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  • Our picks

    • AoA all,

      Is it mandatory to do column concreting upto the soffit of the beam in a single pour ?

      What code says about the construction/cold joint location in column ?

      Majority of the contractors are pouring the column concrete upto the soffit of the beam (full height of the column), some contractors leave the column height about 9" to 12" below the beam level and then fill this 9" to 12" column height with the beams & slab concreting. On one site column concreting was stopped at the mid height and the remaining half was filled on the next day.

      Thanks

       

       
      • 4 replies
    • AOA 

      i am facing problems in shear wall design .what are the pier and spandral ?what will be the difference when we assign pier or spandral? without assigning these the shear wall design is incomplete .

      i am taking about etabsv16

      someone have document about shear wall design plz provide it 

      thank you

       
      • 9 replies
    • Salam Members,

      Congratulations to Engineers, PEC has become full signatory of Washington Accord, what are the benefits to Pakistani engineers for this agreement. 

       

      Regards   

       

       
      • 3 replies
    • Please clarify the following confusions one by one:-

       

      1. If we run P-delta analysis in ETABS, then should we ignore stiffness property modifiers for beams and columns? I have heard that if we perform P-delta analysis and apply stiffness modifiers at the same time then the moment magnification process is doubled...?

       

      2. ETABS considers selenderness of a column by applying moment magnification factors. If we run P-delta analysis also, does it mean that the selenderness of column is being over-estimated? I mean once the moments are magnified in P-delta analysis process and again through moment magnification process?

       

      Please help me understand the software myth and clarify above confusions.
      • 1 reply
    • Assalam o alaikum.
      According to ACI 12.5.2,
      development length for fc' = 3000, fy=60000, for normal weight concrete and epoxy less reinforcement, The required development length comes out to be
      for #3 = 8.2 inch
      for #4 = 10.95 inch
      for #6 = 16.42 inch
      for #8 = 21.9 inch
       
      And if in my case, ACI 12.5.3 is not fulfilled, it means now i have to provide ldh as mentioned above. ldh is STRAIGHT EMBEDMENT LENGTH + RADIUS OF BEND + ONE BAR DIAMETER as shown in figure attached. Now my question is, if in my case, main reinforcement of beam is of #6 and #4, minimum column size required will be 18 inch and 12 inch respectively. Lets say by any means, i can not select #4, #3 bars and size of column where bars are to be terminated is 12 inch, how to fullfil this development length???
      • 11 replies
    • Dear all,

      I am trying to design shearwalls through ETABS with temperature load applied over shell. At various location, spandral section fails in Shear due to temperature and piers (sometime in shear, mostly in flexure).  (See Attached Image)

      Certainly all the problem in Shearwalls are due to temperature. I don't want to increase cross section of spandral or pier at some location just due to temperature load case as it will appears non-uniform with rest of the wall. 

      I have seen stiffness modifier affect distribution of forces and also rigid/semi rigid daiphragm assumption. 

       

      Can anybody guide how to properly design the shear wall with temperature load applied in ETABS or share any similar experience. Thanks in Advance.    
      • 15 replies
    • ENGINEERS;
      I WILL LOOSE MY BRAIN FROM ETABS. 
      I DECIDED TO MAKE MANUAL MESHING FROM AREA ELEMENTS BESIDE EACH OTHER AND EVERY HING WAS FINE .
      BUT AFTER DEVISION SAY 7*7 ELEMNTS FOR EVERY BIG ELEMENT AND MAKING ETABS CHECH..................THEN 500 ERROR MESSAGE THAT ALL ELEMNTS ARE CLOSE TO EACH OTHER.  WHAT ARE GOING...... SOMEONE TELL ME PLEASE...... I WILL LOST MY WORK
      • 6 replies
    • Assalam o alaikum.
      I have just designed a frame structure with SMRF. The out put of shear seams weird to me. Column reports design shear Av/s as 0.045. (Images are attached). but when i right click the member, it must show me the most critical case HIGHLIGHTED AUTOMATICALLY. But it highlights load combo 38 (auto-generated combos have been used) which reports Av/s as 0.038. And 0.045 value is at combo 32. Is their any logic behind it?? More over how to interpret this Av/s?? means 0.045 in kip-in units means what? How can i convert this into spacing?? 
      • 9 replies
    • Hello everyone, I hope all of you will be fine. In etabs when we apply Response Spectrum loading on a multistoried building with 2 basement floors. At what floor level this loading will be applied as in equivalent static seismic analysis, we can apply EQX & EQY on any floor we like as this option is available in etabs but the problem is with response spectrum and time history analysis. please if someone knows and have the experince, share it i shall be very thankful.  
      • 5 replies
    • Salaikom dear professionals,
      First of all I would like to express my sincere thanks to the initiators of this forum for establishing such an exceptional atmosphere for knowledge/experience sharing, I it is really useful, In fact since I have found the forum I am mostly online and busy reading the posts. I would also like to thank the members for their professional comments and advice.
      As my first post in this forum I would like to ask the following queries:
      1-After running the analysis and design when I check the DESIGN DATA through Display >> Show Tables >> DESIGN DATA >> Concrete Frame Output, there is no specific message in Column Summary Data and Beam Summary Data, but in Joint summary data it is showing that “Joint B/C check not done”. Does anyone has any idea? I am sharing the ETABS model for your information and easy reference.
      ETABS MODEL.zip
      2- ETABS provides greater area of steel in the upper column than the column at BASE, perhaps due to higher moment. Could someone explain why this is so? In practice should we maintain maximum steel in both stories? Or we shall follow what the software suggests?
      3- Beside considering the minimum thickness required for deflection control of Beam as per Table 9.a Chapter 9 ACI-318 , using concrete crack behavior in ETABS and checking story drift, Do we have to check the deflection of beams for the serviceability propose elsewhere in ETBAS? If yes, Could anyone explain it?
      Regards, and look forward to any explanation
      • 13 replies
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    • REPLY FROM CSI Ilyas,

      Regarding your questions:

      1, 2 and 3- Results are not expected to be the same, in general,  ETABS is based on 3D analysis of the building while SAFE is based on a single story. If you uncheck thick plate in SAFE slab property it is similar to shell thin in ETABS in which slab shear deformation is not accounted for in both programs. This is also depending on ETABS--->SAFE export option you are using, load cases involved, meshing, rigid zone over columns etc.

      4- Please make sure to run latest version of SAFE 2016 v16.0.1

      5- Concrete strength does not matter for stiff element property as program does not design stiff elements. Program magnify their bending stiffness by a factor of 100 to model the rigidity of the interface.

      Regards, Mohamad
      ____________________________
      Mohamad Ali-Ahmad
      CSI Technical Support

      Computers & Structures, Inc.
      TECHNOLOGY FOR A BETTER WORLD

      1646 N. California Blvd. Suite 600
      Walnut Creek, CA 94596 – USA
      Main (510) 649-2200
      Fax (510) 649-2299
      support@csiamerica.com
      www.csiamerica.com

       
    •  i am not refering to that case my cracking analysis option is off in SAFE, i have already done that my input is same by assuming different cases.
    • You can use moment release to model hinged or pinned ends (depending on what you call rotation unrestrained boundary condition).
    • You will not get same results in both software. In ETABS you are assuming cracking and applying certain modifiers, where as in SAFE cracking analysis is done internally based on required or provided reinforcement iterations.
    • AA. Here is the progress & update regarding the problem described in my original post, for the benefit of the interested SEFP users. 1. Automeshing was adopted in the original ETABS 9 model, with a maximum mesh size of 3 ft for the slabs & walls. The slabs included a raft slab as well, for tranferring the reactions to SAFE. 2. The model was being updated in steps, by refining the geometry along various edges of the slabs according to architectural plans at different floors. Model was running fine at all the steps. 3. The problem most probably occurred when the whole model (including the raft slab) was selected through 'Select all' command & automeshed again as stated in para-1 above. This action meshed the raft slab as well.The meshing of raft slab was haphazard in some regions, because of orientation of slab outer edges in different directions. 4. Following steps were taken in order to sort out the error:- a. Trials were made by automeshing the model at two different maximum mesh sizes of 4 ft & 2 ft (one at a time), but without any positive result. b. Third trial was made using 'default' meshing option ( meshing at grids & in Automesh options, by keeping the 'Further subdivide shell/wall in maximum element size of' option UNCHECKED. This trial helped in running the analysis completely, with 2 Warning Messages indicating presence of unconnected point & frame objects at the specified locations. Deletion of these extra objects removed the warning messages. c. Another trial indicated that thr problem is with the meshing of slabs, and not the walls.   d. Trying to locate affected element # 22836 through the procedure advised by Rana, indicated that the relevant output table designates the slab & wall elements by the number types F### for slab elements & W### for wall elements. It followed that element numbers (like 22836 etc) are generated during analysis only. The same facts have been stated above by Saad Pervez. Thus, the affected element could not be traced once again. e. Keeping in view suggestion made by EngrJunaid, the affected model was opened in ETABS 2016. This time the affected element was located & found to be present in the automeshed Raft Slab, provided at the base level merely for exporting the Base Reactions to SAFE for further processing there.  5. Replacing the affected Automeshed Raft Slab, with a new unmeshed raft slab & remeshing the floor slabs & rc walls (after selecting the floor slabs & walls separately) at desired maximum mesh size finally solved the problem. In the end, thanks to all (especially @EngrJunaid) for contribution to reach the solution of subject problem, by suggesting various courses of action. Regards.  
    • No. You must not refer to or send results obtained using 'cracked' software for advice. It is illegal. Your queries, and attached information or results MUST be those obtained using Licensed software only. You would need to include details of purchased License, while referring the case to CSI for clarification. Regards.
    • even the results you will have same in cracked version.
    • Since you are using Licenced software, the best option would be to refer the case to CSI directly with all relevant details. Regards.
    • There are issues which needs to be addressed: 1-Why there is much difference in punching shear results in SAFE and ETABS models considering same parameters in both models.(same modifier, same geometry,same assignment of shell behavior in both cases  though SAFE does not have the option of thin shell all other the input is same),i have checked both the cases when the automatic rigid zone area over the column is on and the second case is when this option is off.   2- I have analyzed the both cases assuming the shell thick in ETABS and thick plate in SAFE behavior,in other case thin plate in ETABS and thick/thin PLATE  both in SAFE,but results still vary.   3-Even when you export same slab in SAFE the punching shear results vary in both models .There is significant difference in unbalanced moment value in both models.   4-i am using licensed ETABS 16.2.0 and  SAFE 16.0.0.   5-IN SAFE Made MODEL,what should be the concrete strength of stiff elements, it should be of column strength or it should be of slab strength, if you assign the same strength (concrete) as the column have then you will get reduced moments and if you assign the slab strength you will have more moments.   i have read the csi knowledge  , safe manual,thin/thick  shell and plate behaviour and all other data related to these issues.
    • Thank you for the feedback. 
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