateral loads (just check the % of lateral resisting load). This is because for walls, there are multiple points of support (moment from couple). If you want to model it as wall and want to act like a column then just put one point support, then the only difference between shell and line will be 4% difference of stiffness due to poisson's ratio (negligible).
  24. Difference between Etabs 9.6 vs Etabs2015

    That's not what I meant. Please share with us, the results from both analyses of a specific column at the same location, with design load combinations used for them.
  25. Difference between Etabs 9.6 vs Etabs2015

    share the snap shot of result of a specific column or wall here.

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