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Structural Engineering Forum Of Pakistan
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Software Issues

Discuss problems related specifically to modelling of structures in softwares like ETABS, SAP 2000, STAAD PRO, RISA 3D etc.

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  1. Etabs load combos

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  • Our picks

    • Dear All,

      The forum has been updated today with a lot new features.

      You can find the list of all the new improvements by visiting this website.

      Some highlights are:

      1) Improved Search Features


      2) Emoji

      Emoji support is now available in all editors.


      Do check out the link posted above for the complete list.

      One additional announcement that I would like to make is that with reference to last forum update post (read below),  @Rana and @BAZ are forum Admins now. I think it was important to do as it brings more transparency for the forum and also helps spread the responsibility. The forum belongs to the members so it never made sense for one person to be Admin,

      As always, feedback is much appreciated.

      Thanks for taking the time out to read this update.

      Cheers!

       
      • 2 replies
    • Hi guys just to discuss with you my understanding of crack widths in Environmental structures according to ACI. 

       

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      Normal structures

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      1. ACI 318-95 based on statistical method of Gergely & Lutz 1968 limits Z based on exposure. We are calculating crack widths here. (Normal structures)

       

      2. ACI 318-99 proposed limiting the spacing and removed actually calculating the width and also removed the exposure conditions. For example for beams and one-way slabs s (in) = 540/fs -2.5cc or in other words limiting the fs=0.6fy  (For normal structures)

       

      3. ACI 224R-01 references method 1 and 2 above and 3 european codes.

      The most confusing part is the table in which Nawy suggests 0.1mm crack width for water-tight structures. The whole document is for normal structures except this line. And people are following this line and refer to this document for water tight structures. I mean its just a suggestion and by the way this method 1 is obsolete now since ACI 318-99 (see point 2 above).

       

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      Water tight structures

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      1. ACI 318-08 states clearly that for watertight structures ACI 350-06 codes should be used. 

       

      2. ACI 224.4R-13 also specifically states that for watertight structures walls in section 7.4, we should use ACI 350-06. 

       

      3. ACI 350-06 for water tight structures does not recommend calculating a number for crack width but rather limiting max steel stress in bars to be 20k ksi or fs=0.33fy for normal conditions.

       

      ---------------------------------------------------------------------------------------------------------

      To sum it up, 

       

      Philosophy of crack width control is not to calculate probable crack widths but to limit the max stress in steel bars.

       

      For normal structures: fs=0.6fy and for water tight structures fs=0.33fy
      • 1 reply
    • Hi

      I want to know the use of diaphragms in etabs. i discus many people who are use etabs but i can't get justified answer about the application of etabs.

      I read the Technical reference  of  Etabs, where they write about Diaphragms. i get two type of diaphragms (plate or shell and joint or beam). 

      My question.

      1. When do i use Shell diaphragms (if floor present ) 

      2.When do i use joint diaphragms ( grade beam level where no slab are provide) 

       

      NB: Diaphragms use to transfer the lateral load to the resisting element ( frame such as column. beam,shear wall) 
      • 2 replies
    • *SEFP Consistent Design*<br style="color:#272a34">*Pile Design*<br style="color:#272a34">*Doc No: 10-00-CD-0005*<br style="color:#272a34">*Date: Nov 21, 2017*<br style="color:#272a34">
       

      This article is intended to cover design of piles using Ultimate Limit State (ULS) method. The use of ULS method is fairly new for geotechnical design (last decade). The method is being used in multiple countries now (Canada, Australia etc). The following items shall be discussed:

      Overview


      Geotechnical Design of Piles (Compression Loads, Tension Loads and Lateral Loads)


      Structural Design of Piles (Covering both Concrete and Steel)


      Connection of Pile with the foundation (Covering both Concrete and Steel)


      Pile Group Settlement


      Things to consider



       

      1. Overview

      Piles provide a suitable load path to transfer super-structure loads to foundation where shallow foundation are not suitable - this can be due to a number of reasons like existing space constraints or suitable soil strata is not present immediately below structure. Other uses can be to meet design requirements like to have reduced settlement etc.

      This article shall cover the use of straight shaft cast-in-place concrete piles and straight shaft driven steel pipe piles. There are a number of additional piles types like belled concrete piles, precast concrete piles, screw / helical steel piles etc but the discussion to choose a suitable pile type is not in the intended scope of this article. The article is intended  to discuss design requirements for straight shaft piles only (both concrete and steel) . The aforementioned topic about pile selection is a very diverse subject and requires a separate discussion on its own.

      Click on the link to read the full article.
       
      • 9 replies
    • I am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons. 
      I ll appreciate your help in terms of guidance & provision of notes...  
       
      Thank you..
      • 36 replies
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