Changes in AS3600:2018 Amendment 2 (Concrete)

A number of significant updates have been made with AS3600:2018 Amdt 2, whose key effects are on the spacing and quantity of shear fitments / ligatures required.

Capacity Reduction Factor (Bending Moment with compression)

1. Table 2.2.2 (d) has changed the Φ0 factor to be equivalent to 0.65 × kΦ. There is a minor impact on the reduction factor where columns are slender or where Q/G <= 0.25, refer to calculations for kΦ.

Shear Strength

2. Upper limit shear strength (Vumax) has been reduced by 10% in equation 8.2.3.3(1)

3. Factor kv (simplified method) increases the concrete shear capacity (Vuc) by up to 50% from Amendment 1, in particular for thinner depth sections without reinforcement. Previously a limit of kv = 0.10 was placed for any beam where minimum shear reinforcement was not satisfied or no fitments were provided. This has now been increased to kv = 0.15. Refer Cl 8.2.4.3(a)

You can access AS3600-2018 and other Australian Standards in ClearCalcs here.

Fitment Detailing / Spacing requirements

4. The minimum reinforcement spacing is now relaxed for beams with low shear force. Where V* <= ΦVu,min, the fitments may now be spaced at 500mm or 0.75 × D, whereas previously 300mm or 0.5 × D limit was imposed under all circumstances apart from very large beams.

5. For a short column satisfying, L < 5 × depth, Amendment 2 has introduced minor changes to the max allowable fitment spacing to reflect the actual fitment strength. spacing = √(fsyf/500) × 24×d instead of spacing = 24×d previously in accordance with Cl 14.5.4(b)

6. For beams of depth > 300mm, shear fitments are now required even when V* does not exceed ΦVuc. An additional factor ks has been added factoring down the upper limit shear force that may be taken without adding fitments in Eq Cl 8.2.1.6(1).

Renaming of Variables

7. Dc now renamed to b (smaller column cross-sectional dimensions). Refer Cl 1.7.

8. Ks now renamed to ks (Beam Depth Factor to Determine Reinforcement Required). The definition of Ks in Cl 1.7 has not been updated in Amendment 2 from its previous version. It is believed that this definition should be further expanded in future revisions to reflect its use in Cl 8.2.1.6(1).

Assumptions

The above is not a comprehensive list of Amendment 2 changes. However, they do reflect all the changes that are relevant to calculations performed in ClearCalcs. ClearCalcs concrete calculators utilise the Simplified Method for calculating kv and θv in compliance with Cl 8.2.4.1. Therefore the Amendment 2 updates for the "General Method" Cl 8.2.4.2 are not listed above.

ClearCalcs Calculators Affected by Changes

ClearCalcs has updated its calculator for consistency with this new amendment. ClearCalc's concrete calculators affected by Amendment 2 changes are:

• L-Type Cantilever Retaining Wall - Rectangular Concrete Beam
• Rectangular Concrete Column
• Concrete Pad Footing
• One-Way Concrete Flat Slab
• Concrete Wall Footing