HAC_Technical-Guide

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Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
4. Design
Introduction
5. Base material 6. Loading
7. Anchor Channel
Design Code
8. Reinforcing
Bar Anchorage
9. Special Anchor
Channel Design
10. Design
Software
11. Best
Practices
12. Instructions
for Use
13. Field Fixes
14. Design
Example
8.1 Reinforcing Bar Theory
8.2 Development Length
of Straight Bars
8.3 Pullout Strength of Straight
Reinforcing Barsrs
8.4 Pull Out Strength of
Headed Bars In Tension
8.5` Pull Out Strength of
Standard Hooks
8.6 Rebar Lap Splices 8.7 Concrete Cover
ψ
c
= bar-cover factor
No. 11 bar and smaller hooks with side cover (normal to plane
of hook) ≥ 2-1/2 in and for 90-degree hook with cover on bar
extension beyond hook ≥ 2 in .................................................. 0.7
Other ........................................................................................ 1.0
ψ
r
= confining reinforcement factor
For 90-degree hooks of No. 11 and smaller bars
(1) enclosed along ℓ
dh
within ties or stirrups perpendicular to ℓ
dh
at s ≤ 3d
b
, or
(2) enclosed along the bar extension beyond hook including the
bend within ties or stirrups perpendicular to
ℓ
ext
at s ≤ 3d
b
..................................................................... 0.80
For 180-degree hooks of No. 11 and smaller bars enclosed
along ℓ
dh
within ties or stirrups perpendicular to
ℓ
dh
at s ≤ 3d
b
........................................................................... 0.80
Other ...................................................................................... 1.00
Figure 8.5.1.3 — Confinement of hooks by stirrups and ties. Source: Wight,
James & MacGregor, James. Reinforced Concrete Mechanics & Design,
2012.
λ = modification factor for lightweight concrete
When any lightweight-aggregate concrete is used ...............0.75
When the splitting tensile strength f
c,s
is specified, shall be
permitted to be taken as f
c,t
/6.7√f′
c
but not more then ........... 1.0
When normal-weight concrete is used .................................... 1.0
ACI 318-14, §R25.4.2.4 The lightweight factor λ for calculating
development length of deformed bars and deformed wires
in tension is the same for all types of lightweight aggregate
concrete. Research does not support the variations of this factor
in Codes prior to 1989 for all-lightweight and sand-lightweight
concrete. Section 25.4.2.4 allows a higher factor to be used
when the splitting tensile strength of the lightweight concrete is
specified. Refer to 19.2.4.
f′
c
= concrete compressive strength
f′
c
≤ 10,000 psi
d
b
= nominal diameter of the reinforcing bar
Bar hooks are especially susceptible to a concrete splitting
failure if both side cover (perpendicular to plane of hook) and
top or bottom cover (in plane of hook) are small. For bars
being developed by a standard hook at discontinuous ends of
members with both side covers and top (or bottom) cover to
hook less than 2-1/2 in., (a) through (c) shall be satisfied:
(a) The hook shall be enclosed along ℓ
dh
within ties or stirrups
perpendicular to ℓ
dh
at s ≤ 3d
b
(b) The first tie or stirrup shall enclose the bent portion of the
hook within 2d
b
of the outside of the bend
(c) ψ
r
shall be taken as 1.0 in calculating ℓ
dh
in accordance with
25.4.3.1(a)
Reduction of development length for excess
reinforcement
A reduction in development length is permitted in limited
circumstances. If the flexural reinforcement provided exceeds
the amount required to resist the factored moment, the bar
stress that must be developed is less than In such a case, ACI
318-14, §25.4.10 allows to be multiplied by (A
s,required
/A
s,provided
).
A reduction of development length in accordance with 25.4.10.1
is not permitted for (a) through (e):
(a) At non-continuous supports
(b) At locations where anchorage or development for f
y
is
required
(c) Where bars are required to be continuous
(d) For headed and mechanically anchored deformed
reinforcement
(e) In seismic-force-resisting systems in structures assigned to
Seismic Design Categories D, E, or F
Minimum bending requirements: ACI 318-14,
§25.4.3.1.
Standard hooks need to follow some specific geometrical
requirements. Standard hooks should meet the minimum
lengths and bending requirements provided in ACI 318-14.
The primary factors affecting the minimum bend diameter
are feasibility of bending without breakage and avoidance of
crushing the concrete inside the bend.
The minimum inside bend diameter and extension length for a
hooked reinforcing bar is as follows in the table:
[1]
The first tie or stirrup shall enclose the bent portion of the hook within 2db of the outside of the bend.
Pull-out strength reduction factor, ∅
ACI 318-14 development length equation does not require a ∅
factor to be applied to the development length equation. An
allowance for strength reduction is already included in the
expression for determining development length. R25.4.1.3
When calculating the pull-out strength of the reinforcing bar,
per ACI 318-14, §17.4.2.9 a reduction factor, ∅ of 0.75 shall be
applied to the nominal pull-out reinforcing bar strength.
Pull-out strength of L-bolts
If standard hook requirements of ACI are not met, the reinforcing
bar may behave similar to the one of an L-bolt
The pullout strength in tension of a single hooked bolt (N
p
) per
ACI 318-14, §17.4.3.5 shall not exceed
N
p
= 0.9f′
c
e
c
d
a
where: 3d
a
≤ e
h
≤ 4.5d
a
R17.4.3.5 Equation (17.4.3.5) for hooked bolts was developed by
Lutz based on the results of Kuhn and Shaikh (1996). Reliance is
placed on the bearing component only, neglecting any frictional
component because crushing inside the hook will greatly
reduce the stiffness of the connection and generally will be the
beginning of pullout failure. The limits on e
h
are based on the
range of variables used in the three tests programs reported in
Kuhn and Shaikh (1996).
Figure 8.5.1.4 — L-reinforcing bar
Table 8.5.1.1 (ACI 318-14 Table 25.3.1) — Bending Requirements for Development of Standard Hook
Type of standard hook Bar size
Minimum
inside bend
diameter(in)
Straight
extension lext,
(in)
Type of standard hook
90-degree hook
No. 3 through No. 8 6d
b
12d
b
No. 9 through No. 11 8d
b
No. 14 through No. 18 10d
b
180-degree hook
No. 3 through No. 8 6d
b
Greater of: 4d
b
2.5 in
No. 9 through No. 11 8d
b
No. 14 through No. 18 10d
b