Civil Engineering/civil

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Expert: - 9/5/2007


Question
QUESTION: Why putting reinforcement for slab, why do we put steel in both directions.

ANSWER: Hi Raju,

This is for 2 reasons:

1. To prevent shrinkage cracks in the cross-direction.
2. When you load a one-way spanning slab in the middle, it tends to deflect in a dished-shape- i.e. the sagging curvature of deflection is in both directions. So the secondary rebar is designed to resist that.

Hope that helps!

Kind regards,

Arshad

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

QUESTION: I have a roof water tank, where slab is broken. To make new slab what reinf is needed ?. The size is 1.2 m * 1.2 m. The thickness of existing slab is  75 mm. Wall thickness ( rcc) is also 75 mm. The capacity of tank is 1000 Lts . As per contractor 8mm dia reinf both sides is required ? Total = 22 running meters reinf is required. Pl confirm

Answer
Hi Raju,

This is difficult for me to answer without further details and in any case I do not do full designs over this medium. I suggets you seek advice from an engineer who can see the problem- what the contractoe is suggesting is not excessive.

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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