AS 3600-2018 Development Lengths
For AS 3600-2018, no additional extension length is provided. In this standard this effect is handled more directly by modifying the strength design forces on the cross section to account for the level of shear/torsion.
For a user-defined bar, the effective development for any point along the bar is calculated in accordance with the following figure.
Effective development at any point along a bar for the undisplaced moment diagram (for AS3600-2018 only)
- Clause 13.1.2.4 (a) is used to calculate the code minimum development length for both beams and slabs. Clause 13.1.2.4 (b) is not considered.
- For any length less than a code specified minimum development length, the effective development is zero.
- For any length greater than or equal to the code minimum development length, but less than the full development length, the effective percentage development is (provided length)/(full development length) x 100%. This is accomplished by considering a fraction of each bar developed.
- For any length greater than the full development length, the effective development is 100%.
For a program designed bar, when the bar is detailed the bar will be extended the full development length plus the desired extension length. If a bar is unable to be extended this full desired length, RAM Concept will attempt to extend the bar the 90 degree hook development length plus the desired extension length, then the 180 degree development length plus the desired extension length, then the 180 degree development length with no extension length. If there is not enough extension space to satisfy any of these conditions, an "anchor" will be placed at the end of the bar and it will be considered fully developed from that point.
Basic straight tension development length is calculated using equation 13.1.2.2. The following factors are used in this equation:
- k1 = reinforcement location factor
- "concrete below" is taken as the depth from the bar center to the bottom of the concrete section
- 1.3 for concrete below > 300 mm
- 1.0 for concrete below ≤ 300 mm
- k2 = (132 - db)/100
- fsy = yield stress of bar
- cd = assumed to be the vertical clear cover, implying that the minimum bar clear spacing is greater than or equal to twice the clear cover
In addition, the following factors are applied:
- coating factor
- 1.5 for epoxy coated bars
- 1.0 for uncoated bars
- lightweight aggregate concrete factor:
- 1.3 for concrete density ≤ 2100 kg/m3
- 1.0 for concrete density > 2100 kg/m3
For development of standard hooks, basic tension development length is calculated as half the straight tension development length in accordance with Clause 13.1.2.6.