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  1. 4 points

    Pile Design

    *SEFP Consistent Design**Pile Design**Doc No: 10-00-CD-0005**Date: Nov 21, 2017* 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. Before I get into the nitty and gritty of pile design, it is important to highlight that as a structural engineer working on pile design, there are a number of parameters that you would require from the geotechnical engineer. Generally, these parameters are provided in the project geotechnical report. Based on those parameters, the geotechnical design of piles is performed first followed by structural design of pile. The next section talks about the geotechnical design of piles. 2. Geotechnical Design of Piles. Geotechnical design of pile means sizing of pile. This includes determining the following two geometric properties of piles: 1) Diameter or radius 2) Length Straight shaft piles embeded in soil derive their capacity from two sources. The first one is the skin friction along the pile length and the second one is the end bearing. In order to complete the geotechnical design of piles or in simple words to "size up the piles", you will need skin friction values for different soil strata through which the pile would penetrate or lie and the bearing capacity of the layer in which pile would terminate. This information is provided by the geotechnical engineer in the project geotechnical report. Generally, they would provide a table showing skin friction values of each soil layer for both tensile and compressive loads along with end bearing values of each layer. In addition to this, for areas susceptible to frost loading, the geotechnical engineer would also provide ad-freeze and frost heave forces. You can't design a pile without knowing what these values are. So this is something that you need from a geotechnical engineer. Once you have received the project geotechnical report with all the required information, you need to start sizing the piles. The easiest way to do it is to create an excel sheet and do preliminary calculations for different standard diameters like 200mm, 324 mm, 406mm, 460mm, 508mm, 610mm, 762mm and 914mm. The geotechnical report shall also provide recommendations if certain top soil layers need to be ignored or not. Example Problem: From your structural analysis, the maximum factored compressive load is 100 kN. and maximum factored tensile load is 50 kN. You need to size a pile (do geotechnical design) to meet that applied load. Sizing piles for geotechnical capacities is simple. Here is the formula for capacity of pile based on skin friction only (ignoring end bearing for simplicity): ULS Geotechnical Pile Axial Capacity: Pi * Pile Diameter * Total Embedment Length of Pile * Skin Friction Value * Resistance Factor Where, Pi= 3.14 Pile Diameter = 2* Radius Total Embedment Length of Pile = Pile Embedment Length - Frost Depth Skin Friction Values = See geotechnical for values Resistance Factor = 0.4 for compression and 0.3 for tension. For, the above problems, lets assume Skin Friction values of 80 kPa for both tension and compression and initial pile size (diameter) of 324 mm, Frost Depth of 3000 mm. For total length of 10m (lets assume a starting length), Total Embedment Length of Pile = 10m - 3m = 7m (Total Length - Frost Depth) ULS Geotechnical Pile Compressive Capacity= 3.14 * (0.324m) * 7m * 80 kPa * 0.4 = 228 kN > 100 kN Okay. ULS Geotechnical Pile Tensile Capacity = 3.14 * (0.324m) * 7m * 80 kPa * 0.3 = 171 kN > 50 kN Okay. The above problem shows you how to calculate the compressive and tensile capacities (also called the axial capacities) of the pile. For lateral capacity, you will need to know the modulus of sub grade information from the geotechnical engineer and use a software like LPILE to see the response against the lateral load. It is important to note that lateral deflection of pile is a service limit state meaning that it should be checked against unfactored loads. Generally, for petrochemical and oil and gas industries, pile service loads are defined as a deflection limit that will depend upon the maximum allowable movement of pile considering an elastic response from soil as well as the maximum movement piping and its attachments can take. Here is a scenario explaining that. For example, your geotechnical engineer recommends a maximum lateral movement of pile to be limited to 6mm so that soil around pile stays elastic. The structure you are designing, has a wind load deflection of 12mm. The pipes and equipment plus their connections shall be designed for 6mm+12mm = 18mm movement of structure. You need to notify piping of this deflection limit and if they are okay, you are good. If they are not, you will have to stiffen up the structure to lower the overall structure deflection and work with piping to see alternate routing for pipe. For pile design, you need to see what diameter pile shall have a capacity at 6mm lateral deflection greater than the applicable horizontal service load. To calculate pile capacity for different pile head movements, you will need to use LPILE or similar software. LPILE shall provide you a graph that would show you that how much a pile would move under applied lateral load or moment. LPILE is very easy to operate. You can look at the program tutorials and work your way through. It will also provide you the analysis results for a pile embeded in soil with soil modelled as springs along the length. This analysis result is important and allows us to see what is the maximum moment and shear developed in pile due to applicable load and based on combined response of soil and pile interaction. If you don't have LPILE, you can ask the geotechnical engineer, to provide you with pile lateral capacity graphs. In this case, you will need to provide the geotechnical engineer with estimated pile sizes, estimated axial and lateral loads, pile head condition (Fixed or Pinned) upfront. The goetech engineer will run the LPILE for you and provide you the graphs that will show the maximum load a pile can take against different lateral displacement values and would also provide the maximum moment due to max lateral load. I have done this on a number of projects and this is standard industry practice. 3. Structural Design of Piles. After completing the geotechnical design of pile, the structural design of pile needs to be performed. In order to do that, you will need to know the maximum moment in pile due to the application of axial and lateral loads. As mentioned above, the easiest way is to use LPILE output as it provides you with deformed shape of the pile along with the maximum moments and shears due to applied loads - the analysis of pile embedded in soil. Using LPILE analysis results, you can use beam-column capacity formulas to design a steel pile or column interaction diagram to design a concrete pile. Beam-Column capacity formulas vary with different codes so therefore I haven't included any example. For steel piles, corrosion allowance should be considered as per the code requirements. Generally its 1.5mm each exposed face so for pipe piles it will be 3mm considering exterior and interior face of the pile. 4. Connection of Pile with the foundation (Covering both Concrete and Steel) The connection of pile and foundation / pile cap is extremely simple for concrete piles. All you need to do is to develop the bars from concrete pile in concrete foundation/ pile cap. For steel piles, similar concept is there, except for you need to weld rebars on top of cap plate. Hope this article provides the much needed guidance on pile design. It is written for beginners and a lot of things have been kept simple. Your feedback is more than welcome. Please post any questions should you have. 5. Pile Group Settlement Single pile or pile groups should always be check for settlement. Geotechnical consultant shall be contacted to get guidance on what method should be used. Methods like equivalent raft method or finite element analysis can be carried out to get settlement numbers. 6. Things to Consider For pile group, group effects are generally provided by the geotechnical engineer that can be applied to pile group. The group effects are a function of pile diameter and centre to centre spacing. Pile capacities are reduced if they are spaced closely. For straight shaft piles, rule of thumb is to place them greater or equal centre to center distance of to 3 * diameter of pile. For lateral loads, pile capacities are reduced at 3 * diameter spacing and generally piles need to be spaced at 5 * diameter to have no lateral reduction. Also, straight shaft piles if placed too close might result in pile installation issues. Some piles already installed might heave up if other piles are being installed in close proximity. Impact of pile driving to existing structures should also be considered especially if there is sensitive instrumentation installed in close proximity. Thanks.
  2. 3 points
    Experienced Structure Engineer needed in Lahore with minimum 5 years experience. Our main requirements are for the design of tunnels, prestress bridges, steel structures and power houses. Have you ever designed these or are confident you can do all these structures on your own? Salary will be based on your experience. No extra benefits/allowances will be provided, so its better to apply only if you live in Lahore. Engineers with all these capabilities send your CV at hira.malk@mmpkistan.com
  3. 2 points

    Bearing Capacity in Karachi

    It varies from consultant to consultant but my opinion is that the normal design practice has destroyed Pakistan. If you need deep foundation, provide deep foundation.
  4. 2 points
    Hira Malik

    I am jobless (structural Engineer)

    job opportunity available at MM Pakistan Lahore office. kindly send your CV and salary requirements at hira.malik@mmpakistan.com
  5. 2 points
    With connections design you have to be very careful. As you mentioned one end is going to be hinged and other will be roller, Your truss on each side will have a certain width and it wont be resting with one support connection. I mean at each end the truss will have two or three connection points with the beam or corbel. So when you say hinged it be virtually not hinged and will become a kind of fix connection as the number of anchor bolts on each point will be bore than two. So check your building movements in worst cases, like seismic and wind etc and design the slotted hole connections by giving appropriate movement at the joint. For the roller connection you will use the rubber pads any type but you must make vertical pins through sleeves on corbel beam or any connection through your bridge to restrict the dislocation of your truss form the pad. Normally the rubber pads come with these pins and slotted holes are provided in the truss base plates which help them to restrict movements. See Granor Rubber Pad bearings for bridges. I have attached two examples of what I have said above. I hope they make any sense to you. Bridge Connection.pdf
  6. 2 points

    Cold Formed Steel Design

    Both are the same. For more details, check this Link. Regards.
  7. 2 points
    Yes, more bars less dia is better. Also check what is commercialy viable. There is commercial as well as health & safety aspect to it as well. For example using less bars of dia 40 reduce congestion and easy handling and placing but is it safe for workers to carry such huge bar? Accidents?
  8. 2 points

    design Floor Slab in Grade

    1. First of all, you need to understand how to design the slab on grade (SOG) through hand calculations. Later on, you may develop a spreadsheet or use some patent software to do it using a computer. 2. The references given above provide design methods (pca, WRI, COE etc), dealing with different types of SOG (e.g., unreinforced, reinforced concrete, post-tensioned etc.) subjected to various types of loads (uniform, line, wheel & post loads). 3. Before starting the design, you will need to go through the reference available with you (i.e., ACI 360), and a. Select the SOG type from the Section 7 onwards, applicable to your case. b. Study the design requirements from the relevant section c. Determine the type and intensity of various loads, the slab will be subjected to during service. d. Solve the relevant design examples, given in the appendices of ACI 360 to understand various design parameters, charts, equations & their application to the design. e. Using the design prameters applicable to your slab, design the SOG by following the procedure adopted in the reference design example. HTH Regards.
  9. 1 point
    Please see these topics: http://www.eng-tips.com/viewthread.cfm?qid=347923 http://www.eng-tips.com/viewthread.cfm?qid=1734 Thanks.
  10. 1 point

    Pile Design

    Dear Engr @UmarMakhzumi I just want to add something in it, I feel in this quote you wrote”MORE than require by code “by mistake, in simple words when the distance between supporting reactions is less than the twice depth of the member. I would like to add the ACI and AASHTO references in this regard. Thank You
  11. 1 point
    temperature load can be assigned to the members that affected with the temperature variation only (like exterior members)
  12. 1 point

    Pile Design

    @UmarMakhzumi. Dear Engr i would to disagree regarding your statement of design of Pile cap as a typical Slab. Normally pile cap behaves like a Deep Beam action, normal bending/flexural theory is not applicable to Pile Cap design. ACI and AASHTO recommends to use STRUT n Tie model for Pile Cap. However for ease of analysis and design, due to absence of expertise on STM, structural engineers design it the other way. The behaviour of Pile cap supported on Pile follows Bolt Analogy. Furthermore, for modelling in FEM softwares, In Usual analysis of raft slab, you put soil springs under the raft, however for pile cap we ignore effect of soil and pile cap is supported only on piles. Thank You
  13. 1 point

    Multi Tower Seismic Analysis

    You need to provide expansion joint at podium near to all three tower and analyze them separately. Because each tower has different time period Based on there geometry and loading so the lateral forces will be different
  14. 1 point

    Multi Tower Seismic Analysis

    For accidental torsion, podium would share a common diaphragm so you need to consider it as one but levels above podium where buildings are isolated, you should consider individual buildings and individual drift limits. You can search the forum. There is an ETABS manual posted sometime earlier on high rise buildings design. You can let ETABS do it for you. There is a tutorial available about it as well. See first tutorial here: https://www.csiamerica.com/products/etabs/watch-and-learn Thanks.
  15. 1 point
    I will develop the list of consulting engineers firm
  16. 1 point


    plaxis 2D can be used but it it is very costly
  17. 1 point

    point load on slab in Etabs

    Create a point on the desired location (using manual meshing, or dummy beams etc) and apply the point load as a vertical force on that point. Regards.
  18. 1 point
    While performing stability analysis of dams, we have a "shear friction factor" for which we need cohesion value of the material. I am confused that whether i should use cohesion value of concrete or the rock foundation? What is the cohesion value of 3000 psi concrete and how to calculate it? In the book of santosh kumar garg, he has used the shear strength of joint instead of cohesion. Why is that? Because many other books use cohesion in the formula.
  19. 1 point
    That is the intention
  20. 1 point
    yes, in this case most of lateral load carrying by shear wall, so your beam column have lesser lateral forces, thats why the reinforcement has decreased in these members
  21. 1 point

    Negative Stiffness Eigenvalues

    Additional suggestions which may resolve negative-stiffness errors include: Remove auto line constraints. Select all deck/shell objects in the model, then select Assign > Shell Elements > Auto Line Constraint and uncheck the Apply to Full Structure option. This will remove auto line constraints and possibly resolve instabilities. Dear Umar, The above suggestion works! thank you. However, I would love to understand the engineering behind it. How line constraint is affecting the stability of the floors in P-Delta analysis when the slab stiffness modifier is reduced from 1.0 to 0.5 for instance? Do you have some sort of technical explanation to that? Best regards, Wael
  22. 1 point
    Dear All: [1] Please note that Structural Designers in Pakistan are still using DEFUNCT UBC-97. I am a one person team trying to change this practice. [2] In addition, by using ETABS, they use UBC-97 and latest ACI & ASCE CODES, which is incorrect.
  23. 1 point
    FPSC has advertised BPS-17 jobs for Civil, Electrical & Mechanical Engineers as well as for Architects & Town Planners in MES (Military Engineer Service) under Ministry of Defence. More than 40 vacancies have been advertised for each of these categories. Spread this information among your colleagues for all those interested in these job. Last date for applying is 18-12-2017. See the following link for detailed advertisement. http://www.fpsc.gov.pk/icms/user/jobs.php
  24. 1 point

    I am jobless (structural Engineer)

    Thanks for the prompt reply . Actually I was thinking about doing it over Skype but if you think that I should get in touch with one of the guys you mentioned then I will contact them first thank you for your time Asalam O Alaikum
  25. 1 point
    @waqar saleem, @EngrUzair, @BAZ might be a good resources to start. I don't live in Pakistan so can't do anything directly but please touch base with these three and then lets see where it goes from there.
  26. 1 point

    I am jobless (structural Engineer)

    do you have any experience with steel structure design ?
  27. 1 point
    Dear miqureshi77, Are you flexible on work location or would you prefer working in Karachi only? Thanks.
  28. 1 point
    http://www.sepakistan.com/applications/core/interface/file/attachment.php?id=65 pile design link
  29. 1 point
    See this topic. http://www.sepakistan.com/topic/2303-shear-wall-design/
  30. 1 point

    Being an Engineer

    Practicing engineering helps us put food on table.. being an engineer is what will make us wealthy! Being an engineer means being smart in every aspect of life.. Might be little narcissistic but I wanted to share my recent run on stocks! Enjoy and good luck to y’all as well!
  31. 1 point
    You don't need a ledge beam when you can use a truss. I think ledge beam is redundant. Neoprene pad is good on the roller side. If you can share some sketches, I would happily comment on them. Thanks.
  32. 1 point
    Buckling load is calculated in accordance with Section 6.3 of Eurocode 3 (EN 1993-1-1) that includes relevant formulas as well as buckling curves. This information is generally available in Eurocode 3 based Steel Design books in the chapters dealing with compression members. One such book is, "Structural Steelwork Design to Limit State Theory, 4th edition, by Dennis Lam et al." Regards.
  33. 1 point

    moment of inertia in shear walls

    In this connection, you might like to have a look on this link that contains a very useful discussion on use of cracked sections in the stiffness analysis of reinforced concrete members. Regards.
  34. 1 point

    RC Embedded Columns

    Yes. In both cases, you should include the said column in your model. It will make your structural framing more stable, due to availability of an additional vertical support for the superstructure. Regards.
  35. 1 point

    RC Embedded Columns

    model the column
  36. 1 point

    Column Design In Etabs

    Eccentricity can be due to construction activities. There is always construction tolerance that needs to be considered in design. Thanks.
  37. 1 point

    Bearing Capacity

    Known or unknow?
  38. 1 point

    design Floor Slab in Grade

    You could also use concrete society report no. 34 for plastic design of industry ground slabs.
  39. 1 point
    Good point again. In such cases, you have to deal with the notorious huge nerve sapping temperature forces.
  40. 1 point
    For the calculation of kl/r ratio
  41. 1 point
    1) Go to Modify/Show grid >>On Top Right Corner go to reference Points >> Select then Delete . 2) First method shown in this PDF is available in Etabs, Both metgos are available in SAP 2000 Non Uniform Load.pdf
  42. 1 point
    1- Place shear walls opposite to each other, let's say you put a wall at the far right of a building, put another one with the same length and thickness at the far left one, .. etc that is to ensure the center of rigidity ( governed by walls mostly) coincides with the center of mass of the building to eliminate torsional movement of the building. 2- The far the wall is placed from the center of the building the better, as walls near the center doesn't resist much shear force as walls at the outer perimeter and the latter is good to prevent torsional movement. 3- The following is copied directly from the ACI design hand book: '' Shear walls should be located within a building plan to efficiently resist lateral loading. Locating shear walls in the center half of each building is generally a good location for resisting lateral forces. This arrangement, however, can restrict architectural use of space. Although shear walls are commonly located at the ends of a building, such wall locations will increase slab restraint and shrinkage stresses, especially in long buildings and buildings such as parking structures that are exposed to large temperature changes. Symmetrical wall arrangements provide good flexural and torsional stiffness. Walls at the perimeter resist torsional forces most effectively. Walls away from the perimeter, however, could have a higher tributary area and, consequently, larger gravity axial force to resist uplift or overturning. They are, however, less efficient in resisting horizontal torsion An unsymmetrical arrangement, however, does not usually provide predictable torsional stiffness due to their eccentricity. Such a shear wall layout should be designed explicitly for torsion. A symmetrical arrangement is preferable to avoid designing walls for torsion.''
  43. 1 point

    Bearing Capacity

    I have not seen such a limit written anywhere. However, the lowest value of bearing capacity (BC) for the building sites I have come across during my professional practice, was mostly 0.5 tons per square foot (TSF). In only one case, the reported BC was 0.25 TSF. However, the client was advised to change the site, as such a low BC indicates a very weak soil, ordinarily requiring a very heavy & expensive footing design. As such, IMO 0.5 TSF may be considered a reasonable lower limit of BC for a building site. Regards.
  44. 1 point

    design Floor Slab in Grade

    You may use following sources for designing floor slabs resting on ground:- a. Designing Floor Slabs on Grade by Ringo & Anderson, 1996 ( Link ) b. ACI 360R-10 Guide to Design of Slabs-on-Ground Regards.
  45. 1 point


    2d analysis is never recommended with walls above. https://wiki.csiamerica.com/m/view-rendered-page.action?spaceKey=safe&title=Modeling+uplift+and+foundations+on+soil+supports
  46. 1 point
    Ahsan Kazmi


    @Rana i want to understand how it matters?
  47. 1 point
    Hey My name is Omar I'm Jordanian and Palestinian and currently a civil engineering student at Jordan University of Science & Technology in my last semester. I've found this forum while searching for people to help me and I hope I can contribute to this community too Greetings
  48. 1 point

    Footing/ Foundation Jacketing

    Hi Faisal, Please see my comments on your sketch below. I would suggest to add more shear reinforcement (at least 2 layers, one looks flimsy) between existing foundation and the jacket. Obviously, it would be based on your calculations to transfer punching shear, one way shear and moment. Also, I would suggest to add shear connectors/ dowels/ nelson studs to all vertical faces of the foundation and provide continuous reinforcement as shown connecting periphery jacket beams and new pour. Also, if you are excavating around existing foundations, please give some thought to that so that the excavation doesn't undermine adjacent foundation. Hope that helps. Cheers!
  49. 1 point
    Signup with IStructE and start your road toward chartership.
  50. 1 point
    NO Need To Answer. I Understood It Is The Most COMPLETE Program I have ever saw
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