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Civil Engineering/etabs model for twin towers

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Expert: - 10/15/2010


Question
dear sir,
i have a 3 basements+ground floor and above the ground floor 2 towers continue (one 15 floor and other 32 floors:
1-if i model the hole structure (basements and towers ) in the SAME etabs model, do you think that it's good assumption? what about base shear and scaling of results?
2-what's the best way to model the system sir? espaciall that i need dynamic analysis?

N.B: i model already the structure in one model, in somme mode case one building move the other no and vice virsa.sorry about the long question, but i trust u sir,

thanks.

Answer
Hi Robert,

You have not given me the overall plan dimensions of the basement, but if there is no movement joint within the basements (i.e. between the 2 towers), then you must model the whole system in one ETABS model, just as you have done. The reason that one tower moves and the other does not for different modes is because their natural frequencies are different due to the different heights (and possible plan shapes?)

As for base shears and scaling of results, you can do that individually for each tower, assuming that the base is the ground 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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