Clarification on the Interpretation of the Exception on Appendix D

[2H3lp]

IBC 2009 Section 1908.1.9 exception 2 waives the ductile design requirement for anchors that resist wall out of plane forces determined per ASCE 7 eqn. 12.11-1(Fp=0.8*SDS*Wp). My question is: does this wall have to be a non-load bearing only? Or, can it include load bearing (you know axially loaded walls)?

Thanks,

 

[sandman21]

ASCE 7 applies to structural walls, ie load bearing. Non-structural walls fall under ASCE 7 Ch. 13 for there Fp loading with a min. anchorage load per footnote b in table 13.5-1 of equ. 12.11-1. It applies to both structural and non-structural walls, anchorage Fp is increased based on experiences from the Northridge earthquake.

 

[2H3lp]

Thank you Sandman21.

My next question then is: How can one know if (Fp=0.8*SDS*Wp) is greater than the force we get if we multiply by the 2.5? Or should we not even go there? Just check the Fp from the wall and move on?

Thanks again,

 

[sandman21]

The Fp equation was developed after Northridge to account for brittle failures of wall anchors. When you design to it for anchorage Fp you are already taking into account brittle failure, so the provisions of ACI should not apply. It should be noted that anchorage already has a factor of safety of; .8/.4 = 2.0, not the 2.5 in ACI but close.