According to the recommendations of IS 456, expansion joints:
Correct Answer: D. All of the above
📚 Detailed Explanation: IS 456 Expansion Joints — All Three Provisions Are Correct
Why D (All options are correct) is correct: IS 456:2000 Clause 27 gives specific guidance on expansion joints in buildings. All three listed provisions — at abrupt plan changes, to ensure minimum resistance to movement, and supported on separate columns — accurately reflect the IS 456 requirements and reasoning.
IS 456:2000 Expansion Joint Provisions
| IS 456 Provision | Where / How | Reason |
|---|---|---|
| A. Where plane changes abruptly | In L, T, H, E, or U-shaped buildings: at the re-entrant corners and junctions where walls/floors meet at right angles | Stress concentrations form at re-entrant corners during thermal movement. An expansion joint here relieves this stress and prevents cracking at the vulnerable corner. |
| B. Ensure minimum resistance to movement | Joint gap filled with compressible filler (cork, rubber, closed-cell foam); flexible sealant at surface | The joint must offer minimal resistance to thermal expansion and contraction; a stiff filler would negate the joint's purpose by restraining movement |
| C. Supported on separate columns | Twin columns or separate columns at the joint location; slabs and beams terminate at each side independently | Allows each portion of the structure to move independently. A single shared column would restrain movement and be subject to horizontal forces from both sides. |
Expansion Joint in L-Shaped Building (Example)
| Aspect | Detail |
|---|---|
| Location | At the intersection of the two wings of the L |
| Structure at joint | Twin columns (one for each wing); beams and slabs from each wing terminate at their respective column |
| Gap width | 20–25 mm; calculated based on ΔL = αLΔT |
| Filler | Compressible filler (cork board, foam): non-extruding, non-absorbing |
| Sealant | Polysulphide, polyurethane, or silicone sealant at exposed face; prevents water ingress while allowing movement |
- IS 456 expansion joints: at abrupt plan changes (L, T, H, E shapes) + minimum resistance (compressible filler) + separate columns (twin columns for independent movement).
- All three provisions work together: location, filler, and support arrangement each address a different aspect of the joint's function.
- IS 456:2000 Clause 27; also see IS 3414 (Design of Joints in Buildings).