Phi factor for column web panel zone shear strength question

[RobertEIT]

I am looking at <<AISC Seismic Design Manual>>, example 4-11 SMF Beam-Column Connection Design, at page 4-64 and 4-65, it used Phi=1.0, But it should be Phi=0.9 according to <<AISC-13th>> page 16.1-119, section "Web Panel Zone Shear". Is it a mistake or do I missed anything?

Actually, in another place of <<AISC Seismic Design Manual>>, example 4-4 OMF Beam-Column Connection Design, page4-18, it does use Phi=0.9 to calculate column panel zone shear strength.

Or is it because for SMF, we have to use Phi=1.0, while for OMF and IMF we have to use Phi=0.9?

Your help will be appreciated very much, thanks a lot.

 

[JAE]

AISC Seismic Specification Section 9.3a (page 6.1-31 in the manual) - says phi = 1.0.

 

[RobertEIT]

Thanks JAE.

It seems AISC does give different Phi value for SMF vs. OMF and IMF. Don't know what's the theory behind that.

 

[ARLORD]

See section 9.3a, phi = 1, Shear strength for SMF. The Expected Yield Load is used for SMF connections.

Section 10.3 for IMF. The Building Code Load Combinations loads are used and not the Expected Yield, for IMF.

 

[ARLORD]

The Seismic Provisions are additional requirements to AISC Edition 13. If there are no requirements in the Seismic Provisions, then the 13th Edition applies.

 

[ARLORD]

SMF's use higher Expected Yield loads for connections. You do not want to reduce these loads, therefore use phi = 1, otherwise use phi as in the 13th edition.

Similar to concrete SMF connections. Those connections use the yield strength of the rebar to calculate the beam moments for connection design, and again phi =1.