Foundation Pile Cap Design | Structural Engineering

A quick tutorial on the design of a pile cap using beam theory and strut and tie method.
There isn't too much difference in the result but strut and tie has many uses in the design of concrete structures. It can allow you to solve complex problems by breaking it down into smaller problems to solve.
What I haven’t shown is the check for shear or punching shear. This will be an additional check and should be done using either method.
RC beam design tutorial - • Structural Concrete Be...
#strutandtie #foundationdesign #pilecapdesign
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[@ICRPI]

There's nothing like this on KZbin. Thank you for providing such quality information. These quick overviews and pointers to where we can find more info to these common problems in the industry (UK in particular) are unbelievably valuable for Young Engineers. I haven't got much experience as a Stuctural Engineer (2 years) but the few projects I've been apart of, you've saved me a tonne of time and improved my efficiency. Thank you so much.

[@EverydayDazz]

Really appreciate the comment! Glad it’s helped you out and good luck with your career. If you got any questions feel free to get in touch. 🙂

[@michaelyano6094]

Although I use a different codebook, the principles still apply. Your teaching style is excellent, clear and concise. Thank you!

[@dragb6281]

Confinement reinforced bars are needed to confine the compression strut or bursting in concrete is possible . That is quantifiable and presented as confinement bar going a few round at the pile cap circumference .

[@ezabala]

Wow! Solid video. I'm glad I stumbled onto it. I'm subscribing right now.

[@engrahmed7122]

Simply beautiful. Cant praise enough. Thank you so much

[@ponariwilliam]

Thank you for the content. Simple and to the point.

[@lamar2923]

Thank you so much for your videos - very helpful for young graduates starting out in our careers as structural engineers. Could you do some videos on connection design in the future?

[@EverydayDazz]

Yeah it’s on my list to do 👍 thanks for the comment!

[@LKGAMER26]

this is very informative, brillant video. thank you

[@nadjagrbic9651]

Hello :) How can I apply the strut and tie method if my column is under tension, given that I would have a TTT node at the top of the pile cap and a TTC node at the bottom. I guess the formulas for the nodes would be different, but where can I find them for that specific case and what else is important to know if the columm is under tension? Also, is the the shape of the triangle, i.e. the compression and tension lines, the same, or in the case of uplift forces, it is an inverted triangle, i.e. symmetrical in relation to the middle plane of the pile cap? Thanks in advance :) 

[@Er.SenthilGanapathi]

Love from India brother ❤

[@umerbano9145]

Thank you mate

[@user-bt8xj2zw2g]

For a 1 pile group, for a 3 storey block work structure with ground beams (no point loads from columns etc), is it sufficient to have shear links at closer spacings around the pile or is there more to the reinforcement design here?

[@neco0017]

I have 2 rows of 4 piles. Can I still use the same method?

[@yonggaz55]

thank you so much for this video, can i ask a question. where did you get the depth of pilecap?. thank you

[@CarbonTaxLOL]

The standard I am using (AS3600, australia), wants me to design a strut as: phi*beta*0.9*fc*Ac phi and beta are efficiency factors (0.65, 1) the Ac is the "smallest cross-sectional area of the concrete strut at any point along its length and measured normal to the line of action of the strut" How would I calculate this area, if my column was 600x300 (also Diameter of my piles was 600). I assume it is the area of the triangle you drew at 3:47, however this would yield Ac=45000mm2 thus the design strength of the strut would be 547560? seems quite wrong.

[@Joker-oh3lb]

Can't we use finite element analysis to figure out where's tension and where's compression?

[@dipendranathbhowmick6577]

But, I have a question, is it not angle of strut is tan [inv (1300/900)] = 55.3 degree. Accordingly, the calculations may change.... I think it is the angle of strut with the horizontal. Please correct me if I am wrong.

[@LKGAMER26]

please do a punching shear check which need links around,

[@jcz8225]

HOLA, desde Argentina, Me podrias moestrar un ejemplo identico a ese modelo, pero con un proceso inverso?, es decir, teniendo como datos, la cuantia del acero, para poder saber que carga "P" soporta la Viga de gran altura, saludos!!

[@lkj17]

If u do this. Do you still need to do a shear check

[@EverydayDazz]

Yes you should carry out a shear check as well especially if the pile cap is shallow. I would do a beam shear check as well as a punching shear check.

[@lkj17]

@@EverydayDazz make sense, i got reversing loads to check S&T a 20m cantilevered pump LOL little more complex than the gravity column pile cap

[@mottscottison6943]

Question, do you still need to check for shear? I've seen people still check for shear but I personally feel that since all forces has been converted and checked as compressive and tension forces, there are no shear forces. The same reason you don't check shear for truss members. Maybe perimeter punching at the column is still relevant? But again, you have resolved the stresses at the nodes, so why shear check? Kindly advise.

[@EverydayDazz]

Yes you still need to check shear for sure. Shear design in concrete is actually a form of strut and tie.

[@mottscottison6943]

@@EverydayDazz food for thought, like you said, shear is basically a strut and tie. If you were to remove all the other parts of the concrete and left with the triangular truss, where is the shear force? Forces has been resolved through the strut and tie. But i agree better check with the shear method too to be conservative.

[@heavypackbackpacker631]

@@mottscottison6943 I agree - usually designing with STM precludes shear checks for the reasons you stated.

[@georgesmith6399]

Great video! Would I be right in assuming that the only difference for a pile cap with a moment applied, or an eccentric load would be that the reactions from the piles would not be equal?

[@EverydayDazz]

Your tension reinforcement would need to cater for the bending moment as well as the tension due to axial loads.

[@LeviOp27]

Why the area of strut is square area and not triangle or prism? (304x500) Looks wrong to me can anybody explain

[@edg4246]

4:10 - where did you get "0.4" from? Shouldn`t you have "0.57" there?

[@EverydayDazz]

0.6 x fck /1.5. 1.5 is the safety factor for concrete to get fcd. 0.6/1.5 = 0.4

[@cats6184]

​@@EverydayDazz thanks 👍

[@motasemsudani4257]

how did you get the area of the strut ?

[@AO-fg7mo]

First of all, I would like to thank you for the content that your share in KZbin. I got confuse about how you got the width of the strut (500mm/2), where did you get the 500mm from? it was a little bit fast and couldn't get it? Could you please explain this small part? Kind regards and keep it going :)

[@EverydayDazz]

I believe the strut width used was half the column width. Thanks for the comment :)

[@moharirshyamsunder4879]

Can u share sir excel for this? Can we take actual size of pile as our strut size?

[@DJayDNA]

This is amazing. Thank you so much for your videos - highly appreciated and valuable! I wonder how would you design a 1-pile foundation? Is there a certain way? I need to have 1 (and 2) pile foundations in my current project but I realised that there is hardly any information regarding the design of 1-pile foundations.

[@EverydayDazz]

Hey there, you’re welcome! There isn’t much to design for single pile caps and normally single piles are for piled ground beams. In that case the ground beam would be supporting load bearing walls instead of isolated columns. I have done a video on piled ground beams if you’re interested

[@DJayDNA]

@@EverydayDazz thank you for your reply. Is it because the load from the column is assumed to go straight to the pile? But you'd still need to check the foundation for shear, correct? Also, if you'd only have a couple of columns that needs a piled foundation, how would you solve that problem? Do you design a piled ground beam and use the dimensions (HxW) you are given? Apologies for multiple questions but I really haven't been able to find any answers.

[@EverydayDazz]

If a pile is supporting just a single column, then there is little to no shear or bending. The main thing you’d need to design is to make sure the pile cap doesn’t burst under axial loads so you need to design the pile cap for that. But generally, you rarely see just single pile caps on there own as you need to restrain piles in two directions. Similar to that of a column. It’s quite hard to explain with just text 😂

[@kienmaitrung5476]

Hello, I am a 3rd year student currently studying at a university in Vietnam. Thank you for sharing interesting knowledge. Can you give me some documents on how to calculate transfer beams?

[@EverydayDazz]

Same as designing any normal beam except your serviceability criteria needs to be controlled.

[@jeffchia4]

How would you know that the pile cap wouldn't act like a beam in reality (which required more steel reinforcement) instead of struct and tie? Thanks!

[@EverydayDazz]

Hard to answer, mainly because I don’t know the answer! I think due to the fact that the pile cap isn’t very long, it can behave so that strut and tie works. If the distance between the piles was longer than it would be hard to justify using strut and tie and you would want to design it as a normal beam. It is why you can you use strut and tie for deep beams.

[@callanward9344]

Most codes have span to depth guidances

[@CarbonTaxLOL]

what software are you using to draw those lines that automatically straighten?

[@EverydayDazz]

Goodnotes 5 on iPad

[@TheeModerateGamer]

Hi, would this method still apply to a 6 piled pile cap with the centre column acting on the centre of the pile cap? This is such a great video, I was unsure about the strut-and-tie method and unfortunately EC is not the best for explanations, as you probs already know! haha

[@EverydayDazz]

Strut and tie has many applications. And yes it can be used for 6 pile caps

[@TheeModerateGamer]

@@EverydayDazz wow thank you for getting back to me so quickly! Was not expecting that! So with regards to the method, would I create 3 sets of the strut-and-tie system, that is supported by 2 piles. Or 2 sets of the system supported by 3 piles? With regards to the beam method: Would there be 3 identical, single spanning, beams that are modelled? Thank you so much in advance 🙏🏾

[@jasonRhawt]

Is it possible to do your foundation on shallow water into bedrock? Where top surface to water is around 1-2ft?

[@EverydayDazz]

is this to check for water uplift?

[@jasonRhawt]

@@EverydayDazz yeah

[@LvPatriot1]

Hi, can you please do also a Raft foundation design tutorial, thanks in advance.

[@EverydayDazz]

It’s on the list don’t worry :)

[@LvPatriot1]

@@EverydayDazz Thanks a lot.

[@musamahomed]

Is there a design for 1 pile group?

[@EverydayDazz]

There’s not much to design but you would typically use single piles in regular spacing in a ground beam.

[@adamsicmundus3566]

you lost me when you were calculating the width of the strut.. where does your triangle come from? where does the 500 from the 500/2 on the top of the triangle come from? isn't the strut the dashed line that makes the 34.7* with the vertical line? so why are we calculating the length of the diagonal line from that "imaginary" triangle

[@user-rc6po3ng6x]

s

[@user-bt8xj2zw2g]

For a 1 pile group, for a 3 storey block work structure with ground beams (no point loads from columns etc), is it sufficient to have shear links at closer spacings around the pile or is there more to the reinforcement design here?

[@user-bt8xj2zw2g]

For a 1 pile group, for a 3 storey block work structure with ground beams (no point loads from columns etc), is it sufficient to have shear links at closer spacings around the pile or is there more to the reinforcement design here?

[@EverydayDazz]

So you’ve got ground beams spanning between piles at centres. Just design the ground beams like you would any normal concrete beam with links.