Form Work

HIT HITACHI ACHI PLAN PLANT T TECH TECHNO NOL LOGIES OGIES (PVT (PVT) ) LTD

BA SI C IN DU ST RI AL TR AI NI NG

CHAPTER 07

FORMWORK

NATIONAL DIPLOMA IN ENGINEERING SCIENCES INSTITUTE OF ENGINEERING TECHNOLOGY, KATUNAYAKE

HITACHI PLANT TECHNOLOGIES (PVT) LTD


7.1 Introduction

In the modern construction world, concrete is the most widely used construction material. As concrete is a plastic material in green state it has to be kept in an enclosure till it hardens. This enclosure is known as formwork or shuttering. One of the easiest and most obvious ways of judging whether a concrete job is satisfactory or not is by its finished appearance. The formwork and the way it is made and used play a greater role in the finished appearance than anything else. It is made from expensive materials by skilled carpenters and the total cost of fabricating, erecting and striking formwork is often comparable with the concrete. Apart from the appearance considerations, formwork usually needs to be used many times and this can only be done if it is carefully and properly handled, cleaned and stored be it of timber, steel or other material as otherwise time and money will be wasted and the job will not progress smoothly. The formwork must withstand the worst combination of the following loads . 

Total weight of formwork, reinforcement and concrete.



!onstruction loads including dynamic effects of placing, co mpacting.



"ind loads #mainly for column$

7.2 Requirements of Formwork There are essential re%uirements for formwork. Any good formwork should satisfy all of the following re%uirements. 

!ontainment

&ormwork must be capable of shaping and supporting the fresh concrete until it becomes hard. 

'trength

&ormwork must be strong enough to withstand the dead weight of fresh concrete placed on it. Also formwork should be strong enough to bear the imposed loads after concrete placing. 

(esistance to )eakage

All joint in the form face should be either close fittings or covered with some sheet material to make these grout tight. *rout leakage can lead two weak concrete. It can cause honeycombing of the surface + may produce projecting fins #snobs$, which later have to be removed and touched up. 

Accuracy

&ormwork must be accurately set out so that the resulting concreting elements is in the right place and is of the correct shape and dimension. The degree of accuracy concerned will be consistent with the item being cast. NATIONAL DIPLOMA IN ENGINEERING SCIENCES INSTITUTE OF ENGINEERING TECHNOLOGY, KATUNAYAKE





asy of -andling

&orm panels and units should be made so that they can be easily handled by hand or mechanical means. In addition to all form work must also be designed and constructed to include facilities for adjustment, leveling, erecting and striking without damage to the formwork or concrete. 

The material of the formwork should not wrap or get distorted when exposed to sun, rain, and water during concreting.



&ormwork must be capable of gradual and easily remove

To get successful form work,



It must be accurately set out.



The shuttering should be built accurately. 'o that the desired sie, shape, position and finish can be attained.



The formwork should be strong enough to support all dead and live loads without collapse or danger to site personnel and to the structure.



/sing sheet materials and sealing the joints must fill with punch sheet, wetted cement paper, polythene strips to prevent grout leakage.



The formwork should be designed to erect and dismantled easily.

The most commonly used materials for formwork are timber, plywood and steel. In our site we used timber and plywood for formworks. The selection of materials for formwork depends on several factors. 

conomy of materials



0umber of times used



1urability



The availability of sies and shapes of materials



The shape formwork re%uired to be constructed



The ease of handling, constructing, erecting, concreting, removing, etc.

Therefore depending on the situation we have to select the most suitable material.

2.3 4aterials for &ormwork




5lywood  67mm thickness plywood are used in our site. *.I pipes 8arious sie long *.I pipes were used. 5 cone

 To keep the exact distance

&orm tie  /sed to fix the column boxed and beams.

2.3.6 Timber This is the most common material used for formwork construction. It is easy to work with and is also cheap. The moisture content of timber should be between 69: 7;:. 'o if the timber is dry, it will absorb moisture from the wet concrete that could weaken the resultant concrete member. "e used 6
7.3.2 Plywood 5lywood is extensively used material for the formwork construction due to its lightweight, availability, large sies and due to the ease of fabricating. The selected should be of a superior grade and the thickness should be related to the anticipated pressure. In our site we used 67mm thick coated plywood sheets #6>;;x?;;x67mm$.

Advantages of sing Plywood !"eets. 

*ood surface finish can be obtained.



5lywood formwork is economical because this can be used repeatedly although the cost of plywood is higher than class II timber planks.



'ince the plywood sheet covers large area, the time taken to construct the entire shuttering is less.



It can be easily sawn to the re%uired shape.

#isadvantage of sing Plywood !"eets



ven after removing the shuttering, adhered plywood particles can be seen on the surface when normal plywood used.



5eeling of layers with the time.



1ue to the slenderness of the sheet large numbers of strengthening cleats are re%uired, otherwise formwork gets deflected.

7.3.3 !teel NATIONAL DIPLOMA IN ENGINEERING SCIENCES INSTITUTE OF ENGINEERING TECHNOLOGY, KATUNAYAKE



'teel is also used as a material for formworks but it is not common as plywood or timber. It is mainly due to its economy and availability. The steel shuttering are very expensive and they cannot be fabricated at the site. 'o we have to use the prefabricated steel shuttering with limited number of sies. @ut it is more suitable when the same sies of formworks are to be constructed repeatedly. Also in the case of circular sections we have to use steel shuttering.

Advantages of sing !teel !"uttering 

'ince it needs to be assembled only, less timeconsuming.



-ighly durable and can be used many times.



*ood surface finish can be achieved

#isadvantages of sing !teel !"uttering 

Available in limited sies



1ifficult to handle



xpensive

7.3.$ %t"er &aterial used for formwork 

9;mm diameter *I pipes, concrete nails + wire nails

&orm

ties #to tie the separates and *I pipes$ 

?mm diameter 'eparates #thread bar + 5 cone$



5ipe supports and T<,


!lamp #&ix , &ree$



Turn buckles, adjustable steel props, !hain, Turn @uckles



mould oil




7.$ Release Agents The main purpose of treating formwork with a release agent is to make it easy to strike the form from the concrete face. There are a number of different types of release agent and the various form face material such as timber, steel and glass fiber re%uire different release agents. It is important to make sure that the right one is being used. The three most common types of release agents areB 6$ 0eat oil with surfactants: mainly used on steel faces, but can be used on timber and plywood. 7$ 4ould emulsionB for use on timber and plywood. 3$ !hemical release agentsB can be used on all types of form face. @ecause of their absorbency, new and untreated timber and plywood should always be given a coat of the appropriate release agent at least 3C hours before being used. A second application should then be made before using for the first time. The most common fault with release agents is for too much to be put onB this can stain in concrete. On the other hand, if not enough is applied, striking is made difficult and both the concrete and form face can be damaged.

7.' Formwork for (olumns In our site all the columns were rectangular shape. In the case of the rectangular column, the formwork consists of four shutters or panels made out of plywood board nailed securely to timber planks. &irst, the kicker frame was placed in accordance with the kicker lines and fixed firmly. Then, kicker was concreted and vibrated properly. After removing the kicker frame, the surface was roughened for the purpose of well bonding with later concrete. Advantage of the kicker is that it ensures the correct position of the column and prevents the leaking of it. Then the four shutters were fixed together and *I pipes were hung with the nails fixed to the plywood sheet using binding wires in each side vertically. Then the horiontal pipes also fixed to the board by using the &orm ties. The adjustable jacks were fixed between the horiontal *I pipes and to a fixed position of the floor. The cover blocks were also tightened to the reinforcement at the top. NATIONAL DIPLOMA IN ENGINEERING SCIENCES INSTITUTE OF ENGINEERING TECHNOLOGY, KATUNAYAKE



After set the formwork, Then a piece of plywood sheet was placed on the top of the formwork the column formwork was checked for vertical using two plumbs, which were hanging from the top of the formwork. The horiontal distance between the formwork and string line can be measured at the top and the bottom to ensure the vertically of the formwork. The props should be adjusted until the distances between formwork and string at top and bottom are e%ual. &inally all the clamps and props must be checked for tightens. Then it can be concreted.

Obviously four timber framed plywood panels one for each face are used forming the s%uire or rectangular shaped column side, and should be strengthened and securely hold these box together during the placing of concrete. 7.) Formwork for *eams and !la+s &irst 6;;; &inished &loor )evel #&&)$ was marked on columns. @eam bottoms were prepared by referring drawings. In this case *.I. pipes, 7
E @eam

D 69




-

'taff

!olumn

3;;; mm 1umpy )evel 6;;; &&) )ine F

&loor level

)eveling of the @eam and 'lab &ormwork F G -eight from 6;;; &&) line D G @eam 1epth E G 'lab Thickness Therefore while leveling the beam the staff reading, Therefore while leveling the slab the staff reading

G 3;;;  #6;;; H F H D H 69$ G 3;;;  #6;;; H F H E H 69$

*enerally supports #false work$ of the formwork raised or lowered to get the re%uired reading and by this process the formwork for the slab and the beams can be easily leveled

'lab formwork After laying scaffolding or pipe supports, #=
'tair case formwork After reinforcement work for the staircase is done the side boards will be nailed. On one of the sideboard the rise and the tread for the staircase will be drawn. "hile placing this sideboard great care is taken to ensure that it is placed properly that is the stairs drawn starts from the landing. The riser made as shown in &igure will be placed on the rise of the stair drawn on the side board and nailed to the both side boards firmly. "hen fixing the riser a sprit level is used check whether the riser is horiontal. Then after fixing the risers of two adjacent steps it is checked whether the tread of the stair is correct.




7.7 !to, *oard (onstruction

"ire mesh or 'ponge sheet

@eam bottom

@eam 'top @oard #at construction joint$

7
5lywood

"ire nail

'lab 'top @oard #at construction joint$ "ire mesh or 'ponge sheet




7.- Removal of Formwork

&orm work of beams and slabs should not be removed until the concrete reaches a sufficient strength to support its self weight and any other loads transferred. &ormwork should be struck carefully in order to prevent the load being transferred suddenly to the partly hardened concrete.&ormwork can be struck when the concrete has gained enough strength to be self  supporting. The job specification will normally give guidance on when forms can be struck and these times may be governed by the sie and shape of the member, the concrete mix, and the weather.

The minimum period for removing formwork Part of !tructure

Period for removing Formwork

'ide of foundations, columns, beams, And walls. /nder side of slabs up to =.9 meters 'pan /nder side of slabs of above =.9 meters span + under sides of beams up to C m span


7= hours

2 days

6= days



/nder sides of beams over C meters 'pan

76 days

1urations for &ormwork (emoval

2.? &ormwork arrangement

6mm Plywood 16 mm bar Base Reinforcement Form Tie Welding

1x2 Timber

Additional rebar P-Cone




16 mm bar

Plywood Tem$late

) 1

2 !"#" $i$es

6mm t, $lywood '()) x 1*)) +

16 mm bar

) ) %

) 1

2 !"#" $i$es

1&& x 2 timber

%&& x % timber

2 !"#" $i$es Plywood Tem$late

16 mm bar

2 2

2 !"#" $i$es

) %

1&& x 2 timber ) ) % 2

) %

Pi$e s.$$orts ) %

) %

2 2

/ ) )

Plywood Tem$late

/ ) )

1&& x 2 timber

%&& x % timber

2 !"#" $i$es

&orm "ork 'ystem of (adial type "all




12mm tk plywood (900x 1800)

2''x 2"timber 900

2" G.I. pipes

1'' x 2" timber

2" G.I. pipes

250

500

) ) ) 2

2"G.I.pipes

500

500 2 2

250

) % 2 2

4'' x 4" timber

&ormwork type of flat wall



12mm tk plywood (900 x 1800 )


%-) 2"x2" timber ) 2

2" G.I. pipes pipe support

) ) -

1"x2" timber

) ) -

2"G.I. pipes 2"G.I.pipes

) ) -

2 " G . I . p ie ps

) 2

1 " x2 "

t i m b re

4"x4"timber

'upporting system of the &orm "ork of "all

#terb#r($or outside o%ly)

12mm tk plywood (900 x 1800 ) 2"x 2" timber ) 2

2" G.I.pipes pipe support

) ) -

) ) ) 2

) ) -

) ) -

2" G.I.pipes

) 2

i!ker ) - ) - ) -

F"B"0 -"))) %-)

Fig o 1-3 0ift )1 Form Wor, system

)ift ;6 &orm "ork 'ystem



12mmtkplywood (900x 1800 )


0#FT 2 C4CR5T5 F"0  ("-))

2"x 2"timber

2"G.I. pipes pipesupport

/)) 2"G.I. pipes

i!ker

%-)

) / ( 1

) / -

F"B"0"  -"))

) ) /

Fig o 163 0ift )2 Form Wor, system

)ift ;7 &orm "ork 'ystem




7.1 !caffolding 'caffolds are temporary working platforms erected around the perimeter of a building or structure to provide a safe working place at a convenient height. They are usually re%uired when the working height is 6.9m or more above the ground level.

!caffolding

A 'caffolding set has fallowing items •

4itsui frame #vertical support to transfer the load$

•

cross bracing #connect with other frame horiontally$

•

joint pin #connect with other frame vertically$

•

catwalk #working area$

•

steel ladder

Figure 5.2.4

/acks 0 ot"er materials •

Adjustable jacks + (41 jacks

(41 jack can bear heavy load more than normal jacks. (41 jacks have its own fabricated method. *I pipes 9;mm diameter •

Timber #7< F 7<, 7JJ F =JJ$

•

!ouplers

•

Adjustable / head + fabricated / head

•

@ase plate

•

&orm tie with butterfly nut


HITACHI PLANT TECHNOLOGIES (PVT) LTD •

5cones, Thread bar

•

!able, turn buckle + buldo clip

•

'oldgers, steel separator

•

1evidak bar with c
•

upvc pipe


4aximum load on Adjustable / head, fabricated / head + @ase plate is =;=9 K0 with 79; mm maximum length. 'ome of above parts are shown in the

'!A&&O)1I0* A((A0*40T &O( "A))

'!A&&O)1I0* A((A0*40T &O( (A1IO) "A)) NATIONAL DIPLOMA IN ENGINEERING SCIENCES INSTITUTE OF ENGINEERING TECHNOLOGY, KATUNAYAKE




Form Work

Recommend Documents