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Civil Engineering/Etabs (Perimeter beam for flat plate)

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Expert: - 11/7/2009


Question
I am now modeling a 5 Storey car building (flat plate system with perimeter beam). I notice that the perimeter beam (Bending moment and Shear) are very small if compare to my manual calculation.

It seems like the slab (Shell element) is taking/transferring the loading based on its out of plane stiffness.

I just wonder, what is the common practice to design the beam by using Etabs. In this case, can I use the Etabs design directly?

I assign the slab as Shell and use Auto mesh to 1m.

Wish you can assist me. thank you.  

Answer
Hi Jimmy,

Yes, what you assume is correct- if the slab is quite stiff in relation to the beam, then it will not transfer a lot of load on to the beam. However, if you change the out-of-plane stiffness modifiers for the slabs (to simulate cracked sections & long term creep effects), then this will shed more loading on to the edge beam and converge to your manual calculations.

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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: 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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