Shear Lug Design in SDC C, D, E, or F

[VT17]

Section 17.2.3 of ACI 318-14 specifies when the overstrength factor is required to be used for design of anchors subject to tensile and shear loading in structures assigned to SDC C, D, E, or F. If I choose to design the anchors for tension only, then I would apply the overstrength factor to determine the design tensile loads per ACI. However, if I choose to use a shear lug to resist the shear loads, should the overstrength factor be applied for the shear lug design?

AISC DG 1 addresses the design of shear lugs and all it mentions is that when AISC Seismic Design Provisions are triggered (i.e. R > 3) then the "column base" can be designed for amplified forces including the amplified seismic load. I interpret "column base" to include shear lug and "amplified load" to be analogous to the actual load times the overstrength factor.

But what about if you choose to use a less detailed intensive LFRS with R </= 3 in a SDC C? I don't see any code that states the overstrength factor should be applied, but if you're designing the column/brace connection to the concrete to ensure the main LFRS is ductile, wouldn't you want the shear lug to also be designed with the overstrength factor?

Please ignore the fact there are other methods to design if the overstrength factor is to be avoided per ACI.

I appreciate your input in advance!

 

[KootK]

if you're designing the column/brace connection to the concrete to ensure the main LFRS is ductile, wouldn't you want the shear lug to also be designed with the over-strength factor?

I agree with that reasoning and would do the same. I'd view the shear lug as really a component of the anchorage and, therefore, apply over-strength to the shear lug design if over-strength would have been applied to the shear design of the anchor bolts in the absence of the shear lug. I think that a philosophically consistent approach to your entire load path is the key thing here and it sounds as though that's the direction that your own instincts are taking you.

 

[VT17]

Thank you KootK for your input. I agree with maintaining a philosophically consistent approach to the design. If anyone disagrees or knows of a resources that explains why shouldn't, I would love to hear from you.