Civil Engineering/surge tank

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QUESTION: I am designing a cylindrical steel surge tank of diameter 2.5m and height 14m from the ground.Below 14m (ground) the steel portion of tank is inserted in to a concrete cylinder of height 2.9m.can i design the concrete portion like a chimney as done in book of N krishnan Raju? No doubt we should consider weight of water for checking the bearing capacity, but do we need to take in account the weight of water for the RCC design of foundation? can we design the circular foundation similar to a square foundation for a column of a building?
THANKING YOU
nIRANJAN

ANSWER: Hi Niranjan,

I do not know about the book you are referring to, but the walls of the concrete section should be designed with hoop rebar and vertical rebar. As for the foundation, this depend son the soil conditions and the structure of the steel tank bottom. If this is simply a circular plate sitting directly on top of the concrete foundation then the load will be more or less UDL and you can design the foundation like a pad footing, except that for any lateral loading (wind, seismic)the distribution of pressure under the circular footing will be different from that of a square.

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surge tank
surge tank  
QUESTION: Dear sir,
Thanks
I have attached here the elevation of the surge tank.The steel is inserted in to the concrete wall. Hope some more suggestion for the foundation design.

ANSWER: Hi Niranjan,

That looks fine- just design the foundation for normal bending/shear forces after getting the analysis results. Put some extra hoop rebar in the walls near the end of the steel tank, to resist extra bursting forces from vertical reaction of the steel tank.

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QUESTION: Thanku sir,

I find out radial and circumference moments and design the foundation for flexure taking refrence from the foundation design of chimney. But I could not find the formula for finding out the shear force.  Could you please help me out.

Answer
Hi Niranjan,

Just work out the vertical reaction per metre from the ground pressure adjacent to the wall  and calculate the shear capacity of the foundation- probably it will be within capacity of the concrete and you will not need any extra shear links.

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Arshad Khan

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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: 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.

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 •2013: IEK International Conference, Kisumu, Kenya

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 2010)

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