Civil Engineering/pile cap


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what is the main purpose of pile cap in pile foundations
is it required to have a pile cap for single pile also

ANSWER: Hi Priyantha,

The main purposes of pile caps are:

1. To connect together groups of piles
2. To provide a zone of transition between rebar of piles and columns
3. To minimise moments at the tops of piles (caps act as ties/ground beams)

If you do not have much moment at the bottom of a column/top of a pile and so long as they align vertically (to avoid eccentricity moments), you can omit the pile cap.

---------- FOLLOW-UP ----------

QUESTION: Dear sir
Say bottom of a column has significant moment and  axial load. Should we design pile cap for moment. in most of the text books pile caps were designed only for axial loads

Hi Priyantha,

Columns and piles/pile caps are suited for high axial loads. If you have significant moments at the bottom of a column, you should have a 2-pile group (if moments are along one plane) or 3 or 4-pile group for bi-axial moments. That way the pile cap will distribute the axial and moment loads via strut-and-tie action into the piles as vertical axial loads.

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Arshad Khan


I can answer any questions to do with civil and structural engineering consultancy and construction industry in East Africa and the Middle East, and specifically with the analysis and design of reinforced concrete structures. My particular expertise is in the aseismic design and optimisation of tall buildings.


Employment history: 40 years in Construction and consultancy in the UK, Kenya, Tanzania, Uganda, Ethiopia, Eritrea, South Africa, Somalia, Zambia, Austria, Bahrain, Kuwait, Doha and the U.A.E.

.Fellow of Institution of Structural Engineers (UK) .Fellow of Institution of Civil Engineers(UK) .Member of the Institution of Engineers, Kenya .Registered Engineer, ERB, Kenya .Member of the Architectural Association of Kenya (Engineers Chapter) .Chartered Engineer (UK)

•1984: International Conference on the Art and Practice of Structural Design, London •1994: 3rd Int. Kerensky Conference in Structural Engineering, Singapore •2008: International Conference on High-Rise Towers, Abu Dhabi •2013: IEK International Conference, Kisumu, Kenya

BSc, 1st Class Hons, in Building Engineering, University of Bath, UK MSc in Concrete Structures and Technology, University of London. Diploma of Imperial College, UK.

Awards and Honors
•Science Congress Special Award (for 2-seater Hovercraft - 1968) •Institution of Civil Engineers Award for outstanding performance at Bath University (1975) •Concrete Society Postgraduate study Bursary Award (1976) •Consular Representative for British High Commission, Nairobi. (1995 to 1998) •Examiner for Institution of Civil Engineers Professional Interviews, Nairobi. (1997 to 1998) •Branch Representative in Vienna for PI assessment for Inst. of Struct. Engrs. (1999 to 2010)

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