the ends of two vertical reinforcing bars. The hairpins
are then placed in the end of the panel before the
concrete is poured. These lifting attachments must
protrude from the top of the form for attaching the
lifting chains or cables, but go deep enough in the
panel form so they wont pull out.
Among the commercial types of lifting
attachments, you will find many styles with greater
lifting capacities that are more dependable than
hairpins if properly installed. These are used with
lifting plates. For proper placement of lifting inserts,
refer to the plans or specs.
Spreader bars (shown in figure 6-9) may be
permanent or adjustable, but must be designed and
made according to the heaviest load they will carry
plus a safety factor. They are used to distribute the
lifting stresses evenly, reduce the lateral force applied
by slings, and reduce the tendency of panels to bow.
POINT PICKUP METHODS
Once the concrete has reached the desired
strength, the panels are ready to be lifted. The
strength of the inserts is governed by the strength of
An early lift may result in cracking the
panel, pulling out the insert, or total concrete
failure. The time taken to wait until the
concrete has reached its full strength prevents
problems and minimizes the risk of injury.
There are several different pickup methods. The
following are just some of the basics. Before using
these methods on a job, make sure that you check
plans and specs to see if these are stated there.
Figure 6-11 shows four different pickup methods: 2,
2-2, 4-4, and 2-2-2.
The 2-point pickup is the simplest method,
particularly for smaller panels. The pickup cables or
chains are fastened directly from the crane hook or
spreader bar to two pickup points on or near the top of
the precast panel.
The 2-2 point pickup is a better method and is
more commonly used. Variations of the 2-2 are 4-4
and 2-2-2, or combinations of pickup points as
designated in the job site specifications. These
methods use a combination of spreader bars, sheaves,
and equal-length cables.
The main purpose is to
distribute the lifting stresses throughout the panel
during erection. Remember, the cables must be long
enough to allow ample clearance between the top of
the panel and the sheaves or spreader bar.
ERECTING, BRACING, AND JOINTING
Erecting is an important step in the construction
phase of the project.
Before you start the erecting
phase and for increased safety, you should make sure
that all your tools, equipment, and braces are in
proper working order.
All personnel must be well
informed and the signalman and crane operator
understand and agree on the signals to be used.
During the erection of the panels, make sure that the
signalman and line handler are not under the panel
and that all unnecessary personnel and equipment are
away from the lifting area. After the erection is done,
make sure that all panels are properly braced and
secured before unhooking the lifting cables.
Bracing is an especially important step. After all
the work of casting and placing the panels, you want
them to stay in place. The following are some steps to
take before lifting the panels:
Install the brace inserts into the panels during
casting if possible.
Install the brace inserts into the floor slab
either during pouring or the day before
Install solid brace anchors before the day of
If brace anchors must be set during erection,
use a method that is fast and accurate.
Although there are several types of bracing, pipe
or tubular braces are the most common. They usually
have a turnbuckle welded between sections for
Some braces are also made with
telescoping sleeves for greater adaptability.
Figure 6-10 shows tube-type braces used to hold up
panels. Cable braces are normally used for temporary
bracing and for very tall panels. Their flexibility and
tendency to stretch, however, make them unsuitable
for most projects.
Wood bracing is seldom used
except for low, small panels or for temporary bracing,
Jointing the panels is simple. Just tie all the
panels together, covering the gap between them. You
can weld, bolt, or pour concrete columns or beams.
Steps used to tie the panels should be stated in the
plans and specs.