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Civil Engineering/best options for 24m long span beams

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Expert: - 11/14/2011


Question
Hello sir,

good day,
sir,we are designing commercial building in India. In which, there are 24m long span beams spaced at 9.0m c/c, loading is 180 kN/m. We are proposing following options,

option-1  RCC beam with size 1200x1500mm
option-2  Steel buildup I-section with 1000mm depth
option-3  Warren Truss with 300mm hollow box steel sections.
option-4  steel box girder of 1000x1000 with 20mm plate think.

Please advise which is best option or could you suggest any other proposal. thanking you for your guidance..

Answer
Hi Venkat,

Technically, I would say that only options 1, 2 and 3 should be considered- there is not much benefit in using box girder and there are complications in design and construction.

Another option you can consider is to cast the concrete beam in the shape of an I, so that you reduce weight and cost. Of course pre- or post tensioning is also an option.

As to which option is best can only be determined on the basis of:

1. Local materials costs (steel vs concrete)
2. Local materials availability
3. Local resources/manpower expertise (steelwork, post-tensioning, etc).
4. Aesthetics/ architectural & services requirements

Civil Engineering

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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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