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Civil Engineering/SAFE Raft analysis


Dear Sir,
Good Day
While doing design of raft slab in safe ,Normally the subgrade modulus is assigning to all the slab area.Do I need to add point spring properties and line spring properties to the bottom of columns/shear walls
if its needed ,how I will get the values of spring stiffness (ie translation in x,y and z )to enter in the point spring property data..
appreciate for your valuable advice
Thanks & Regards

Hi Ravi,

In SAFE you have two options:

1. Manually mesh the raft, ensuring all point and line loads are connected at nodes, then manually apply spring stiffnesses at nodes depending on element sizes.(This is similar to doing it in STAAD.Pro)

2. Just adopt the soil properties for whole raft as offered in the menu and the program does the rest.

Obviously the second option is much easier!

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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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