Civil Engineering/column design


QUESTION: Dear sir

in a proposed building there is a column 675X675 mm . it is proposed to have 225x2025mm column instead of it so that X'sectional area is equal and to avoid disturbance due to large column. main beam can be connected to long direction of column.

Is it possible and what  are the limitations


ANSWER: Hi Priyantha,

With the proposed dimensions the column has to be designed as a wall and you will end up with concentrated axial loads from beams at each end of the 2.025m length. Also you need to consider slenderness in the 225mm direction.

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

QUESTION: Dear sir

"concentrated axial loads from beams at each end of the 2.025m length"
that means whole length of column/wall will not be effective in design against axial load. is it required to consider end and middle parts separately. what are the percentage of loads to these portions


Hi Priyantha,

This depends on the height of the wall, as well as the relative stiffness of the framing beams - but as a rule of thumb, consider the wall section at the edges to be maximum 3xT = 3x 225 = 675mm as being effective at the top- due to load distribution, this width can increase as you go down the wall, but the governing section will be at the top..

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Arshad Khan


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.


Employment history: 40 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.

.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)

•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 •2013: IEK International Conference, Kisumu, Kenya

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 2010)

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