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Civil Engineering/rings on columns /stirrups on beams

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Expert: - 5/3/2007


Question
QUESTION: 1. for columns , which is better - to provide rings horizontally or spirally?
2. for beams , i believe , stirrups provided in an inclined position produce better results- am i right?
ANSWER: Hi Shiju...,

1. Rings horizontally are better for control of spacing and location of main rebar.

2. They can help in certain circumstances, but in general it is best to stick with vertical ones. Normally if you incline anything, it is the main rebar, cranked down/up, rather than placing stirrups at an angle.

Hope that helps!

Kind regards,

Arshad

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

QUESTION: arshad-thank you very much, can you just get me a bit more about the technical significance,plz?

Answer
Hi Shiju,

Basically, shear cracks in beams are at 45-60 degrees angle to horizontal, so an inclined bar will help prevent cracking. However, the failure leads to the unsupported part of the beam moving downwards by gravity, so vertical hangers/stirrups work just as well and are more practical to construct/fix on site accurately (with angles, they could be set wrong, so the spacing of top and bottom rebar could change). The force priciples are similar to a truss analogy- the diagonals and the vertical structs/ties.

Hope that helps!

Kind regards,

Arshad

Civil Engineering

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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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