1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
V ns Nominal steel strength of anchor channel loaded in
shear (lowest value of V sa , V sc , and V sl ), lbf (N)
V ns,a nominal shear strength for steel failure of anchor or
connection between anchor and channel (lowest
value of V sa and V sc ), lbf (N)
V sa,x,seis nominal seismic shear steel strength in longitudinal
channel axis of a single anchor, lbf (N)
V sc,y nominal shear strength of connection between one
anchor bolt and the anchor channel, lbf (N)
factored shear load on anchor channel, lbf (N)
V aua factored shear load on a single anchor of the
anchor channel, lbf (N)
V aua,i factored shear load on anchor i of the anchor
channel, lbf (N)
V sua
factored shear load on a channel bolt, lbf (N)
α exponent of interaction equation
α ASD conversion factor for allowable stress design
α ch,N factor to account for the influence of channel size
on concrete breakout strength in tension [-]
ψ cp,N modification factor for anchor channels to control
splitting
ψ ed,N modification factor for edge effect on concrete
breakout strength for anchors loaded in tension [-]
ψ g,Nb modification factor to account for influence of
bearing area of neighboring anchors on concrete
blowout strength for anchors loaded in tension [-]
ψ h,Nb modification factor to account for influence of
member thickness on concrete blowout strength
for anchors loaded in tension [-]
Tension Loads:
Calculation of t-bolt loads induced by tension loads and
bending moments acting on the fixture per elastic theory
involves the following assumptions (Fig. 7.2.7.1)
a) T
he fixture remains plane (flat) under the influence of internal
forces. In order to warrant this supposition, the fixture must
be sufficiently stiff and must be in contact with the base
material. A stiff fixture may be assumed if under the design
actions, the stresses in the fixture are smaller than the design
resistance of the fixture material. The stiff fixture assumption
corresponds to the Bernoulli hypothesis in reinforced
concrete design, wherein plane cross-sections are assumed
to remain plane.
b) I n the part of the fixture subjected to compression, t-bolts do
not act in either tension or compression.
c) T
he stiffness of all t-bolt in a group are identical. The t-bolt
stiffness is directly proportional to the area of the stressed
cross-section and the modulus of elasticity of the steel.
The stiffness of the concrete is characterized by its elastic
modulus and the stressed area.
Consequently, the calculation of the tension forces in the t-bolts
corresponds to how one determines the tension resultant in the
reinforcing bars of a reinforced concrete member. However, in
contrast to strength design of reinforced concrete members,
we assume here that the response of the concrete and steel
elements remains linear elastic.
Figure 7.2.7.2 — Distribution of shear forces in an anchor group Example of
connections in which all t-bolts participate in resisting the shear load.
In most cases, elastic analysis yields satisfactory results
and is recommended. It should be noted, however, that
the assumption of anchor load linearly proportional to *the
magnitude of the applied load and the distance from the neutral
axis of the group is valid only if the attachment (e.g. baseplate)
is sufficiently stiff in comparison to the axial stiffness of the
t-bolts. Note: Assuming a rigid base plate condition, Hilti’s
PROFIS Anchor channel analysis and design software performs
a simplified finite element analysis to establish anchor load
distribution on an elastic basis.
ψ h,V modification factor to account for influence of
member thickness on concrete edge breakout
strength for anchors channels loaded in shear [-]
ψ s,N modification factor to account for influence of
location and loading of neighboring anchors on
concrete breakout strength for anchor channels
loaded in tension [-]
ψ s,Nb modification factor to account for influence of
location and loading of neighboring anchors on
concrete blowout strength for anchor channels
loaded in tension [-]
ψ s,V modification factor to account for influence of
location and loading of neighboring anchors
on concrete edge breakout strength for anchor
channels loaded in shear [-]
Figure 7.2.7.1 — Distribution of forces predicted by elastic theory in an
t-bolt group subjected to tension force and bending moment.
α M factor to account for the influence of restraint of
fixture on the flexural strength of the channel bolt [-]
158
Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
159
V ua
ψ co,V modification factor for corner effects on concrete
edge breakout strength for anchor channels loaded
in shear [-]
In calculating the distribution of shear loads through a fixture
to the t-bolts of a group positioned away from an edge, it
is assumed that all t-bolts exhibit the same shear stiffness.
Additionally, it is generally assumed that all t-bolts participate
in accommodating the shear loads (Fig. 7.2.7.2). It is assumed
that the shear load acts at the center of gravity of the group of
t-bolts. When the shear load acts eccentrically, the forces in the
anchors should be calculated taking into account equilibrium
conditions based on steel design principles.
V ss nominal strength of channel bolt in shear, lbf (N)
ψ co,Nb modification factor for corner effects on concrete
blowout strength for anchors loaded in tension [-]
Shear Loads:
V sl,x,seis nominal seismic shear steel strength in longitudinal
channel axis of connection between channel bolt
and channel lips, lbf (N)
ψ co,N modification factor for corner effects on concrete
breakout strength for anchors loaded in tension [-]
14. Design
Example
V sl,y,seis nominal seismic shear steel strength perpendicular
to the channel axis of the local bending of the
channel lips, lbf (N)
ψ c,V modification factor to account for influence of
cracked or uncracked concrete for concrete edge
breakout strength [-]
The forces on a t-bolt can generally be determined using
general principles of structural mechanics. In doing so, the
displacement of the t-bolt is usually assumed to be small
(i.e negligible). The distribution of forces acting on a fixture
of a t-bolt group to the individual t-bolt of the group can be
calculated with elastic theory.
13. Field Fixes
V sl,x nominal shear steel strength in longitudinal channel
axis of connection between channel bolt and
channel lips, lbf (N)
ψ c,Nb modification factor to account for influence of
cracked or uncracked concrete on concrete
blowout strength [-]
Determination of t-bolt forces acting on
anchor channels
12. Instructions
for Use
V sl,y nominal shear steel strength perpendicular to the
channel axis of the local bending of the channel
lips, lbf (N)
ψ c,N modification factor to account for influence of
cracked or uncracked concrete on concrete
breakout strength [-]
7.2.7 LOAD DISTRIBUTION
11. Best
Practices
V sc,x,seis nominal seismic shear strength in longitudinal
channel axis of connection between one anchor
bolt and the anchor channel, lbf (N)
α v,seis,x adjustment factor for seismic loading (x-direction,
in longitudinal channel axis)
10. Design
Software
V sc,y,seis nominal seismic shear strength perpendicular
to the channel axis of connection between one
anchor bolt and the anchor channel, lbf (N)
α v,seis,y adjustment factor for seismic loading (y-direction,
perpendicular to the channel axis)
9. Special Anchor
Channel Design
V sc,x nominal shear strength in longitudinal channel axis
of connection between one anchor bolt and the
anchor channel, lbf (N)
α ch,V factor to account for the influence of channel size
and anchor diameter on concrete edge breakout
strength in shear (lbf 0.5 /in) 0.33 (N 0. 5/mm 0.33 )
8. Reinforcing
Bar Anchorage
V sa,y,seis nominal seismic shear steel strength perpendicular
to the channel axis of a single anchor, lbf (N)
λ Modification factor for sand-lightweight concrete in
accordance with Section 8.6.1 of ACI 318-08 and
318-11 or Section 19.2.4 of ACI 318-14
7. Anchor Channel
Design Code
V sa,x nominal shear steel strength in longitudinal channel
axis of a single anchor, lbf (N)
6. Loading
V sa,y nominal shear steel strength perpendicular to the
channel axis of a single anchor, lbf (N)
5. Base material
shear loads) or V ca (anchor channels with anchor
reinforcement to take up shear loads) and V cp )
4. Design
Introduction