The document provides information about formwork systems used in building and construction. It discusses different types of formwork materials like sawn timber, plywood, steel, aluminum, glass fiber reinforced plastic, rubber and plastic. It explains formwork components for walls, columns, slabs and beams. It also covers formwork inspection, erection, concreting procedures and factors affecting removal of formwork. Falsework is described as the temporary structure used to support formwork until the permanent structure can support itself.

1. Building & Construction Unit
Industrial Centre
July 2009
July 2009
Website: - http://www.ic.polyu.edu.hk/bcu/

2. To introduce different types of formwork system and
common site practices of formwork construction
common site practices of formwork construction
To provide ‘hands-on’ experience for students to
design and fabricate formwork for placing concrete.
To appreciate different types of metal falsework; and
the critical issues in design and construction of
To appreciate different types of metal falsework; and
the critical issues in design and construction of
falsework in supporting formworks
2

3. Formwork is the term given to either
Formwork is the term given to either
temporary or permanent moulds into
which concrete or similar materials are
poured. In the context of concrete
construction, the falsework supports
the shuttering moulds.
3
http://en.wikipedia.org/wiki/Formwork

4. Sawn Timber and plywood
most commonly used in Hong Kong. Plywood surfaces may be:
Untreated 1 to 10 uses
Resin-coated 5 to 20 uses
Resin-coated 5 to 20 uses
Steel
The use of steel is largely confined to proprietary formwork systems.
Aluminum
Aluminum has many of the properties of steel with substantial weight savings.
Glass fiber reinforced plastic ( GRP )
GRP material is strong light weight material manufactured from polyester resin,
reinforced with glass fiber.
Rubber
Rubber
Rubber materials are generally used as form liners when complex shapes are
required to be cast into the concrete.
Plastic
Plastic formwork is claimed to be faster than traditional methods of construction.
The used materials could be collected to recycle.
4

5. Sawn timber and
Sawn timber and
Plywood are
generally used in
Hong Kong for in-
situ concrete work
5

6. Steel formwork is also
Steel formwork is also
used, particularly in
Harmony and Concord
public housing work.
6

7. 7
http://en.wikipedia.org/wiki/File:Moladi_plastic_formwork.jpg

8. Facing panel
the sheet material directly contact to concrete that forming the surface into
preferred shape and finish.
preferred shape and finish.
Soldier
acts as Joist but in wall form system. They receive loading from the facing panels
of wall form.
Waling
acts as Runner but in wall form system, and directly clamped by tie bolts.
Tie bolt
Tie bolt
to through the two pieces of wall from and tie them together, which acts in
tension due to pressure from elevated height difference of fresh concrete.
Spreader
spreader are short length of wood, concrete or steel that fixed between the faces
of wall form. They keep the formwork apart to the required thickness of the wall
unit the concrete is poured.
8

9. Wall Form
Wall Form
Soldier
Waling
Facing
panel
Waling
Tie bolt
9

10. Wall Form
Wall Form
10

11. Column Form
Column Form
Facing
panel
Soldier
Waling
Tie bolt
Telescopic
prop
11

12. Column Form
Column Form
12

13. Kicker and Cleanout Port
Kicker and Cleanout Port
Kicker
a small concrete upstaged cast
above floor level to position
wall or column forms for the
next lift and to assist the
prevention of grout loss.
Cleanout Port (Pocket)
a small opening to be cut away
from formwork surface at the
lowest level to provide access
13
lowest level to provide access
for cleaning out before
concrete casting

14. Falsework
the part of a formwork which supports the form usually for a horizontal structure
such as beam and slab.
such as beam and slab.
Brace
a member usually diagonal, which acts in tension or compression and stiffened a
frame against distortion.
Prop
a strut which is light enough to be man-handled, which responds to support
vertical load under beam or column. When its length is adjustable, it is known as an
adjustable prop.
Runner
a horizontal member direct on the falsework, it spanning across a number of joists
a horizontal member direct on the falsework, it spanning across a number of joists
and lacing them together (may be used to carry a beam soffit).
Joist
the horizontal members lied on runners perpendicularly, they receive loading from
the soffit panels.
Decking
the form platform directly under R.C. slab and beams.
14

15. (Joist)
350
(Runner)
RC
Beam
Formwork
Strong
Lacing
Props
Falsework
300
Support
1500
1500
600
Props
Sole plate
Foot ties
15

16. Runner
Joist
Prop
16

17. Slab/Beam Formwork
Slab/Beam Formwork Falsework
Falsework
Falsework
Standard
Runner
Joist
Decking
Bracing
17

18. Reusable times of Forms.
Designed for easy striking and quick reassemble.
Strong enough to withstand the tamping of
concrete.
Special forms examples
Special forms examples
Formwork Design refer to AS3610:1995–
Australian Standard on Formwork for Concrete
18
http://www.specialformwork.com/products/main-products.html

19. Conventional timber formwork
Longer construction duration
Double the cost of using steel panel in
Large steel panel forms
High efficiency, twice faster than timber
formwork system
High initial cost but balanced by the long
terms savings in timber
Double the cost of using steel panel in
long run
Plastering need for leveling concrete
surface
Labour intensive for erecting and striking
formwork
Reused 8-15 times, several sets of timber
forms needed for a high-rise block
High initial cost but balanced by the long
terms savings in timber
Better quality concrete products, concrete
surfaces suitable for applying tiles and paints
directly
Less labour force required for erecting and
striking formwork
Reused over 100 times, one set of forms
sufficient to complete a block and can be
forms needed for a high-rise block
Hand lift timber board from floor to floor
Considerable timber waste produced
sufficient to complete a block and can be
reused in another sites
Tower cranes needed for lifting formwork
Waste steel scrapped for recycling, less waste
produced
19
Source: http://www.cse.polyu.edu.hk/~cecspoon/lwbt/Comparison/Comparison.htm

20. Item Material
cost %
Labour and
plant cost %
Total cost %
cost % plant cost %
Concrete 12 8 20
Reinforcement 19 6 25
Form system 6 22 28
Sundries 18 9 27
Sundries 18 9 27
Total 55 45 100
20

21. Type of formwork Minimum period before
formwork may be
formwork may be
removed
Vertical formwork to column, walls and large
beams
12 hours
Soffit formwork to slabs with props left in 4 days
Soffit formwork to beams with props left in 7 days
Props to slabs 10 days
21
Props to slabs 10 days
Props to beams 14 days

22. Formed finish of concrete is classified into F1, F2, F3, F4, F5.
It specified materials used, patterns, tolerances appearances.
It specified materials used, patterns, tolerances appearances.
type of surface Vs class of finish
e.g.
◦ Below ground F1
◦ To be covered with render, plaster F2
◦ To be covered with paint F4
◦ To be covered with paint F4
◦ Walls above FGL, exposed to direct public view F5
22
Reference: General specification for civil engineering works of HKSAR:- section 14

23. 1) Density of concrete, ∆(2400kg/m³)
2) Workability of the concrete mix, Slump (mm)
3) Rate of placing, R (m/h)
3) Rate of placing, R (m/h)
4) Method of concrete discharge
5) Concrete temperature, t° Celsius
6) Vibration, (% continuity)
7) Height of lifting, H(m)
8) Dimension of the section cast, minimum dimension, d (mm)
9) Reinforcement detail
9) Reinforcement detail
10) Stiffness of the formwork structure
23

24. Precast concrete usually has to be made within fine limit of accuracy and to a high
degree of finish.
Precast units have to fit and easily install when delivery on site.
Precast units have to fit and easily install when delivery on site.
The mould boxes have therefore to be carefully made to permit these standards in
casting.
For mass production purpose, it is necessary to be able to strike a mould when the
concrete is in a vary green state, both to permit early re-use of the forms and to
enable the finished article to be cleaned down when in a workable state.
Its panel or unit should come square away from the concrete face and not side off it.
Its panel or unit should come square away from the concrete face and not side off it.
Hinge, tenon and easy bolt shall be used for joint of erection.
The placing direction is always different from the design on site.
24

25. 25

26. The form is erected on site in location.
Inspection is very important in all stage formwork and should
consist of checking the various forms, to ensure sufficiently
Inspection is very important in all stage formwork and should
consist of checking the various forms, to ensure sufficiently
strong and rigid enough.
The checking should be included all part of formwork i.e.
wedges, braces and ties etc.
The size, level, plumb and alignment also be check time to
time.
time.
Falsework, scaffolding and working platform are the main
accessories.
26

27. 27

28. 28

29. 29

30. 30

31. 31

32. 32

33. 33

34. 34

35. Setting-out
35

36. Erecting wall/column forms (and concreting 1st stage)
36
Source: http://www.perime.com/products.cfm

37. Erecting Falsework (after struck wall/column forms)
37
Source: http://www.perime.com/products.cfm

38. Sides Soffit of Beams
38
Source: http://www.perime.com/products.cfm

39. Erecting Decking
39
Source: http://www.cse.polyu.edu.hk/~civcal/defaultIE.htm

40. Form Edges (and concreting 2nd stage)
40
Source: http://www.perime.com/products.cfm

41. The surface of the formwork should be inspected for defects and for
conformity to the surface finishes.
Inspect the completed formwork and reinforcement.
Rubbish should be removed from the interior of the forms before the
concrete is placed.
The faces of the forms in contact with the concrete should be clean.
Release agents should be applied so as to provide a thin uniform coating to
the forms without contaminating the reinforcement
41

42. Formwork
Correct position
Line and level
Accuracy within permitted tolerances
Waterstops
Correctly positioned
Fixed and suitably supported
Formwork Checklist before concreting
Accuracy within permitted tolerances
Shape of members
Verticality (plumb)
Correct angles for batters etc.
Finishing heights (mark off)
Joint
Formwork joints flush and tight
No nails protruding into the concrete
Ties and Fixings
Correct number
Correct lengths
Tight enough and not too tight
Fitted with the proper washers
Finish
All forms perfectly cleaned out
No nails protruding into the concrete
Formwork joints sealed as required
Construction joints strutted and
supported
All forms perfectly cleaned out
Release agents correctly applied
42
Source: http://www.cityu.edu.hk/CIVCAL/production/traditional/

43. Formwork shall be removed without hammering or levering and in
such a manner that there is no shock, disturbance, damage or loading
to the concrete.
to the concrete.
After removal, formwork which is intended for re-use shall be cleaned
and stored properly with protection.
Falsework and formwork shall not be loosened or removed before the
minimum times stated, the times stated are for a minimum ambient
temperature of 15°C.
e.g. Surface of class F5 finish concrete without PFA:
Vertical (non-profiled) _ _ _ 48 hours
Soffits of beams (props left in) _ _ _ 10 days
Props of beams _ _ _ 14 days
Props of slab _ _ _ 10 days
43
Reference: General specification for civil engineering works of HKSAR:- section 14

44. It may be possible to use shorter periods before striking formwork by
determining the strength of the concrete in the structural element.
Formwork supporting cast in-situ concrete in flexure may be struck when the
strength of the concrete in the element is 10 N/mm² or twice the stress to
which it will be subjected, whichever is the greater, provided that striking at
this time will not result in unacceptable deflection.
This strength may be assessed by test on cubes cured, as far as possible, under
the same conditions as the concrete in the element.
For cantilever element, formwork shall be struck until concrete reached the
designed strength.
44
Reference: General specification for civil engineering works of HKSAR:- section 14

45. 1. Honeycomb due to inadequate
concrete compaction
2. Fin due to Improper Joints in
Wall Form
Bulking due to inadequate Formwork Support
45

46. A temporary structure used to support a permanent
structure while the permanent structure is not self-
structure while the permanent structure is not self-
supporting
Temporary support structures for formwork used to
mold concrete to form a desired shape.
46

47. Steel Frame
47
Structural Steelwork

48. Failure of Falsework
48
Buckling of Columns

49. (Joist)
350
(Runner)
RC
Beam
Formwork (Loadings… are supported
By Falsework)
Strong
Lacing
Props
Falsework
300
Support
1500
1500
600
Props
(Behave as Slender
Columns – liable to
buckling problem)
Sole plate
Foot ties
49

50. Nominal wall thickness = 4 mm (+0.8/-0.4)
Nominal outside diameter = 48.3 mm (+0.5)
Nominal mass per unit length = 4.37 kg/m (-7.5% max.)
Straightness = 1/1600 length (Max dev.)
Cross sectional area A = 547 mm2
Moment of Inertia about dia., I = 138000 mm4
Elastic modulus, Z = 5700 mm3
Elastic modulus, Z = 5700 mm3
Radius of gyration, r = 15.7 mm
Steel, Young's Modulus E = 205000 N/mm2
50

51. Column under compression may cause great lateral
deflection suddenly - called buckling.
deflection suddenly - called buckling.
If axial compression force P Pcr critical load,
Buckling will not happen, it is just shortened
If P Pcr , Column will buckle
If P Pcr , Column will buckle
51
Ref. http://webclass.ncu.edu.tw/~ymhuang/ch12/ch12.html

52. If P Pcr , Column will buckle
52
Ref: http://vcity.ou.edu/demoModules/analysis/stability/stability.htm

53. Euler's formula
Constant value
Young‘s Modulus of Elasticity (values
related to TYPES of materials,
Moment of Inertia about dia., I
(values related to SIZES DIMENSIONS
of materials,)
P =
π2EI
53
L e = effective length,
(values related to LENGTH OF MATERIALS
METHOD OF CONNECTION)
Pcr =
π EI
Le
2
Ref: http://www.engineersedge.com/column_buckling/column_ideal.htm

54. 80
30
40
50
60
70
Perm axial load (new)
kN
Perm axial load (old)
0
10
20
Perm axial load (old)
kN
l =1000
l/r =63.7
l =3000
l/r =191.1
l =2000
l/r =127.4
(l = effective length)
(l/r=slenderness ratio)
(r = radius of gyration of tube section)
54

55. Self-weights
Permanent works to be supported
Permanent works to be supported
Impact due to placing permanent works
Construction operations
Temporary storage of materials
Traffic loads
Plant
Plant
Induce wind loads
Uplift loads due to wind and floatation
55

56. Wind loads
Hydrostatic pressure
Hydrostatic pressure
Lateral earth pressure
Differential movements of supports
Vibration effects
Flowing current
Unsymmetrical distribution of vertical loads
Unsymmetrical distribution of vertical loads
Unsynchronized jacking of permanent work against
falsework
56

57. Loading Capacity of
Loading Capacity of
Frame Falsework –
depending on where
and how the loads
are applied on the
frame
frame
57

58. 100% 75% 50% 20%
HKIE, 1998, Symposium on Bamboo and Metal Scaffolding Proceedings, P.105
(Reference L in Subject Web) 58

59. Moment due to possible
eccentricity of Axial Load
eccentricity of Axial Load
Centralising Joist
by Wedges
59

60. i.e.
The L e (effective length)
is divided into several
sections to come
shorter
60
Lacing
Bracing

61. e.g.
Mechanical soil
compaction and tests
before erecting of
falsework
61
http://upload.wikimedia.org/wikipedia/commons/1/1d/Road_roller_ride-on_articulating-swivel_small_01.jpg
ride-on road roller

62. In cases of used systems –
check sections:
check sections:
◦ rust cavitation
◦ cracked elements
◦ weld fatigue
◦ bent
◦ crushes
◦ crushes
◦ buckled
62

63. Check loads including Dead Loads, Live Loads, Wind
Loads others in x, y, z directions
Loads others in x, y, z directions
Check formwork for strength, forces, deflection
Check the vertical capacity
Check overall stability
Check design and fixity of connections
Check deflections of overall falsework system parts
Check load distribution at transfer points achieved an
appropriate manner
Check load distribution at transfer points achieved an
appropriate manner
Check adequacy of foundation
63

64. http://en.wikipedia.org/wiki/Formwork
Building (Construction) Regulations, HKSAR)
General Specification For Civil Engineering Works (Civil Engineering Department, HKSAR)
General Specification For Civil Engineering Works (Civil Engineering Department, HKSAR)
PERI GmbH Formwork and Shoring http://www.perime.com/products.cfm
http://www.rmdaustralia.com.au/
Code of Practice on Metal Scaffolding Safety – Labour Department, HKSAR, 2001
BS5975: 1996, Code of Practice for Falsework
Irwin AW. Sibbald WI, 1983, Falsework – A handbook of Design and Practice
http://www.cse.polyu.edu.hk/~civcal/defaultIE.htm
Australian Standard on Formwork (and falsework) for concrete AS3610:1995
64