Jump to content
Structural Engineering Forum Of Pakistan
  • Welcome to SEFP!


    Welcome to our community forums, full of great discussions about Structural Engineering. Please register to become a part of our thriving group or login if you are already registered.

Recommended Posts


One question regarding Collector elements. The code specifies that we need collector elements to transmit the lateral loads from the diaphragm to shear walls or vertical elements.True, but there are cases where we have a flat slab or due to architectural limitations cannot provide beams or collectors in that region. How are lateral forces transmitted in such cases. Where there are no collector elements the lateral forces are not transmitted to vertical elements effectively. Or we have another solution apart from Collectors to transmit the lateral forces from diaphragm to vertical elements.



Share this post

Link to post
Share on other sites

In most cases, the force in the collector is not enough to enforce enlarged-section in the form of a beam. The reinforcement can be provided within the slab. There is no other way, One has to complete the load path.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • 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.


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



      Normal structures



      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).



      Water tight structures



      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:


      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
    • Material behavior can be idealized as consisting of an 'elastic' domain and a 'plastic' domain. For almost 200 years, structural design has been
      based on an elastic theory which assumes that structures display a linear response throughout their loading history, ignoring the post-yielding
      stage of behavior. Current design practice for reinforced concrete structures is a curious blend of elastic analysis to compute forces and moments, plasticity theory to proportion cross-sections for the moment and axial, load, and empirical mumbo-jumbo to proportion members for shear.


      From the book "Design of Concrete Structures with Stress Fields" by A. Muttoni,  J. Schwartz and  B.Thurliman.

      • 0 replies
    • 9th International Civil Engineering Conference (ICEC 2017), December 22-23, 2017, Karachi, Pakistan
      Dear Fellow Researchers, Academicians, and research students,


      NED University of Engineering & Technology in collaboration with Institution of Engineers Pakistan (IEP) is organizing 9th International Civil Engineering Conference (ICEC 2017) on December 22-23, 2017 at Karachi, Pakistan.

       The congress details are available at its website www.neduet.edu.pk/icec

       Also attached is congress flyer for information and dissemination among your peers.

       Abstracts submission deadline has been extended till October 31, 2017.

      Please click on the link to see the full description.
      • 0 replies
    • 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.



      • 5 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

      • 10 replies
    • Salam Members,

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




      • 3 replies
  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Mujtaba Haider
      I need some relative data either papers,books or articles which describes the background of following topic in seismic dynamics:
      How exponential of complex numbers is related with "sinx+cosx". The result is e^+ix=cosx+isinx and e^-ix=cosx-isinx
    • By Waqas Haider
      Assalam o alaikum, 
      i m confused whether collectors and chords are only required in Flat plates/slabs or also required in beam slabs? because in beam slab we are having beams at perimeter of every panel and they can act as chords and for diaphragm bending and as collectors at junction of slab to shear wall. Usually, in seismic zone 4, i dont design diaphragm exclusively. i just design it as simple slab and design my beams in SMRF or Dual Frame in etabs. 
      Also i m confused in excerpt from a document stating
      The Special Seismic Load combination is also indirectly identified in Chapter 18, Section 1809, Foundation Construction – Seismic Zones 3 and 4.
      1809.3 Superstructure-to-Foundation Connection. The connection of superstructure elements to
      the foundation shall be adequate to transmit to the foundation the forces for which the elements
      were required to be designed.
      For instance, since Section 2213.5 Column Requirements specifically identifies the Ω0 factor, Section
      1809.3 requires the column-to-foundation connection to be designed for a load combination which includes
      the Ω0 factor.
      What does it mean? In seismic zone 3 or 4, we need to design foundations for special seismic combos ALWAYS or only if we r having discontinuous system? The full document is also attached. Thanks.
    • By Alaa Masoud Abd EL-Rahman
      First , I am Very Happy to Participate in Forum Such As This Forum , I need to Make Engineering Discussion With These Questions
      1.       Why We Make Scale Factor Between Static And Dynamic Seismic Analysis ?
      2.       After Scale Factor We Design By Load Combinations Included Dynamic Cases Only
                Or Static Load Only Or Dynamic And Static ?
      3.       What is Diaphragm And What is Importance of Diaphragm In Seismic And Wind?
      4.       When We Define Diaphragm? And We Define As Rigid Or Semi Rigid And What is the Different Between Them?
      5.       Different Between Displacement And Drift Due to Seismic ?
      6.       Displacement Due to Seismic Results From Etabs We Multiply it X 0.70 X R ,Why And What About Drift ?
      7.       We Make 3 Cases For Each Case ( X AND Y ) in Static Analysis What About Dynamic Same Or Not
                Static Analysis
                Ex With + Eccentricity
                Ex With – Eccentricity
                Ey With + Eccentricity
                Ey With – Eccentricity
      8.       Why We Don't Combine Seismic And Wind in Load Combinations?
      9.       In Dynamic Analysis , Forces Cause Mode Shapes Or Mode Shapes Cause Forces?
      10.   Difference Between Response Spectrum ( Dynamic ) And Time History , Which Best?
      11.   What is the Effect of Seismic in Slabs And Beams?
      12.   Design Of Slabs And Beams By Load Combination Included Seismic Right Or Wrong?
      13.   After Finishing 3D Model , What are the Checks For Seismic?
      14.   Slab On Grade , I Put In Etabs Or Not ?
      15.   How Building Make Damping For Seismic ,What is Factors Damping Depend on?
      16.   Different Between Point Drift – Story Drift – Diaphragm Drift ?
    • By Waqas Haider
      Assalam o alaikum.
      My building has special moment frames and 3 to 4 shear walls. The bay where shear walls are placed, no column is in the bay and beams are coming directly at top of shear wall and for the very specific bay, slab is also resting directly at shear wall at that location. How to decide in which category, exactly, my structure comes? UBC structural systems are
      1629.6 Structural Systems.
      1629.6.1 General. Structural systems shall be classified as one of the types listed in Table 16-N and defined in this section.
      1629.6.2 Bearing wall system. A structural system without a complete vertical load-carrying space frame. Bearing walls or bracing systems provide support for all or most gravity loads. Resistance to lateral load is provided by shear walls or braced frames.
      I think my structure does not lie in this category because majority of slab and walls are resting at beams connected with columns. Am i right?
      1629.6.3 Building frame system. A structural system with an essentially complete space frame providing support for gravity loads. Resistance to lateral load is provided by shear walls or
      braced frames.
      Is this structure is where no lateral load is resisted by frame and shear walls resist lateral loads? How is it possible that no lateral load is resisted by frames?

      1629.6.4 Moment-resisting frame system. A structural system with an essentially complete space frame providing support for gravity loads. Moment-resisting frames provide resistance to lateral load primarily by flexural action of members.
      If I have 7 bays in a direction at a grid and I have 5 to 6 grids in building. An only end grids have shear walls in one or two bays, Will it be considered as building MRF or Dual system? What is exact differentiation between them?

      1629.6.5 Dual system. A structural system with the following features:
      1. An essentially complete space frame that provides support for gravity loads.
      2. Resistance to lateral load is provided by shear walls or braced frames and moment-resisting frames (SMRF, IMRF, MMRWF or
      steel OMRF). The moment-resisting frames shall be designed to independently resist at least 25 percent of the design base shear.
      3. The two systems shall be designed to resist the total design base shear in proportion to their relative rigidities considering the
      interaction of the dual system at all levels.
      Is there any limit that at least this much of base shear must be resisted by shear wall to consider it as Dual system otherwise it is MRF?
    • By Waqas Haider
      Assalam o alaikum.
      I have gone through previous posts regarding this topic but still i m unable to get the exact way to check torsional irregularity. What I have concluded through surfing and conversation regarding this topic with some of forum members, I m posting it with uncertainty that I have get it right or not. Kindly place your valuable comment.
      I m attaching a  simple plan with the deformed floor shape under EQx loading with minimum eccentricity. I have labeled points. If X axis towards right, as marked in picture, For EQx loading with (say) 5% eccentricity, the following shape is gotten. Now UBC97 says, the building will be irregular if 
      "Maximum story drift, computed including accidental torsion, at one end of the structure transverse to an axis is more than 1.2 times the average of the story drifts of the two ends of the structure

      ." My confusion lies specially in the bold part. Transverse to an axis (What axis) and two end of the structure (when two ends of structure)?
      Besides the confusion under wording, what i have been guided by other fellows is that, we need to check for EQx, the displacement of Point 1 under EQx drift combos (This will be the maximum displacement) and the displacement of Point 2 under EQx drift combos (This will be the minimum displacement). Then we need to compare the maximum displacement that is of point 1, to the average of this maximum and minimum displacements of point 1 and 2 respectively  If this ratio is greater than 1.2, there will be torsional irregularity and if it is greater than 1.4, there will be extreme torsional irregularity. And we need to provide stiff columns or shear walls accordingly to reduce this ratio under 1.2 to eliminate torsional irregularity.
      Am i getting it right? Thanks. 

    • By MArifZahid
      Please tell me what is Design system Rho and Design system Sds?
    • By MMohsinlive
      Assalam Alikum
      I am pursuing my fyp on Performance of RC Beam Column joint with effects of steel strips as confinement.
      My advisor is a post-doc and is not feeding me the basics of it.
      I will  be performing a Quasi-static test and an Ansys model !
      Need some advices on online sources or any good books that I can use for development of concepts as it quite a task for me being a Ugrad..
      Thanks alot
  • Recent Discussions

  • Latest Forum and Club Posts

    • Could you help me understand how moment will be distributed in two ends of beams if one end of beam is fixed and other end is partially fixed? Say, previous 24ft beam with 15k/ft udl....FEM are -720 k-ft both sides.....now one of end has been partially released so that it can develop 360k-ft how will moment be distributed to other end...I am getting 900 k-ft at fully fixed end and shears at 2 ends became 157.5 and 202.5 kips..., I fail understand how to solve this indeterminate beam with one partial fixed end...   Thanks for your help
    • The settlement is likely due to weakening of soil support beneath the columns. There may be several reasons for this, like ingress of moisture in the underneath soil, sudden subsidence of some underground cavity etc. This may be investigated through some geotech engineer. Underground water tank, some nearby leaking water supply or sewerage line might also be the reason for weakening of the soil. To start with, these should also be checked & any leakage observed should be promptly & properly rectified.  Futher advice can be given on knowing the results of geotechnical investigation, carried out for determining the most likely cause of settlement.
    • Thanks for your reply. Actually your blog was one of the first I studied before doing it. 
      I understood it now. ETABS is using equation like M=(n/(n-1))*4EI/L*theta. so rotational stifness constant k=(n/(n-1))*2EI/L. If you are reducing stiffness on both sides consider using spring constant of (n/(n-1))*2EI/L n=% of moment to be resisted.....for n=1 we will get fully fixed, for n=0 we will get fully hinged.  The graph can be considered to be n(Y-Axis) and (n/(1-n))*2 as X axis. The data makes sense now. i am worried about 3D now, I have 55 story building in which i have to model connection loss in terms of decrease of stiffness. I don't know if I could use 
    • What kind of foundation system is there. you can consult a geotechnical engineer as well to get some option interms of soil improvement etc. From a structural point of view, you can  always introduce more columns and reduce load per existing column to reduce settlement. Thanks. 
    • plz help me out of this problem.. the foundation is settling down week by week. it is a warehouse. a big  Under ground water tank is adjacent to the failed column. we have only little space to work. this is in dubai. Suggestions please what so i can do. plz do reply
    • First, the stiffness of this beam is 2EI/L. See here; http://classes.mst.edu/civeng217/concept/12/03/index.html Second, see the fixed end beam in this link, hope it clarifies. Do share the findings afterwards please. https://waseemrana.com/2013/04/16/how-to-partial-fixity-in-etabs/
    • I am trying to understand how rotational spring constants work in ETABS. I have considered 24ft long beam with 15kips udl applied so that fixed end moment is 720k-ft I assume that spring constant will be function of EI/L. I assumed that ETABS would have linear spring, so that if I find lowest spring constant to give me 720k-ft fixed end moment, I would half that spring constant to give me half restain so that moment will be 260k-ft. In reality results are far from it. the graph attached shows factor which I multiplied to (EI/L) to get spring constant in kip-in/rad in X axis and Y axis shows corresponding end moment/720. Can somebody explain how etabs spring constant work so I find factors representing fraction of total restrain.
    • Did you got the answer of your question?
    • PEB structures are a special type of steel structures. These are less common in our country, as compared to RC structures . Accordingly, very few firms or structural engineers design these structures. Some locally known such firms include Zamil Steel, PEB Steel, Mammut, Izhar Steel etc. Larger firms have their own design manuals (and in some cases, their own special  software as well), which you may search on the internet.  UmarMakhzumi  has pointed out to the proper source & authority dealing with this type of structures.  Analysis & design of PEB structures is similar to normal steel structures. However, MBMA Manual provides better design aids (based mainly on ASCE 7), especially with reference to application of wind loads to this type of steel structures. In addition, it has several detailed wind analysis examples dealing with Enclosed, Partially Enclosed & Open type steel buildings. This manual will be a very useful source for understanding the design of steel & PEB structures covered in MBMA , in case you already have a good command on the use of AISC Manual of Steel Construction.  
    • MBMA guidelines might be used in PEB structures. I know @BAZ used to have a MBMA design document. http://www.mbma.com/  

Important Information

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