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Waqas Haider

Venice, The floating City

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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.

https://sites.google.com/site/engineeringvenice/

 

canals-venice-italy-acqua-alta-600x400.jpg

Edited by Waqas Haider

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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. 

       

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

      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:

      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
    • 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.

      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

       
      • 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. 

       

      Regards   

       

       
      • 3 replies
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  • Similar Content

    • By Vamshi
      DEAR SIR,
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      Hi All,
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    • By UmarMakhzumi
      *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.
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      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.
       
    • 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 muneeb1213
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    • By muneeb1213
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    • By Waqas Haider
      Assalam o alaikum, 
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      OmegaFactorDiscussion.pdf
  • Recent Discussions

  • Latest Forum and Club Posts

    • Sir's thnakq so much for you reply but are they any structural rectification for this problem . can I give another footing adjacent to the settled column. If so which type of steel structure I can design.
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    • 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?
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