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Civil Engineering/Point Restraint while modelling Raft

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Expert: - 6/5/2011


Question
Dear Sir,
1. While i try to expert the Raft Foundation to Etabs, what is the restraints that i should provide to columns at support and raft. Do we need to release rotation in all directions and Translation in global z direction? I have applied the soil subgrade modulus also.

2. My design require a piled raft as a foundation due to unavailability of bearing area. Can i model both raft and pile in ETABS.

Thank You

Answer
Hi Sajeev,

If you have modelled a raft in ETABS, then the columns support restraint should remain as fully-fixed, as the raft is usually much stiffer than the columns.

Yes, you can model a piled raft in ETABS- just increase the spring stiffness at the piles locations to simulate the actual load/settlement criteria obtained from the pile tests or from any report prepared by a geotechnical engineer.  

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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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