1. Anchor
Channel Systems
2. HAC
Portfolio
3. HAC
Applications
11.5.3 POST-TENSIONED SLABS
5. Base material
6. Loading
types of conditions shall be assessed on a case-by-case basis
and requires additional coordination between different parties
such as Engineer of Record, Specialty Engineers (Curtain
Wall Designer and Post-Tensioning Engineer), and Anchor
Manufacturers. For additional support, please contact Hilti at
[email protected].
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
11.5.4 UNCRACKED CONCRETE 11.5.5 CONCRETE CURB
Per ACI 318-14, anchors located in a region of a concrete
member where analysis indicates no cracking at service load
levels, the modification factors for uncracked concrete can
be applied. Figure 11.5.4.1 illustrates compression zones in
different concrete structures. Although concrete curbs tend to not be the predominant
condition, it is a typical condition encountered in buildings
and presents additional challenges on it own such as reduced
geometrical parameter and lower concrete compressive
strengths. The following best practices can help to ease the
design, approval process, and minimize field fixes.
1) A
lways verify the concrete compressive strength as it typically
different from the slab or beam which is connected to.
Simple supported slab
Cantilever slab
3) For installation purposes of top of slab applications, it is
recommended to leave exposed areas in front and behind
the channel to ensure proper concrete compaction and
inspection as air pockets tends to be a common field issue in
this type of configurations.
Continuous Slab
Generally, if the live or dead end of the tendon does not induce
additional stresses in the anchorage zone, the capacity of the
anchor can be predicted based on applicable anchoring-to-
concrete provisions. The anchorage zone of an anchor (concrete
volume due to projected area) can be predicted by idealizing the
failure planes in shear and tension.
2) D
esign of anchors is limited to the anchor design. Therefore,
its design verifies the adequacy of the concrete at a local
level; it ensures the concrete can take resist the applied
loads. If a cold joint between the main structure and concrete
curb is present, ensure there is proper load transfer between
both structures. Additional reinforcement may be required.
Current model codes provide minimal guidance to account for
the influence of post-tensioned cables on anchors. The use
of cast-in anchor channels in post-tensioned slabs is ideal
since compared to other anchoring technologies such as
post-installed anchors, it does not require drilling. However,
additional measurements need to be taken to ensure the
concrete is not overstressed and the concrete capacity of the
anchor is not overestimated.
7. Anchor Channel
Design Code
Clashing between embeds and post-tensioned tendons are
often overlooked. Clashing between post-tensioned tendons
and anchor channels tends to be a common type of field issue.
It is always a good practice to coordinate the curtain wall
anchorage and posttensioned cables layout, in order to avoid
last minute remediations.
4. Design
Introduction
Cantilever beam
Compression zone
Figure 11.5.3.1 — Face of slab configuration with live end of post-tensioned
slab outside the anchorage zone.
Figure 11.5.4.1 — Compression zones in different concrete structures
Figure 11.5.3.3 — Anchor channels installed near live end of post-tensioned
cables. Contact Hilti for additional information.
Figure 11.5.3.2 — Top of slab configuration with live end of post-tensioned
slab outside the anchorage zone.
If the live or dead end of a post-tensioned cable is located or
induces additional stresses in the anchorage zone, additional
measurements should be taken. Due to model code limitations,
a wide range of possible configurations, different types of
anchors, and the complexities of this topic in general, these
358
Figure 11.5.5.1 — Installation of HAC in top of slab curbs.
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