Civil Engineering/rcc beam

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Expert: - 4/25/2008


Question
hi.at one of our existing single storey car wash building, a contractor has cut concrete from the top of a fixed end -two span uniformly loaded rcc beam, to pass a water supply pipe sleeve.The beam is 20cmX60cm with 2nos 16mm dia bars at top and bottom.He has cut 15cm deep for complete width at 1.20m from one support,where span of beam is 5.50m.Will this affect the structural strength.He did not cut any steel R/F, and repaired the concrete with FOSROC grout, after laying the pipe. Please advise.

Answer
Hi Ahmed,

This is a bit difficult to say for sure, without looking at the drawings and loading, but in general for a continuous beam (i.e. not simply supported at the ends), the point of contraflexure (where there is minimum moment/shear) is at about 0.25x span, so if the hole is there at or near the  middle of beam depth, then you may be OK.

If the beam is simply supported, then the shear nearer the supports is critical and any holes cut through reduce the shear capacity- thsi depends also on the number/size/spacing of the shear links.

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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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