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Expert: - 11/13/2008


Question
QUESTION: Is there any special procedure for calculation of shear stress in prestressed members(beams/slabs) as they are thin in thickness?

ANSWER: Hi Sreekanth,

In principle there is no difference from normal RC design as the maximum permissible shear stress in the concrete is the same for prestressed concrete. However the formulae are slightly different- refer to section 4.3.8 of BS8110-Part1.

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

QUESTION: In which type of frame construction i.e the flat slabs construction or slabs with beams, the column will be exposed to max. moments?
and which frame is better choice to resist sesmic forces?

Answer
Hi Sreekanth,

Flat slabs will impose less moments to columns than beams/slab systems when considering lateral loading or gravity loading from un-equal adjacent spans.

For seismic forces, a beam/slab system is better as that has more lateral stiffness and by suitable rebar detailing you can increase the ductility (and hence energy dissipation), which is good for seismic resistant structures.

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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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