Civil Engineering/Silo Foundation

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Expert: - 11/16/2007


Question
QUESTION: Dear Sir:
Is 1 kg / sq.cm. a very safe soil loading capacity as a thumb rule when the area has many warehouses around built on general pedestal foundations.
In such an area what shall be the foundation for a metal silo 11 meter high, 40 tons total weight ?
Thanking you for your kind help.
Regards.

ANSWER: Hi Anwar,

This very much depends on the ground conditions, as in some cases to limit settlement you may have to restrict laoding to 0.5-0.8 kg/cm2.

You have not given me the diameter- but basically assume a stricp foundation say 2m wide under the circumference and divide that with total load to get the net vertical foundation pressure. You will need yo also check pressure due to lateral loading such as wind/earthquake.

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

QUESTION: Respected Sir:

Your way of response is highly praise worthy. Thankyou.

I forgot the diameter and another important part of the question: - The diameter is 3meters. Please let me know that after calculating the foundation area per your advice what shall be the depth so that the silo does not tilt over. What is the safety margin to be considered over & above the basic design if any ?
Is there any publication/book or computer programme which is in simple english and without heavy mathematics that can be used for very basic structures designing for people without structural engineering formal education ?
Many thanks & Best Regards.
ANWAR


Answer
Hi Anwar,

Well, it the diameter is only 3m, then you may only need a strip footing of 1.0m wide, depending on the vertical loading. In general, you should place the footing at least 1.0m below fround, or deeper if the soil is not good or if there are trees/roots nearby. Try this website for reference:

http://www.vulcanhammer.net/download/foundations.php

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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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