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  • Our picks

    • *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
    • 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.

      Thanks

       

       
      • 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. 

       

      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
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  • Similar Content

    • By Omar Khalid
      Hello,
      While I was modeling a 20 story building with symmetrical concrete slab sections and loads in each story, I noticed that the deflection of the slab increases the more I go higher in elevations despite having the same sections, dimensions and loads.

      I know that floors with symmetrical shapes and loads must endure the same stresses so it has the same reinforcement.

      Can someone explain this behavior or explains why it occurs if I was wrong ?

      Thanks in advance 
    • By waqar saleem
      1-how to calculate deflection for a t-beam?
      2-will it be different from the rectangular beam?
      3-will concrete strength effect the deflection?
    • By Waqas Haider
      Assalam o alaikum,
      For assuring deflection check of flexural members, we compare immediate deflection due to live load with L/180 or L/360. Also we compare total deflection (sum of immediate deflection due live load and long term deflection due to "dead +sustained loads") with L/240 or L/480.
      These deflections are calculated using corresponding effective moment of inertia "Ie" using equation 9-8 of section 9.5.2.3.
      To find out immediate deflection due to dead load we find out it using Ie calculated using cracking moment due to dead loads.
      To find out immediate deflection due to sustained loads we find out it using cracking moment due to sustained loads.
      To find out immediate deflection due to D+L  we find out it using cracking moment due to dead + live loads.
      But to find out immediate deflection due to live load, we don't find it using cracking moment due to live load. We find out it by the difference of deflection due to dead + live load with the deflection due to dead load only.
      as shown by following results of manual calculations (Results from example 10.1 of PCA notes of ACI 318)
      Del.dead = 0.098 in      (calculated using Ma due to dead load only and corresponding Ie came out to be 10648 in4 = i.e. Ig because Ma is less than cracking moment)
      Del.live = 0.0744 (calculated using Ma due to live only and corresponding  Ie came out to be 10648 in4 = i.e. Ig because Ma is less than cracking moment)
      Del.(dead+live) = 0.344 in (calculated using Ma due to dead+live combo and corresponding  Ie came out to be 5345 in4 < Ig because Ma is greater than cracking moment)
      Note that 0.344 is not the simple sum of 0.098(Del.dead) + 0.0744 (Del.live) because here for Del.live, Ie used was based on live only i.e. Ig =10648 in4; for Del.dead, Ie used was based on dead load only i.e. Ig = 10648 in4; and for Del.(dead+live) Ie used was based on (dead+live) load combo i.e. 5345 in4.
      All three "Ie" are different".
       
      My question is, how to cater this in etabs modeling because in etabs it simply super impose deflections due to dead and live for D+L combo which must not be the case. More over, does modifier 0.35 is enough to cater effect of effective moment of inertia?
      Thanks.
       
       
       
       
       
    • By Hira Malik
      While checking the allowable deflection in member in ETABS, which deflection is to be considered, absolute or relative? Which one represents the actual deflection of the member?
    • By Ahmad Shabaneh
      I work in a project with large spans (9.2m X 8m) and large service loads (4kn/m^2 SDL+Partitions), (7.5kn/m^2 Live load)
      In modeling the project on ETABS I set the property modifiers for slab (thin shell as 0.25) and this affected the deflection in slabs ( about 5 cm deflection from service loads)
      Hence: Slab thickness is 22 cm and interior beams 50X50 and the owner didn't allowed to increase the thickness
      Any suggestions to solve the problem.  
    • By Nasir Malhi
      Do etabs or sap has allowable deflection checks for beams if it is analysed and designed through these softwares.
    • By Omer Anwaar
      This particular slab (19x18 ft) is expereincing too much displacement, giving rise to very close spacing in slab panel in the middle strip. It has three interior beams placed to carry line load of the walls above. How can this displacement be reduced?
      Slab 19x18.bmp
    • By danny740
      Hi,

      I have a problem with  a simply supported deep beam which has a uniformly distributed load. The beam is simply supported at both ends but I have to consider the results for the following 3 scenarios
      - where the support is at the bottom of each end of the beam
      - where the support is at the mid point at each end of the beam
      - where support is at top of each end of the beam

      I have run this using FEA and I'm finding significantly different deflections and stresses when the beam is supported at the midpoint at its end and the other two scenarios...can anyone explain the exact reasoning for this?

      Sincere thanks
       
      Daniel
  • 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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