Wednesday - February 21, 2024
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Joints | Joints a large Building

Provision/necessity of joints in a large building

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  • All building materials expand about contract due to changes in temperature including variations in moisture content.
  • The magnitude of such expansion about contraction depends upon the type of material used in construction and the range of variation in some temperatures including moisture content.
  • Components of a structure are not allowed free movements, therefore, internal stresses will be set up which may result in the formation of cracks.
  • To control either isolate thermal including other movements to avoid danger over a structure.
  • To break the continuity of a structure.
  • Joints sub-divide each building toward smaller units including also permitting free movement of an individual unit.
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The recommended spacing of expansion joints for different types of works as per I.S.3414-1168

  • Walls:-  c/c spacing of joints
  1. For load-bearing walls with cross-walls at intervals. A traditional type of one-brick thick or more. =30m
  2. Walls of warehouse-type construction (without cross walls.) =30 m
  • Chajja’s, balconies and parapets. = 6 to 12 m
  • Ordinary roof slabs of R.C.C. 20 to 30 m intervals and protected by layers of mud changes in direction as in paska or other insulating media in L, T, H &U shaped struct. un-framed construction.
  • The unprotected slabs. =15 m
  • Frames:- At 30 m intervals and corners of L, T, H, and U-shaped structures.
  • Copings:- Corresponding to joints in the roof slabs.

Location of Construction Joints for Different Members

Some recommended position during the construction of joints into different structural components is as supporting.

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For slabs Joints

  • In the case of slabs supported on two sides, the construction joints should be vertical at support.
  • It can also, be provided at the middle of the span at right angles to the main reinforcement
  • Inside the case of two-way slabs, the joint tin be provided near the centre of either span.

For Beams Joints

  • During the case of beams, the construction joint should be located in the centre about within the middle third of the span including it should be vertical
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For columns Joints

  • In the case of columns, the construction joint should be formed horizontally by stopping the concrete in a column about 75 mm below its junction with the lowest soffit of the beam 
  • The operation of concreting over the construction joint should be exerted after a break of at least 4 hours
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For walls Joints

  • The horizontal construction joint in walls should be located at the top of the plinth, top or bottom of the window opening or at any other convenient height.

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