TYPES OF FORMWORK AND THEIR APPLICATION.

A. N. PRAKASH CONSTRUCTION PROJECT
MANAGEMENT CONSULTANTS PVT. LTD.
ANP TALK SERIES
Saturday, June 20th, 2015

FORMWORK
for Concrete Structures
A. N. PRAKASH CONSTRUCTION PROJECT MANAGEMENT CONSULTANTS PVT. LTD. 2

― Definition of Formwork
― Classification of formwork
― Scaffolds
― Failure of Formwork

DEFINITION OF
FORMWORK

Definition of formwork
“Formwork is a complete system of
temporary supporting structures and
mould to create structural elements of
required shape and size out of
concrete when poured into these
moulds”.
“Complete system of temporary
supporting structure which includes the
surface in contact built to contain the
fresh concrete so as to form it to the
required shape and dimensions and to
support it until it hardens sufficiently to
become self supporting”.
- IS 6461 Part 5 - 1972

Requirements of a formwork
• To carry following loads :
 Its own load (self load).
 Freshly placed concrete till it gains
enough strength to carry its own weight.
 Live load during concreting.
 Impact load when concrete is placed
from a height such as a skip or a boom
placer.
• Should be easily dismantled / struck with
minimum effort and shall without damage
concrete.
• Arrangement should facilitate easy placing
of concrete.
• Should be water tight to avoid leakage of
cement slurry / grout.

Requirements of a formwork
• Should be re-usable.
• Easy for handling both by men and machine.
• Should be able to retain dimensions without
distortion.
• Minimum sawing and cutting etc.
• Must have safety arrangements for working
areas.

CLASSIFICATION OF
FORMWORK

Classification of Formwork
Formwork
System adopted Material used Application
• Conventional
• Proprietary or patented
• Modular
• Custom made
• Wood / Timber/ Plywood
• Wooden planks
• Plastic
• Glass fibre reinforced plastic
• Metal
 Steel sheets
 Aluminium sheets
 MS Pipes
• Pre-casting
• In-situ Casting
• Form finish
(Architectural Finish)
• Architectural shapes

Classification of formwork
Formwork may be classified based on :
a. System adopted.
• Conventional
• Proprietary or patented
• Modular
• Custom made
Contd…

Classification of formwork
Formwork may be classified based on :
b. Material used
• Wood / Timber /Plywood
• Wooden planks
• Plastic
• Glass fibre reinforced plastic
Contd…
Contd…

…contd Classification of formwork
Metal
• Steel sheets
• Aluminium sheets
• MS Pipes
Contd…

c. Application
• Pre-casting
• In situ Casting
• Form finish (Architectural Finish)
• Architectural shapes

14
Architectural
Shapes

Conventional system
• Built of Timbers or steel props, wooden
planks / plywood, wooden runners
etc.
• Produced at site.
• Custom made each time.
• Time consuming, particularly for large
structures.
• Preferred where the labour cost are
cheap and skills available are limited.
Contd…

Conventional system
• Very flexible and can be used in combination with
modular/ patented system.
• Structural properties of the materials being used not known.
• Quality of finished product could suffer.

Proprietary or Patented
• Mostly modular.
• Made of timber and plywood.
• Factory produced mostly.
• Custom made.
• Preferred for large structures.
• Can be handled easily by men and
machine.
• Designed specifically to carry the
load.
• Quality of the finished concrete high
in terms of line and length and
surface finish.
• Can be used repetitively gaining
high economy

Formwork
Flying Formwork
Tunnel Formwork
Aluminium Formwork
Slip Formwork

Disposable Column Forms
• A cost effective solution to problems for
forming round columns.
• Great versatility to the architectural
design.
• Provides the contractors an easy means of
achieving the desired quality standard.
• Strong yet light and easy to handle.
• One-use disposable design.
• Supplied to site ready prepared to length.
• Base and top are easily secured.
• No mould oil or release agent required.
• Stripped in seconds.
• Protects finished column from site
damage.
• Available in a wide range of sizes.
• Can be made available within short span
of time.
• Suitable for horizontal void cutting.

Formwork liners
• Elastomeric form liner
• Rigid
• Fibre glass reinforced
• Foam polyurethane
• Expanded polystyrene
• Rubber
• Vacuum liners (treatment) very expensive
• Absorption liners (cotton cloth paper)

How are pre-cast formwork different from cast-in-
situ formwork.
• Pre-cast moulds are subject to much more
repetitions.
• Have to be sturdy and strong.
• Have to be designed to take external vibrations
on the mould.
• Dimensional accuracy is very important.
• Mould bottoms are normally stationary and the
sides removable.
• Must have sufficient chamfers and batter.
• Preferable to mount the moulds on rubber pads
for vibration.
• Absence of elaborate supporting system.
• Economy of scale
• Controlled quality.
• Slip form is similar to extrusion.
• Used to build high rise structures very quickly.
• Should be designed to normally carry ultimate
design but also erection loads.

Components of Aluminium Formwork
RockerBeam Side Panel Deck Prop Length Deck Beam Bar External CornerProp head for Soffit
beam
Beam Soffit-panel Beam Soffit bulk head Deck Mid-beam
Internal Soffit
Corner
Internal Corners Kicker
Deck Panel Deck Prop Soffit Length
External Soffit
Corner
Wall Panel Stub Pin

Aluminium Formwork

Flying forms
• Flying forms are a system of formwork.
• They are called ‘flying forms’ since they
are literally flown from one place to
another.
• They are assembled on ground.
• They are placed in the location.
• Suitable for typical slabs of high rise
building.
• Suitable for large slabs.
• Slabs – Flat slabs / flat plates, high numbers
of repetition.
• High productivity.
• Suitable only when cranes are there.
Contd…

Flying forms
Limitations
• Requires large open space for assembling.
• Crane required to remove and erect.
• Requires elaborate planning.

Tunnel forms (slabs)
Limitations
• High capital cost.
• Requires very good spacing.
• Architectural limitations
• Crane dependent,
• Limited in terms of changes to
the structural configuration.
• Economy can be achieved only
when there is large repetition to
get ROI. (South city, Bangalore)

Tunnel forms (slabs)
• For use of repetition cellular structures.
• Can construct both horizontal and vertical
elements.
• Suitable for both high and low rise
buildings.
• High quality finishes.
• Dimensional accuracy.
• Savings upto 25% in Time and 15% in Cost.
• Work possible in all weather.
• An excellent structural solution.
• The formwork is available for purchase or
rent.
• Suppliers / contractors provide full design
and technical support.
• Supplier’s site training quickly brings them
up to speed.

Typical Tunnel Formwork Cycle

Tunnel formwork in housing project

Slip forms
How does it work :
• The forms more either vertically or horizontally.
• Concrete is shaped in the design profile as the form moves
up.
• Forms use the set concrete for gripping and moving.
• The movement is normally slow to allow the concrete to set.
• The concrete would be strong enough to carry the weight of
the shutters.
• Designed to carry the concrete load as well as the wind
load.
Most suited for :
• Chimneys.
• Silos.
• Water towers.
• Telecommunications towers.
• Bridge piers.
• Pylons.
• Elevator shaft lines.

Other forms
• Fibre forms
• Lost forms
• Pre-cast planks
• Sand wash
• ‘Roladeck’ forms for slabs
• Column mounted shoring system

System comparison for various features
Features Conventional system Proprietary / patented Modular formwork system
Flexibility It has high flexibility.
It has reasonably good
flexibility.
The system brings in
standardization and makes
entire formwork operation very
easy.
Reuse
Values
Limited reuse value.
Nailing renders
materials unusable
after a few uses.
The system has high
reuse value.
A large number of repetitions
(reuse) of modular formwork
are
Making
involved at
site
There is large making
of formwork involved
at site.
There is very little making
of formwork involved at
site.
Very less making at site, only
assembly of standard
components required
Expertise
required at
site
Considerable expert
carpentry effort is
required.
These can be assembled
and dismantled easily with
unskilled/semiskilled labour.
The work can be
accomplished
even by the less skilled worker.
Contd…

System comparison for various features
Features Conventional system Proprietary / patented Modular formwork system
Assembling at site
Considerable effort is
required for assembly at
site
Uses features and
accessories developed over
many to save time and
labour and gives higher
productivity.
Assembled very quickly at site.
Considerable reduction in the
erection time. The installation
process is also simple
Quality of
concrete surface
The quality of formwork
and productivity varies
depending on the skill of
labour.
Uniform quality
The quality of concrete
surface
obtained is extremely good
Productivity Low High Higher
Cost
Not economical for
large Projects
Very economical compared
to conventional formwork
for large projects.
Cost of formwork being
considerably on a lower side.
Planning
requirement
Planning is difficult. The
indiscriminate cutting of
timber is difficult to be
controlled.
Preplanning is easy and
effective and also
contributes to the efficiency
of work at site.
The standardization offers ease
in planning.

PROCESS OF FORMWORK
CONSTRUCTION & STRUCTURING
Columns, Walls, Slabs

PROCESS OF FORMWORK
CONSTRUCTION
FORMWORK FOR VARIOUS STRUCTURAL MEMBERS
Construction of formwork:
This normally involves the following operations:
1. Propping and centering
2. Shuttering
3. Provision of camber
4. Cleaning and surface treatment

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.
FORMWORK FOR WALL

Wall Formworks and its components

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.

Erection sequence for a column
Prior to positioning column formwork check that steel for the column
has been inspected and cleared for casting.
• Position formwork for the column from predetermined grids.
• Plumb formwork both ways and securely support using adjustable
steel props.
• The propping angle should be 45° to the floor.
• Ensure the steel props are safely secured to the column formwork
and the floor, and that adjustment for pushing and pulling is
operational.
• Set out the positions of column clamps from a storey rod.
• Transfer the column clamp positions from the storey rod onto
column formwork.
• Use nails to support the arms of column clamps while wedging.
• Position and wedge the bottom, middle and top clamps sets.
• Check the formwork at the top for square.
• Position and wedge the remainder of the column clamps.
• Using a plumb bob suspended from a gauge block plumb the
column.
When all the column formwork is securely propped a final check must
be made for plumb and column alignment before and immediately
after the concrete has been poured and vibrated.
Column clamps are created to give extra
external support to the formwork from
avoiding circularing of the column

CIRCULAR AND OCTAGONAL COLUMNS
• Circular column formwork
• Fabricated steel, usually two piece, and
often with a hinge.
• Fibre cement pipes which are left in place
as permanent formwork.
• Timber sheathing tied with standard column
clamps. Corners need to have infill pieces.
Alternatively, metal strap can be used
without the need for corner infills.

Column formwork bracing performs two functions:
• It must maintain the accuracy of the column form position and plumb so that it is
within tolerance.
• Withstand results of forces acting on either the column formwork or the bracing.
The forces may be wind or impact. These impact forces can occur from the
collision of concrete buckets or cranes hoisting materials
COLUMN BRACING FORMWORK

FORMWORK FOR BEAM
• Beam soffit must be thickened timber or strengthened plywood.
• Beam sides 18mm plywood or 25mm boards, with studs (cleats)
at 500 to 600mm centre.
• Deep beams (over 600mm) should have walkers and ties.
• Use angle fillets in the beam side to soffit joint where possible.
• Allowance must be made for height adjustment of the props or
falsework.
Erection sequence for constructing beam formwork includes
• Position of sole plates;
• Marking out and setting heights for falseworks;
• Assemble and position props, adjustable head jacks, falseworks,
bearers and Spreaders;
• Construct and erect side walls and beam soffit.
• Position of sole plates
43

FORMWORK FOR STAIRCASE
Points to consider when designing stair form work :
• Stair formwork must support the weight of concrete.
The weight of the throat of the stair and the steps will
have to be supported.
• Because of the slope of the stair, some of the force is
transmitted sideways. All formwork must be well tied
together to prevent sideway movement.
• Consider the finish of the stair treads and type of
nosing. Space may have to be left for purpose made
nosing.
44

SUSPENDED SLABS
Suspended floor slabs can be constructed using cast in‐
situ, precast units or a combination of both.
Whichever method is used, it is important to support the
proposed method of construction using a combination
of timber or steel bearers and adjustable shoring.
The spacing and type of support system required is
determined by the load imposed during the
construction process.
Manufacturers provide tables to assist in the selection
and spacing of adjustable shoring systems. The erection sequence for constructing
a suspended floor slab includes:
• Determining the bearer spacing;
• Erecting bearers and joists;
• Fixing the sheeting;
• Preparation for concrete.

SOLE PLATE
The purpose of a sole plate is to transfer vertical load from
one vertical support member to the foundation
• The vertical support requires a base plate fitted to help
distribute the load to the sole plate, which is usually a
sleeper.
• If the sole plate is positioned on natural ground, it is
important the ground is graded and consolidated to a
level surface.
• The objective is to achieve maximum bearing beneath
sole plate. Once sole plates are positioned and firmly
bedded they should be checked for level.

Screw Anchor Screw Anchor Bolt Hair Pin Anchor
Loop Anchor
A She-bolt
Pig Tail Anchor
Patented Tie
Systems
Formwork Accessories

SCAFFOLDS

Scaffolds
Classification of scaffolds
• Platform scaffolds
• Tower scaffolds
• Cantilever type
• Suspended type / cradle
Cantilever
scaffolds
Tower scaffolds
Platform scaffolds
suspended scaffolds
Contd…

Scaffolds
Classification of scaffolds
• Based on material – timber and metal
• Based on type of construction
• Out log scaffolds or single pole
• Double pole / independent scaffolds
Individual
Component
Type
Unit Frame
Type

Plan of formwork
arrangement using shoring
towers
A. N. PRAKASH CONSTRUCTION PROJECT MANAGEMENT CONSULTANTS PVT. LTD.
51

Arrangement of shoring
towers in plan for slab and
beam formwork
52

Sectional view of formwork
arrangement using shoring
towers

Sectional view of shoring
towers for slab and beam
formwork

Beam formwork supported on
shoring tower

Scaffolds
Possible causes for collapse of scaffold
systems.
• Construction load exceeding the critical
load of the scaffold system.
• Horizontal instability
• Diagonal bracing not being used in the
scaffold.

Scaffolds Safety
• Scaffold should be braced by means of
longitudinal and transverse bracing systems so as
to form a rigid and stable structure.
• Install additional ties to the scaffold to prevent
overturning and collapse.
• Guide rails and toe boards must be provided.
• All working platforms should be fully covered to
prevent materials falling.
• Safety nets and other screens should be
provided.
• Care should be taken to see that no uninsulated
wire exists within 3 m of the working platforms
gangways etc.
• Men should not be allowed on scaffolds during
storms and high winds.
• Grease, mud, paint etc should be removed from
the scaffolds.
• All projecting nails from the platforms or other
members should be removed.

FAILURE OF
FORMWORK

Reasons for failure of Formwork
• Not designed for specific purpose.
• Improper stripping or shoring removal (cantilever).
• Not designed for horizontal thrust.
• Damaged elements .(span weld, broken u clamps
• Inadequate bracing.
• Vibration (passing traffic).
• Unstable soil under the props, Sole plates.

Failure of Formwork
• The problem with formwork is that it is
‘temporary’
• The word temporary is associated with
lack of need for :
• Design
• Planning
• Care
• Strength
• Safety

Reasons for failure of Formwork
• Shoring not plumb.
• Rate of concreting.
• On site modifications due to site conditions.
• When formwork is not at fault.
• Ingress of water
• Removal of wedges by workers.

Cantilever
Place concrete into the beams first and the
more towards the free end
Strike / de-shutter in the direction opposite
to that of concreting
De-shuttering
Concrete

Sequence of Beams and Slabs
Beam and Slab
• Start with beams.
• After beams start from beam more towards centre of
slab.
Precautions:
• Don’t store large quantities of concrete at one
place.
• Spread concrete immediately.
• Make sure that the scaffolding / staging is designed
to take horizontal movement of the pipe.
• Place from the centre and go towards the beams /
supports.
De-Shuttering
Beams

Sloping Slab Shuttering
Double Shuttering
• IS 1200 Part 5, Classification 5.1.D.ii.
• Top shutter not payable.
>300
Spacer
Bottom Shutter
Top Shutter

Method of Measurement – IS 1200
• Method of measurement of
building and Civil Engineering
works – Part V Formwork : IS 1200
(Part V) 1982.
• Code of practices for steel tubular
scaffolding – II IS 4014 (Part 2) 1967.
• Building and other construction
workers (BOCW) act (Regulation of
employment and conditions of
service) Act 1996.
Beam
Column
Depth of
beam
Beam

Specification writing for formwork
66
Points to be noted :
• The loads and the lateral pressure, the maximum permitted
deflection.
• Instructions on formwork detailing and fabrication and guidelines on
the required dimensions, the plumb, and the joints.
• Instructions on supervision of the formwork activities.
• Instruction on delivery, storage, protection and handling of the
formwork materials. Acceptance criteria of the formwork materials.
• Prior to commencement of the work, existing dimensions, elevations,
locations and conditions applicable to the work shall be field
verified.
• Instruction on the time allowed between erection of the forms and
placing of the concrete for the various trades to properly install their
work.
• Instruction on application of load on recently cast concrete.
• Specifications for lumber, sheathing material, and shoring.
Instruction on fabrication of form panels in conformity with the
approved submittals.
Contd…

• Specifications for formwork accessories, such as form ties, hangers,
clamps, lugs, cones, washers, form liners or other devices.
• Specifications for triangular fillets if applicable.
• Instructions for cleaning and maintaining the form work materials.
• Instruction on inspections for cleanliness and accuracy of the
alignment prior to the placement of the concrete.
• Instruction on location, snugness and tightness of joints.
• Instruction on level of horizontal joints and plumb of vertical joints.
• Location size and construction of openings.
• Specification on expansion joint material, water stops, and other
embedded items to be built in to the forms and the instructions on
their placement and support against displacement.
• Filling of voids in sleeves, inserts and anchor slots.
Contd…
67A. N. PRAKASH CONSTRUCTION PROJECT MANAGEMENT CONSULTANTS PVT. LTD.

68
• Setting up of edge forms or bulkheads and intermediate screed
strips for the slabs to obtain required elevations and contours in the
finished slab surface.
• Supervision for checking deviations from desired elevation,
alignment, plumb and camber at the time of concreting.
• Guidelines for taking remedial measures in case at the time of
casting, weakness develops and the formwork shows settlement,
deflection or distortion.
• Specification on form coating material and instruction for their
application.
• Re-shoring, permissible loading on re-shores, timing of placement of
re-shores, instruction on tightening of re-shores.
• Guidelines for removal of forms, form ties and bracings to insure
complete safety to the structure.

Thank You
69

TYPES OF FORMWORK AND THEIR APPLICATION.

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