Formwork For Structural Member.pptx

Formwork & Centering Design
-facts and reality
Presented by
Mr. A.V. Ghogare
Department of Civil Engineering,
SRES’s Sanjivani College of Engineering,
Kopargaon
An Autonomous Institute,
Dist: Ahmednagar, MH, India

FORMWORK FOR STRUCTURAL ELEMENTS
 Slab
 Beam
 Column
 Footing
 Staircase
 Wall

SLAB FORMWORK
 Slab formwork is designed
as per the depth of concrete slab.
 The loads on plywood are usually considered as
being uniformly distributed over the entire surface of
the formwork.
 The slab is supported on 25mm thick sheathing laid
parallel to the main beams
 The sheathing is supported on wooden battens which
are laid between the beams.
 In order to reduce the deflection, the battens may be
propped at middle of the span through joists.

BEAM FORMWORK
 The side forms of the beam is 30mm thick sheathing
while bottom sheathing may be 50 to 70 mm thick.
 The ends of the battens are supported on the ledger
which is fixed to the cleat throughout the length.
 Cleats 100mm X20 to 30mm are fixed to the side forms.
 The beam form is supported on a head tree.
 The shore or post is connected to head tree through
cleats.
 At bottom of the shore, two wedges of hard wood are
provided over a sole piece.

FORMWORK FOR COLUMNS
 Sheathing all around the column
periphery, 2 Side yoke and end
yoke, 4 Wedges, 2 bolts and 4
washers.
 Two side yokes are comparatively
heavier sections and are connected
together by two long bolts of 16mm
dia. The sheathing are nailed to the
yoke.
 Ex. Square, rectangular, circular or
any other shape, etc

COLUMN FORMWORK
 Column forms should be capable of
being stripped easily.
 In tall forms it is desirable to provided
windows at appropriate levels on at
least one face to facilitate inspection,
concrete placement and vibration.
 Any method (standard or patented) such as adjustable
clamps, bolts, and purpose made yokes, etc. to hold
the panels in place may be used.
 The spacing and size of these clamps should depend
upon the lateral pressure of fresh concrete.

FORMWORK FOR FOUNDATIONS
 It depends on whether sides of foundations are
vertical or inclined (slopped).
 For vertical sides, construct hollow box open at top
and bottom as shown in figure.
 It should be rigid when filled with concrete.
 Ex. Square, rectangular or Box footing, combined
footings, Raft foundation, etc
 For slopped footing, up to 150-200mm, box is
prepared, over which trapezoidal forms should be
fixed to provide required slopes.
 Yokes of size 75mmX100mm and Bolts are used to
secure the boards at suitable interval (300-600mm)

WALL FORMWORKS
 The boarding may be 40-50mm
thick for wall up to 4m height.
 The boards are fixed to 50mmX100m posts known as
studs, about 0.7 to 1m apart.
 Horizontal walling of size 75mm X 100mm are fixed
to the post at 1 to 1.25m interval.
 The whole assembly is than strutted using
75mmX100mm struts.

FORM WORK FOR STAIRS
 The sheathing or decking for the deck slab is
carried on cross joists which are in turn supported
to raking ledgers.
 The ledger is generally of 75mm X 100mm size.
 The cross joist may be of 50mm X 100mm size.
 The riser planks are 40-50mm thick and width
equal to the riser.
 A stiffener joist of size 50mmX100mm is placed
along the middle of the riser planks.

MONOLITHIC FORMWORKS
 walls, columns, slabs, beams and stairways are
realized using the monolithic construction method.
 The system offers a suitable and fast solution for
forming frequently repetitive floor plans -
horizontally or vertically.
 The individual panels can be easily moved and
transported by hand. Through the use of special
wedge couplers, the wall and slab panels are
assembled in a very short time.
 The individual panels are produced according to
project specifications .
 As a result, all structural dimensions and building
shapes are possible.

CLIMBING FORMWORKS
 It is a special type formwork for vertical
concrete structures that rises with the building
process.
 While relatively complicated and costly, it can be
an effective solution for buildings that are either
very repetitive in form (such as towers or
skyscrapers) or that require a seamless wall
structure .
 Various types of climbing formwork exist, which
are either relocated from time to time, or can
even move on their own (usually on hydraulic
jacks, required for self-climbing and gliding
formworks).

GUIDELINES FOR FORMWORK
 Type of concrete and temperature of the concrete are important for
selecting formwork as they exert pressure.
 The formwork sides must be capable of resisting the hydrostatic
pressure of the wet concrete depending on the rate of setting and
curing.
 The formwork base must be capable of resisting dead and live load
of the wet concrete, workmen and machinery.
 Once the concrete as gained sufficient strength, the formwork can
be removed.
 A minimum of 5 MPa strength of concrete can be achieved
before striking vertical formwork.
 Both shuttering and formwork in its various forms will be
supported by false work.

REQUIREMENTS OF GOOD FORMWORK
 It should be strong enough to carry all types of dead and live
loads.
 It should be rigidly constructed and efficiently propped and
braced both horizontally and vertically,
 The joints in the formwork should be stiff so that the
deformations caused by loads shall be minimum.
 The joints in the formwork should be water tight.
 Construction of formwork should permit removal of various
parts in desired sequences without damage to the concrete.
 The material of the formwork should be cheap, easily available
and should be suitable for reuse.
 The formwork should be set accurately to the desired line and
levels should have plane surface.
 It should be as light as possible.
 The material of the formwork should not warp or get distorted.

MATERIAL SELECTION
 The type of material to be used for formwork depends
upon the nature of construction as well as the availability
and cost of material.
 Formwork can be made out of timber, steel, plywood,
pre-cast concrete or fibre-glass, used separately or in
combination.
 Timber and plywood are the most commonly used
materials for formwork because these can be cut or
assembled easily on site.
 Use of wooden props (ballies) and bamboo props are still
persisting in many construction works.

 With the introduction of steel forms, use of
timber formwork is getting reduced especially in
case of major construction projects.
 Large numbers of re-use of the same forms are
possible then steel, aluminium and plastic forms
are used.
 However, for small works involving less number
of re-uses, timber formwork proves economical.
 Formwork commercially available may be
fabricated at site, or partially or wholly
prefabricated and may be used.

PROCESS INVOLVED IN CONCRETE FORMWORK
 This normally involves the following operations:
 Propping and centring
 Shuttering
 Provision of camber
 Cleaning and surface treatment

TOLERANCE IN SHAPE, LINES & DIMENSIONS
 The formwork shall be designed and constructed
so as to remain sufficiently rigid during placing
and compaction of concrete, and shall be such as
to prevent loss of slurry from the concrete.
 The tolerances on the shapes, lines and
dimensions shown in the drawing shall be within
the limits given in table given in IS 456-2000

CLEANING & TREATMENT OF FORMWORK
 All rubbish, particularly, chippings, shavings and
sawdust, shall be removed from the interior of the
forms before the concrete is placed.
 The face of formwork in contact with the
concrete shall be cleaned and treated with form
release agent.
 Release agents should be applied so as to provide
a thin uniform coating to the forms without
coating the reinforcement.

STRIPPING TIME
Forms shall not be released until the concrete has
achieved a strength of at least twice the stress to
which the concrete may be subjected at the time of
removal of form work.
While the above criteria of strength shall be the
guiding factor for removal of formwork, in normal
circumstances where ambient temperature does not
fall below 150C and where ordinary Portland
cement is used and adequate curing is done,
following stripping period may deem to satisfy the
guideline given in IS 456-2000

ORDER AND METHOD OF REMOVING FORMWORK
 The sequence of orders and method of removal of
formwork are as follows:
 The vertical faces of walls beams and column sides should
be removed first as they bear no load.
 Shuttering forming soffit of slabs should be removed next.
 Shuttering forming soffit of beams, girders or other heavily
loaded shuttering should be removed in the end.
 Rapid hardening cement, warm weather and light loading
conditions allow early removal of formwork.
 All formworks should be eased gradually and carefully in
order to prevent the load being suddenly transferred to
concrete.

Formwork For Structural Member.pptx

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Formwork For Structural Member.pptx