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Rebar lap splice transverse reinforcement additional to shear links
9

Rebar lap splice transverse reinforcement additional to shear links

Rebar lap splice transverse reinforcement additional to shear links

(OP)
Hi buddy
We know transverse reinforcement is required to be provided at the lap zone of rc beam, I would like to know your practice if shear links are already provided for the beam, the area of transverse reinforcement in additional to the shear links area or not

Thanks

RE: Rebar lap splice transverse reinforcement additional to shear links

Quote:

We know transverse reinforcement is required to be provided at the lap zone of rc beam,...

From where you have learnt this requirement? Are you talking about a typical beam-slab condition at the location of splice of beam main reinforcement? If this is the case, no, the transverse reinforcement can't be counted for shear strength of the beam.

RE: Rebar lap splice transverse reinforcement additional to shear links

I believe you can count any shear reinforcement that's present towards any reduction in lap length or to provide the requirements for confinement of the lapped regions. It isn't additional to the requirement for shear strength.

I.E. The opposite of what r13 is stating if I'm understanding his response correctly?

RE: Rebar lap splice transverse reinforcement additional to shear links

I was thinking the transverse reinforcement in the OP's statement is slab reinforcement transverse to the beam. If you are adding more stirrups/shear links, then it shall be counted towards the shear strength of the beam. But I don't think the additional stirrups can be counted on to reduce the splice length for bars enclosed in the stirrups. As the splice length is the length required to transfer tension from one bar to the other, that has nothing to do with shear. Correct me, if I am wrong.

RE: Rebar lap splice transverse reinforcement additional to shear links

Transverse reinforcement is the shear reinforcement in a RC beam. Most codes would disagree with you on the fact that lap lengths cannot be reduced with sufficient transverse reinforcement.

RE: Rebar lap splice transverse reinforcement additional to shear links

Agent,

Where I said it can? I am confused. However, Per ACI, the splice length is less if they can meet the conditions stated below:

— Lap splices of deformed bars and deformed
wire in tension shall be Class B (1.3 ld) splices except that
Class A (1.0 ld) splices are allowed when:
(a) the area of reinforcement provided is at least
twice that required by analysis over the entire length
of the splice; and
(b) one-half or less of the total reinforcement is
spliced within the required lap length.

Note that both cases have nothing to do with stirrups, nor shear.

RE: Rebar lap splice transverse reinforcement additional to shear links

Quote:

But I don't think the additional stirrups can be counted on to reduce the splice length for bars enclosed in the stirrups.

Your words. This statement is wrong.

RE: Rebar lap splice transverse reinforcement additional to shear links

@Agent: gave you a LPS just to emphasize the importance of your post... deserved, too.

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

-Dik

RE: Rebar lap splice transverse reinforcement additional to shear links

Agent and dik,

So both of you think the stirrups can be counted towards reducing the "splice length"? Please clarify and provide your code provisions that allow it, if you don't mind. Thanks.

RE: Rebar lap splice transverse reinforcement additional to shear links

The OP's focus point/question need to be clarified. I might have misunderstood it. But let me be clear on my stance:

- Additional stirrups CAN BE counted towards shear strength of the beam, so the answer will be "YES", it is in addition to the already provided shear links.
- Stirrups CAN NOT be counted on to reduce the splice length of the bars it encloses, there is no such rule in the ACI.

RE: Rebar lap splice transverse reinforcement additional to shear links

The splice length is a function of the development length. For example in ACI take a look at how this is calculated and you'll find the answer. For example in ACI318-19 look into 25.4.2. development length clauses, in particular the Ktr factor.

Earlier versions of ACI318 had similar reductions. Other international codes all have similar reduction factors to the development lengths and hence splice lengths where there is sufficient confinement of splices.

There are also specific reductions to column splices allowed if you have sufficient confinement (CL 10.7.5.2.1).

r13, probably best to start your own thread in future if you have gaps in your knowledge of codes and principles involved rather than get into sideline conversations in others threads.

To the OP, did you get your answer in amongst that? No need to double count the requirement, all transverse reinforcement contributes.

RE: Rebar lap splice transverse reinforcement additional to shear links

Regarding your edit r13 to previous.

Quote (r13)

- Additional stirrups CAN BE counted towards shear strength of the beam, so the answer will be "YES", it is in addition to the already provided shear links.
- Stirrups CAN NOT be counted on to reduce the splice length of the bars it encloses, there is no such rule in the ACI.

See above post, you're mistaken/incorrect/wrong in this instance.

RE: Rebar lap splice transverse reinforcement additional to shear links

Below is copied from ACI318-08. I've no access to, nor knowledge on, ACI318-19 though. Please let me know my "gap" in my knowledge on the code.



12.2.4 — The factors used in the expressions for development of deformed bars and deformed wires in tension in 12.2 are as follows:
(a) Where horizontal reinforcement is placed such that more than 12 in. of fresh concrete is cast below the development length or splice, ψt = 1.3. For other situations, ψt = 1.0.
(b) For epoxy-coated bars or wires with cover less than 3db, or clear spacing less than 6db, ψe = 1.5. For all other epoxy-coated bars or wires, ψe = 1.2. For uncoated and zinc-coated (galvanized) reinforcement, ψe = 1.0.
However, the product ψtψe need not be greater than 1.7.
(c) For No. 6 and smaller bars and deformed wires, ψs = 0.8. For No. 7 and larger bars, ψs = 1.0.
(d) Where lightweight concrete is used, λ shall not exceed 0.75 unless fct is specified (see 8.6.1). Where normal weight concrete is used, λ = 1.0.

RE: Rebar lap splice transverse reinforcement additional to shear links

Hint.... bowrightK_trbowleft

Perhaps re-read my reply. Requirements are similar in 2008 and 2019 code.

RE: Rebar lap splice transverse reinforcement additional to shear links

Thanks Agent... I wasn't going to reply... it was becomming an engineering Monty Python skit... I think this topic has been resolved... it may be best for the OP if it is dropped unless the OP needs clarification or additional information...

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

-Dik

RE: Rebar lap splice transverse reinforcement additional to shear links

I think the confusion here is the phrase "We know transverse reinforcement is required to be provided at the lap zone of rc beam, ...". I don't think it is addressing the development of hooked bars in tension, which allows a 0.8 reduction for the development length Ldh, but again, it has nothing to do with splice length.

Please let's be courteous towards each other. None of us are perfect, but facts and truth will come after sensible discussions.

RE: Rebar lap splice transverse reinforcement additional to shear links

R13,
The below link is for high strength concrete beam, but does give you some very good perspective on the transverse reo and the effect on the behavior of lapped slices.

https://www.researchgate.net/publication/284028999...

The transverse reo in my mind is providing some confinement to the reo, as would shear ligs in a concrete beam, which would increase the bond stress of teh reo, making the laps more efficient.



https://www.mdpi.com/1996-1944/13/17/3701/htm

In seismic zones, often teh concrete codes have minimum requirements around confinement to ensure the bonds of reo do not reduce over the period of an earthquake.

RE: Rebar lap splice transverse reinforcement additional to shear links

rowingengineer,

Thanks for the information, I'll look into it. But I am not a researcher, so I don't have the knowledge to judge the "permissibility" of reducing splice length due to confinement of stirrups, or any other transverse reinforcement. At this moment, I am not aware of any proposed change in ACI regarding this matter, I chose to stick to the code for now, which can be very conservative. BTW, as a side note, that the excessive reinforcement clause is also not to be considered for splice length calculation.

Does Euro Code permits reducing splice length due to confinement? I am curios to know.

RE: Rebar lap splice transverse reinforcement additional to shear links

Quote (r13)

Does Euro Code permits reducing splice length due to confinement? I am curios to know.

Yes eurocode 2 does consider transverse reinforcement to reduce the development and hence splice length. Most codes consider this in one form or another, some codes only consider for compression or tension, not both.

RE: Rebar lap splice transverse reinforcement additional to shear links

Agent,

I think your answer is a welcome news for the OP, who should be use one of the country code using Euro code as the mother code. Unfortunately, ACI does not allow it for tension splice, and I wouldn't argue with it, as it is a conservative practice. Also, I question the wisdom in providing more shear links just to save a little in splice length, unless shear is a concern too.

RE: Rebar lap splice transverse reinforcement additional to shear links

I just checked ACI, for splice for compression, it is allowed to reduce the splice length for bars enclosed in spirals, and ties with spacing not greater than 4". Also, the reduction is allowed for the excess reinforcement too.

RE: Rebar lap splice transverse reinforcement additional to shear links

2

Quote (r13)

ACI does not allow it for tension splice,

I'm sorry but [again] this is incorrect. Read the ACI development clause again, the 12-1 development equation considers this effect. Honestly, I don't know how to say it again and again and get through?

So let's approach it from your side, you prove why you're saying ACI318 does not consider this when the K_tr factor [as I've noted twice previously now] considers A_tr [the transverse steel total area and spacing and number of bars crossing a split all form part of eqn 12-2],

In ACI318-08 clause 12.2.1 states you can use eqn 12-1 for L_d which then uses eqn 12-2 for calculating K_tr.

So why are you stating ACI318 does not consider this effect? I'm at a loss to understand your logic, it's in black and white in ACI318.

Just because you say it repeatedly does not make your view any more correct.

RE: Rebar lap splice transverse reinforcement additional to shear links

2
ACI318 commentary definition - Ktr is a factor that represents the contribution of confining reinforcement across potential splitting planes.



in 12.2.2 the (cd+krt)/db is assumed to be 1.5 hence why 12.2.2 doesn't mention Ktr or Atr.



if the world was according to me, I would push all engineers to understand the reason behind codes, not just apply.

RE: Rebar lap splice transverse reinforcement additional to shear links

2
Here's another vote for it contributing in ACI through the development length facto Ktr.

R13, there is an ongoing issue with your tendency to express incomplete or incorrect statements as definitive fact. There's nothing wrong with expressing when your understanding of a subject is limited, or waiting for another member who will be able to better address the question. None of us have all the answers -- but we all share the ethical responsibility to represent our abilities and limitations truthfully. Even on internet forums.

----
just call me Lo.

RE: Rebar lap splice transverse reinforcement additional to shear links

Very glad to have participated in this discussion, and finally reached the root of my knowledge lapse after a big circle. This is not an excuse, but since the change in code for calculating development length (in the 90s?), I've conveniently and conservatively taken KTR = 0, thus the reason for it has been neglected until now.

Quote:

R13, there is an ongoing issue with your tendency to express incomplete or incorrect statements as definitive fact.
Please take issue with me whenever you see the incomplete or incorrect statements been pushed by me as the definite fact. I have been carefully phrasing my responses/comments/opinions, in order not to be construed as "authoritative/definitive", but I guess I've not worked hard enough though.

RE: Rebar lap splice transverse reinforcement additional to shear links

Quote (r13)

I have been carefully phrasing my responses/comments/opinions, in order not to be construed as "authoritative/definitive", but I guess I've not worked hard enough though.

#MeToo. Even when I'm right about stuff, choosing language that in any way implies that my statements are "facts" tends to get people's hackles up in a hurry. As a result, you'll see a lot of this kind of thing in my writing here:

In my opinion... (I don't bother with the "humble" part as nobody would fall for that)

In my experience...

I believe...

It is my belief that...


It gets so repetitive that I can barely stand it. But it is effective.

RE: Rebar lap splice transverse reinforcement additional to shear links

KootK,

Thanks for the understanding and suggestions. For this case, I forgot to add the words "I think.." in my statement, which is often seen in my responses.

My reminder to all critics, while I appreciate your efforts to correct my mistake, please do not assume everybody is so smart as you to figure out your hint(s), go to the point directly, as Agent666 did in his response posted on 11 Jan 21 05:31, but with his hint started from response posted on 10 Jan 21 18:44, after 18 exchanges in between. I did have missed his "hint" made on 10 Jan 21 20:25 though. Damn stupid is the only word I can put on myself for the miss.

RE: Rebar lap splice transverse reinforcement additional to shear links

Quote:

but we all share the ethical responsibility to represent our abilities and limitations truthfully. Even on internet forums.

I agree completely. To my standard - unethical behavior is 1) to mislead less experienced intentionally, and 2) seeing a mistake, but not to put up efforts to correct the mistake forcefully in a direct manner. A vague answer, or challenge, could lead to more unnecessary mistakes, and degrade the thread. Name calling is not the best strategy to correct a wrong, as it is insulting in nature.

RE: Rebar lap splice transverse reinforcement additional to shear links

As one who tends to draw a little ire, the following suggestions have also been made to me, by moderators, in the past (not here at Eng-Tips, yet):

1) Try to avoid contributing more that four comments to any one thread and;

2) Avoid directly addressing anyone other than the originating poster unless responding to a question directly asked of me.

I do not follow these recommendations rigorously because doing so would utterly neuter me for some of the deep dives that I like to go on. That said, when I do drift past these limits, I will pause to ask myself if I'm still contributing something meaningful to the discussion. As in all things... judgment and moderation tend to smooth the path.

RE: Rebar lap splice transverse reinforcement additional to shear links

KootK,

Obviously I've violate your "4 comments" rule, ad advise received from moderator of this forum - try to avoid direct conflict with other members buy walk away. But, due to personality, I hate to walk away from vague comments, and not to acknowledge my mistake once the fact/truth is coming out. I shall refine my temper through learning from the hard lessons. Thanks again.

RE: Rebar lap splice transverse reinforcement additional to shear links

Thanks R13 and KootK... I appreciate and agree with your perspectives in these last several posts.

----
just call me Lo.

RE: Rebar lap splice transverse reinforcement additional to shear links

Lo,

Appreciate your understanding. Thanks.

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