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Civil Engineering/exporting to SAFE from ETABS


Dear Sir,
Good Day
While exporting raft footing from etabs to safe for a G+3 building,I didnt get any bottom extra bars needed on the raft (I provided 60 cm raft with T16@150c/c top and bottom)
My question is ,(1)Is it right to consider the bottom of all columns on the raft to be restrained ?or I need to remove the restrain of all columns rest on the raft?
(2)do I need to assign the point spring and line spring? or need to remove all the springs except subgrade modulus of soil?
Thanks So much

Hi Ravi,

For proper soil-structure interaction the raft should only be supported on springs depending on soil modulus. The columns supports on the raft can be fixed or pinned depending on your boundary conditions- e.g. if there are no basements, they should be fixed, otherwise they can be pinned.

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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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