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Civil Engineering/mass tuned dampers(MTD) and expansion joint in building


Respected sir,
I am working on a high rise tower project of 35 storay. It a irrerugalar L shape building. I have few questions as follows.

1) considering differential settlement, strees at joint i make the expansion joint and divide the buildng as 2 I connecting each other with expansion joint. Is it a good practice or i should consider more parameters to fix expansion joint.

2) mechanical department is pushing us to allow them to put their HVAC chillers on the top of roof(35 floors). Shall i treat this chiller load as MTD.

3) is it a good practice to put chillers on the roof slab(since chiller have very heavy loads and lots of vibratiobs)...

Thanks and regards,
Syed mujahed ul islam.

Hi Syed,

1. If the two wings are same height and on similar ground strata then differential settlement should not be an issue.

2. If it is a seismic zone, then the joint will lead to pounding problems unless the width of the joint is sufficient (may be more than 100mm depending on zone, etc)

3. Chillers should just be considered as DL

4. Yes, no problem with that- chillers are usually on the roof.

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Arshad Khan


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.


Employment history: 40 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.

.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)

•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 •2013: IEK International Conference, Kisumu, Kenya

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 2010)

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