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Anchor Bolt Design Seismic Provisions - ACI 318-19
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Anchor Bolt Design Seismic Provisions - ACI 318-19





Step 1: Check Seismic design category SDC >= C         Back to Top

Seismic Design Category SDC
ACI 318-19  17.10.1

Anchors in structures assigned to Seismic Design Category (SDC) C, D, E, or F shall satisfy the additional requirements of this section.


ACI 318-19 17.10.1

 

How to find out your structure's  Seismic Design Category SDC


1) Refer to ASCE 7-16 page 2 Table 1.3-1 to find out the Risk Category of your structure based on your structure's type and usage.

2) Refer to ASCE 7-16 page 84 Section 11.4.5 to find out the design spectral response acceleration parameters SDS and SD1 based on your structure's location

3) Refer to ASCE 7-16 page 85 Section 11.6 Table 11.6-1 and 11.6-2 to find out the SDC for your structure.


 ASCE 7-16 page 85 Section 11.6

 



Step 2: When SDC >= C, Check If Anchor Bolt Load E <= 0.2U - Tensile         Back to Top

ACI 318-19  17.10.5.1

This input is required when seismic SDC>=C. User can ignore this input when seismic SDC=A or B

Select Yes when E <= 0.2U
Select No   when E > 0.2U

E - Seismic component in the total factored tensile load Nu user input above
U - Total factored tensile load Nu user input above

Below are load combinations from ACI 318-19  5.3.1 by which user uses to get the total factored tensile load Nu for anchor bolt design.

 ACI 318-19   5.3.1 ACI 318-19  17.10.5.1

 


Step 3: When E > 0.2U , Select Anchor Bolt Seismic Design Option - Tensile         Back to Top

Tensile - Options to Satisfy Additional Seismic Requirements
ACI 318-19  17.10.5.3 (a) ~ (d)

This input is required        when     Seismic SDC >= C (17.10.1)     AND
                                                   Tensile E > 0.2U    (17.10.5.2)


User can ignore this input when     Seismic SDC < C   (17.10.1)      OR  
                                                   Tensile E <= 0.2U (17.10.5.1)


If user selects Option D below, check this help file  for more details on Ωo factor


If user selects Option D above, check this help file  for more details on Ωo factor



Step 4: When SDC >= C, Check If Anchor Bolt Load E <= 0.2U - Shear         Back to Top

Anchor Bolt Shear Load Seismic Component E<=0.2U
ACI 318-19  17.10.6.1

This input is required when seismic SDC>=C
User can ignore this input when seismic SDC=A or B

Select Yes when E <= 0.2U
Select No   when E > 0.2U

E - Seismic component in the total factored shear load Vu user input above
U - Total factored shear load Vu user input above

Below are load combinations from ACI 318-19  5.3.1 by which user uses to get the total factored shear load Vu for anchor bolt design.
 
 ACI 318-19   5.3.1 ACI 318-19  17.10.6.1


 


Step 5: When E > 0.2U , Select Anchor Bolt Seismic Design Option - Shear         Back to Top

Shear - Options to Satisfy Additional Seismic Requirements
ACI 318-19  17.10.6.3 (a) ~ (c)

This input is required          when   Seismic SDC >= C (17.10.1)       AND
                                                   Shear E > 0.2U      (17.10.6.2)


User can ignore this input  when   Seismic SDC < C     (17.10.1)       OR
                                                  Shear E <= 0.2U     (17.10.6.1)


If user selects Option C below, check this help file  for more details on Ωo factor


If user selects Option C above, check this help file  for more details on Ωo factor



Anchor Bolt Seismic Design Provision - Seismic Overstrength Factor Ωo         Back to Top

For anchor bolt design when SDC>=C and E>0.2U, anchor bolt design shall satisfy
For tension , one of the 4 options in ACI 318-19 17.10.5.3 (a)~(d)  or
For shear ,   one of the 3 options in ACI 318-19 17.10.6.3 (a)~(c)

The most practical option engineer can choose is
For tension , ACI 318-19 17.10.5.3 (a)~(d) , use option  (d)
For shear ,   ACI 318-19 17.10.6.3 (a)~(c) , use option  (c)

For both tension 17.10.5.3 (d) and shear 17.10.6.3 (c) option, user need to increase the seismic load E by multiplying overstrength factor Ωo

ACI 318-19 17.10.5.3 Option (d) ACI 318-19 17.10.6.3 Option (c)



Where Can I Find This Seismic Design Overstrength Factor Ωo for My Anchor Bolt Design         Back to Top

For building column or industrial structure such as piperack column anchorage, the structural overstrength factor obtained from ASCE 7-16
Table 12.2-1 shall be used.

In summary, the Ωo values for steel frames are


ASCE 7-16 Table 12.2-1


For nonbuilding structure or equipment such as vessel, tank, or pump foundation anchorage, the overstrength factors for various nonstructural
components are given in ASCE 7-16 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 Ωo for My Anchor Bolt Design         Back to Top

1. Once you get the overstrength Factor Ωo , you can incorporate this Ωo factor into the seismic component in the load combinations as shown
    below in red.

2. In Civilbay anchorage program load input fields, input the tensile Nu and shear Vu loads getting from load combinations where the E component
    was increased by multiplying overstrength factor Ωo.

ACI 318-19  5.3.1

3. Select Tensile = Option D and Shear = Option C as shown below in Civilbay anchorage design program.