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Expert: - 11/25/2007


Question
Respected Mr.Khan,In the case of Ribbed slab with hidden beams & column as supporting structure, what is the basic concept for designing the column part. Generally a column is designed for axis moments and the load coming on. is there any roll of moment in this type of case or not, if the roll is there then mostly size of hidden beams is more than width of a column so in this case how the distribution of end moments shall be done or it is not required please clarify the concept behind it. will it be designed simply for gravity loading or any consideration of moment is required if yes then please guide. with many thanks.

Answer
Hi Vijay,

If by hidden beams you mean flush beams, then you can still take full frame action and moment distribution into the column so long as the width of the beam is not more than 2- 2.5 time the width of the column- although this also depends on the relative stiffnesses of the beams when compared with the columns. If the beam is much wider/stiffer, then you can the proportionate part of the moment goind straight through to the otehr side- unless it is an edge column, in which case some moment will go into the edge beam as torsion.

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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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