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How do fixed and pinned connections between piles and pile caps affect the load carrying capacity of piles?

The type of connection between piles and pile caps affects the load carrying capacity of pile groups. The fixity of pile head into pile cap, instead of pinning into pile cap, enhances higher lateral stiffness of the pile groups. For instance, for the same deflections, a cap with fixed connected piles can sustain far more loads than that of pinned connected piles. To satisfy the criterion of fixed connection, the minimum embedded length of piles into pile caps should be at least two times the diameter of piles.

Moreover, the fixed connection of piles at pile caps allows significant bending moment to be transmitted through the connections when compared with pinned connections.


This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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4 comments on "How do fixed and pinned connections between piles and pile caps affect the load carrying capacity of piles?"

droaun says:

what does it mean by embedded by 2 times diameter for fixed pile cap. say if pile diameter is 200mm, embed length would be 400mm. so how deep should the pile cap be?

in general a depth of pile cap is = Ø pile * 3/2

bhola m. sontakke says:

i want some idea how to fix diameter of pile &how to fix the depth of pile
please guide me or please send me data about pile foundation.

Tashi says:

In construction of bored castinsitu concrete piles with permanent steel liner, can the additional liners be welded on top of bored liner to increase the height of the pile cap? This is in case When the ground level Is below the pile cutoff level.

Saroj Bhattarai says:

Bridge foundations (abutments/piers): We know the moments on the top of the pile cap from abutment or pier stem (due to earth pressure, seismic forces, etc.) transferred on to the piles as axial forces according to their position in the pile group. Similarly horizontal forces at the level of the pile cap is distributed equally to all the piles. Do we also have to distribute the moments from the stems to the piles?

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