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Expert: - 1/29/2011


Question
Hi Arshad ... is it approriate to apply load cases (e.g. the IBC 2006 ASD Basic counteractive case 0.6DL-Wind)when determining the resisting and overturning moments for the design of a masonry screen wall footing?  If so, is then also approprate to decrease the overturning effects by 25% at the soil interface per the footnotes of these equations?  The concern here is that this effects the determination of the eccentricity and how that,in turn, effects the derived soil pressure and ultimately the concrete design.

Thanks.

Answer
Hi Wayne,

I am not too familiar with IBC, but on first principles you should design the RC structure for the worst loading, which could be an envelope of wind and ultimate gravity loading. If the worst case includes wind, and if that moment is much higher than gravity, then yes you could assume a 25% over-stress.

Eccentricity and stability against over-turning should be determined without taking any soil or structure overstress into account.

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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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