ACI 318M-02 Anchorage rules

[Artymote]

I have had the argument put forward 'that the standard hook is one of the authorised method that can be substituted for the development length by the ACI 318M-02'
Referring to Clause 12.1.1.

I do not accept this argument where full tension strength of the member is required. For example, in the case of high moments in beam-column connection where anchorage is critical.

The argument that by hooking a bar one no longer needs to pay attention to the development length is ludicrous.

In BS 8110, it is clear that there is no substitute for the development of the tension bars with or without hooks. I do not believe the ACI is any different.

Is there anywhere in the ACI codes that clearly draws the distinction ?

 

[Taro]

See Section 12.5 for hooked bar development length.

 

[Artymote]

I am aware of section 12.5 for hooked bar development length, but does it really mean one can substitute one for the other ?

For the development of the full strength of the tension bars, I would say if you have to bend it to fit it in (which is common in my line of work), the hooked sections are a sub-component of the full length still required, not a substitute.

 

[Taro]

Yes, it really is a substitute for the straight bar development length. The hooked bar development length is also meant to develop the full tensile yield strength of the bar.

 

[Tryan]

Just passing through, saw your light on...!!I think I'm with Artymote on this one! How can a hook make any difference, other than it seems like it would!!!I would put it in the same category as a" belled pier", haven't done one of those for 20 years! All the pier foundations[up to 10 meters deep x 1.2 mtrs dia ] I've done in the past 10 years have been straight deformed bars! I will digress a little. A pretensioned concrete beam is made by tensioning cables through a mold and pouring concrete into the mold. The concrete is cured and then the cables are cut flush with the end of the beam!! And my point, are yes my point,why not leave them anchored,..... like a hook!Probably because it would serve no purpose other than to seem right...! I'll be on my way...

 

[mgg]

I'm with Taro. Realize that code requirements are not conjured up. They entail years of comprehensive research and development.

 

[BryanStein]

Hooked bars have a clearly defined developement length per ACI-318. Additionally, hooked bars for shear purposed are considered "anchored" (ACI-318's word, not mine) when they are below a #5 and are bent around the flexural reinforcing. Does this mean they are fully developed? It is unusual for ACI to be this vague, but in this case they are.

 

[etompos]

I conducted research on this matter albeit related to the development of hooked stirrups (see ACI Structural Journal vol. 99, no. 5, doc 99-S57). My research validated the equations for hook bar development length--meaning that hooked bars will develope yield when the hook development length complies with ACI 12.5. It must be noted, however, that for full development, the hook bend must be properly detailed so a compressive strut can form at the hook bend, and confining reinforcement must be provided. See ACI Committee report 352R-91 for a more detailed explaination of these principles.