Bar Hooks and Cogs

Hooks are defined in AS3600 Clauses 8.2.12.4, 13.1.2.7 and 17.2.3.2. The
length of steel needed to physically make each hook is given in Tables 16,17
and 18. The length of steel in a bar with a hook is the overall length of the
straight portion plus hook or cog length.

AS3600-2009 no longer requires a longer hook to provide end anchorage of a
beam ligature. Clause 8.2.12.4 only requires that detailing be such as not to induce
splitting or spalling of the concrete cover. Fitment cogs may be used but must
have at least 50mm cover, another relaxation of AS3600-2001 requirements.

AS3600-2009 Clause 8.2.12.4 Anchorage of Shear Reinforcement

The anchorage of shear reinforcement transverse to the longitudinal flexural reinforcement may be achieved by a hook or cog complying with Clause 13.1.2.7 or by welding of the fitment to a longitudinal bar or by a welded splice.

NOTE: The type of anchorage used should not induce splitting or spalling of the concrete cover.

Notwithstanding the above, fitment cogs are not to be used when the fitment cog is located within 50mm of any concrete surface.

Fitment hooks may again be considered as standard hooks provided adequate
cover. The requirement for 10d_b fitment hooks has been dropped.

Length of steel required to bend a hook and cog

Notes:

1. See AS3600-2009 Section 10.8 for background information, including rebent and coated bars.
2. A pin size equal to or less than the quality control bend test must never be used.

Approximate overall dimensions for a 180^o hook

Approximate overall dimensions for a 90^o cog

In the above tables, no allowance has been made for spring-back after bending.
All dimensions are therefore nominal. The real overall diameter of a deformed
bar is approximately 112% of the nominal diameter. A 90º bend longer than
10d_b overall gives the same anchorage as a 90º cog.