PART 4 SHEAR LOAD
Stand-off Failure Mode
Equations L b = z + ( n )( d 0
)
Equations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
L b
= z + ( n )( d 0
) 4.2.2.4 Shear loads with lever arm
If the conditions a ) and b ) of 4.2.2.3 are not fulfilled the lever arm is calculated according to Equation ( 4.2 )
( see Figure 4.8 )
with l = a 3 + e 1
( 4.2 ) e 1
= distance between shear load and concrete surface
a 3
= 0.5d
a 3
= 0 if a washer and a nut are directly clamped to the concrete surface ( see Figure 4.8b ) d = nominal diameter of the anchor bolt or thread diameter ( see Figure 4.8a )
ETAG 001 Annex C : Figure 4.8 Definition of lever arm
4.2.2.3 Shear loads without lever arm
Shear loads acting on anchors may be assumed to act without lever arm if both of the following conditions are fulfilled :
a ) The fixture shall be made of metal and in the area of the anchorage be fixed directly to the concrete either without an intermediate layer or with a levelling layer of mortar ( compression strength ≥ 30 N / mm 2 ) with a thickness ≤ d / 2 .
b ) The fixture shall be in contact with the anchor over its entire thickness .
PROFIS Engineering uses the provisions given in the European Technical Approval Guideline ( ETAG ) titled ETAG 001 Metal Anchors for Use in Concrete Annex C : Design Methods for Anchorages to consider bolt bending as a possible shear failure mode . The parameter “ l ” in ETAG 001 Equation ( 4.2 ) is designated “ L b
” in
PROFIS Engineering . “ L b
” corresponds to the “ lever arm ”, i . e . distance from where the shear resistance V Rk , s
( ϕV s
M in PROFIS Engineering ) acts , to the “ point of fixity ” where the internal bending moment M Rk , s
( M s in PROFIS Engineering ) acts . Bending develops within the anchor element when a shear load V ( V ua in PROFIS Engineering ) acts on a fixture having stand-off . ETAG 001 Equation ( 5.5 ) can be modified as follows using PROFIS Engineering nomenclature :
nominal shear strength ( resistance ): |
M
V s
= α M
M s
/ L b
|
design shear strength ( resistance ): |
M ϕV s
= ϕ [ α M
M s
/ Lb ]
|
design check : ϕV s
M
≥ V ua
Mechanical and adhesive anchors are installed into a hole drilled in concrete . When the anchor is subjected to bending , local concrete spalling can occur if it comes in contact with the side of the drilled hole . ETAG 001 provisions assume this spalling occurs at the surface of the concrete to a depth of one half the nominal anchor diameter . This depth is defined as “ a 3
” in ETAG 001 Equation ( 4.2 ), and as “( n )( d 0
)” in PROFIS Engineering . The value for “ n ” in PROFIS Engineering depends on whether “ stand-off without clamping ”, “ stand-off with clamping ” or “ stand-off with grouting ” is selected .
PROFIS Engineering assumes V ua and ϕV s
M act at the center of the fixture thickness . The distance from where V ua and ϕV s
M act to the surface of the concrete is defined as the parameter “ e 1
” in ETAG 001 Equation ( 4.2 ), and as “ z ” in
PROFIS Engineering .
PROFIS Engineering stand-off calculations : without clamping and with grouting
t plate
= plate or fixture thickness z = standoff + 0.5 ( t plate ) n = 0.5 L b = z + ( 0.5 )( d 0
) d 0
= nominal anchor diameter
When “ stand-off without clamping ” or “ stand-off with grouting ” are selected in PROFIS Engineering , ( n )( d 0
) = ( 0.5 )( d 0 ) and L b
= z + ( 0.5 )( d 0
). Adhesive anchors and cast-in anchors can be modeled in PROFIS Engineering when “ stand-off without clamping ” is selected . Expansion anchors cannot be modeled for this condition .
5.2.3.2 Steel failure b ) Shear load with lever arm
The characteristic resistance of an anchor , V Rk , s , is given by Equation ( 5.5 ).
V Rk , s
= α M M Rk , s [ N ] ( 5.5 ) l where α M
= see 4.2.2.4 l = lever arm according to Equation ( 4.2 )
M Rk , s
= M 0 ( 1 - N / N ) [ Nm ] ( 5 . 5a )
Rk , s sd Rd , s
322 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions