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Civil Engineering/Openings in RC beams

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Expert: - 4/6/2009


Question
i have 1000 mm x 300 mm beam (10 meter long) in first floor in 35 story building. This is well designed. how big Width x depth opening can be allowed without any calculations. what location (vertically and horizontally)it can be allowed.  Also what to do with shear reinforcement. what is additional reinforcement is to be allowed and why ?
thanks and regards

Answer
Hi Sandeep,

This depends on whether you have any concentrated loads- if it is mainly UDL, then the safest place to locate the openings is within the middle 1/3rd span and you can probably have it up to 400mm deep and around 300-400 wide. You will need to check that the remaining section at top and bottom can take not just the shear force due to UDL, but additional shear force imposed from local bending effects- these should be fairly nominal if you minimise the width of the opening.

If the opening extends above the neutral axis, you may need to put some additional horizontal rebar to take care of the loss of compression block within the concrete.

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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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