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How to Plan a Large Tilt-Up Project - Concrete Construction

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How to Plan a Large
Tilt-Up Project
To ensure a successful job, don’t overlook these five important steps
BY RAY KNOTTS
mplementing a bulletproof
plan is critical to the success of
a tilt-up project, especially on
a large, fast-track job. A missed
date on material deliveries, a misfigured crew requirement, a specialty tool breaking down or a postponed panel pour can put your
project in jeopardy.
As the founder of Concrete Concepts Co., a tilt-up contracting firm
in Kings Mountain, N.C., I’ve
learned from experience what it
takes to develop an effective plan
for large, complex tilt-up jobs. The
a ve rage size of our projects is
70,000 to 100,000 square feet, but
some projects are as large as
750,000 square feet. Preparing for
such big jobs often requires coordinating the activities of as many as
50 workers, so it’s necessary to start
planning early to make sure everyone involved knows what to do and
when. A good plan must also have
contingencies for common jobsite
problems that can lead to costly
project delays, such as equipment
breakdowns. The following five
steps are essential to developing an
effective plan.
I
1. REVIEW THE STRUCTURAL
DRAWINGS
Thoroughly review the structural
drawings to make sure the architect’s plans agree with the engineer’s intent. Details to check include:
• Panel size, thickness and weight
• Reveals
Figure 1. Staging plan for grocery-facility project.
• Chamfers
• Door swings
• Surface finishes
2. PREPARE SHOP DRAWINGS
AND MATERIALS SUBMITTALS
Shop drawings for a tilt-up project should clearly show:
• Reinforcing-steel location, size
and spacing
• Lifting and bracing insert book
(from your insert supplier) and
panel embeds (from your structural-steel supplier)
• Panel fabrication and erection
sequences
(with special attention given to
their compatibility)
• Form liners and reveal details
(size, shape and composition)
• Grouting and patching materials
• Any other materials integrated
into the panel
3. PLAN JOBSITE STAGING
One way Concrete Concepts Co. adheres to its tilt-up plans is by using efficient
equipment. Sporting custom-designed rolling outriggers, this crane eliminates
problems with floor-slab cracking and lets crews set panels up to 50% faster.
( For examples of shop dra w i n g s,
see “Ti l t - Up Ba s i c s,” C o n c re t e
C o n s t r u c t i o n , May 1993, pp.
337-344.)
Materials submittals should include specifications for:
• Concrete mix design
• Bond breakers and curing agents
Once the architect has approved
the submittals, you can begin staging the jobsite. This step involves
choosing strategic locations for
toolsheds, equipment, materials
and temporary casting beds. You
must also establish access routes
for ready-mix trucks, concrete
pumps and cranes. Figure 1 shows
a staging plan for a tilt-up project
involving four separate buildings
totaling over 1 million square feet.
The importance of the staging
process is often overlooked, even
though effective staging can dramatically increase construction
productivity once panel fabrication
begins. Planning access routes for
MODIFIED CRANE REDUCES PANEL SETTING TIME
Knotts believes the safest,
most efficient way to crane-set tiltup panels is from the concrete
floor slab. But the weight that’s
applied to the crane’s two rear
outriggers during panel lifting can
crack the slab.
To solve this problem, Knotts
spent the winter of 1995 designing and fabricating a custom set
of rolling outriggers that disperses
the total lifting load over 16 points
instead of just two (see drawing).
In March 1996, the conventional
outrigger pads on the company’s
100-ton Link-Belt crane were replaced with rolling dollies that allow the operator to keep the boom
at a sharper angle while lifting a
panel, then simply roll the crane
back before lowering the panel to
its final destination.
“The rolling outriggers greatly
decrease the pound-per-squareinch load you typically have under
conventional stationary outrigger
pads,” explains Knotts. “In addition to solving the floor-slab cracking problem, this method of set-
Rotation
11'-8 11вЃ„16"
CONCRETE
CONCEPTS
Link-Belt
Model 218-A
100 Ton
3'-4"
58"
10'
16'-10"
58"
13'- 3вЃ„8"
10'-6"
60-1вЃ„8"
1'-107вЃ„8"
35'-10 78вЃ„ "
ting panels has increased production by as much as 50%.”
Because the rolling outriggers
allow the crane operator to carry
the weight of the panel closer to
the crane’s center pin, it’s easier
to stay inside the load limit of the
crane. “Panels in the 50-ton range
that would have required a monster crane can now be set with a
smaller, lighter, more mobile
crane because the operator has
the ability to stay closer to his
load,” Knotts claims.
Since the crane was equipped
with the special outriggers, crews
have used it to place more than a
thousand panels, all set from
floor slabs ranging in thickness
from 4 to 8 inches. They haven’t
experienced any cracking problems in floors that have been
properly installed on well-consolidated subbases.
TYPICAL CREW SEQUENCING
Sequence
Crew
AND
BASIC TASKS
No. of Workers
Basic Tasks
1
Floor preparation
2
Cleans floor surface, fills contraction
joints and applies bond breaker. Keeps
work area clean and organized.
2
Panel layout
2
Establishes chalk lines for panel perimeters, doors, windows, louvers, lifting and
brace inserts, joist pockets, reveals and
any other items to be installed before
concrete placement.
3
Formwork installation
4-6
Installs all formwork and form liners,
chamfers, reveals, and door and window
blockouts.
4
Rebar installation
4
Installs all panel reinforcing per shop
drawings, including any additional rebar
required for lifting. Installs all lifting and
bracing inserts and miscellaneous steel
embeds.
5
Panel inspection
1
Checks that panels meet the requirements specified in the structural plans
and shop drawings before concrete
placement. Tags each panel with a “pour
card,” which tells the concrete crew that
the panel is ready to pour.
6
Concrete placement
8-12
Places, on average, about 200 to 300
cubic yards (enough for about 20 to 25
panels) twice a week. The crew size
needed depends on the type of finish
required on the inside panel face and how
much jointing and detail work the panels
receive.
7
Pre-erection
4-6
Cleans out the lifting and bracing inserts,
strips forms, attaches braces, sets
footing pads and clears crane access
ways.
8
Panel erection
6-8
This is the crew that makes it all happen,
using a crane to lift into place as much as
400 lineal feet of wall panels in one day.
9
Panel grouting
and patching
6-8
Using aerial lifts, a skilled crew should be
able to patch and grout 25,000 square
feet of tilt-up walls in one week, primarily
to correct surface imperfections that
paint won’t hide.
2
Takes care of the last-minute details that
make the difference between having a
satisfied customer or a long list of callbacks. Typical activities include panel
touchup, patching holes in the floor slab
and cleaning floor joints.
10
Punch list
Figure 2. Typical production schedule for a 12-week project.
trucks and equipment is especially
critical on restricted jobsites or in
wet or wintry weather.
Typically, the total square footage
needed for materials staging equals
approximately 20% of the floor
area. If the floor slab isn’t large
enough for casting all the panels
and you don’t want to stack them,
designate areas for temporary casting beds in the staging plan. These
beds should be located as close as
possible to the floor slab.
carefully to ensure that the project
goes according to schedule. Too few
workers on a crew can cause delays,
and too many workers can overrun
the production of the crew that
works ahead of it. The table plots the
crew sequencing—including the approximate number of workers per
crew—for a typical panel-fabrication
process. Figure 2 shows a typical production schedule.
4. PLAN CREW SIZE AND
SEQUENCING
Almost as important as having the
right crew size and sequencing is
having the right tools and equipment for the job. During periods of
peak production, it’s not uncommon to have as many as 40 people
Because a number of crews, each
with different responsibilities, are required for a large tilt-up job, crew size
and sequencing must be planned
just working on the panel phase.
Unless you have ample tools, equipment and materials available, your
labor costs can skyrocket, since just
one broken tool can stop the whole
40-person train. The key is to have a
backup if an important tool or piece
of equipment goes down.
Every contractor has a preferred
way of doing things. To find the
equipment and methods that work
best for you, it’s often necessary to
do some experimenting. For example, my crews recently began using
air-powered tools because the
cords and switches on electric tools
were inconvenient. We also customized a Link-Belt 100-ton mobile
crane, outfitting it with a special
rolling outrigger designed specifically for tilt-up work (see box on
page 570). Concrete Concepts is
constantly finding faster, more efficient ways to build tilt-up structures.
Ray Knotts, president of Concrete
Concepts Co., has been a concrete
contractor since 1974.
5. PLAN TOOL AND
EQUIPMENT NEEDS
PUBLICATION #C970569
Copyright В© 1997, The Aberdeen Group
All rights reserved
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