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

    Welcome!

    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.

waqar saleem

Foundation Design Floodlight Pole

Recommended Posts

Salam

Dear Sefpians!!

I have to design a foundation for a 15m high floodlight pole, dia of the pole is 10 inches, pole is welded with the baseplate (provided by manufacturer), how the forces will be transferred to anchors. what forces will be on anchors. how forces will be transferred from anchors to foundation. anchors will be embedded in-situ concrete.

Regards

Share this post


Link to post
Share on other sites

Hello Waqar,

Do you have the baseplate size from vendor. If yes, what is the bolt pattern (Bolt holes and distance). Also, did the vendor give you design loads for anchor bolts? If yes, great. If you don't have anchor bolt loads, you need to manually calculate wind on the floodlights and pole and the reaction at the base and design anchor bolts and foundation accordingly.

If you have the bolt pattern, I can show you how to resolve the forces to anchor bolts and other things that you should keep in mind. For foundation, a square foundation with a concrete pedestal would do the job.

Thanks.

 

Share this post


Link to post
Share on other sites

Thanks Sir umar

pole has 10 inches dia and base plate is 15in x 15in, with four anchors option on four sides. no loads for anchors are provided by manufacturer, an approx weight of pole is given 350Kgs mounted with 2x lights panels weight 80Kgs . wind speed 100mph for islamabad area. i am not clear if wind will be applied on one side of the pole (half area) or suction may also be applied.

Regards

Share this post


Link to post
Share on other sites

So it's no very heavy. Applying 100mph, what is the factored shear and moment that you get at the base of the pole (Use the exposed area of lights and pole to calculate that). I would also like to know the center to center distance of proposed bolts as well.

Thanks.

Share this post


Link to post
Share on other sites

You should use the load combination with wind loads. I don't know what the latest is for ACI so make sure your factors reflect wind not live load.

Assuming we go with 4 bolts as proposed at 12" c/c, You need to design your anchor bolts for tension : T = 40 kip ft / ( 1 ft * 2 bolts) = 20 kips per bolt on tension side. I have used 2 bolts as the other two bolts would be in compression.

Shear per bolt would be (assuming 2 bolts take shear) = 1.76/ 2 = Almost 1 kips per bolt.

Now with these forces, you need to size your bolt based on ACI Appendix D. Start with a 1" bolt. Have you used Appendix D before? If yes, great. If no, give it a try for a day and if you can't figure out let me know.

Thanks.

Share this post


Link to post
Share on other sites
5 hours ago, UmarMakhzumi said:

Shear per bolt would be (assuming 2 bolts take shear) = 1.76/ 2 = Almost 1 kips per bolt.

Why r u asumimg only two bolts effective in shear? R u assuming bolts in tension would not be effective in shear or what? 

Also why earth quack load is not being used to calculated base forces?

@waqar saleem as umer said your bolts will not only be designed for tension only but also for some failure moods associated with bolts i.e. breakout failure, pryout failure etc. so appendix D of ACI deals with it. 

Share this post


Link to post
Share on other sites
3 hours ago, Engr Waqas said:

Why r u asumimg only two bolts effective in shear? R u assuming bolts in tension would not be effective in shear or what?

Most of the time, base plate holes are oversized for easier installation. That makes it hard to determine how many bolts would be effective in shear so that is why 50% of the bolts are ignored. The one in tension are considered to take shear. For the case here, shear is very small and can also be ignored.

3 hours ago, Engr Waqas said:

Also why earth quack load is not being used to calculated base forces?

Earthquake load can be checked and the max of earthquake or wind should be considered for all design situations. However, looking at the weight here, you can tell that earthquake would not govern.

Thanks.

Share this post


Link to post
Share on other sites

In calculating design forces, have you considered the application of point load on a panel, which will support lights, at the top of the pole, in addition to the UDL on the pole itself.

Is it possible that only two bolts will be effective in resisting moment for a wind direction in which two bolts will lie on the neutral axis, and the moment arm will be sqrt(2) x 12.

Share this post


Link to post
Share on other sites
4 hours ago, BAZ said:

In calculating design forces, have you considered the application of point load on a panel, which will support lights, at the top of the pole, in addition to the UDL on the pole itself.

Is it possible that only two bolts will be effective in resisting moment for a wind direction in which two bolts will lie on the neutral axis, and the moment arm will be sqrt(2) x 12.

This is a very good point and would result in higher tension. This is a very likely limit state.

Thanks.

Share this post


Link to post
Share on other sites

Eq will likely not govern, as a rough value 1kpax1.6 is the wind load. You get mu=wl2/2 and vu=1.6kn. T=C on each side will be mu/arm between bolts. For each bolt tension will be T/2 and shear will be Vu/2 (only 2 bolts resist shear). Remember there will be tension shear interaction for bolt design plus use Appendix D of ACI. This is a simple example. For complex base plate patterns use RisaBase software for biaxial design or make a model with assumption that base plate is stiff (use very thick shell) and frame elements as bolts. Or use the formula to calculate tension compression on bolts from applied moment and P which depends on distance of bolt from centroid divided by group x2 or y2. See any foundation book.

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.

      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
  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Vamshi
      DEAR SIR,
      can you please tell me,
      Why foundation is designed for STATIC LOAD CASES only.
      Why not we design foundation for RESPONSE SPECTRUM CASES.
      In our office  for G+24 also we design foundation only  for STATIC LOAD CASES,  is it wrong if we do foundation for static load cases
    • By Shamim Ahmmed
      Salam to all,
      Is there any rules to depth of foundation(Df)
      Say, I need MAT foundation on SBC=1.43 ksf.
      what would be the depth of Mat Foundation (Df) from Existing Ground Level.
    • By Muti Ur Rehman
      Assalamu Aalikum,
      Hi, I am a new member. I have a plot measuring 30*70 feet. Most of houses being built here (in Rawalpindi) have masonry foundations (a pyramid of bricks on PCC or sometimes the PCC layer has three to four iron rods of size 3/8 or 4/8  in this "PCC" layer. I want to make a raft foundation instead of masonry foundation but the cost seems to be high. I want to ask if I make a raft  1 feet thick and put a single mesh of center to center distance  12 inch. Even this will cost more but if it gives more strength then I want to  go for this. Would such foundation more durable and strong?
    • By Fatima Al Zahraa Olleik
      Dear fellow engineers,
      In a refugee camp reconstruction, we have the following dilemma:
      First, we have an existing retaining wall, height up to 4.5 meters, thickness ranging from 0.25 to 0.4 m. On the back of the wall we have existing an layer of cyclopean concrete :height up to 4.5, width 3m, and length along the wall.
      A 5 story building is to be built over the cyclopean concrete. This means that the Raft of the building (0.5m thick) will lie directly above the existing wall.
      The question is, what is the calculation required to ensure that this wall will withstand the loads of the raft?
       
       
    • By muneeb1213
      For calculating the bearing capacity of soil (using N values), the equations for mat foundation and single footings is the same or its separate for each??
    • By muneeb1213
      I m designing a 4 storey building on a poorly graded sand with SPN value of 5 and allowable bearing capacity of 0.5 tonn/sq.ft..... for the mat foundation, i provided beams of 18 x 36 and mat thickness as 24 inches ... however the soil pressure are still above safe bearing capacity.. My question is should i assign line spring property to the footing beams or not???
      The area of footing is also increased but the stresses are still high...
    • 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.
      https://sites.google.com/site/engineeringvenice/
       

    • 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.
       
       
      OmegaFactorDiscussion.pdf
    • By waqar saleem
      Salam
      Dr.Amjad Saqib!!! I love this person for his efforts to reduce the poverty with dignity. Founder of Akhuwat Foundation speaks from his heart,wondefully . Listen to his speech at TEDx
       
    • By israr_sari
      How to  import multilevel raft foundation from etabs to safe.
      main designer has designed it as a raft foundation with a bearing capacity of 150 kn/m2 but after the site development and excavation we found a hard strata that can with stand with 250 kn/m2(as per the soil report). as total depth of raft is 1 m that is too much for 5 storey car parking, i want to modify it with 250 raft overall with inverted panels under column. but i am not able to import that multi level foundation reactions as a one file in Safe. because in etabs u can only export one storey . 
      please give your helpful suggestions.

  • 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.