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Civil Engineering/Joints: Construction, expansion, contraction, isolation, pour strip


can you please explain in simple English the meanings of the following
1. construction joint
2. Expansion joint.
3.contraction joint
4. Isolation joint.
5. Pour joint.

Please point out their meanings and  illustrate applications about where a particular joint is used.

ANSWER: Hi Arsalan,

1. Where one pour ends and the next starts maybe after 1-2 days.

2. A joint that has complete break in rebar and a gap filled with compressible material- usually between 20mm to 40mm wide to allow for expansion of members either side

3. A joint that may have reduced (50%) or no rebar across, to enable it to crack and allow members either side to shrink away from the crack.

4. A complete break, similar to 2. above

5. Usually a strip of slab or wall, between 0.5m to 1.5m wide where the horizontal rebar is lapped. The concrete either side is poured first and left for a few days until it has cured and shrunk, after which the pour strip is poured. This is used for very long structures without EJ or CJ, and using this method you can build structures in excess of the usual 50m limitation.

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

Thanks for your prompt reply , can you briefly illustrate at what locations and where Expansion joint and contraction joint are used.

Hi Arsalan,

That is not easy to define as it depends on a lot of variables, such as overall geometry, weather conditions, soils conditions (e.g. differential settlement may require an expansion/isolation joint), method of construction (e.g. pour strips may avoid need for contraction joints),amount of rebar (more rebar means less number of joints required) etc.

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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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