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Strength of Bolts PCI 7th Edition vs. AISC

Strength of Bolts PCI 7th Edition vs. AISC

Strength of Bolts PCI 7th Edition vs. AISC

(OP)
Hello,

I have a design that requires bolts capable of withstanding 50kips (service) in pure tension. I looked at A307 bolts. My background is in the precast industry, so I first looked at the attached table from PCI. When I looked at AISC(14th) Table 7-2 I see that the LRFD values are identical to the loads listed in PCI but the ASD loads in the steel manual are almost 13% higher than what PCI published. Any reason why PCI used an Ω factor of 2.25 while AISC only uses 2.0? What's really strange to me is that PCI names AISC 13th edition as the source for the attached table. I think the 13th edition uses 2.0 also, correct?

RE: Strength of Bolts PCI 7th Edition vs. AISC

AISC revised bolt shear strengths between the 2005 and 2010 Specifications. Briefly, a connection length reduction factor was increased from 0.80 in AISC 360-05 to 0.90 in AISC 360-10. Thus, the published shear strengths increased by 12.5%. This is covered in more detail in a first quarter 2010 AISC Engineering Journal article ("Bolt Shear Design Considerations") by Ray Tide. The article is available for download (free for AISC members) at www.aisc.org.

RE: Strength of Bolts PCI 7th Edition vs. AISC

(OP)
Ok, thank you so much!

RE: Strength of Bolts PCI 7th Edition vs. AISC

You're right in regard to shear strengths Hokie, but my curiosity led me to do a little digging. Regarding bolt tensile capacities, the PCI table corresponds to values published in the AISC ASD (9th) and LRFD (3rd) edition manuals. There must have been a separate, older increase in allowable bolt tension stresses.

The bolt tensile capacity values are unchanged between AISC 13th to 14th.

RE: Strength of Bolts PCI 7th Edition vs. AISC

(OP)
Yes, I was specifically referring to the tension stresses originally.

RE: Strength of Bolts PCI 7th Edition vs. AISC

In regards to tension, the 1989 (and earlier) AISC Specifications included a 5 ksi "discount" in allowable tensile strength for ASTM A307 bolts. This is mentioned in the Commentary to the 1986 AISC Specification (in the first edition LRFD Specification) because the 5 ksi discount was removed. Thus, the factor of safety for the 1989 AISC Specification (in the green Manual) for A307 bolts in tension was 2.25 (the allowable tensile stress was 20 ksi). In AISC 360-05 and 360-10, the factor of safety is 2.00 and the allowable stress is 22.5 ksi.

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