ACI 318-11 Lap Splice Class A B

[LannyBudd]

I have a few questions about how to interpret ACI 318-11

1) I don't understand the difference between Class A and Class B Lap splices. Do you always assume Class B unless you satisfy 12.15.2.a &12.15.2.b?

2) When determining the lap splice length, is it acceptable to use the table in 12.2.2? When should equation 12-1 be used? The way that I interpret ACI 318-11, the table in 12.2.2 can always be used in-lieu of equation 12-1.

The result from table 12.2.2 are significantly more conservative than equation 12-1, especially if you have to multiply by 1.3 for Class B splice. So I would like to use equation 12-1. I just do not understand K_tr term. Conservatively, I can assume that Ktr=0 even if I transverse reinforcement, however occasionally I would like to sharpen the pencil and justify the use of a smaller lap splice length.

3) Can someone please explain how to calculate A_tr in equation 12-2 for K_tr?

Thank you!

 

[JAE]

1) yes - for columns, etc. you use Class B unless you meet the requirements for class A in Table R12.15.2. Class B splices are used in beams per section 7.13.

2) Table 12.2.2 is a slightly simplified method of applying Eq. 12-1. In the table, there are a few assumptions with respect to bar spacing, cover, etc.

Yes - you can use Ktr = 0 as it indicates - more simple but more conservative, too.

3) Look at the definition of Atr in Chapter 2.



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[PSEPK]

I second JAE.

Commentary to ACI section 12.2.3 discusses some points regarding use of Ktr.

Section 4 of PCA Notes on ACI318-08 explains the requirements for splicing of reinforcement, given in ACI 318 chapter 12. Detailed procedure of calculating Ktr has been given in Example 4.3 of PCA Notes, at the end of this section.