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Expert: - 12/29/2008


Question
what is the defference between a pad and raft foundation

Answer
Hi Folashade,

The main difference is in proportions and how many applied loading points there are. A pad is usually quite thick in relation to the length and breadth (t= 1/3 to 1/4 of plan dimensions), so it is very stiff in out-of plane bending. Normally a pad will carry a single column load, maybe two if it is a combined pad footing. A raft's thickness in relation to its plan dimension is much less and therefore it can deform under influence of loading. A raft normally carry multiply loads from columns, shear walls, lift core walls, basement walls, etc.

A pad is easy to analyse and design, but raft is more complex- it is more like an upside down flat slab when it comes to analysis and design.

A raft tends to minimise differential settlement between adjacent columns, but pad footings may end up settling differentially due to different loads or different ground conditions.

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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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