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Civil Engineering/shortening of concrete columns

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Expert: - 9/26/2011


Question
QUESTION: Dear SIR,
i am searching for a good reference or software to calculate the shortening of columns according to creep, shrinkage, and elastic shortening, humidity, ..etc.

i found some books but it was not helpful enough, this issue is critical and my building is 52 story.

thanks too much in advance and waiting your reply,

Best Regards,
Robert Saad
Structural engineer.

ANSWER: Hi Robert,

One of the best reference for this, with step-by-step guidance is the book by Mark Fintel, SK Ghosh and Hal Iyendar. It is called "Column Shortening in Tall Structures- prediction and compensation" The ISBN no. is 0-89312-083-9.

Remember that it is the differential shortening (between adjacent columns or between a column and adjacent RC wall) that is a problem. If there is fairly good stress balance between the vertical members, then your problem will be minimised or even eliminated.

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

QUESTION: thank you very much , it's helpful :)
is there any software or spreadsheet that calculate the long term shortening that i can buy ?
thanks in advance
BEST AND BEST REGARDS.

Answer
Hi Robert,

Yes, the RCC in UK sells one at their website:

http://www.concretecentre.com/online_services/design_tools/rc_spreadsheets_v4.as

You can also download a free earlier version from the web. The limitaion is for 24 storeys, but you can get around that by inputting data for every 2 floors (so can do a 48 storey building) or every 3 floors (so can do a 72 storey building). This makes the analysis an approximation, but it is still valid. When I say input every 2 storey data, that means your column height will be 2 X normal floor-to-floor height, and floor construction cycle (time, in days) will be twice what you would normally have for each floor.

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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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