1. FORMWORK BUILDING CONSTRUCTION PREPARE BY:-
1. Sojitra Ashish R ( )
2. Khandla Chetan K ( )
3. Khaped Vishal C ( )
4. Sarvaiya Navneet P ( )
5. Sindhav Bhavani P ( )

2. DEFINITION:
Its is an artificial support provided below and around the precast or cast insitu concrete work.
Formwork is commonly made of
Steel
wood
Formwork construction & casting is of prime importance in concrete industry. It share a significant amount of concrete cost.
Formwork is designed according to The ACI document SP-4.

3. Qualities of formwork:
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.
Uses:
Formwork molds the concrete to the desired shape and size, and controls its position and alignment.
It is used to transfer the temporary external loads.

4. Major objectives considered in formwork:
Quality
Safety
Economy

5. Quality:
Forms must be designed and built with sufficient stiffness and accuracy so that the size, shape, position, and finish of the cast concrete are maintained.
Safety:
Forms must be built sufficient strength and factor of safety so that they have the capable of all supporting loads.
Economy:
Forms must be built efficiently, minimizing time and cost..

6. Requirements of formwork:
Material should be cheap and re usable,
It should be practically water proof, so that it should not absorb water from concrete,
Swelling and shrinkage should be minimum,
Strong enough to with stand all external loads,
Deflection should be minimum,
Surface should be smooth, and afford easy striping,
Light in weight, so that easy to transfer,
Joints should be stiff, so that lateral deformation and leak is minimum .

7. THREE STAGES: Assembly and erection Concrete placement
Stripping and dismantling

8. Formwork detail for different structural members
In concrete construction formwork is commonly provided for the following structural members.
Wall
Column
Slabs & Beams
Stairs
Chimneys
Water tanks
Cooling Towers

9. Formwork for Wall 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.

10. Wall forms:
Wall forms principally resist the lateral pressure generated by fresh concrete as a liquid or semi liquid material.
The pressure can be quite large, certainly many times the magnitude of live loads on permanent floors.
So design often involves closely spaced and well-supported members.
The tension capacity of heavy ties around 27,230 kg.

11. Wall forms:

12. 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.

13. Column forms:
Column-forms materials tend to vary with the column shape.
Wood or steel is often used with square or rectangular column.
Round column forms more typically pre manufactured in a range of standard diameters, are available in steel, paper board, and fiber reinforced plastic.
Round column are more structural efficient compared to square, since the internal pressures can be resisted by the hoop membrane.
Round steel forms are generally used for larger columns and bridge piers and come in diameters about 0.36m to 3mts..

15. Formwork for columns

16. 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.

17. Lintel or Beam Formwork:

18. FORMWORK FOR SLAB:

19. Vertical & inclined posts Inclined members Wooden Planks or sheeting
FORMWORK FOR STAIRS:
It consists of
Vertical & inclined posts
Inclined members
Wooden Planks or sheeting
Stringer
Riser Planks

20. FORMWORK FOR STAIRS:
The sheathing or decking for deck slabs is carried on cross-joists which are in turn supported on raking ledgers
The ledgers are generally of 7.5cm x 10cm size .
The cross- joists may be 5cm x 10cm size
The riser planks are 4-5 cm thick and equal to the height of riser
The riser planks are placed after the reinforcement is placed in position

21. FORMWORK FOR STAIRS:

22. FORMWORK FOR CIRCULAR STAIRS:

23. FORMWORK FOR CHIMNEYS:
For tall chimneys two types of forms techniques are in generally use in our country
a) Jump form
b) Slip form

24. Jump Form:
In this type jacking bars are either cast in concrete or else are carried in tubes which are cast in concrete.
After casting a lift, concrete is allowed to set and then the forms are raised by jacks and the next lift is cast.
Jacks are usually placed about 2m apart and are designed.

26. Slip Form:
The slip form method of concrete construction is used for forming both horizontal and vertical concrete structures.
It often used for forming highway pavements as continuous operation.
Slip form methods is also been used for forming various types of vertical concrete structures.

27. FORMWORK FOR CHIMNEYS:

28. FORMWORK FOR CHIMNEYS:

29. Removal of formwork:
Time of formwork removal 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.

30. 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

31. 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.

32. Cost of formwork
For normal works cost of formwork is about 30%-40% of the concrete cost.
For special works cost of formwork is about 50%-60% of the concrete cost.
Formwork cost is controlled by the following factors
Formwork Material cost
Formwork erecting cost
Formwork removal cost
Formwork jointing cost (Nails and Cables)
Labor charges.

33. Advantages of steel form work:
It can be used for a no. of times.
It is non absorbent.
Smooth finish surface obtained.
No shrinkage of formwork occurs.
Easy to use.
Its volume is less
Its strength is more.

34. LOADS ON FORMWORK: Formwork is subjected to following loads:
Dead weight of concrete
Hydrostatic pressure of the concrete
Live load due to working laborers
Impact effect at the time of pouring concrete into the formwork
Vibrations transmitted to formwork during pouring concrete

35. THANK YOU