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Badar (BAZ)

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Everything posted by Badar (BAZ)

  1. Mat cannot be part of inertial forces. The slabs with in basements can participate depending upon the level of grade on both sides of building, the stiffness of basement walls or other below-grade vertical members and type of soil. You can take a look at this document: asce-003_asce_7-10_commentar.pdf https://cdn.ymaws.com/www.nibs.org/resource/resmgr/bssc/asce-003_asce_7-10_commentar.pdf
  2. I have not understood that why are you thinking that there is some discrepancy. As far as the ultimate design is concerned, I believe you mean: strength based design. This is the only procedure that we follow. No body uses working stress design procedure. As far as your wall is concerned, it is not necessary that every structural component that you will encounter in actual structures will be subjected to a moment which is at-least grater than the cracking moment. If the demand is less than what is require to cause stresses-inelastic-section-cracked situation, the strength design is not applicable on the cross-section. However, the section must have minimum reinforcement to initiate ductile failure as per applicable code.
  3. I never went through this situation. Having said, there are other options within the nonlinear settings proforma to reduce the time taken by the software like step size, number of iterations per search and likewise. One can play with them to see their effect.
  4. There are number of ways to deal with the walls. First, make sure that you have satisfied the force-demand on the wall. As you have said, ETABS gave you the distribution of reinforcement in the wall. This distribution should satisfy the demand for flexure. For shear, the reinforcement suggested by the ETABS may not be adequate. You need to confirm it by adopting the capacity-based design approach. The requirement of boundary element is there to ensure that your wall does not crush, or reinforcement doesn't buckle, due to compression. For that, ETABS only specifies the region where you need to confine the concrete as per ACI code's direction, which depends on the location of neutral axis. Make sure to confine this region; no extra reinforcement is needed if you have provided the vertical reinforcement suggested by the software. However, in order to satisfy the confinement criteria, you may need to add additional vertical reinforcement and thus you may deviate from the arrangement suggested by the software. This can increase the moment capacity of your wall, and thus the shear demand (Capacity-design approach). There is another approach, simplified one, in which engineer only considers the vertical reinforcement within the boundary region to be effective as far as in-plane moment is concerned. In that case Asfy x moment arm should be equal to in-plane demand of moment. Where d is the moment-arm created by boundary zones on either ends of the wall, and As is the total area of steel in boundary zone.
  5. You can to study the "anchorage in concrete" guidelines provided by the ACI 318 to see if is possible to do that. Yes, these post-installed epoxy-fixed bars are durable. You can attach the overhang with steel.
  6. it may be due to a software bug. PMM does not necessary mean that the software is designing for compression. Anyway you can always perform your own checks if you are confident about the analysis results.
  7. You must include them in the model. In addition to resisting out-of-plane forces, in the form of soil pressure, it will resist in-plane forces even if the base is located at higher level due to back-stay effect. You can find the approach to tackle it in following documents. https://www.structuremag.org/wp-content/uploads/C-StructPractices-Tocci-June121.pdf http://www.tallbuildings.org/PDFFiles/2017-LATBSDC-CRITERIA_Final_w_2018_ Supplements_FINAL_20180320.pdf
  8. Label the wall elements as pier and spandrels, and get out their forces in text file once you are done with analysis.
  9. The Outrigger should be able to transfer at least shear and moment to the wall, but only the shear-transfer will do between outrigger and columns.
  10. Yes, if you want to scale the base shear obtained from RSA with respect to the value from Equivalent static procedure.
  11. Scaling is done in most softwares by changing the value of "g". You can change the scaling factor to bring it down to the required range.
  12. Reinforcement's effect is normally neglecting while calculating the elastic modulus of concrete. It is the only function of the compressive strength of concrete: 57000 x sqrt(f'c) as per ACI 318 in feet-pound system.
  13. If you set loading type as nonlinear and set the load application control as displacement, then check if you are able to get convergence in your model. I tried to model material nonlinearity of RCC in a different context, I couldn't get the desired result in SAP 2000.
  14. You need to consult ACI 313-16. Ensiled material load to be treated as live load
  15. Assuming you will be doing elastic analysis- no factor is required for nonlinear analysis- it depends on the design-code you are using. Find the attached document for an elaborate answer to your query. Effective stiffness for modelling concrete members C-StrucAnalysis-Wong-Jan17-1.pdf
  16. You already mentioned the reason in your earlier post. It can be put this way: the shear wall is a member whose stiffness in one direction is at least 20 times the stiffness in the other direction.
  17. As per the requirements defined for column.
  18. If you are doing elastic analysis, then you need compressive stress, Elastic modulus, Poisson's ratio and density. You can put these properties to define the material in any software. If you want to do nonlinear analysis, then you can use the concrete model available in both software to represent the strut.
  19. Guys take a look at the interaction curve of columns. The curve where every point gives the value of moment and axial load for which the column will yield. When the axial compression reduces the moment capacity will also reduce. So, you need more reinforcement to meet the demand.
  20. You can apply the load through a dummy( zero-weight & zero-stiffness) beams. Check the wall for shear and axial stresses. You can consult the wall-related chapter of 318-14 for corresponding design strengths.
  21. Multiply 7 tones by a factor of 1.5 to take into to the account the dynamic effect of that loading. Apply that loading either in the form of point load, or gravity-directed UDL, on area elements representing the elevator shaft.
  22. Find out the first order moment (The moment without considering P-delta effect)as well as the moment by considering the P-delta effect.
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