What is FormworkWhat is Formwork??

The Temporary structure erected to The Temporary structure erected to support the concrete in its required support the concrete in its required shape (as the concrete will be in Plastic shape (as the concrete will be in Plastic state when laid), till it hardens and state when laid), till it hardens and becomes self supporting is known as becomes self supporting is known as Formwork or centering or Shuttering.Formwork or centering or Shuttering.

Components of Components of FormworkFormwork

Cost of Formwork MaterialCost of Formwork Material

Cost of erecting, placing and removal of Cost of erecting, placing and removal of formworkformwork

Cost of joining material such as nails, wires, etcCost of joining material such as nails, wires, etc

Cost of labour for fabrication of formworkCost of labour for fabrication of formwork

Objective of Formwork Objective of Formwork Planning:Planning:

To Plan for Materials / Methodology to be used To Plan for Materials / Methodology to be used adopted for executionadopted for execution

SafeSafe and Economical Utilization of the Resources and Economical Utilization of the Resources by way of proper Formwork Design and Drawing.by way of proper Formwork Design and Drawing.

Importance of Formwork Importance of Formwork Planning Planning

Plays vital role in Construction Industry both Plays vital role in Construction Industry both technically and financially as it costs about 8% of technically and financially as it costs about 8% of total building total building

cost.cost.

Leads Management to take decision for Leads Management to take decision for investment in Materials purchase depending uponinvestment in Materials purchase depending upon

Currents Projects availableCurrents Projects available

Future expected ProjectsFuture expected Projects

Financial aspectsFinancial aspects

for the requirement given by the Formwork planning for the requirement given by the Formwork planning division division Continued . . . . .

Planning of Formwork will have important Planning of Formwork will have important role in overall project role in overall project Planning. Proper Formwork Planning will Planning. Proper Formwork Planning will ensure thatensure that

o Timely availability of right materials with Timely availability of right materials with acceptable quality standards.acceptable quality standards.

o Formwork is executed with the optimum Formwork is executed with the optimum cost.cost.

o Avoids delay of subsequent activities / Avoids delay of subsequent activities / Project thereby saving in the Variable Project thereby saving in the Variable overheads / Project Overrun. overheads / Project Overrun.

Continued . . . . .

Continued . . . . .

Since Failure of Formwork results in Since Failure of Formwork results in Financial Loss, loss of life and loss of Financial Loss, loss of life and loss of time.time.

Guides Tendering team to take Guides Tendering team to take decisions while quoting new tenders decisions while quoting new tenders from the past experiences. from the past experiences.

Continued . . . . .

Continued . . . . .

What to plan for?What to plan for?

Safe and Economical Formwork Construction

o Plan for Materials to suit the height / design of Formwork o Arrangement methodology.

Planning for available resources

oTo arrange locally or oTo invest in new materials (Which results in additional cost implication and additional time to mobilize)

•Plan for Maximum Reuse (ie., Maximum no. of Repetitions).

• Type of Shuttering as the labor requirement depends upon the type of shuttering. For example, MAIWAN shuttering is a type of shuttering in which the readymade shutters are available for a floor where there is no beams and the floor height remains unchanged and around there is RCC wall. In this case, the labor work will not be much more.

• Efficient method of Erection and stripping of Formwork so as to avoid the damage of Materials.

Continued . . . . .

Continued . . . . .

How to Plan for and How to Plan for and Points to keep in Points to keep in

MindMind To obtain and Study all the necessary Structural drawings

including all plans sections and elevations.

To obtain and Study other related information’s from Bill of Quantities such as Floor height, type of structure and structural details such as Depth / thickness etc.

To examine the best method of formwork for the contract.

To study the amount of time available (to execute the project) to determine the material requirement. .

Quantum of Materials to be provided to site depends Quantum of Materials to be provided to site depends

uponupon

oDeshuttering time (Since if the Deshuttering time is Deshuttering time (Since if the Deshuttering time is

more, we have to provide additional set of materials)more, we have to provide additional set of materials)

oDeshuttering scheme Deshuttering scheme

Working constraints (To plan for suitable shuttering Working constraints (To plan for suitable shuttering

methodology) methodology)

Continued . . . . .

Continued . . . . .

To analyze for Type of Concrete – Light weight To analyze for Type of Concrete – Light weight concrete / Heavy weight Concreteconcrete / Heavy weight Concreteo Heavy weight concrete – Concrete with Hematite (Iron Heavy weight concrete – Concrete with Hematite (Iron

ore) mainly for structures controlling radiation. ore) mainly for structures controlling radiation.

To study the type of Vibration ie., Internal or External To study the type of Vibration ie., Internal or External o Internal Vibration – Vibrating the concrete after Internal Vibration – Vibrating the concrete after

concreting from inside the member . concreting from inside the member . o External Vibration – Vibrating the structure from External Vibration – Vibrating the structure from

outside (ie. Vibrating the shutter to level the concrete)outside (ie. Vibrating the shutter to level the concrete)

Continued . . . . .

Continued . . . . .

To plan for Construction Joints for stoppage of Shuttering To plan for Construction Joints for stoppage of Shuttering

for Structural point of view. for Structural point of view.

To Design the formwork after considering the Live Load for To Design the formwork after considering the Live Load for which the structure has been designed since the Structure which the structure has been designed since the Structure below the formwork should be able to take the Load of the below the formwork should be able to take the Load of the Formwork + Wet concrete of immediate floor above.Formwork + Wet concrete of immediate floor above.

To plan the Deshuttering period depends upon the type of To plan the Deshuttering period depends upon the type of cement (For example, PPC cement will take more time for cement (For example, PPC cement will take more time for Setting and hence Deshuttering will take more time).Setting and hence Deshuttering will take more time).

Continued . . . . .

Continued . . . . .

Rate of pour of concrete, temperature of concrete, Rate of pour of concrete, temperature of concrete, Surrounding climate temperature shall also be taken Surrounding climate temperature shall also be taken into account while designing into account while designing

Type of Laying of concrete such as o By Manual By Manual o By Mechanical ie., by Pumping shall By Mechanical ie., by Pumping shall

also be noted.also be noted.

Continued . . . . .

Continued . . . . .

The Formwork should be Waterproofed, so as prevent the The Formwork should be Waterproofed, so as prevent the absorption of water from the concreteabsorption of water from the concrete

The Form work must be strong enough to bear the load of The Form work must be strong enough to bear the load of concrete, workmen, the liquid pressure of the fresh concrete concrete, workmen, the liquid pressure of the fresh concrete and the impact effect of concrete pump and vibration.and the impact effect of concrete pump and vibration.

All joints in the Form work should be true and the surface be All joints in the Form work should be true and the surface be plane to minimize the cost of finishing.plane to minimize the cost of finishing.

The Form work should be easily removableThe Form work should be easily removable

What to Achieve?What to Achieve?

Plywood ShutteringPlywood Shuttering

Steel ShutteringSteel Shuttering

Types of FormworkTypes of Formwork

Plywood Shuttering:Plywood Shuttering:What?What?

Shuttering done with Plywood, Timber connected with nails. Shuttering done with Plywood, Timber connected with nails.

Where?Where?

In ColumnsIn Columns

In Beam Bottom and Beam sidesIn Beam Bottom and Beam sides

In Slabs also (Depending on the Customer Requirement)In Slabs also (Depending on the Customer Requirement)

Advantages:Advantages:

To Achieve the smoother and better looking finish.To Achieve the smoother and better looking finish.

Initial Cost is LowInitial Cost is Low

Can avoid joints and grinding at a later stage if we are planning for exposed ceiling.Can avoid joints and grinding at a later stage if we are planning for exposed ceiling.

Less time consumption for erection.Less time consumption for erection.

Precautions to be Taken:Precautions to be Taken:

More care to be taken for Deshuttering since more wastage will lead to more cost..More care to be taken for Deshuttering since more wastage will lead to more cost..

What?What?Shuttering with Steel PlatesShuttering with Steel Plates

Where?Where?Mainly in SlabsMainly in Slabs

Advantages:Advantages:More Repetitions / Less Cost because of steel memberMore Repetitions / Less Cost because of steel memberEasy Handling because of smaller in sizeEasy Handling because of smaller in sizeLesser cost of consumables like nails and oilLesser cost of consumables like nails and oil

Disadvantages:Disadvantages:Needs Plastering if planned for exposed ceilingNeeds Plastering if planned for exposed ceilingInitial Cost is HighInitial Cost is HighNeeds treatment of jointsNeeds treatment of jointsTime consuming for erectionTime consuming for erection

Steel ShutteringSteel Shuttering

Deshuttering is the process in which the shuttering Deshuttering is the process in which the shuttering made is being stripped after the concrete gains its made is being stripped after the concrete gains its full strength.full strength.

Deshuttering:Deshuttering:

All the Loads are uniformly distributed.All the Loads are uniformly distributed.

All the members are simply supported. Even though some All the members are simply supported. Even though some members like Beam are continuous in nature, the end will members like Beam are continuous in nature, the end will become simply supported and moreover we should design for become simply supported and moreover we should design for worst case.worst case.

Density of Concrete – 2500 kg / mDensity of Concrete – 2500 kg / m33

Bending Stress of Plywood – 140 kg / cm2Bending Stress of Plywood – 140 kg / cm2

Bending Stress of Timber – 90 kg / cm2Bending Stress of Timber – 90 kg / cm2

Bending Stress of ISMC 100 – 1650 kg / cm2Bending Stress of ISMC 100 – 1650 kg / cm2

Assumptions in formwork Assumptions in formwork designdesign

Things to NoteThings to Note

The formwork should be rigid enough so as to retain the shape without any appreciable deformation.

For visible surface in the completed work, the deflection is limited to 1/300 of span

For hidden surface, it is limited to 1/150 of span

Continued . . . . .

Continued . . . . .

Do’s and Don’ts:

Continued . . . . .

Continued . . . . .

Do’s:

Formwork for all structures shall be designed as individual member

I.e., for The Load applied on every member should be well within

permissible limit.

All formwork supports should be placed on hard strata.

The formwork materials should be used for the purpose it meant for.

I.e., Props should only be used for supports and not for bracing purpose.

Formwork materials should be properly stacked.

The floor forms shall be well cleaned and oiled before concreting.

The channels / beams should be vertically placed unless otherwise

mentioned to place horizontally in shuttering design.

Don’ts:

The formwork supports should not be placed on loose soil.

Load carrying capacity of member should not be calculated as Total weight

of concrete divided by total no. of members supported. Ie., care should be

taken that no individual member is overloaded than its rated capacity.

Prop over prop support as supports should be avoided.

While deshuttering, the materials should not be thrown away.

The materials should be lowered slowly by Labours through staging.

Materials should not be stacked in such a way that the materials lying

below get damaged.

The Hat section should not be used without runner inside.

Components of materials should not be split up ie. Inner and outer

parts of Acrow span and props.

OTHER POINTS TO CONSIDER:

BEST FORM FORMWORK IS ONE WHO PLANS FOR STRIP

BEFORE THEY BUILD.

ITS BETTER TO HAVE TEN TOO MANY PROPS THAN ONE SHORT

Edge protection should be taken care of.

Access and Platforms for workers

Protection from falling objects

Don’t cut timber to exact length unless it is necessary. You might need

that extra length next time.

The Deshuttering shall start from point of maximum deflection and shall

proceed towards the point of minimum deflection.

SHUTTERING MATERIALSHUTTERING MATERIAL

PROJECTION STATEMENTPROJECTION STATEMENT

SHUTTERING PROJECTION STATEMENTSHUTTERING PROJECTION STATEMENT

FLOORWISE MATERIALFLOORWISE MATERIALABSTARCTABSTARCT

MATERIAL REQUIREMENTMATERIAL REQUIREMENT

ANALYSISANALYSIS

From the figure seen above,

The plywood should be used with the Face veneer perpendicular to the grain so that the bending strength of Ply will increase.

If the plywood is placed with face veneer parallely to the grain, the bending strength will be low.

THE END