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    • *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
    • 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

      • 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. 




      • 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
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  • Similar Content

    • By Sohaib Akhtar
      Hi All,
      currently I am involved in a pile foundation design for a 50-55m high transmission pole ( 1.8m dua circular pole having cross arms and supporting 220kV transmission line).
      Site soil condition: high plastic clay uptill 5-6m and after that it's rock ( good density basalt) 
      loading : maximum moment= 14000kN-m moment at pole base with approx 280-290 kN shear at pole base... compressive load is about 150-200kN at base...
      Due to site limitations and existing utilities only one pile can be given under pole ...
      Priliminary foundation sizing:
      pile cap: 2.5mx2.5m * 1.5m deep 
      prelimary pile /pier size  = 1.8m
      preliminary depth of pile /pier = 10m with 5m embedded in to rock ...
      has as any one worked on heavy transmission line project before ? Or any one can suggest me the type  of foundation normally given? 
      As as this is my first experience with such type of structure I am open to ur expeirience regarding  this Heavy  pier/pile type foundations ....What is the normal practice ??
      i am working with a senior guy and he is confident that this arrangement will work... but I need suggestions as well...
      kindly share  your experiences in this regards...
    • By Wajahat
      AOA all members ! in designing RC piles what factors govern in providing steel in piles either we consider only for compression section or any others factors too.....that should be consider?
    • By Waqas Haider
      From engineering point of view, it is really very amazing to see a complete city builtup in water ways, in a lagoon. How did they make the foundation system of buildings completely all the time underwater? Really interesting article here is. It also explains some modern challanges to the city i.e. flooding due to raised levels of sea and an inteseting solution to this problem.

    • By UmarMakhzumi
      Hello Everyone, 
      This log is intended to keep track of all consistent design articles. It would also help me assign the document numbers as the articles come out. If you have an article or post that you will like to get included in SEFP Consistent Design Series, please PM me or any of the moderators.
      Torsion - Reinforced Concrete Members; Doc No: 10-00-CD-0001 1997 UBC Vertical Earthquake Term; Doc No: 10-00-CD-0002 UBC Seismic Drift Limits; Doc No: 10-00-CD-0003 Diaphragm Flexibility; Doc No: 10-00-CD-0004 Pile Design; Doc No: 10-00-CD-0005 (Coming next week) Comments/ Observations regarding modelling in Etabs: Doc No: 10-00-CD-0006 There are other phenomenal articles written by other contributors (mainly @Rana). Please do check them out as well.
    • By BAZ
      *Comments/Observations regarding modelling in ETABS*
      *Doc No: 10-00-CD-0006*
      *Date: May 06, 2017*
      Some of the observations made during extraction of results from ETABS (v 9.7.4), for design of reinforced concrete members, are being share in this article.,
      1) Minimum Eccentricity
      ETABS always considers the minimum eccentricity for selecting the design moment of columns irrespective of the probable behavior of the column, whether short or long column. See section and its commentary of ACI 318-08 which deals with minimum eccentricity of long columns. You should always check the design moments that ETABS uses for columns if you want to bring down the cost of construction.
      2) Unbraced/ Braced Preference
      ETABS always performs analysis of frame as if it is un-braced. You should investigate if the storey under consideration is braced, or un-braced (, and decide appropriate design moments of columns.
      3) Time Period
      ETABS has a tendency to select a time period of the building that is considerably less than the value obtained by the approximate method, Method A, of the section 1630.2.2  of UBC 97. To quote the FEMA 451 document: ''Because this formula is based on lower bound regression analysis of measured building response in California, it will generally result in periods that are lower (hence, more conservative for use in predicting base shear) than those computed from a more rigorous mathematical model". So, there is no need to use the value of time period that is lot less than Ta. One should always check the time period used by the software; ETABS can overestimate the seismic force by more than 2 times.
      Method A gives lower T and higher V, so FEMA 451 has advised not to use the value of time period less than this value even if rigorous analysis gives a lower value.
      I have seen the results where Etabs have use the value of time period less than Ta; in-fact as low as 0.5Ta, which can increase the base shear two times. (For a complete discussion on time period, please see the following this thread that complements this section).
      4) Stiffness Modifiers
      First thing is related to modelling the bending stiffness of flexural members, for strength level loads, that is representative of their condition near failure. The ACI code specifies the modifier of 0.35 on gross moment of inertia to represent its condition at yielding. 
      Some people say that the factor should be multiplied by 2 to represent the stiffness of T-beam. This approach would be justified if you are not taking into the account the out of plan bending stiffness of slab.
      But, ETABS does include the out of plane bending stiffness if you have modelled the slab by using shell elements. So, a factor of 0.7 would overestimate the stiffness of your structure in this case, and will lead to under-design.
      If one has used the modifier of 0.35 in ETABS for beams in beam-slab floor system, then what value should be adopted for slab? It should not be 0.25, as this value has been specified for flat plates and flat sab floor system.
      If one is using some value of modifier for out of plane bending stiffness on shells, then the share of the bending moment in beams will be reduced accordingly. This approach is correct if one will be providing the reinforcement in column strips of slab. But, if you are providing reinforcement in slab in the direction perpendicular to supports only, i.e. beams, as is the general practice in Pakistan, then you are under-estimating the flexural demand in beams.
      Now, there is also a question of factors to be used while deciding the amount of reinforcement required in beams, columns and shear walls.
      If you are using factors 0.35 for beams and shear walls, and 0.7 for columns, then you are finding out the demand in members at the point of yielding, and this conforms to the code. But, this also means that the structure might experience unacceptable cracks widths. So, if you are using 0.35 for calculating the demand at strength-level forces, then you should also perform crack-control-check at service-level loads by using the factor of 1.
      If you are calculating the strength-level demand with a modifier of 1 for all structural members, after you have decided the location and the number of shear walls with modifier of 0.35, then you are overestimating seismic forces, as you are underestimating the time-period. But, the structural performance will improve.
      This article is based on my two separate posts regarding the subject matter. You can view the discussion on the items raised above by viewing the following links:
      1) http://www.sepakistan.com/topic/2008-issues-in-etabs-results/
      2) http://www.sepakistan.com/topic/2290-modelling-issuesconsideration-in-etabs/
    • By Hira Malik
      Does anyone have the soft version of Muni Budhu? If not then any other book which describes the pile foundation topic in such detail as in Muni Budhu.
    • By Sohaib Iqbal
      please give me suggestions for the designing of this project. ie pile foundation and type of slab. bearing capacity is too low 1.04 tsf. we are discusing abt providing pile fondation and for slab , post tensioning or waffle slab. is it safe for 44ft by 46ft span?
      i have uploaded the plan.  G+5 stories.
      ground floor plan.pdf
    • By saleem khan
      i am using csi safev12 for modeling piled raft foundation.i draw raft and piles but i am unable to assign springs along the length of piles in csi safe.line springs can be assigned to beam element but i did not find to assign line springs to column i-e piles below raft.
    • By waqar saleem
      Do modelling piles in CSI SAFE as springs is right practice or do we have to model actual piles.which one is better?
      any other easily available software for pile design?
      what are the critical points for pile design if one is doing peer review?
      how the pile cap behave?means how it transfer load to the group of piles.
    • By BAZ
      *SEFP Consistent Design*
      *Diaphragm Flexibility*
      *Doc No: 10-00-CD-0004*
      *Date: August 07, 2014*

      I am writing this article about a very important, but mostly neglected topic of flexibility of diaphragm. I used to assume that all reinforced concrete slabs can be treated as rigid diaphragms. But as it turns out, only the slab with span-to-depth (depth is length of slab in direction of lateral loads) ratio of less than 3 and without horizontal irregularity can be treated as rigid diaphragm. The more important thing is that the span-to-depth ratio and horizontal irregularity is not the only criteria and one other factor also needs to be kept in mind before assigning rigid diaphragm to concrete slabs in numerical model of building.

      Another important concept that I learned, and it was a moment of epiphany for me, is about TRANSFER diaphragms. I had posted a topic “Amplification Of Forces In Etabs” earlier in this forum but we were not able to reach at a satisfactory conclusion. Now, I have the answer to that query: Back Stay effect. Another article is required to explain it , and this concept is not discussed in this article. This article is about flexibility of diaphragm.

      Diaphragms are horizontal members of the lateral-force resisting system of building structures. Their function is to distribute inertial forces, generated at its own level, as well as other levels, to vertical members of lateral-force resisting system.

      One kind of diaphragm only distributes inertial forces generated at its own level. This kind of behaviour is observed in buildings where there is a continuity of vertical members of lateral-force resisting system: building should not have a setback or podium at lower levels, or below grade levels. The other kind of diaphragm, known as “Transfer diaphragm”, not only distributes inertial forces generated at its own level, but also re-distributes forces coming from upper levels. This type of behaviour is typical of a building having setback or podium at lower levels, or below grade levels. Transfer slabs can attract huge forces due to a behaviour dubbed as BACKSTAY EFFECT.

      Now, coming to the issue of flexibility of diaphragm. According to ASCE 7-10,

      In addition to considering aspect ratio and horizontal irregularity as a basis for assuming concrete slab as a rigid diaphragm, the relative stiffness of adjoining vertical lateral load resisting system. Buildings with shear walls at ends and flexible frames in between are the ones where the assumption of rigid diaphragm leads to underestimation of drifts and erroneous distribution of base shear in vertical as well as horizontal direction (1)(2)(3); shear forces in middle frames can be reduced to 23% if rigid diaphragm is assigned in the model (1) for buildings with this type of structural configuration.

      M. Moeini et al. (2008) (3) conducted a parametric study using numerical analysis and proposed formulae that predicts the error associated with assuming concrete slab as rigid diaphragm. They also concluded that for buildings, without shear walls, rigid diaphragm assumption is suitable for irregular buildings as well. But, for long and narrow buildings with shear walls at ends, the assumption of rigid diaphragm is not suitable.

      The objective of writing this article was to warn engineers about the tendency of blindly assigning rigid diaphragm to concrete slab in any type of building configuration. The result could be underestimation of forces as well as drifts.
      Nakashima, M., Huang, T., Lu, L-W. “ Effect of Diaphragm Flexibility on Seismic Response of Building Structures”, In proceedings of 8th world conference on earthquake engineering. San Luis Obispo, MSc Thesis , “ An Investigation of influence of diaphragm flexibility on building design through comparison of forced vibration testing and computational analysis”, 2010. M. Moeini, B. Rafzey, W.P. Howsen, “Investigation into the floor diaphragm flexibility in rectangular reinforced concrete buildings and error formulae”, In proceedings of 14th world conference on earthquake engineering.
      The article is not finalized and would be completed in coming weeks.
  • Recent Discussions

  • Latest Forum and Club Posts

    • @ali7988 hameed.. I think you want to apply partition wall load on floor slab, for this purpose you can simply draw a null/negligible frame element and apply load over it.
    • Sorry, I m not sure what you meant. You don't need to include a member in the model just to add its load. You need to model only those members that are essential for completing the load path (structural members).
    • Looking at the figure, one cannot figure out the complete load path for a particular loading scenario. So, it is not possible to give a specific advice. But, the way these pipes are connected, there be moment due to the eccentricity of connections in addition to axial forces. In addition to axial and flexural stress, shear stresses can also dictate the thickness required for the pipe, if the load path includes these forces.
    • Assalamualaikum,  Im designing a connection a pipe to pipe, between this pipe i have to add a plate to connect the pipe with welds. How can i determine the thickness of the pipe? Do i just design it based on tension load on the pipe? Cause my senior said that theres an eccentricity and i have to design it to resist such loads, but im not sure. Heres the figure of the drawing. Regards Groszni
    • do you calculate the dimension of the stiffner as a tension member by using these load-> required load for stiffener = force load by beam flage - column web resistance ?
    • Please see these topics: http://www.eng-tips.com/viewthread.cfm?qid=347923 http://www.eng-tips.com/viewthread.cfm?qid=1734 Thanks.
    • W/s Imran, It is very hard to say if your FYP would help you in securing a job but one thing that is for sure, is that you will get skills like assessing an existing structure, doing base isolation and information about seismic codes and the response of a building to a seismic event - such skills would help you wherever you go. I am not aware of use of base isolators in Pakistan, there might be sensitive military installations where these are being used but I don't know if the market is really big for that and there is immediate need for people having that experience. But like I said above, you will get a skillset that any structural firm in Pakistan would value provided you do your project correct and develop understanding of what you are doing. Thanks.    
    • Can I model the load of partion load(brick wall load) by modeling a beam with very small dimensions such as 1 cm * cm
    • @UmarMakhzumi.. @Ayesha...Thank You for your concern. Yes we r on the same page . However my interest was only to highlight the fact that pile cap design is not like slab, due to pile spacing criteria and typical patterns, it will behave like a deep beam in almost every structure. However i feel there is no proper technical inputs on this component of structure and engineers follows whatever practices are in their offices. In this regard i would like to add little knowledge as per my experience , that unlike the normal slab, the critical sections for maximum FORCES will also be changed , it needs 5 to 6 special investigation as per the reference handbook mentioned in commentary of ACI.  Regards  
    • @ZOHAIB SATTAR NAGRA..  Applying temperature to vertical elements (Wall) will hardly effect your design, this is my observation.      "It is pertinent to mention that biggest trouble for frames/walls will arise due to the application of temperature loading on slab area".  

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