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Civil Engineering/cranking of rebar


QUESTION: Does cranking of reinforcement bar affects its strength in concrete work?

ANSWER: Hi Godswill,

So long as the crank angle is no steeper than 1:10, there is no structural effect apart from some bursting forces at columns splices, which can be catered for by having additional links.

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QUESTION: Sir,In a structural element, say precast beam that needs to be installed on an insitu column structural element but because of the differential in the spacing of the bars in each of the structural element, I decided to crank the re-bar from the precast beam for proper installation on to the column,is it structurally right? because this is what i do on the field daily.

Hi Godswill,

I presume you are cranking the bars inwards from the faces of the beam? In that case, so long as the crank slope is not more than 1:10, the only concern you may have is that the effective width for shear (as the shear links need to hang from the longitudinal rebar) will be reduced, so you may need to just check the reduced shear capacity.

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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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