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Background

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. 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

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Capacity Reduction Factor (Bending Moment with compression)

  1. Table 2.2.2 (d) has changed the Φ0 factor to be equivalent to math 0.65 \times k_\Phi. There is a minor impact on the reduction factor where columns are slender or where math Q/G \leq 0.25, refer to calculations for math k_\Phi.

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Shear Strength

  1. Upper limit shear strength (math V_{u,max}) has been reduced by 10% in equation 8.2.3.3(1)

  2. Factor kv (simplified method) increases the concrete shear capacity (math V_{uc}) by up to 50% from Amendment 1, in particular for thinner depth sections without reinforcement. Previously a limit of math k_v = 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 math k_v = 0.15. Refer Cl 8.2.4.3(a)

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Fitment Detailing / Spacing requirements

  1. The minimum reinforcement spacing is now relaxed for beams with low shear force. Where math V^* \leq \Phi V_{u,min}, the fitments may now be spaced at 500mm or math 0.75 \times D, whereas previously 300mm or math 0.5 \times D limit was imposed under all circumstances apart from very large beams.

  2. For a short column satisfying, math L < 5 \times \text{depth}, Amendment 2 has introduced minor changes to the max allowable fitment spacing to reflect the actual fitment strength. math \text{spacing} = \sqrt{(f_{syf}/500)} \times 24 \times d instead of math \text{spacing} = 24 \times d previously in accordance with Cl 14.5.4(b)

  3. For beams of math \text{depth} > 300\text{mm}, shear fitments are now required even when math V^* does not exceed math \Phi V_{uc}. An additional factor math k_s 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).

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Renaming of Variables

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

8. math K_s now renamed to math k_s (Beam Depth Factor to Determine Reinforcement Required). The definition of math K_s 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).

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Assumptions

  1. 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.
  2. ClearCalcs concrete calculators utilise the Simplified Method for calculating math k_v and math \theta_v 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.