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Civil Engineering/Von-mises for beams

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Question
when we analyse a beam using simple beam theory,we got B.M.,SHEAR. from which we calculate bending stress and shear stress. how to calculate von-mises stress from these values which is to be considered as 61(sigma-1) & 62 & 63. or the von misses theory is only for solid plate cant be use to predict failure behavior of our normal beam. please help me.

Answer
Hi Daimi,

Von-mises stresses are only important for 3-D analysis and design of plates (slabs/matt foundations) as the most critical stress can be other than in the main 3 orthogonal directions.

As beams in civil engineering are primarily designed in the 2 principal directions, von-mises does not really apply or is not relevant. Beams in aircraft and aerospace or marine structures may require this criterion to be taken into account.

For RC columns, it could apply but then we use the method of the 3-D interaction diagram to work out the worst combination of axial load and bi-axial moments, so that again takes care of the worst stresses for designing.

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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: 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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