Standardisations of hooks in AS 3600

![CDATA[In all types of reinforced-concrete members including beams, slabs, walls and columns, there are cases when the ends of steel reinforcing D500N bars or R250N bars in tension must be bent into hooks or cogs to provide additional anchorage over a short distance. Hooks with a minimum bending radius and straight extension length beyond the bend are specified in the Concrete Structures Standard AS 3600, but their details depend on the application and the type of reinforcement. For example, hooks on stirrups in beams must have a longer straight extension than on column ligatures of the same diameter, while fitments made from wire may be bent around smaller diameter pins than bars. Reference is also made to a standard hook in AS 3600, which confusingly can be a hook or a cog, that cannot be used in all applications. Lack of standardisation considerably complicates reinforcement detailing and checking on site, which increases costs and the chance of error. A detailed review has been made of the requirements for hooks and cogs in reinforced-concrete members in order to arrive at standard details suitable for all applications. Several series of pull-out tests have been performed to examine the influence that important variables have on the anchorage strength of bars and wires with different hook and cog details in different applications. The main variables investigated are bar type, bar diameter, radius of bend., straight extension length, trimmer bar diameter, concrete cover and concrete compressive strength. The effects of confining forces and pre-cracking have also been modelled to represent different applications, e.g. columns and beams. Simple improvements to the current rules in AS 3600 are recommended.]]