Reducing Development Length by 20%

[pob11646]

In ACI 318-05 and also 318-08, Section 12.2.2 commentary, it is stated that "In the development of ACI 318-95, a comparison with past provisions and a check of a database of experimental results maintained by ACI Committee 408 indicated that for No. 6 deformed bars and smaller as well as for deformed wire, the development lengths could be reduced 20 percent using psi s = 0.8."

Am I reading this right, and is anyone doing this, i.e. reducing their development lenghts by 20 percent for No. 6 bars or smaller? Thanks.

 

[Lion06]

This is a pretty common reduction. It's even taken into account automatically in the handy table they give you in 12.2.2 - That is the difference in the coefficients (1/25 compared to 1/20, and 3/50 compared to 3/40).

 

[pob11646]

Thank you very much, StructuralEIT. I take it that the 20 percent reduction has already been applied, and that we cannot take any further reduction.

 

[Lion06]

That is correct if you are using the formulas in the table in chapter 12. If, however, you use the general equation it will have the psi s term in it. You will want to use 0.8 for #6 bars and smaller.