ACI Requirements for Bottom Bar Splice Location

[Nick6781]

Hi everyone,

Can you please advise on the following questions?

1. Per ACI 318-11, Section 12.15, the use of Class A splices is intended to encourage splicing locations away from areas of high tensile stress. Does this imply that Class B tension splices can be used anywhere, since they are intended to develop full tension in high tensile stress locations? For example, although it may not be a good practice, using a Class B tension splice to lap the bottom bar in a two-way slab in the middle of the span is not prohibited. If a contractor chooses to do this, the engineer does not have code backup to refuse it.

2. One exception is for the continuous integrity bar over the supports. ACI 318-11, Fig. 13.3.8, shows that the allowed splice region is within 0.3 ln from the face of an interior support. What is the purpose of this region? Am I required to locate the centerline of the splice within this region, or must the entire spliced length be within it? I have a scenario where the required splice length is larger than the region. I don’t think it’s a problem but would like to get some consensus.

Thank you!

 

[Nick6781]

Any thoughts on this?

 

[KootK]

For many application, I believe that you can indeed splice wherever you like so long as you increase the splice length accordingly.

As for the integrity steel, that is meant to form a post punching shear caternary system. If you imagine the deflected shape of the slab:

1) steep slope but little curvature near supports.

2) Lots and lots of curvature (and soffit cracking) at midspan.

So it kind of makes sense not to splice integrity bars at midspan where tensile stresses will be very high.

 

[OldDawgNewTricks]

For your example of two-way slab splice locations in ACI 318-11, see 13.3.8.5 and Figure 13.3.8 for some limitations on where splices are permitted.