Civil Engineering/Strap Footing

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Expert: - 4/7/2010


Question
Sir,

I have a problem designing an isolated footing for a
400mmx600mm RC column because of large moment due to windload(the structure is situated on typhoon prone area-250 Kph wind Speed) and the footing dimension I get is so large that is why I am trying to make a combined footing(2 center footings) via strap beam but I'm not sure if it is going to work. My question is: Does the moment induced by windload is being transfered to the strap beam? Most of the samples of combined ftg w/ strap I see do not have moment load. Please advise how to deal with this.

Thank you in advance!

columns are 9m. O.C.

Answer
Hi Gilbert,

This depends on the relative stiffnesses of the sub-grade, the pad footings and the strap beam. It will only really work as a combined footing if the strap beam is as stiff in the vertical plane as the pad footings. Also, you can frame the strap beam straight into the columns to assist in moment transfer. This can be done by having part of the depth as upstanding beam above the top surface of the pads.

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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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