1. FORMWORK for Civil Engineering Construction Works
Dr V Srinivasa Reddy
Professor of Civil Engineering
GRIET
Lecture 1

2. Code Standards on Formwork
INTERNATIONAL STANDARDS
• ACI 347r-94 - guide to formwork for concrete • ACI SP-4 - formwork for concrete. • OHSAS - Occupational Health and Safety Act standards • BS British standards • CAN/CSA - S Canadian standard • SAA Australian standards • DIN German standards
The above standards covers all topics in detail, including lateral pressure of concrete, superimposed loads like P&M (plants and Machinery)loads, impact loads and environmental loads like wind loads etc.
INDIAN STANDARDS
• IS , Indian Standard - False work for Concrete Structures - Guidelines • The other code available for reference “IRC Guidelines on design and erection of formwork for road bridges” is derived from the British and American codes.
The above codes do not elaborate on design factors and special applications when compared to the treatise of international codes.
The code itself was made available only in 1999.

4. Definition of Formwork:
When concrete is placed, it is in plastic state. It requires to be supported by temporary supports and castings of desired shape till it becomes sufficiently strong to support its own weight. This temporary casing is known as the formwork or forms or shuttering.
Formwork also carries the weight of freshly placed concrete and itself besides live load due to materials, equipment and workmen
In the Construction of any building concreting and reinforcement binding is the main activity after that to hold them in their position Formwork is most important

5. Formwork is a classic temporary structure in the sense that:
it is erected quickly
highly loaded for a few hours during the concrete placement
and within a few days disassembled for future use
The term "Temporary Structures" may not fully imply the temporary, since some forms, tie hardware, and accessories are used hundreds of times, which necessitates high durability and maintainability characteristics and design that maximizes productivity
Unlike conventional structures, the formwork disassembly characteristics are severely restricted by concrete bond, rigidity, and shrinkage, which not only restricts access to the formwork structure but causes residual loads that have to be released to allow stripping from the concrete which initiates disassembly.

6. Today modular panel forming is the norm.
In 1908 the use of wood versus steel formwork was debated at the ACI convention. Also, the advantages of modular panel forming with its own connecting hardware, and good for extensive reuse were realized.
By 1910 steel forms for paving were being produced commercially and used in the field
Today modular panel forming is the norm.

7. Why Formwork For the different construction activities like
Brick work above 5 ft
Surface finishing works like plastering, painting, walling etc.
Renovation, repair and alteration works.
Roof and slab pouring
Some temporary nature supports and structures are required like
Formwork (Supporting Structure)
Scaffoldings (arrangement for working plate forms)
Shoring (supporting method for unsafe structure)
Underpinning (Method of strengthening an existing
structure’s footing)

11. Form work : All arrangement done to support the green concrete till it attains the strength is known as form work or temporary work.  Form work determines the geometry, shape, size and finish of the form work.
Centering : Part of the form work which supports the horizontal surface is called centering for example slab bottom  , beam bottom etc. Shuttering :Part of the form work which supports the Vertical surface is called Shuttering for example column sides, beam sides, slab side ,wall side etc. Staging : That portion which support centering & shuttering is called Staging. Pipes/Props/Jacks
Scaffolding : That arrangement which is meant to be a supporting platform for people ( labor , supervisor, mason ,fitter, painter, carpenter etc. ) is known as scaffolding.
Scaffolding is nothing but a fixed/movable platform which can be used for working at heights . They are usually used for activities such as plastering, painting, brick work at heights etc. 

12. There are various types of scaffolding :
1. Tube and Coupler Scaffolding: Assembled using tubes and couplers at joints.

13. 2. Bamboo/Wooden Scaffold : It is made using bamboo materials
2. Bamboo/Wooden Scaffold : It is made using bamboo materials. It is considered unfit for industrial use.

14. 3. Suspended Scaffold : It is used for cleaning glass at malls usually.

15. Shuttering/Formwork 
the falsework supports the
shuttering moulds

16. Objectives of Form Building
Basic objectives in form building are three fold:
Quality - In terms of strength, rigidity, position, and dimensions of the forms
Safety - for both the workers and the concrete structure
Economy - the least cost consistent with quality and safety requirements
Cooperation and coordination between engineer / architect and the contractor are necessary to achieve these goals.
Economy is a major concern since formwork costs constitutes up to 60 percent of the total cost of concrete work in a project.
In designing and building formwork, the contractor should aim for maximum economy without sacrificing quality or safety.

17. How Formwork Affects Concrete Quality
Size, shape, and alignment of slabs, beams, and other concrete structural elements depend on accurate construction of the forms.
The forms must be:
Sufficiently rigid under the construction loads to maintain the designed shape of the concrete,
Stable and strong enough to maintain large members in alignment, and
Substantially constructed to withstand handling and reuse without losing their dimensional integrity.
The formwork must remain in place until the concrete is strong enough to carry its own weight, or the finished structure may be damaged.

18. Causes of Formwork Failure
The main causes of formwork failure are:
- Improper stripping and shore removal
- Inadequate bracing
- Vibration
- Unstable soil under mudsills*, shoring not plumb
- Inadequate control of concrete placement
- Lack of attention to formwork details.
*Mudsill: A plank, frame, or small footing on the ground used as a base for a shore or post in formwork.

19. Formwork failures are the cause of many accidents and failures that occur during concrete construction which usually happen when fresh concrete is being placed.
Generally some unexpected event causes one member to fail, then others become overloaded or misaligned and the entire formwork structure collapses.
Forms sometimes collapse when their supporting shores or jacks are displaced by vibration caused by:
passing traffic
movement of workers and equipment on the formwork
the effect of vibrating concrete to consolidate it.
Diagonal bracing can help prevent failure due to vibration.

20. Causes of Failure Improper Stripping and Shore Removal
Case study:
Too early shore removal at Bailey's Crossroads in Virginia (1972):
26-stories + apartment building
Forms were supported by floors 7-days old or older
Failure occurred on the 24th floor, where it was shored to the 5-day-old 23rd floor.
The overloaded 23rd floor failed in shear around one or more columns,
triggering a collapse that carried through the entire height of the building.
Premature stripping of forms, premature removal of shores, and careless practices in reshoring can produce catastrophic results.

21. Inadequate Bracing
The more frequent causes of formwork failure, however, are other effects that induce lateral force components or induce displacement of supporting members.
Inadequate cross bracing and horizontal bracing of shores is one of the factors most frequently involved in formwork accidents.
Investigations prove that many accidents causing thousands of dollars of damage could have been prevented only if a few hundred dollars had been spent on diagonal bracing for the formwork support.
Diagonal bracing improves the stability of such a structure.
Suppose a worker accidentally rams or wheelbarrow into some vertical shores and dislodges a couple of them. This may set up a chain of reaction that brings down the entire floor.
One major objective of bracing is to prevent such a minor accident or failure from becoming a disaster.

22. Inadequate Control of Concrete Placement
The temperature and rate of vertical placement of concrete are factors influencing the development of lateral pressures that act on the forms.
If temperature drops during construction operations, rate of concreting often has to be slowed down to prevent a build up of lateral pressure overloading the forms. If this is not done, formwork failure may result.
Failure to regulate properly the rate and order of placing concrete on horizontal surfaces or curved roofs may produce unbalanced loadings and consequent failures of formwork.

24. Qualities of formwork It should be according to ACI document SP-4
It should be water tight
It should be strong
It can be reusable
Its contact surface should be uniform
It should be according to the size of member.

25. Requirements of a Good Formwork
The essential requirements of formwork or shuttering are:
a)   It should be strong enough to take the dead and live loads during construction.
b)  The joints in the formwork should be rigid so that the bulging, twisting, or sagging due to dead and live load is as small as possible. Excessive deformation may disfigure the surface of concrete.
c)  The construction lines in the formwork should be true and the surface plane so that the cost finishing the surface of concrete on removing the shuttering is the least.
A formwork should be easily removable without damage to itself so that it could be used repeatedly

26. Classification of Formwork
The different categories in which formwork can be classified are: a) According to size. b) According to location of use. c) According to materials of construction. d) According to nature of operation. e) According to brand name of the product.

27. Classification according to size
In practice, there are only two sizes for formwork; small-sized and large-sized.
Any size which is designed for operation by workers manually is small-sized.
At present, the most common systems are made of timber and aluminium, and are usually in the form of small panels. There is seldom medium-sized formwork.
In cases in which large-sized formwork is used, the size of the form can be designed as large as practicable to reduce the amount of jointing and to minimize the amount of lift. The stiffness required by large-sized formwork can be dealt with by the introduction of more stiffening components such as studs and soldiers. The increase in the weight of the formwork panels is insignificant as a crane will be used in most cases.

28. Classification according to the location of use
Foundations
Wall
Column
Slabs & beams
Stairs
Classification according to materials of construction
Timber in general is still the most popular formwork material for its relative low initial cost and adaptability .
Steel, in the form of either hot-rolled or cold-formed sections and in combination with other sheeting materials, is another popular choice for formwork materials.
In the past two to three years, full aluminium formwork systems have been used in some cases but the performance is still being questioned by many users, especially in concern to cost and labor control

29. Classification according to nature of operation
Formwork can be operated manually or by other power-lifted methods.
Timber and aluminium forms are the only manually-operable types of formwork. They are designed and constructed in ways that they can be completely handled independently without the aid of any lifting appliances.

30. Classification according to brand name of the product
Several patented or branded formwork systems have successfully entered the local construction market in the past decade. Each of these firms offers its own specialized products, while some can even provide a very wide range of services including design support or tender estimating advice.
As the use of innovative building methods is gaining more attention from various sectors in the community, advanced formwork systems are obviously a promising solution. VSL FORMWORK (Source Raymond, 2001)

32. Minimum Plank Thickness for Formwork
18 mm is the minimum for small formworks and requires closer cross planks
20 – 24 mm is the standard
Thin planks can give way to the pressure of the concrete

33. Nail Size
1 1/2” = 40mm nails are too week and cannot stand the pressure of the concrete
The standard length for nails is 2 ½ “ = 65mm

34. Column Formwork
Sizing of Panels
Column +2X thickness
Column

35. Nail all edges with 2 1/2” nails
Join the braces as well

36. Verticality Use a plum bob Mark the centre
Check verticality and straightness
Do this in both directions and secure the position

37. Cut out in outer dimension of formwork
Cutout in Column
Cut out in outer dimension of formwork
Support for beam

38. Erect and align the column

39. Set up support Beams and Props for the Beam

40. Insert Panels one by one if they are large.. and fix them
Double support
Prop

42. Fair face Columns and Brickwork
No Bond!

43. Column added to brickwork
Build first the walls
Add the column for maximum bond
Formwork

44. Column
Groove for Mortar

45. Fair Face Formwork Rough planks do not provide a smooth surface
Plywood or steel sheets make a smooth surface for concrete
Fair face formwork is designed for easy removal and reuse

46. Apply Formwork Oil
Mix Oil and Grease 1:2
Engine Oil
Grease
Grease

47. Formwork oil prevents the formwork from sticking to the concrete
Formwork oil prevents the formwork from sticking to the concrete. It eases dismantling
Formwork oil gives the concrete a fine finish
Never use burnt engine oil. It will blacken the concrete and spoil the formwork

48. Column Footing
After excavation a screed of 5..10cm concrete is laid to provide a clean ground
Next comes the footing, a large block of concrete that provides a base for the column

49. TIMBER FORMWORK
Timber Formwork : For The Slab

50. Timber Formwork: After Concrete Was Poured

51. ADVANTAGES OF TIMBER FORMWORK a) Easy handling because it’s light weight b) Easy to disassemble c) Damaged parts can be replaced with new one d) Very flexible DISADVANTAGES OF TIMBER FORMWORK a) Can’t be used for long. Have limited re-use. Can only be re-used 5 or 6 times b) If the timber is dry, it will absorb moisture from wet concrete which could weaken the resultant concrete member. c) Timber with high moisture content (more than 20 % moisture content), wet concrete will shrink & cup leading to open joints & leakage of grout.

52. Timber formwork used for the construction of 2nd and the 3rd floor.

53. ADVANTAGES OF STEEL FORMWORK a) Very strong and able to carry heavy load b) Easy to be fixed c) Uniform size and surface d) Can be used for a very long time DISADVANTAGES OF STEEL FORMWORK a) Limited size or shape b) Excessive loss of heat c) A very smooth surface will be produced which would give problems for finishing process

54. STEEL FORMWORK

55. The first floor circular columns were constructed using steel column forms. The steel column form should be oiled before concreting.

56. After concreting to the first floor columns, the steel column forms were dismantled easily.

57. ADVANTAGES OF GLASS REINFORCED PLASTIC FORMWORK
a) Very useful for complex shape and special features
b) Easy to disassemble
c) Light (not heavy)
d) Damages on the formwork can be easily be repaired
DISADVANTAGES OF GLASS REINFORCED PLASTIC FORMWORK
a) Expensive

58. Formwork systems in India
A formwork system refers to the moulds used to hold and support wet concrete until it cures, which is pretty much a vital element in concrete construction. formwork systems have evolved from being customized timber-based to pre- engineered systems made of steel, aluminium, manufactured timber, plywood and plastics. This advancement, especially in the case of high-rise projects has translated into faster implementation with lesser labour, implying enhanced productivity while delivering a better finished product The only IS code available is IS 14687:1999 which only provides guidelines on the usage of formwork and these too are very vague. Hence, standards that are followed for the designing of its formwork and scaffolding systems are ACI SP-4

59. Formwork detail for different structural members
In concrete construction , formwork is commonly provided for the following structural members.
Foundations
Wall
Column
Slabs & beams
Stairs

60. Formwork for Foundations
Wall foundations
It consists of
Plywood Sheeting
Struts

61. Formwork for Foundations
Column Foundations
It consists of
Side Supports
Side Planks
Cleats
Cleats
Side Support
Side Planks

62. Formwork for Wall Struts It consists of Timber sheeting Vertical posts
Horizontal members
Rackers
Stakes
Wedges
After completing one side of formwork reinforcement is provided at the place then the second side formwork is provided.
Struts

63. Formwork for Column It consists of the following Side & End Planks
Yoke
Nut & Bolts
Two end & two side planks are joined by the yokes and bolts.

64. Column formwork

66. Formwork for Slabs & beams
It consists of
Sole plates
Wedges
Props
Head tree
Planks
Batten
Ledgers
Beam formwork rests on head tree
Slab form work rests on battens and joists
If prop height are more than 8’ provide horizontal braces.

67. Lintel or Beam Formwork

68. Formwork for Stairs Riser Planks It consists of
Vertical & inclined posts
Inclined members
Wooden Planks or sheeting
Stringer
Riser Planks
Riser Planks

70. Removal of formwork
Time of formwork removal mainly depends on the following factors
Type of Cement
Rapid hardening cements require lesser time as compared to OPC (Ordinary Portland Cement)
Ratio of concrete mix
Rich ratio concrete gain strength earlier as compared to weak ratio concrete.
Weather condition
Hydration process accelerates in hot weather conditions as compared to cold and humid weather conditions.

71. Time of Removal of formwork
Sr. No
Structural Member
OPC
(Ordinary Portland Cement)
Rapid Hardening Cement 1
Beam sides, walls & Columns
2-3 Days
2 Days 2
Slab (Vertical Supports remains intact)
4 Days
3 Days 3
Slab (Complete Formwork removal)
10 Days
5 Days 4
Beams (Removal of Sheeting, Props remains intact)
8 Days 5
Beams & Arches (Complete formwork removal) (up to 6 m span)
14 Days
5-8 Days 6
Beams & Arches (Complete formwork removal) (more than 6 m span)
21 Days
8-10 Days

72. Maintenance of formwork
Due to continuous use wooden planks & steel plates surfaces become uneven and require maintenance.
For wooden formwork use cardboard or plastic fiber board. Bolt hole places must also be repaired.
For steel formwork plates must be leveled by mallet and loose corners must be welded.