The maximum spacing for spiral reinforcement is

The maximum spacing for spiral reinforcement is 75 mm. This is according to the following standards:

• ACI 318-19 (American Concrete Institute): Section 25.7.3
• IS 456:2000 (Indian Standard): Clause 39.4
• BS EN 1992-1-1:2004 (European Standard): Clause 6.3.4.2

The maximum spacing is specified to ensure that the spiral reinforcement is effective in preventing the concrete from buckling under compression. A smaller spacing will provide more reinforcement and therefore be more effective in preventing buckling. However, a smaller spacing will also make it more difficult to place and compact the concrete. The maximum spacing of 75 mm is a compromise between these two factors.

Here are some additional details about spiral reinforcement:

• Spiral reinforcement is a type of transverse reinforcement that is used in concrete columns. It consists of a continuous helical coil of steel bar that is wrapped around the column.
• Spiral reinforcement helps to prevent the concrete from buckling under compression. It does this by providing a continuous lateral restraint to the concrete.
• The minimum diameter of spiral reinforcement is typically 10 mm. The maximum spacing between turns of spiral reinforcement is 75 mm.
• Spiral reinforcement is typically placed in the center of the concrete column. It is anchored at each end of the column by 1.5 extra turns of spiral bar.