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o
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ACI 318-11/ ACI 318-14 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 318-11 D.3.3.4.3 Option (d)
ACI 318-11 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 7-10 Table 12.2-1 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 7-10. It's available in the
third print
of ASCE 7-10 or Supplement 1 to the first or second print of ASCE 7-10. The overstrength factors for various nonstructural components are given in ASCE 7-10 Tables 13.5-1 [Coefficients for Architectural Components] and 13.6-1 [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 318-11 9.2.1
U = 1.2D +
Ωo
(1.0E)+ 1.0L + 0.2S
U = 0.9D +
Ωo
(1.0E)
Eq. (9-5)
Eq. (9-7)
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 318-11 / ACI 318-14 Seismic Anchor Bolt Design Overstrength Factor Omega