1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
4. Design
Introduction
5. Base material
6. Loading
8. Reinforcing
Bar Anchorage
9. Special Anchor
Channel Design
10. Design
Software
The information presented in this chapter is mainly based
on Reinforced Concrete Mechanics & Design, by Jams K.
Wight and James G. MacGregor, chapter 8 and ACI 318-14.
Introduction
In reinforced concrete structures, concrete resists flexural
compressive forces, while the reinforcement resists the flexural
tensile forces. Therefore, the bond between the two materials is
necessary to ensure the transfer of forces. If no bond stresses
are present, the bar will pull out of the concrete causing the
reinforced concrete structure to fail.
12. Instructions
for Use
13. Field Fixes
14. Design
Example
Splitting cracks occur mainly due to the wedging action of the
reinforcing bar bearing against the concrete. Horizontal splitting
cracks generally begin diagonally. The dowel action increases
the tendency toward splitting.
After development of the cracks occurs, the bond transfer drops
rapidly unless reinforcement is provided to restrain the opening
of the splitting crack.
When reinforcing bars are loaded beyond the bond strength,
the concrete will split parallel to the bar. The resulting crack
will follow the path of least resistance, propagating out to
the surface of the substrate. The splitting cracks follow the
reinforcing bars along the bottom, top, and side surfaces.
Splitting cracks along the reinforcing bar will generally occur
in vertical and horizontal planes. The splitting crack may
also occur between two rebars if the spacing is less than the
distance between the reinforcing bar and an edge. Figure 8.1.1.3
illustrates different potential splitting cracks patterns.
11. Best
Practices
Bond refers to the interaction between reinforcing steel and the
surrounding concrete which allows for transferring of tensile
stress from the steel into the concrete.
The load at which splitting failure develops is a function of
b) Side cover and half
the bar spacing both
less than bottom cover.
1. T
he minimum distance from the reinforcing bar to the surface
of the concrete or to the next reinforcing bars — the smaller
this distance, the smaller is the splitting load.
3. T
he average bond stress—as this increases, the wedging
forces increase, leading to a splitting failure.
Figure 8.1.1.1 — Bond stresses on a reinforcing bar.
Figure 8.1.1.2 — Stresses and forces on a reinforcing bar and concrete.
Source: Wight, James & MacGregor, James. Reinforced Concrete
Mechanics & Design, 2012.
a) splitting stresses due to
overstressed reinforcing bars c)
Side cover equal to bttom cover,
both less than half the bar spacing.
The bond-transfer mechanism via mechanical interlock between
reinforcing bar (transverse ribs on reinforcing bar) and concrete
is shown in Figure 8.1.1.1. The reinforcing bar acts to transfer the
forces into the concrete via bearing on the deformations of the
reinforcing bar. While adhesion and friction are present initially,
they are quickly lost as the rebar is loaded in tension. Figure
8.1.1.2 a, b, c, and d illustrate the equal and opposite bearing
stresses that act on the concrete. The forces on the concrete
have a longitudinal and a radial component. The component
force causes circumferential tensile stresses in the concrete
around the reinforcing bar as illustrated on Figure 8.1.1.2 f and g.
If the cover and reinforcing bar spacing are large compared
to the bar diameter, a pull-out failure can occur, where the bar
and the annulus of concrete between successive deformations
pull out along a cylindrical failure surface joining the tips of the
deformations.
d) Bottom cover less than side
cover and half the bar spacing
e) Side cover and
half reinforcing bars
spacing less than
bottom cover.
Figure 8.1.1.3 — Radial splitting stresses and splitting crack patterns.
Source: Wight, James & MacGregor, James. Reinforced Concrete
Mechanics & Design, 2012.
202
2. The tensile strength of the concrete.
Figure 8.1.1.4 — Potential plane of splitting due to closely
spaced reinforcing bars.
a) splitting stresses
due to overstressed
reinforcing bars.
8.1 REINFORCING BAR THEORY
7. Anchor Channel
Design Code
Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019
203