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Civil Engineering/ductility & stiffness

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Expert: - 10/29/2011


Question
Dear Sir,
Good  Day!
I would like to clarify
1.what is the relation between ductility and stiffness of a structure.
2.while considering the lateral loads(seismic and wind) in multistorey building ,which lateral load dominating in a high mutistorey buling and a small multistorey building.
3.Is the stiffness more for the seismic resisted multistorey building as compared to normal buildings.
Thanks so much for your valuable advice on these , as these are the questions I have faced while for an interview.thanks so much.....

Answer
Hi Ravi,

1. Stiffness determines how much a structure will deflect for a given load. Ductility determines how much the structure can deflect without failing/collapsing, and how much energy can be dissipated by that deflection/deformation.

2. This depends on the aspect ratio of the building, the ductility of the building and where the building is located and what the relative lateral loads are. In Dubai, probably any building higher than about 25-30 storeys will have wind loading as governing, but at lower levels seismic will be governing.

3. Higher stiffness is required for resisting wind loading, and to a lesser extent seismic. Ductility is important only for seismic loading, so that you can reduce the sesimic load. Increased ductility will not reduce overall wind loading.
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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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