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Chapter 22
Forming Systems
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FORMING SYSTEMS
FORMWORK
Formwork accounts for 30 to 70%
of the construction cost for
concrete framed buildings, hence
its importance as a major
component of the equipment array
used on such construction projects.
FORMWORK
The selection and use of forming systems
are inseparable from the selection and
operation of the on-site cranes and other
lifting and concrete-placing equipment.
Forming systems—for slabs, walls,
columns, and other repetitious concrete
elements of the structure—are designed
and fabricated for many reuses.
FORMWORK
The constructor’s project engineer is
extensively involved with various
planning aspects of their selection,
ordering, erection, stripping, and
reuse.
Construction companies procure
forming systems by either direct
purchase or short-term rentals.
FORMWORK
The labor cost associated with
any selected system is an
essential part of the economic
calculations and comparison of
forming alternatives
FORMWORK
CLASSIFICATION
• Conventional formwork
– assembled in situ from
standard elements new for
each use and is disassembled
after each use
FORMWORK
CLASSIFICATION
• Industrialized formwork
– mostly factory-fabricated products
and are used many times as one unit
without being disassembled and
assembled again for each use
FORMWORK AND THE
PROJECT ENGINEER
Close interrelationship between project
engineering, site management, and the formwork
supplier on the new Parliament House project in
Berlin, Germany
FORMWORK DESIGN
Vertical loads on horizontal forms
Dead loads
Live loads
FORMWORK DESIGN
Lateral pressure of concrete on
vertical forms
Horizontal pressure on the surface of
the forms, proportional to the density
and depth of the concrete in a liquid or
semiliquid state
LATERAL PRESSURE OF
CONCRETE ON VERTICAL
FORMS
Figure (a) shows a full liquid head
pressure
LATERAL PRESSURE OF
CONCRETE ON VERTICAL
FORMS
Figure (b) shows a situation where the
concrete began to harden, thus
exerting a pressure at the lower
part of the form that is less than
the full liquid head pressure (depth
of fluid concrete from top of placement is h1)
LATERAL PRESSURE OF
CONCRETE ON VERTICAL
FORMS
Figure (c) shows a situation similar
to Fig. (b), but with a lower rate of
filling the forms; this results in yet
a lower maximum pressure and a
smaller height of liquid head
pressure, h2 < h1
FORMWORK: A LAYERED
SYSTEM (horizontal)
FORMWORK: A LAYERED
SYSTEM (horizontal)
Stringers
Joist
Joist
Shores
Joist
FORMWORK:
A LAYERED
SYSTEM
(vertical)
FORMWORK: A LAYERED
SYSTEM (vertical)
Strongback
Large custommade wall
forms with
timber studs
and steel wales
and strongbacks
Ties
Wale
Studs
Brace/stabilizer
Brace/stabilizer
MATERIAL COST
USCRF = unified series capital recovery factor
Ln = salvage value after n years
REPAIR &
MAINTENANCE
USSFF = unified series sinking fund factor
MODIFICATION COST
PWCAF = present worth compound amount
factor
LABOR COST
EXAMPLE
Construction company considers the
purchase of a set of half-tunnel forms
for $20/sf.
The forms are to be used 200 times for
the forming of 1,000 sf of walls and
1,000 sf of slabs per use on a series of
residential buildings over a period of 4
yr, and then they will be sold.
EXAMPLE
Salvage value is expected to be 10% of
original purchase price. No
maintenance costs are expected.
Labor productivity is estimated at 0.025
labor hr/sf. Hourly wages are $22.
Consider 5% annual interest rate.
What is the average formwork cost
(material and labor) per use for this
project?
EXAMPLE
Note that for every 1
sf of wall, 2 sf of
forms, both sides of
the wall, are required
Actual area of forms:
(1,000 sf slab + 2 × 1,000 sf wall) × 1.15 =
3,450 sf
EXAMPLE
Purchase price:
3,450 sf × $20/sf = $69,000
Average number of uses per year:
200/4 = 50
Salvage value:
$69,000 × 10% = $6,900
EXAMPLE
Material cost per use:
$69,000  0.9  USCRF (4.5%)  $6,900  0.05
CF 

50
$62,100  0.28201  $345

 $357.16
50
Labor cost per sf:
0.025labor hr sf  $22 / hr  $0.55/ sf
EXAMPLE
Labor cost per use:
3, 450sf  $0.55 / sf  $1,897.50
Formwork cost per use:
material labor
$0  $357.16  $1,897.50  $2, 254.66
maintenance
VERTICAL SYSTEMS
Vertical formwork is designed
based on a rate of placement and
the resulting lateral pressure
curve—the pressure of liquid
concrete and timing of initial set.
WALL
FORMS
Ganged
forms
WALL FORMS
Steel largepanel wall
forms
WALL FORMS
Large
custom-made
wall forms
Wall form system
including main work
platform, upper
concreting platform,
and finishing trailing
platform
WALL
FORMS
WALL
FORMS
Single-sided wall
forming system
WALL
FORMS
Self-climbing
forms in
high-rise
construction
of the Park
Tower
in Chicago
COLUMN
FORMS
Custom-made
forms for small
series of columns
Site-fabricated
timber forms
COLUMN
FORMS
Custom-made
forms for small
series of columns
Site-fabricated steel forms
COLUMN
FORMS
Custom-made
forms for large
series of columns
Factoryfabricated
steel forms
HORIZONTAL SYSTEMS
Typically come in two configurations:
– hand-set forms
– table (flying) forms
– column mounted forms (also termed
“drawer” forms)
Stripping times much longer than for
vertical elements
PLYWOOD-AND-ALUMINUM
HAND-SET SLAB FORMS
With
drophead
system
DROPHEAD
SYSTEM
FOR HANDSET SLABFORM
ALUMINUM TABLE FORM
(TRUSS SYSTEM)
SUPPORTED ON JACKS
Table on screw-jacks
ALUMINUM TABLE FORM
(TRUSS SYSTEM)
SUPPORTED ON JACKS
Lowered table
TABLE
FORM
Lifted by a
crane using a
c-frame
TABLE
FORM
Being removed
by a crane
located near
the facade of
the building
Tables with extension
spandrel beam
forming and working
deck chained to the
floor to withstand
overturning
COMBINED VERTICAL
& HORIZONTAL SYSTEMS
Wall-and-slab forming systems come in
two configurations:
– half-tunnel forms
– full-tunnel forms (not to be confused
with forming systems for tunnels)
Both are commonly referred to as
tunnel forms, or simply tunnels
TUNNEL
FORMS
Cellular-type
building
suitable for
using tunnel
forms
HALFTUNNEL
FORMS
HALF-TUNNEL
FORMS
TUNNEL
FORMS
Two tunnel form
halves are
connected to
create a full unit
form
TUNNEL FORMS
Hydraulic contraction of a
full tunnel form for stripping
Inside view of a tunnel form with hydraulic
knee struts and heating blowers
FULL-TUNNEL FORMS
Hotel construction
SHORING TOWERS
Formwork for cast-in-place
concrete in high-clearance
construction is commonly based
on multitier shoring towers, also
termed load towers or support
towers
Family A
Family B
Family A
Family B
Family C
Family D
Family C
Family D
Form support using
240-ft-high aluminum
shoring towers with
carrying capacity of
18,000 lb/leg
TRAVELING FORM
SYSTEM FOR A TRAIN
TUNNEL
SAFETY
The mechanical handling of formwork
on site, a characteristic of industrialized
forming systems, is a critical operation
All parties involved in crane handling
of the form should be aware of form’s
weight and the proper handling method