Civil Engineering/Pad Foundation

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Expert: - 9/11/2006


Question
I am in the process of calculating the foundation size for a second floor extionsion, supported by 2 corner brick piers. i am assuming i will need pad foundations at the 2 piers, but how would i calculate their depth and area? Thank you very much,
Adam

Answer
Hi Adam,

Basically you will need to work out the total weight of the pier and the floor/walls/live load that will be transmitted down to the pad and divide that with the safe bearing capacity of the soil. This will give you an area for the pad and so the if it is square, just do a square root of the arae.

So, assuming total load is 1000 kN, and assuming the safe bearing pressure is 100 kn/m2, then the pad area is 10m2. This can then be a 4x2.5m pad or a 3.33x 3.33m pad, etc. The depth of the pad should be about a third to a quarter of the shortest plan dimension, with a minimum of 250mm and the top of the pad should be at least 600mm below the finished ground level (if you are in place that has cold weather/frost). Depending on the soil conditions you may also need rebar in the pad.

I hope that helps!

Kind regards,

Arshad.

Civil Engineering

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Arshad Khan

Expertise

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.

Experience

Employment history: 36 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.

Organizations
.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)

Publications
•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

Education/Credentials
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 date)

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