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Civil Engineering/Expansion joint in G+4 rcc building


Dear Arshad Bhai,

Thanks for helping all with your guidance.
I have G+4 building of L type with size 77x16 m and 30x17 m, so I provide an exp.joint at the intersection so the size is now 61x16m and 45x17m with thermal consideration for 61x6m building.
Now when I want to calculate the size for exp.joint considering static seismic with uncracked section(i.e divided by 0.7)I am getting the width around 125mm using the formula Dm=Sq(dm1^2+dm2^2).
My question is do this size is correct or not for this type of building and if I need to reduce it how can I do it.



Hi Musherib,

Yes, depending on the R factor used for seismic loading and the slenderness of the building, one can end up with quite a wide seismic gap to avoid pounding. This gap should be bridged using crushable filler with low modulus and for pedestrian traffic you can detail a steel plate fixed to one building and sliding at the other side.

Ways of reducing this gap is to reduce ductility demand on the frame and design just using stiff (bearing) shear walls, so that your seismic sways are reduced. Of course you can also reduce the gap as you go down the building- the maximum gap width being at roof level.

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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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