Reinforcement detailing at end of member - does the end face need to be reinforced?

[bugbus]

My question is about the reinforcement detail at the end of a slab, footing, wall, etc.

I have noticed that in older drawings (possibly up until the 80s), the end face of the member was often left "unreinforced", similar to Detail 'A' or 'B' below. Note that although 'A' is fully closed off, this would be nowhere near enough for a lap length.

Nowadays, at least in Australia, Detail 'C' is ubiquitous.

Is there a particular need to 'close' the reinforcement at this face of the member? I have heard the word 'splitting' being thrown around a lot in this situation, but I've never seen a situation where a member has split through its full thickness before.

Another example would be a retaining wall as shown below (please ignore the fact that not all the wall reinforcement is shown). Would the below detail be acceptable from your point of view? (Noting that the single bend in the reinforcement would allow some more flexibility from a construction point of view).

 

[dik]

I've seen it done, more often in older projects that other's have done. I don't.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[bugbus]

Fair enough dik, any particular reason why or just happy to go with the common practice?

 

[rapt]

I think it started with PT slabs in Australia where it helps with bursting reinforcement and became standard for all slabs. Plus it helps not having special bars with cogs where you have varying bar lengths due to sloping sides etc. Easier with straight bars + 1 size U-Bar.

Same as deformed bar for stirrups in beams. When I started it was all plain bar stirrups. We changed to deformed for PT in the mid 1970's as we needed to use short cross bars to support the tendons and they tended to slip too often with plain bar stirrups so we changed to deformed bars for the stirrups. Eventually all stirrups were deformed bars.

 

[dik]

I don't think it's needed...

as rapt notes we used to use it in the edges of PT slabs for containment... I haven't done a PT slab in decades and don't know what current practice is. I seem to recall just using a couple of #4 bars continuous, with 'end ties', one on, ea side of the anchor... and I've never used plain bars...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[bugbus]

Thanks rapt, that's really interesting to know.

About what time did PT slabs become the standard construction type in most buildings in Australia? I assume somewhere around the 70s like you mentioned?

 

[Settingsun]

I was told long ago that the U-bar provides some tolerance on main bar length. Later went to an inspection where the U-bars weren't bent to 90 degrees and had a cover problem instead...

I think not required unless for a specific concentrated load. Eurocode 2 or Model Code requires it for slab edges though IIRC.

 

[rapt]

Gusmurr,

It was really only starting in the 1970's. First were done in the mid 60's but most consultants tried to avoid them as they either did not want the increased design cost or did not understand them so lost control over the design.

It probably wasn't until at least the late 80's when consultants were more willing to attempt the design themselves once software was available to reduce the design time that PT slabs really started to become more prevalent.