STEEL STRENGTH FOR ALL ELEMENTS
The steel strength is provided on a separate table and is based on calculations from ACI 318 Chapter 17 and CSA A23.3 Annex D . ACI and CSA have different reduction factors for steel strength , thus the values for both ACI and CSA are published .
How to calculate anchor capacity using simplified tables
Adjustment factors are applied for all applicable near edge and spacing conditions .
For example , the capacity in tension corresponding to the anchor group based on worst case anchor “ a ” in the figure below is evaluated as follows :
ACI : CSA :
N des
= 4 • ФN n
• f A , x
• f A , y
• f R , x
• f R , y
N des
= 4 • N r
• f A , x
• f A , y
• f R , x
• f R , y
The process for calculating the capacity of a single anchor or anchor group is similar to the ASD calculation process currently outlined in section 3.1.9 of this document .
The design strength ( factored resistance ) of an anchor is obtained as follows :
Tension : ACI : N des
= n • min | ФN n
• f AN
• f RN ; ФN sa
|
CSA : N des = n • min | N r
• f AN
• f RN ; N sr
|
Shear :
where :
ACI : V des = n • min | ФV n
• f AV
• f RV
• f HV ; ФV sa
|
CSA : V des = n • min | V r
• f AV
• f RV
• f HV ; V sr
| n =
N des
=
ФN n
=
ФN sa
=
N r
=
N sr
=
V des
=
ФV n
=
ФV sa
=
V r
=
V sr
=
f AN
=
f RN
= f AV
=
f RV
=
f HV
= number of anchors design resistance in tension design strength in tension considering concrete breakout , pullout , or bond failure ( ACI ) design strength in tension considering steel failure ( ACI ) factored resistance in tension considering concrete breakout , pullout , or bond failure ( CSA ) factored resistance in tension considering steel failure ( CSA ) design resistance in shear design strength in shear considering concrete failure ( ACI ) design strength in shear considering steel failure ( ACI ) factored resistance in shear considering concrete failure ( CSA ) factored resistance in shear considering steel failure ( CSA ) adjustment factor for spacing in tension adjustment factor for edge distance in tension adjustment factor for spacing in shear adjustment factor for edge distance in shear adjustment factor for concrete thickness in shear ( this is a new factor that ASD did not use previously )
Note : designs are for orthogonal anchor bolt patterns and no reduction factor for the diagonally located adjacent anchor is required .
Where anchors are loaded simultaneously in tension and shear , interaction must be considered . The interaction equation is as follows :
where :
N ua
V ua
ACI : ____ + ____ ≤ 1.2
N des
V des
N f
V f
CSA : ____ + ____ ≤ 1.2
N des
V des
N ua
=
V ua
=
N f
=
V f
=
Required strength in tension based on factored load combinations of ACI 318 Chapter 5 . Required strength in shear based on factored load combinations of ACI 318 Chapter 5 . Required strength in tension based on factored load combinations of CSA A23.3 Chapter 8 . Required strength in shear based on factored load combinations of CSA A23.3 Chapter 8 .
18 Anchor Fastening Technical Guide Edition 22 | 3.0 ANCHORING SYSTEMS | 3.1 ANCHOR PRINCIPLES AND DESIGN Hilti , Inc . 1-800-879-8000 | en español 1-800-879-5000 | www . hilti . com | Hilti ( Canada ) Corporation | www . hilti . ca | 1-800-363-4458