In this article, we will focus on the details of column reinforcement and elaborate the basic requirements for adopting column reinforcement details.
Column reinforcement details can be designed for normal or seismic conditions. There are significant changes in the design of earthquake pillar reinforcement.
The Earthquake Detail article For more information about the arrangement of column reinforcement during earthquakes, you can refer to the Beams and Pillars website.
In this article we will focus on the details of column reinforcement in accordance with BS 8110 Part 01 . Additionally, some of the information is provided as Eurocode 2 .
Let's discuss the detailing requirements for column reinforcement.
- Minimum reinforcement in the pillar
The minimum area of reinforcement in the column is 0.4% of the cross-sectional area of the column in accordance with BS 8110.
100As/Ac = 0.4
- Maximum reinforcement in the pillar
The maximum reinforcing area of columns is: The following values are calculated as a percentage of the gross cross-sectional area of the concrete.
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- Vertically cast support 6%
- Horizontally molded column 8%
- Vertical/horizontal cast column lobes 10%
- Containment Links
The diameter, spacing, and number of links per section are determined using the following guidelines.
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- Connection diameter: at least one-quarter the size of the largest rod or 6 mm, whichever is larger.
- Connection distance: The maximum distance is 12 times the smallest compression beam.
- All column reinforcement must have at least one connection passing through it.
- No rebar in the column should be wider than 150mm from the support rod. This means that if the distance between a reinforcing bar and the support bar is greater than 150 mm, this bar must be held in place with a link.
- Flap with limited coverage
If the diameter of both bars in the overlap exceeds 20 mm and the coverage is less than 1.5 times the size of the smaller bar, cross-connections must be provided along the entire length of the overlap.
When overlapping, the diameter of the connecting links is at least one-quarter the size of the smaller rail. The distance between the connecting links must not exceed 200 mm.
- Project Compression Overlay
The compression overlap length must be at least 25% longer than the pressure anchor length.
The column overlap length can be found in Table 3.27 of BS 8110 Part 01.
In addition to lapping, mechanical clutches could be used in place of normal rounds.
- Crank reinforcement
The minimum crank pitch is 1:10. However, this value can be increased up to 1:20 for uniform load transfer.
To avoid creating internal tensile stresses, thrust elements can be provided in the crank. These can be at a distance of 75 mm as shown in the following figure. This is one of the best spine strengthening details to implement.
- Overlapping and connection arrangement – according to Eurocode 2 – IStrucutE
Shear connections must be provided within the foundation and certain tolerances must be allowed for construction works.
- Reinforcement arrangement when reducing column size – according to Eurocode 2 – IStrucutE
More information can be found in the corresponding code. This article on column reinforcement details is based on the detailing rules set out in BS 8110 Part 01 and some of the sketches are from the IStructE standard structure detailing method.
