Re: ACI 318-05, Section 11.6.1

If my memory serves me (and it is getting more rusty these days) without digging out my various versions, this happened when going from ACI 318-99 to ACI 318-02 when the “alternative” load combinations from Appendix C in ACI 318-99 (aka the “ASCE 7 load combinations”) were moved into the main body of ACI 318 and the “traditional” ACI load combinations (i.e. 1.4D+1.7L, etc) were moved to Appendix C as well as the “alternative provisions for flexural and compression members” of Appendix B of ACI 318-99 were moved into the main body of the code for the 2002 version and the more “traditional” provisions were moved into Appendix B.  As part of this change, there was a new reliability study done if I recall correctly.  Thus, it was more than just the Phi factors moving from the ACI 318-99 Appendix C into the main body of ACI 318-02...they also adjusted the ACI 318-99 Appendix C Phi factors based upon this new reliability study.

HTH,

Scott
Adrian, MI


On 7/7/09 8:43 PM, "FSRahbar@aol.com" <FSRahbar@aol.com> wrote:

According to ACI 318-05, Section 11.6.1, the formula for calculating the Threshold Torsion for a concrete beam, is the same as formula given in ACI 318-99. Except that Strength Reduction factor, φ (Phi) has been reduce from 0.85 (ACI 318-99) to 0.75 (ACI 318-05).
 
Looks like the Threshold Torsion, has been reduce by about 13%. Or, am I missing another factor?

Thank you,

Farzin S. Rahbar, SE
David C. Weiss Structural Engineer & Associates, Inc.
(818) 227-8040 Ex. 13 Fax: (818) 227-8041

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