Civil Engineering/SILO

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Expert: - 5/4/2008


Question
QUESTION: dear sir,
i want to design metal silo foundation, silo is 32m dia & 23 m height & its grain capacity is 8000 tonns, SBC is 25 t/m2 at 3m depth, & grain load on floor is 12 t/m2 & load on each stiffner is 30t in periphery & there are 88 stiffners
sir, i am approaching by two ways one by designning external wall as shear wall & inside filling compacted gravel material & putting Raft over it to support grain load & shear wall to support stiffners my question is what would be horizontal thrust on shear wall of central load as shear wall height would be 3 below ground+1.5 above ground=4.5m & wether in central portion top oose soil before filling 1.5m ht material reqd to be removed.
Second option for me to design end bearing piles in periphery & support wall above gr over it & inside also to provide piles & supporting slab over it this option is costly

thanks

regards

sailesh

ANSWER: Hi Silesh,

Much as I would like to help you, I cannot picture what you mean about the shear wall and stiffners.

The best advice I can give you is to design a ring foundation below the silo walls- this can be either strip foundation or a cap to sit on piles. As for the floor slab, again- that can be either a spread foundation (as the applied load is half the SBC)or piled- whatever works out economical.

---------- FOLLOW-UP ----------

QUESTION: sir,
very thanks for your prompt reply
One thing i want to know that MS shell of 23 m will be supported on ring wall which would be 4.5m deep ie 3m deep below NGL & 1.5 above, what shall be lateral pressure of grain loading in silo & shall ring wall be designed as cantilever shear wall or as per hoop stress
thanks
regards

sailesh

Answer
Hi Silesh,

If the RC wall is also subjected to grain pressure then you can design it in hoop stress, with the bottom say 0.5m also reinforced vertically as part-cantilever in order to prevent cracking due to hoop strain. Hope you understand. The actual pressure I cannot work out for you as that depends on the properties of the grain, etc.

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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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