PART 4 SHEAR LOAD
Pryout Failure Mode ( Concrete Breakout )
Results V ua
Results 318-14 Chapter 17 Provision Comments for PROFIS Engineering
V ua
17.3.1.1 The design of anchors shall be in accordance with Table 17.3.1.1 . In addition , the design of anchors shall satisfy 17.2.3 for earthquake loading and 17.3.1.2 for adhesive anchors subject to sustained tensile loading .
Excerpt from Table 17.3.1.1 showing the shear failure modes considered in ACI 318-14 anchoringto-concrete provisions .
Table 17.3.1.1 — Required strength of anchors , except as noted in 17.2.3
Failure Mode Single Anchor
Individual anchor in a Group
Steel strength in shear ( 17.5.1 ) ϕV sa ≥ V ua ϕV sa
≥ V ua , i
Concrete breakout strength in shear ( 17.5 . 2 )
Concrete pryout strength in shear ( 17.5.3 ) ϕV cb
≥ V ua
ϕV cp
≥ V ua
Anchor Group
Anchors as a group
ϕV cbg
≥ V ua , g
ϕV cpg
≥ V ua , g
ACI 318-14 strength design provisions for concrete pryout failure in shear require calculation of a nominal concrete pryout strength ( V cp or V cpg
). The nominal strength is multiplied by a strength reduction factor ( ϕ-factor ) to obtain a design strength ( ϕV cp or ϕV cpg
). Design strength is checked against a factored shear load , defined by the parameter “ V ua
”. Chapter 2 in ACI 318-14 gives the following definitions for the factored shear load parameter “ V ua
”.
• V ua
= factored shear force applied to a single anchor or group of anchors ( lb )
• V ua , i
= factored shear force applied to most highly stressed anchor in a group of anchors ( lb )
• V ua , g
= total factored shear force applied to anchor group ( lb ) The design concrete pryout strength for a single anchor in shear ( ϕV cp
) calculated per Section 17.5.3 is checked against the factored shear load acting on the anchor , which is designated “ V ua
” in Table 17.3.1.1 . If ϕV cp ≥ V ua
, the provisions for considering concrete pryout failure in shear have been satisfied per Table 17.3.1.1 .
The design concrete pryout strength for a group of anchors in shear ( ϕV cpg
) calculated per Section 17.5.3 is checked against the total factored shear load acting on the anchors that are in shear , which is designated “ V ua , g
” in Table 17.3.1.1 . If ϕV cpg ≥ V ua , g
, the provisions for considering concrete pryout failure in shear have been satisfied per Table 17.3.1.1 .
The PROFIS Engineering report uses the generic designation “ V ua
” to define the factored shear load being checked against the calculated design concrete pryout strength ϕV cp or ϕV cpg
. The PROFIS Engineering Load Engine permits users to input service loads that will then be factored per IBC factored load equations . Users can also import factored load combinations via a spreadsheet , or input factored load combinations directly on the main screen . PROFIS Engineering users are responsible for inputting shear loads . The software only performs shear load checks per Table 17.3.1.1 if shear loads have been input via one of the load input functionalities .
If a single anchor in shear is being modeled , PROFIS Engineering calculates the parameter ϕV cp
, and checks this value against either ( a ) the factored shear load acting on the anchor , which has been calculated using the loads input via the Load Engine , ( b ) the factored shear load acting on the anchor , which has been calculated using the loads imported from a spreadsheet or ( c ) the factored shear load acting on the anchor , which has been calculated using the loads input in the matrix on the main screen . The value for V ua shown in the report corresponds to the factored shear load determined to be acting on the anchor .
If a group of anchors in shear is being modeled , PROFIS Engineering calculates the parameter ϕV cpg
, and checks this value against either ( a ) the total factored shear load acting on the anchor group , which has been calculated using the loads input via the Load Engine , ( b ) the total factored shear load acting on the anchor group , which has been calculated using the loads imported from a spreadsheet or ( c ) the total factored shear load acting on the anchor group , which has been calculated using the loads input in the matrix on the main screen . The value for V ua shown in the report corresponds to the total factored shear load determined to be acting on the anchor group .
Reference the Results section of the PROFIS Engineering report for more information on the following parameters :
V cp
: Nominal shear concrete pryout strength for a single anchor
V cpg
: Nominal shear concrete pryout strength an anchor group
ϕ concrete
: Strength reduction factor for concrete failure modes
ϕ seismic
: Strength reduction factor for seismic loads
ϕ nonductile
: Strength reduction factor for non-ductile failure modes
294 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions