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Ω_{o}




ACI 31811/ ACI 31814 Anchor Bolt Seismic Design Overstrength Factor Ω_{o}
For anchor bolt design when SDC>=C and E>0.2U, anchor bolt design shall satisfy
one of the 4 options in D.3.3.4.3 (a)~(d) for tension or one of the 3 options in D.3.3.5.3
(a)~(c) for shear.
D.3.3.4.3 option (d) for tension or D.3.3.5.3 option (c) for shear is the most practical
option engineer can choose to satisfy this additional seismic design requirement.
It's an approach to increase the seismic load E by multiplying overstrength
factor Ω_{o}


ACI 31811 D.3.3.4.3 Option (d)

ACI 31811 D.3.3.5.3 Option (c)









Where Can I Find This Seismic Design Overstrength Factor Ω_{o}
for My Anchor Bolt Design 
For building column or industrial structure such as
piperack column anchorage,
the structural overstrength factor obtained from ASCE 710 Table 12.21 shall be
used. 


For nonbuilding structure or equipment such as vessel,
tank, or pump foundation anchorage, the overstrength Factor Ω_{o} is not available in the first or second print
of ASCE 710.
It's available in the third print
of ASCE 710 or Supplement 1 to the first or second print of ASCE 710.
The overstrength factors for various nonstructural components are given in ASCE
710 Tables 13.51 [Coefficients for Architectural Components] and 13.61
[Seismic Coefficients for Mechanical and Electrical Components].








How Can I Incorporate This Seismic Design Overstrength Factor Ω_{o}
for My Anchor Bolt Design 
Once you get the overstrength Factor Ω_{o} , you can multiply this
factor to the seismic component in the load combinations as shown below in red.
In Civilbay spreadsheet load input fields, input the tensile N_{u} and shear V_{u}
loads derived from load combinations where the E
component was increased by multiplying
overstrength factor Ω_{o}.
Select Tensile=Option D and
Shear=Option C as shown
below in Civilbay anchor bolt design spreadsheet. 



ACI 31811 9.2.1 
U = 1.2D + Ωo (1.0E)+ 1.0L + 0.2S
U = 0.9D + Ωo(1.0E) 
Eq. (95)
Eq. (97) 



Select Tensile=Option D and
Shear=Option C in
Civilbay anchor bolt design spreadsheet. 





ASCE Anchorage Design for Petrochemical Facilities 
Seismic Anchorage Design for Petrochemical Facilities NBCC 2010 
ASCE Guidelines For Seismic Evaluation And Design Of Petrochemical Facilities
2nd Edition 
Seismic Design for Petrochemical Facilities NBCC 2010
NBCC 2005 
ACI 31811 / ACI 31814 Seismic Anchor Bolt Design Overstrength Factor Omega 



















