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Civil Engineering/Slab load distribution to beams

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Question
QUESTION: A reinforced concrete slab is supported by four beams, the shorther span being 3.5 m and the longer span being 5m. The slab carries a  uniform load. What would be the uniform load (wl) distribution carried by each beam? if the the deflection is inversely proportional to the fourth power of the span of each beam, can i use this ratio-and-proportion to determine the load distribution?

ANSWER: Hi Roy,

Assuming that the slab is designed and reinforced as 2-way spanning, you will have a trapezoidal shape of loading on the longer beams and triangular loading on the shorter span- just draw lines at 45 degrees on plan from each corner and where they meet this is the triangular loading on the shorter spans.

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

QUESTION: Can i design this as one way spanning,wherein the tributary area for the shorter span would be the area of the slab. How do i determine the loading in
the longer span?

Answer
Hi Roy,

Assuming that this is an internal span (or slab is simply supported at the beams), then just take 50% load onto each of the longer spans. If it is an edge span and the slab is part of a continuous multi-span slab then the edge beam would carry around 40% of the span loading and the first internal beam will carry about 60% of the span loading.

For the shorter span you can consider them carry a trip of slab loading around 0.6m wide

All these factors are give in text books or in codes such as BS8110

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Arshad Khan

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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: 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.

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 •2013: IEK International Conference, Kisumu, Kenya

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 2010)

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