Tie requirements for rebar lap splices per ACI

[abusementpark]

Can anyone tell me which ACI document defines how rebar lap splices are required to be tied (i.e. how many ties, spacing, etc.), assuming there is a requirement?

Also, what is the difference between a regular lap splice and "development" splice where the bars are not tied?

 

[ron9876]

Not a requirement unless you are doing something unusual.

Development length is the length required to embed a bar into concrete to develop it. A lap splice is the length required to overlap bars to transfer load from one bar to the other.

ACI318 has requirements.

 

[msquared48]

Just tied sufficiently to maintain the alignment of the bars, to include the lap requirement, and keep the cage from falling apart during the pour.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[DST148]

abusementpark: Your question has already been answered as above.
As an aside: Reference ACI 318-05. The general development length equation has a parameter that represents the contribution of confining reinforcement. ACI gives two-tier approach for calculating development lengths. Section 12.2.2 is a simplified approach. Per this section stirrups or ties are not required per say, but if you want to take advantage of the presence of ties then they have to conform to the code minimum.
Section 12.2.3 represents the general development length equation. Here transverse reinforcement index is calculated based on area of ties, spacing of ties, and the number of bars being developed or spliced. The development lengths, and in turn the splice lengths, can be significantly reduced by taking advantage of the presence of the confining reinforcement. The designer has an option here.

 

[hokie66]

Don't confuse tie wire to hold the bars in place for placement with structural ties which confine the reinforcement.

 

[DST148]

hokie66 - I agree that I should have said ron9876 in place of as above in my post. There is no confusion between tie wires and ties here.

 

[TXStructural]

ACI 318-11 7.8.1, in part: "Reinforcement...shall be accurately supported before concrete is placed, and shall be secured against displacement within tolerances..."
In general, the bars should stay in place, or deflect under the weight of workers and construction loads (like wheelbarrows) and then rebound to the required position when the load is removed. Tying of bars, in all cases, is "temporary" and ONLY required for maintaining location during construction and in wet concrete. Wire ties have no effect on design, or on installed performance.

Caution, sales pitch: For field personnel, CRSI's "Placing Reinforcing Bars" covers most placing issues encountered by placers and inspectors.

 

[abusementpark]

Development length is the length required to embed a bar into concrete to develop it. A lap splice is the length required to overlap bars to transfer load from one bar to the other.

So when I overlap bars to transfer tension, they don't have to be tied? For instance, can I lap bars but have a couple inches of space between them and still transfer the tension?

 

[TXStructural]

That is referred to as a noncontact lap splice, and it is acceptable. ACI 318 paragraph 12.14.2.3 covers this.

 

[ToadJones]

abusement-
I think this is similar to the approach I use when developing anchor rods with high tension loads.

 

[abusementpark]

That is referred to as a noncontact lap splice, and it is acceptable. ACI 318 paragraph 12.14.2.3 covers this.

Ok, I will check that section out tomorrow when I get to the office. Thanks!

 

[abusementpark]

abusement-
I think this is similar to the approach I use when developing anchor rods with high tension loads.

Exactly. I usually apply the same logic. I just wasn't sure if it was "codified."

 

[DST148]

abusementpark: noncontact lap splices are permitted subjected to the limit of 6" or one-fifth the splice length whichever is less. The commentary clarifies that most research was conducted with reinforcing within this spacing.
Moreover noncontact lap splices are permitted only in flexural members. My understandng is that noncontact lap splices would not be applicable in (direct) tension members.