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Pile Cap Design
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es_jayakumar
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PostPosted: Mon Sep 21, 2015 12:49 pm    Post subject: Reply with quote

Dear Er.Zia,
Thanks for your explanation. But at which point should we take P/Delta to get the genuine stiffness of the pile, in view of the non-linearity of the graph ? Need we take into consideration the very scant rebound, upon the removal of the load, also ?

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E S Jayakumar
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Zia
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PostPosted: Tue Sep 22, 2015 12:40 pm    Post subject: Reply with quote

Dear Engr Jayakumar,

From the load test data you can determine initial stiffness by drawing a tangent to the initial portion of the curve.  Or you can determine settlement over the design load and determine stiffness.

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Zia
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sknsrinivasan
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PostPosted: Thu Jan 11, 2018 8:30 am    Post subject: Reply with quote

Dear all
  I have one doubt in Pile cap Design. In pile cap whether Top Reinforcement Necessary or Not (If the pile cap depth is lees than 1M) If there is any Necessary of providing Top Reinforcement,I Request you all give explain the reson

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N.Srinivasan
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es_jayakumar
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PostPosted: Fri Jan 12, 2018 1:56 am    Post subject: Reply with quote

Er.Srinivasan,
Except in the case of a pile cap large in plan with several rows of piles, designed by either bending theory or truss analogy, a pile cap will not need top reinforcement for structural action. However, it is desirable to provide some nominal steel at top.

E S Jayakumar
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N. Prabhakar
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PostPosted: Fri Jan 12, 2018 1:24 pm    Post subject: Reply with quote

Dear Sefians,

If Pile Cap thickness is equal to or more than 1 m, and where there is no requirement of design reinforcement at top, nominal reinforcement is to be provided at top of Pile Cap, Ast in either direction at top is 360 mm2 / m width as per Clause 34.5.2 of IS 456: 2000.

With best wishes,

N. Prabhakar
Chartered Structural Engineer
Vasai (E), Pin 401 208
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john_jeevan
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PostPosted: Fri Apr 27, 2018 5:04 pm    Post subject: Pile cap depth Reply with quote

Is the pile cap depth finalised based on the emperical formula in Reynolds Handbook? Is it recommended to provide a smaller depth than specified in Reynolds handbook if it satifisfies the prescribed checks?
In the Text book of Prof. PC varghese, effective depth of half pile spacing is considered in one example...

Kindly offer a feedback on this
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Dr. N. Subramanian
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PostPosted: Sat Apr 28, 2018 1:40 am    Post subject: Re: Pile cap depth Reply with quote

Dear Er. John
The pile cap is subjected to a complex system of forces including bursting forces and punching and hence it is better to use the empirical formula as given in Reynolds Handbook and also quoted by Prof. Varghese and also by me in my book. It is also advisable to provide reinforcement for bursting forces as shown in IS handbook on detailing.

Best wishes
NS


john_jeevan wrote:
Is the pile cap depth finalised based on the emperical formula in Reynolds Handbook? Is it recommended to provide a smaller depth than specified in Reynolds handbook if it satifisfies the prescribed checks?
In the Text book of Prof. PC varghese, effective depth of half pile spacing is considered in one example...

Kindly offer a feedback on this
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john_jeevan
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PostPosted: Sat Apr 28, 2018 5:01 am    Post subject: Reply with quote

Thank you sir
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N. Prabhakar
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PostPosted: Sat Apr 28, 2018 6:24 am    Post subject: Reply with quote

Dear Sefians,

As we all know , Pile Caps are designed on the basis of 'tie and strut' action.  The tensile force acting at the bottom level is resisted by bottom reinforcement in the pile cap.  The detailing of pile caps require extra care in anchoring of bottom reinforcement and to deal with bursting action.

The bottom reinforcement has to be anchored fully at  both ends beyond pile location.   Normally, the horizontal distance beyond pile location, before the bend of the reinforcement bar, is very small which would cause high bearing bearing stress in concrete at bend.  The normal radius of bend is 4 x bar dia. for HYSD bars, and 2 x bar dia. for MS bars, which would be insufficient in these cases. A larger radius of bend is required to have control on the bearing stress in concrete at bend.
Please see the attachment.

Besides, to control the bursting action due to outward tensile force, horizontal links are to be provided as shown in the attached sketch.  This is based on the full scale tests conducted by Cement and Concrete Association, UK.

With best wishes,

N. Prabhakar
Chartered Structural Engineer
Vasai (E), Pin 401208



Pile Cap Reinforcement Anchorage.png
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Pile Cap Reinforcement Anchorage.png



Pile Cap Details.png
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Pile Cap Details.png


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