Using hooked bars in lieu of threaded bars for soil nailed wall

[augustus50]

I wonder if anyone has experience using bars with a standard 90 degree bend instead of threaded bars for soil nailed retaining walls (shotcrete fascia). We typically use a minimum 3 inch thick shotcrete facing, although actual concrete use indicates an average thickness of more than 4 inches.. Typically these walls are temporary (1-6 months).

I understand there may be a problem with minimum cover in attaining required development length in the bend. I also understand ties may be necessary to compensate for the minimum cover. However,the shotcrete facing is almost always very thick in the immediate vicintiy of the nail.

Would a layer of welded wire fabric (6"x6"X WW2.9, the old 6x6x6 gage)placed over the full length of the bend with at least 2.5 inches of shotcrete placed over the bend be sufficient to reach the full tensile strength of the bar with an ACI standard bend length?

 

[civilperson]

Depends on the diameter of the bar with the hook.

 

[PEinc]

It seems to me that you would need a lot of shotcrete thickness to fully cover the 90 degree bend. A #8 bar calls for a 6" diameter bend. If the whole bend needs to be in the concrete, the concrete would probably need to be 6" = about 2" cover = 8" thick at the nails. If not, the bar may try to straighten out. If you want to use rebar, you may be better off buying a larger diameter bar and then threading the end.

 

[augustus50]

Regarding my question about hooked bars in shotcrete-soil nailed walls, the hook is embedded almost completely in the soil nail. Thus, the wall can be 3-4 inches in most areas and 5.5-6 inches around the hook. My main question concerns the need for reinforcement surrounding the hooked portion of the rebar and the required length of the hook or bend.

The code normally requires closely spaced stirrups along the hooked length if you are using the minimum development length for hooked bars. We are using wire mesh (6x6x6 gage) above and below the bar instead of stirrups. I am wondering if I could use a hooked length somewhere in between the minimum development length for hooked and straight bars.

 

[PEinc]

I think you are barking up the wrong tree with the hooked bar and extra shotcrete concept. Just use thread bars with bearing plates and nuts, like the rest of the wall designers and builders do.