When concrete is placed, it is in plastic state. It requires to be supported by temporary supports and castings of desired shape till it becomes sufficiently strong to support its own weight. This temporary casing is known as the formwork or forms or shuttering. The term moulds is sometimes used to indicate formwork of relatively small units such as lintels, cornices etc.
Definition of formwork:-
"Forms or moulds or shutters are the receptacles in which concrete is placed, so that it will have desired shape or outline when hardened. Once concrete develops the adequate strength to support its own weight they can be taken out". .. (ACC).
"Formwork is the term given to either temporary or permanent moulds into which concrete or similar materials are poured". … (Wikipedia Encyclopedia).
Requirements of a good formwork
The essential requirements of formwork or shuttering are: -
a) It should be strong enough to take the dead and live loads during construction.
b) The joints in the formwork should be rigid so that the bulging, twisting, or sagging due to dead and live load is as small as possible. Excessive deformation may disfigure the surface of concrete.
c) The construction lines in the formwork should be true and the surface plane so that the cost finishing the surface of concrete on removing the shuttering is the least.
d) The formwork should be easily removable without damage to itself so that it could be used repeatedly.
Classification of Formwork
Formwork can be classified according to a variety of categories, relating to the differences in sizes, the location of use, construction materials, nature of operation, or simply by the brand name of the products. However, the huge amount of tropical wood being consumed each year for formwork has resulted in criticism from environmentalists, as well as the continual escalation of timber prices. As a result, there has been a strong tendency to use other formwork materials or systems to replace timber. The different categories in which formwork can be classified are:
a) According to size.
b) According to location of use.
c) According to materials of construction.
d) According to nature of operation.
e) According to brand name of the product.
Classification according to size
Classification according to the size of formwork can be very straightforward. In practice, there are only two sizes for formwork; small-sized and large-sized. Any size which is designed for operation by workers manually is small-sized. Very often, the erection process is preferably handled by a single worker, with site work best done independently to avoid possible waiting times. Due to reasons of size and weight, the materials and construction of small-sized formwork are thus limited. At present, the most common systems are made of timber and aluminium, and are usually in the form of small panels. There is seldom medium-sized formwork. In cases in which large-sized formwork is used, the size of the form can be designed as large as practicable to reduce the amount of jointing and to minimize the amount of lift. The stiffness required by large-sized formwork can be dealt with by the introduction of more stiffening components such as studs and soldiers. The increase in the weight of the formwork panels is insignificant as a crane will be used in most cases.
Classification according to the location of use: -
There are not many effective formwork systems for stairs and staircases. The complicated three-dimensional nature of an element involving suspended panels and riser boards, as well as the need to cope with very different spatial and dimensional variances as required by individual design situations, cannot be achieved by a universally adaptable formwork system
Classification according to materials of construction
Materials used for formwork are traditionally quite limited due to finding the difficult balance between cost and performance. Timber in general is still the most popular formwork material for its relative low initial cost and adaptability Steel, in the form of either hot-rolled or cold-formed sections and in combination with other sheeting materials, is another popular choice for formwork materials. In the past two to three years, full aluminium formwork systems have been used in some cases but the performance is still being questioned by many users, especially in concern to cost and labor control.
Classification according to nature of operation
Formwork can be operated manually or by other power-lifted methods. Some systems are equipped with a certain degree of mobility to ease the erection and striking processes, or to allow horizontal moment using rollers, rails or tracks.
Timber and aluminium forms are the only manually-operable types of formwork. They are designed and constructed in ways that they can be completely handled independently without the aid of any lifting appliances. On the other end of the scale, such systems are used in very large-sized and horizontally-spread buildings with complicated layout designs which require the systems' flexibility. Fig 2.4 & 2.5 shows the formwork system allowing the incorporation of pre-cast elements and self climbing form with hydraulic jack devices respectively.
formwork system allowing the example of a self-climbing form with
Incorporation of pre-cast elements (govt. quarters) detail of the hydraulic jack devices (source Raymond, 2001)
Classification according to brand name of the product
Several patented or branded formwork systems have successfully entered the local construction market in the past decade. These include products from brands SGB, RMD, VSL, MIVAN, Thyssen and Cantilever. Each of these firms offers its own specialized products, while some can even provide a very wide range of services including design support or tender estimating advice. As the use of innovative building methods is gaining more attention from various sectors in the community, advanced formwork systems are obviously a promising solution. The input through research and development by the well-established formwork manufacturers is of no doubt contributing to efforts in these areas. (Fig 2.6)
VSL FORMWORK (Source Raymond, 2001)
Loads acting on Formwork
In Construction, the formwork has to bear, besides its own weight, the weight of wet concrete, the live load due to labor, and the impact due to pouring concrete and workmen on it. The vibration caused due to vibrators used to compact the concrete should also be taken care off. Thus, the design of the formwork is an essential part during the construction of the building.
For the design of planks and joists in bending & shear, a live load including the impact may be taken as 370kg/m². It is however, usual to work with a small factor of safety in the design of formwork. The surfaces of formwork should be dressed in such a manner that after deflection due to weight of concrete and reinforcement, the surface remains horizontal, or as desired by the designer. The sheathing with full live load of 370 kg/m² should not deflect more than 0.25 cm and the joists with 200kg/m² of live load should not deflect more than 0.25cm.
In the design of formwork for columns or walls, the hydrostatic pressure of the concrete should be taken into account. This pressure depends upon the quantity of water in the concrete, rate of pouring and the temperature.
The hydrostatic pressure of the concrete increases with the following cases:-
· Increase in quantity of water in the mix.
· The smaller size of the aggregate.
· The lower temperature.
· The higher rate of pouring concrete.
If the concrete is poured in layers at an interval such that concrete has time to set, there will be very little chance of bulging.
Aluminium as usual is not a very strong material. So the basic elements of the formwork system are the panel which is a framework of extruded aluminium sections welded to an aluminium sheet. It consists of high strength special aluminium components. This produces a light weight panel with an excellent stiffness-to-weight ratio, yielding minimal deflections when subjected to the load of weight concrete. The panels are manufactured in standard sizes with non-standard elements produced to the required size and size to suit the project requirements.
In MIVAN formwork we give stress on shear wall rather than conventional framed structure of columns and beams. In general the design of a wall formwork is described as under.
Consider designing a wall for 30 cm thick and 5 m high. The concrete is poured at shifts of 1.5 m each. The sheathing is placed horizontally and spans between vertical studs are under horizontal pressure due to wet concrete. These Studs are backed by the horizontal pieces called Wales which are tied by bolts, passing through the wall. Thus pressure on either side of the wall is self balanced as shown fig 2.4.1.
The pressure exerted by concrete will be 2300 equivalent weight of fluid at a depth of h meters. Taking lowest portion of the sheathing, the pressure is equal to 2300 x 1.5 =3450 kg/ sq.m. If the sheathing is 25 cm thick, the spacing x of the studs is given by M=bd²/6 x σ;
σ = 102 kg/ sq cm where σ is safe fiber-stress.
Or, 3450 x x² = 1 x 2.5²/6 x 102
100² x 10
Or, x = 55.5 cm.
Adopt the spacing of 55 cm apart.
If the spacing of wales is 68cm, the average pressure on the studs between two bolts will be 2300(1.5-68/2) x .55 =1468 kg per meter run, assuming concrete pouring is started at level of a low bolts.
Max S.F. at edges of clear span = 1468 x 0.6/2 = 440 kg.
Assume studs to be 7.5 cm x 10 cm,
Shear stress = 3/2 x 440/ (7.5 x 10) = 8.8 kg/ sq cm.
Maximum fiber stress = 6785 x 10/2 = 54.3 kg/ sq cm.
7.5 x 10³/12
So the section adopted is satisfactory.
The panels of aluminium formwork are made from high strength aluminium alloy, with the face or contact surface of the panel, made up of 4mm thick plate, which is welded to a formwork of specially designed extruded sections, to form a robust component. The panels are held in position by a simple pin and wedge arrangement system that passes through holes in the outside rib of each panel. The panel fits precisely, securely and requires no bracing. The walls are held together with high strength wall ties, while the decks are supported by beams and props.
Since the equipment is made of aluminium, it has sections that are large enough to be effective, yet light enough in the weight to be handled by a single worker. Individual workers can handle all the elements necessary for forming the system with no requirement for heavy lifting equipment or skilled labor. By ensuring repetition of work tasks on daily basis it is possible for the system to bring assembly line techniques to construction site and to ensure quality work, by unskilled or semi-skilled workers.
Trial erection of the formwork is carried out in factory conditions which ensure that all components are correctly manufactured and no components are missed out. Also, they are numbered and packed in such a manner so as to enable easy site erection and dismantling.
MERITS OF ALUMINIUM FORMWORK:-
i.In contrast to most of the modern construction systems, which are machine and equipment oriented, the formwork does not depend upon heavy lifting equipment and can be handled by unskilled labors.
ii.Fast construction is assured and is particularly suitable for large magnitude construction of respective nature at one project site.
iii.Construction carried out by this system has exceptionally good quality with accurate dimensions for all openings to receive windows and doors, right angles at meeting points of wall to wall, wall to floor, wall to ceiling, etc, concrete surface finishes are good to receive painting directly without plaster.
iv.System components are durable and can be used several times without sacrificing the quality or correctness of dimensions and surface.
v.Monolithic construction of load bearing walls and slabs in concrete produces structurally superior quality with very few constructions joined compared to the conventional column and beam slabs construction combined with filter brick work or block work subsequently covered by plaster.
vi.In view of the four – day cycle of casting the floor together with all slabs as against 14 to 20 – day cycle in the conventional method, completed RCC structure is available for subsequent finish trades much faster, resulting in a saving of 10 to 15 days per floor in the overall completion period.
vii.As all the walls are cast monolithic and simultaneously with floor slabs requiring no further plasters finish. Therefore the time required in the conventional method for construction of walls and plastering is saved.
viii.As fully completed structural frame is made available in one stretch for subsequent – finishing items, uninterrupted progress can be planned ensuring, continuity in each trade, thereby providing as cope for employing increased labor force on finishing item.
ix.As the system establishes a kind of "Assembly line production" phase – wise completion in desired groups of buildings can be planned to achieve early utilization of the buildings.
2.5.2: -Comparison of Aluminum Form Construction Technique Over Conventional Forms:
Advantages of aluminium formwork over conventional construction
i.More seismic resistance: - The box type construction provides more seismic resistance to the structure.
ii.Increased durability: - The durability of a complete concrete structure is more than conventional brick bat masonry.
iii.Lesser number of joints thereby reducing the leakages and enhancing the durability.
iv.Higher carpet area- Due to shear walls the walls are thin thus increasing area.
v.Integral and smooth finishing of wall and slab- Smooth finish of aluminium can be seen vividly on walls.
vi.Uniform quality of construction – Uniform grade of concrete is used.
vii.Negligible maintenance – Strong built up of concrete needs no maintenance.
viii.Faster completion – Unsurpassed construction speed can be achieved due to light weight of forms
ix.Lesser manual labor- Less labor is required for carrying formworks.
x.Simplified foundation design due to consistent load distribution.
xi.The natural density of concrete wall result in better sound transmission coefficient.
RELATIVE COMPARISON OF IN – SITU "ALUMINIUM FORM" SYSTEM WITH CONVENTIONAL CONSTRUCTION.
IN – SITU ALUMINIUM FORM SYSTEM
Superior. In – Situ casting of whole structure and transverse walls done in a continuous operation, using controlled concrete mixers obtained from central batching, mixing plants and mechanically placed through concrete buckets using crane and compacted in leak proof moulds using high frequency vibrators
Superior quality in "System housing"
Speed of construction.
The pace of construction is slow due to step – by – step completion of different stages of activity the masonry is required to be laid brick by brick. Erection of formwork, concreting and deshuttering forms is a two – week cycle. The plastering and other finishing activities can commence only thereafter.
In this system, the walls and floors are cast together in one continuous operation in matter of few hours and in built accelerated curing overnight enable removal and re-use of forms on daily cycle basis.
System construction is much faster.
In the case of RCC structural framework of column and beams with partition brick walls is used for construction, the columns and beams show unsightly projections in room interiors.
The Room – Sized wall panels and the ceiling elements cast against steel plates have smooth finishing and the interiors have neat and clean lines without unsightly projections in various corners. The walls and ceilings also have smooth even surfaces, which only need colour/white wash
Cement plastered brickwork, painted with cement – based paint. Finishing needs painting every in three years.
Textured / pattern coloured concrete facia can be provided. This will need no frequent repainting.
Permanent facia finishes feasible with minor extra initial cost
Useful carpet area as % of plinth area.
Efficiency around 83.5%
Efficiency around 87.5%
More efficient utilization of land for useful living space.
Consumption of basic raw materials
Reinforcing steel required is less as compared to the in situ construction as RCC framework uses brick wall as alternative
Consumption somewhat more than that used in conventional structures.
It may, however will be slightly more than corresponding load – bearing brick wall construction for which, requirements of IS 456 have to be followed for system housing.
Although greater consumption strength and durability is also more
Steel requirement is more, as it is required for the shear wall construction. But shear wall construction increases safety against earthquake.
In maintenance cost, the major expenditure is involved due to :
· Repairs and maintenance of plaster of walls / ceiling etc.
· Painting of outer and inner walls.
Leakages due to plumbing and sanitation installation.
The walls and ceiling being smooth and high quality concrete repairs for plastering and leakage's are not at all required frequently.
It can be concluded that maintenance cost is negligible.
MIVAN: - A Versatile Formwork
The system of aluminum forms (MIVAN) has been used widely in the construction of residential units and mass housing projects. It is fast, simple, adaptable and cost – effective. It produces total quality work which requires minimum maintenance and when durability is the prime consideration. This system is most suitable for Indian condition as a tailor–made aluminum formwork for cast–in–situ fully concrete structure.
Mivan is basically an aluminium formwork system developed by one of the construction company from Europe. In 1990, the Mivan Company Ltd from Malaysia started the manufacturing of such formwork systems. Now a day more than 30,000 sq m of formwork used in the world are under their operation. In Mumbai, India there are number of buildings constructed with the help of the above system which has been proved to be very economical and satisfactory for Indian Construction Environment.
The technology has been used extensively in other countries such as Europe, Gulf Countries, Asia and all other parts of the world. MIVAN technology is suitable for constructing large number of houses within short time using room size forms to construct walls and slabs in one continuous pour on concrete. Early removal of forms can be achieved by hot air curing / curing compounds. This facilitates fast construction, say two flats per day. All the activities are planned in assembly line manner and hence result into more accurate, well – controlled and high quality production at optimum cost and in shortest possible time.
In this system of formwork construction, cast – in – situ concrete wall and floor slabs cast monolithic provides the structural system in one continuous pour. Large room sized forms for walls and floors slabs are erected at site. These forms are made strong and sturdy, fabricated with accuracy and easy to handle. They afford large number of repetitions (around 250). The concrete is produced in RMC batching plants under strict quality control and convey it to site with transit mixers.
The frames for windows and door as well as ducts for services are placed in the form before concreting. Staircase flights, façade panels, chejjas and jails etc. and other pre-fabricated items are also integrated into the structure. This proves to be a major advantage as compared to other modern construction techniques.
The method of construction adopted is no difference except for that the sub – structure is constructed using conventional techniques. The super–structure is constructed using MIVAN techniques. The integrated use the technology results in a durable structure.
The formwork system is precisely-engineered system fabricated in aluminium. Using this system, all the elements of a building namely, load bearing walls, columns, beams, floor slabs, stairs, balconies etc can be constructed with cast in place concrete. The resulting structure has a good quality surface finish and accurate dimensional tolerances. Further, the construction speed is high and the work can be done in a cost effective manner.
The modular nature of the formwork system allows easy fixing and removal of formwork and the construction can proceed speedily with very little deviation in dimensional tolerances. Further, the system is quite flexible and can be easily adapted for any variations in the layout.
The availability of concrete from ready mix concrete facility has augured well for the use of this work system. However, the proliferation of RMC facilities in the cities in India and the willingness to use mechanized means of transport and placing of concrete, the use of aluminium formwork system has received a boost. The quality of the resulting concrete is found to be superior.
Structurally speaking, the adoption of the closed box system using monolithic concrete construction has been found to be the most efficient alternatives. The stresses in both the concrete and steel are observed to be much lower even when horizontal forces due to wind or earthquake are taken into consideration.
The formwork system can be used for construction for all types of concrete systems, that is, for a framed structure involving column beam –slab elements or for box-type structure involving slab-walls combination.
FORMWORK – COMPONENTS:
The basic element of the formwork is the panel, which is an extruded aluminium rail section, welded to an aluminium sheet. This produces a lightweight panel with an excellent stiffness to weight ratio, yielding minimal deflection under concrete loading. Panels are manufactured in the size and shape to suit the requirements of specific projects.
The panels are made from high strength aluminium alloy with a 4 mm thick skin plate and 6mm thick ribbing behind to stiffen the panels. The panels are manufactured in MIVAN'S dedicated factories in Europe and South East Asia. Once they are assembled they are subjected to a trial erection in order to eliminate any dimensional or on site problems.
All the formwork components are received at the site whining three months after they are ordered. Following are the components that are regularly used in the construction.
1) Wall Panel: - It forms the face of the wall. It is an Aluminium sheet properly cut to fit the exact size of the wall.
FIG 3.1: WALL PANEL
2) Rocker: - It is a supporting component of wall. It is L-shaped panel having allotment holes for stub pin.
FIG 3.2: ROCKER
3) Kicker: - It forms the wall face at the top of the panels and acts as a ledge to support.
FIG 3.3: KICKER
4) Stub Pin: - It helps in joining two wall panels. It helps in joining two joints.
FIG 3.4: STUB PIN
3.2.2: - BEAM COMPONENTS:
1) Beam Side Panel: - It forms the side of the beams. It is a rectangular structure and is cut according to the size of the beam.
FIG 3.5: BEAM SIDE PANEL
2) Prop Head for Soffit Beam: - It forms the soffit beam. It is a V-shaped head for easy dislodging of the formwork.
FIG 3.6: PROP HEAD FOR SOFFIT BEAM.
3) Beam Soffit Panel: - It supports the soffit beam. It is a plain rectangular structure of aluminium.
FIG 3.7: BEAM SOFFIT-PANEL
4) Beam Soffit Bulkhead: - It is the bulkhead for beam. It carries most of the bulk load.
FIG 3.8: - BEAM SOFFIT BULKHEAD
3.2.3: DECK COMPONENT:
1) Deck Panel: - It forms the horizontal surface for casting of slabs. It is built for proper safety of workers.
FIG 3.9: - DECK PANEL
2) Deck Prop: - It forms a V-shaped prop head. It supports the deck and bears the load coming on the deck panel.
FIG 3.10: -DECK PROP
3) Prop Length: - It is the length of the prop. It depends upon the length of the slab.
FIG 3.11: - DECK PROP LENGTH
4) Deck mid – Beam: - It supports the middle portion of the beam. It holds the concrete.
FIG 3.12: - DECK MID-BEAM
5) Soffit Length: - It provides support to the edge of the deck panels at their perimeter of the room.
FIG 3.13: - SOFFIT LENGTH
6) Deck Beam Bar: - It is the deck for the beam. This component supports the deck and beam.
FIG 3.14: -DECK BEAM BAR
3.2.4: OTHER COMPONENTS:
1) Internal Soffit Corner: - It forms the vertical internal corner between the walls and the beams, slabs, and the horizontal internal cornice between the walls and the beam slabs and the beam soffit.
FIG 3.15: -INTERNAL SOFFIT CORNER
2) External Soffit Corner: - The external soffit corners forms the vertical external corner between walls and / or beam faces and horizontal external corners between wall / beam face and soffit of slabs.
FIG 3.16: -EXTERNAL SOFFIT CORNER
3) External Corner: - The external corner connects vertical or horizontal form work together at right angles.
FIG 3.17: - EXTENAL CORNER
4) Internal Corner: - It connects two pieces of vertical formwork pieces at their internal intersections.
FIG 3.18: - INTERNAL CORNERS
MIVAN aims in using modern construction techniques and equipment in all its projects. On leaving the MIVAN factory all panels are clearly labeled to ensure that they are easily identifiable on site and can be smoothly fitted together using the formwork modulation drawings. All formwork begins at a corner and proceeds from there.
FIG 3.19: - WALL ASSEMBLY DETAILS
FIG 3.20: - BEAM ASSEMBLY DETAILS
SIMPLICITY – PIN AND WEDGE SYSTEM:
The panels are held in position by a simple pin and wedge system that passes through holes in the outside rib of each panel. (Fig.No.3.21)
The panels fit precisely, simply and securely and require no bracing. Buildings can be constructed quickly and easily by unskilled labor with hammer being the only tool required. Once the panels have been numbered, measuring is not necessary. As the erection process is manually, tower cranes are not required. The result is a typical 4 to 5 day cycle for floor – to – floor construction.
EFFICIENT – QUICK STRIP PROP HEAD:
One of the principal technical features which enables this aped to be attained using a single set of formwork panel is the unique V shaped a prop head which allows the 'quick strip' to take place whilst leaving the propping undisturbed. The deck panels can therefore be resumed immediately. (Fig.No.3.22).
CONSTRUCTION ACTIVITIES WITH MIVAN AS FORMWORK
The construction activities are divided as pre – concrete activities, during concreting and post – concrete activities. They are as follows:
PRE – CONCRETE ACTIVITIES:
i) RECEIPT OF EQUIPMENT ON SITE:
a) Unload components from transport and where possible, stack by code and size panels can normally be stacked safely up to 25 panels high on skids or pallets.
b) When stacked, holing in the formwork should be aligned allowing easy identification by code.
c) Ensure the first panel at the bottom of the stack has the contact face upwards.
d) All pins, wedges, wall ties, P.E sleeves, L.D.P.E sheet and special tools to be put into proper storage and only distributed as required.
e) A check requires to be carried out against the packing list ensuring all items stated are received.
ii) LEVEL SURVEYS:
a) A concrete level survey should be taken on all sites and remedial work carried out prior to the erecting of formwork.
b) All level surveys should be taken from T.B.M (Temporary Bench Mark).
c) In certain cases it is good practice to mark the slabs with paint indicating a plus (+) or minus (-) as the survey is being conducted. The eliminates unnecessary circulation of paper copies to site personnel, and supervisor can identify at a glance any remedial work required.
d) High spots along the wall line to be chipped off to the proper level.
Low spots along the wall line should be packed to the required level, using plywood or timber.
Packing the corner and the centre of the wall length to the required level will be normally be adequate, as the formwork when pinned together will bridge across low spots.
e) Concrete (+8mm) and above must be chipped to the correct level.
After concreting, level surveys should also be carried out on the top of the kickers. One reason for structural deviation from the centre line can be on a – level kicker. This in turn means the formwork is not in plumb.
f) Kickers are manufactured with a 26mm slotted hole on the face to allow for adjustment after concreting.
g) As with the concrete level survey, proper records of the kicker survey should be kept on file by the allocated supervisor.
h) Also a deviation survey requires to be carrying out and keeping on fire.
iii) SETTING OUT:
a) Only approved shell drawings supplied by Mivan Formwork Design should be used for setting out.
b) Setting out lines should continue through openings, external corners etc, by a minimum of 150mm. This makes it easier to fix formwork in position prior to concreting.
c) It is very important that the reference points and the setting out points are protected against accidental movement or damage.
d) Transferring of reference points from the level below requires to be done quite accurately. Incorrect reference points give incorrect deviations therefore creating unnecessary work for the formwork erection. It is suggested a theodolite be used for transferring the points through openings provided in the slab.
iv) CONTROL/CORRECTING OF DEVIATIONS:
a) A study of the deviation and kicker level survey should confirm what, if any, corrective action is required.
b) If the kicker requires adjustment for level, loosen the holding- in bolt by turning anti-clockwise, adjust kicker to the required position and retighten the bolt.
c) Once the vertical formwork is fixed in position, the external corners should be checked for plumbness. This will determine if further action is required to control the deviation.
d) In addition to the kicker levels, the formwork can be pulled by using bottle screws and chain blocks; if the formwork requires to be pushed adjustable props can be used.
v) ERECT FORM WORK:
For the initial set up only 50mm*25mm timber stays can be nailed to the concrete slab, close to the internal and external corners, to ensure the formwork is erected to the setting out lines.
All formwork begins at a corner and proceeds from there. This is to provide temporary lateral stability. A single panel at a corner will give sufficient lateral support to a very long section of wall.
Ensure all edges of the formwork and contact face are properly cleaned ad oiled prior to fixing in place.
When satisfied the corner is stable and the internal corner is positioned to the setting out lines continue erecting the formwork to one wall. Use only 2 no of pins and wedges to connect the formwork at this stage a the pins and wedges will have to be removed later to insert the wall ties. Alternatively the wall ties can be positioned as the formwork is erected. For ease of striping, pin the wall panels to the internal corners with the head of pin to the inside of the internal corner if possible.
Wall ties should be coated with the releasing agent provided before being fixed to the formwork. Fit the wall ties through slots in the wall formwork and secure in position with pins and wedges.
Prior to closing the formwork, pre-wrapped corrugated PVC sleeves are placed over the wall ties. Please ensure, since preparation of the sleeves they have not been abused in any way before installing, as this can have an adverse effect in the removal of the wall tie after concreting. Also, ensure they are located properly to the contact face of the formwork on each side of the wall. Sleeves installed with one end fixed between the side rails of two adjoining panels, exposes the wall tie at the opposite end, therefore impossible to retrieve the wall tie after concreting.
When deviation of external walls occurs, they must be brought back to the correct plan location as quickly as possible. This is done by slightly tilting the external wall forms in one plane. If a deviation from plumb has occurred in two directions, then this should be improved over two floors, one for each direction. Realignment in two directions should not attempted on a single lift.
A maximum of 8mm in vertically improvement in one lift is sufficient.
vi) METHOD OF ERECTING FORMWORK:
It is important maximum efficiency to define a sequence of erection to be followed by each team. One side is erected using only on upper and lower pin and wedge connection. Later, ties are inserted at the the connection and fixing
With pin and wedge. Then previously installed pins are removed and those ties inserted and pinned. Subsequently, panels for the other side are inserted between the existing ties and fixed with pins and wedges.
The advantages of this Erection Method are as Follows:-
1) Rooms can be closed and squared by assembling only one side of wall panels. If misaligned, it is easier to shift rows of single panels.
2) If steel reinforcement is likely to interfere with the placement of the ties, it can be seen and corrected without delaying the pane erection.
3) Enables fast start up of deck teams as the first rooms can be closed quickly.
4) Continuous steel reinforcement for the walls, creates a barrier between the two sides of the formwork, so the work proceeds at the pace of single erector.
Special care must be taken at the lift shafts. The interior panels will align properly on their own because they are set of the kicker from the formwork below. Ensure the kickers are level and will not effect the vertically of the lift shaft. However, the matching panels are set on the concrete that may not be level. If the concrete is too high in place, it can distort the alignment of the four sides of the lift shaft and must be broken out to allow a level base.
Care must be taken so that the concrete and in particular the reinforcement does not become contaminated due to excessive or negligent application of the releasing agent.
The ends of walls and door openings should be secured in position by nailing timber stays to the concrete slab. Walls require to be straightened by using a string line and securing in place by nailing timber stays to concrete slab. During this p\operation vertically of door openings also require to be checked for plumb. Where possible, door spacers should be lifted.
vii) ERECT DECK FORMWORK:
Normally deck panels can be struck after 36 hours. Striking times should be confirmed on a project to project basis.
The striking begins with the removal of deck beam. Remove the 132mm pin and the beam bars from the beam which has been identified for removal.
This is followed by removing the pins and wedges from the deck panels adjacent to the deck beam to be removed.
The deck beam can now be taken out.
As the first panel in are rests on the support lip of the soffit length, the adjacent panel should be removed first. After removing the pins and wedges from the panel to be removed, a panel puller can be used to beak the bond from the adjacent formwork.
Where there is no deck beam support and the panels span from wall to wall, one wall will have the supporting lip of the soffit length removed.
Pins and wedges only to be removed on the identified component that is to be struck.
Deck panel's remains in place longer than wall panels and will not come away easily unless proper cleaning and oiling is done during the erection process. Panels should confirm to the sequence of erection.
PROP LENGTHS :
Whenever the PL's is to be removed, use a wooden mallet to strike the bottom of the PL in the same direction as the beam and holding the PL with your other hand.
POST CONCRETE ACTIVITIES:
All components should be cleaned with scrapers and wire brushes as soon as they are struck. Wire brush is to be used on side rails only.
The longer cleaning is delayed, the more difficult the task will be. It is usually best to clean panels in the area where they are struck.
There are basic three methods recommended when transporting to the next floor:
i. The heaviest and the longest, which is a full height wall panel, can be carried up the nearest stairway.
ii. Passes through void areas.
iii. Rose through slots specially formed in the floor slab for this purpose. Once they have served their purpose they are closed by casting in concrete filter.
Once cleaned and transported to the next point of erection, panels should be stacked at right place and in right order.
Proper stacking is a clean sign of a wall – managed operation greatly aids the next sequence of erection as well as prevents clutters and impend other activities.
ON CONCRETE ACTIVITIES:
At least two operatives should be on stand by during concreting for checking pins, wedges and wall ties as the pour is in progress. Pins, wedges or wall ties missing could lead to a movement of the formwork and possibility of the formwork being damaged. This – effected area will then required remedial work after striking of the formwork.
Things to look for during concreting:
i. Dislodging of pins / wedges due to vibration.
ii. Beam / deck props adjacent to drop areas slipping due to vibration.
iii. Ensure all bracing at special areas slipping due to vibration.
iv. Overspill of concrete at window opening etc.
Before commencing the operation, ensure the following equipment has been procured:-
a) Scaffold brackets and all the necessary fixings.
b) Scaffolding bracket, vertical safety post.
c) Safety harness and all materials for the platform decking and handrails.
d) Timber and all materials for the platform decking and handrails.
For the initial set up of the formwork and when using the wall mounted scaffold brackets, 20mm diameter holes require to be drilled through the formwork to position the PVC sleeves, which when cast in the concrete should be used for fixing the scaffold brackets. This hole also accommodates the bolting up of the formwork to control the alignment at the kicker level.
As the external formwork is being removed, a team of allocated people working in pairs will commence erecting the working platform. With the tie-rod through the hole provided in the working platform. With the tie-rod through the hole providing in the working platform bracket, and using a small ladder, fix the bracket by pushing the tie rod through the PVC sleeve which is cast in the concrete. A helper inside the building can fix and tighten the locking nut.
During this operation, the person on the external must have his safety belt secured to the kicker above. As this operation progresses along the building, another pair of the team should follow, placing the decking, toe-board and handrails. One person should remain on the lower platform and pass the decking to his helper n the upper level
When working on the outside edge, safety equipment MUST be worn at all times.
To be imposed on every worker, are the following things not to be done:
· Do not lay bottom panel contact face down, when starting a stack
· Do not drop equipment from any height
· Do not use panels as ramp, bridges or scaffold
· Do not use hammer and wedges to pull panels together
· Do not drive wedges until full length of panels are butted together
· Do not use extreme hammer force when installing wedges
· Do not erect elements not properly cleaned and oiled
(Deck panel faces are oiled after erection)
a) Ensure all scaffold brackets are in good condition and have not been damaged since the last installation
b) Ensue platform is fully decked out and toe-board and handrail installed.
c) Penetration holes in the slab for transferring panels must be covered when not in use until cast with correct.
d) Any workers working above platform level must wear safety belt attached to a secured formwork component or the wall steel.
e) When removing of the timber batons from the floor after casting ensure no nails have been left exposed.
f) Pins and wedges to be removed with care especially on the external of the building.
g) Handling of equipment.
h) Formwork should not be stacked on the scaffold.
POST – CONCRETE ACTIVITIES:
i) Strike Wall Form- It is required to strike down the wall form.
ii) Strike Deck Form- The deck form is then removed.
iii) Clean, Transport and stack formwork
iv) Strike Kicker Formwork – The kicker are removed.
v) Strike wall – Mounted on a Working Platform the wall are fitted on next floor.
vi) Erect Wall – Mount Working Platform and the wall is erected.
Normally all formwork can be struck after 12 hours.
Erection of Platform
Striking of formwork
- Positioning of Platform
Removal of kicker
The essence of the system is that it provides a production line approach in the construction industry. The laborers are grouped together to form small teams to carry out various tasks within a certain time frame such as, reinforcement, fabrication and erection, formwork erection, concreting etc.
Scheduling involves the design and development of the work cycle required to maximize efficiency in the field. The establishment of a daily cycle of work, which when fully coordinated with different trades such as reinforcement fixing, mechanical services installation, and the placing of concrete, includes a highly efficient working schedule in the system, not just for formwork but for all parallel trades as well.
Optimum use of the labor force is made by ensuring that each trade has sufficient work on each working day. Experienced site supervisors are sent to site to train supervisory staff and labor for proper handling of the equipment and to assist in establishing the desired work cycle. The disciplined and efficient handling of work ensures that all other trades follow in a united and predetermined manner. The improved coordination and construction management enables the equipment to be used at optimum speed and efficiency and speed of the output are outstanding. Thus a disciplined and systemized approach to construction is achieved.
SPEED OF CONSTRUCTION
MIVAN is a system for scheduling & controlling the work of other connected construction trades such as steel reinforcement, concrete placements & electrical inserts. The work at site hence follows a particular sequence. The work cycle begins with the deshuttering of the panels. It takes about 12-15hrs. It is followed by positioning of the brackets & platforms on the level. It takes about 10-15hrs simultaneously.
The deshuttered panels are lifted & fixed on the floor .The activity requires 7-10 hrs.Kicker & External shutters are fixed in 7 hrs. The wall shutters are erected in 6-8 hrs One of the major activity reinforcement requires 10-12 hrs. The fixing of the electrical conduits takes about 10 hrs and finally pouring of concrete takes place in these.
This is a well synchronized work cycle for a period of 7 days. A period of 10-12 hrs is left after concreting for the concrete to gain strength before the beginning of the next cycle. This work schedule has been planned for 1010-1080 sq m of formwork with 72-25cu m of concreting & approximate reinforcement.
The formwork assembling at the site is a quick & easy process. On leaving the MIVAN factory all panels are clearly labeled to ensure that they are easily identifiable on site and can be smoothly fitted together using formwork modulation drawings. All formwork begins from corners and proceeds from there.
The system usually follows a four day cycle: -
Day 1: -The first activity consists of erection of vertical reinforcement bars and one side of the vertical formwork for the entire floor or a part of one floor.
Day 2: -The second activity involves erection of the second side of the vertical formwork and formwork for the floor
Day 3: - Fixing reinforcement bars for floor slabs and casting of walls and slabs. Day 4: -Removal of vertical form work panels after 24hours, leaving the props in place for 7 days and floor slab formwork in place for 2.5 days.
The comparison is done between buildings constructed by: -
i) Conventional RC columns, beams, and slab construction (RC moment resisting frame d structure)
ii) RC load-bearing walls and slabs.
In the case of RC moment-resisting framed structures, the horizontal forces due to wind or earthquake are resisted by the frames resulting in the bending moments in columns to resist bending moment and vertical loads would be more than that required to resist vertical loads without bending moment. Similarly, additional reinforcement will be required in beams at supports.
In the case of RC load-bearing walls, monolithic casting of slab along with RC walls results in a box type structure, which is very strong in resisting horizontal forces due to wind or earthquake. In view of large depth of shear walls, the resulting stresses due to bending moment and vertical loads are smaller and in many cases, concrete alone is capable of resisting these forces.
On evaluating these alternatives, it is seen that the beam column frame system in
i) Performs poorly against earthquake forces compared to RCC wall and slab construction. Recent changes in the IS Codes, as well as recommended good practice demand provision of additional reinforcement comply with ductility requirements.
ii) The sizing and detailing of columns needed to be –that they are 20% stronger than beams they support.
Comparative costs of building using load bearing wall and slab system and conventional framed system of column, beams, slab for the construction of a ground-plus-seven building is given in Table 3.8.1. It can be seen that the total cost of ground-plus-seven building using MIVAN System is Rs.5344/m² which is lower than that in conventional system is Rs.6034/m².( As calculated by Srinivaschar.P.H, July 2005).
The cost per flat (or per m² built up area) using MIVAN shuttering system depends upon the number of repetition and period of completion of the project. As the formwork can be reused over 250 times, the initial cost per unit of forming area is less when compared to traditional methods. The reduction of cost is also due to the elimination of brickwork and plaster and also due to reduction in time. The cost of the project gets substantially reduced due to shear wall construction. These are due to the reduced consumption of steel, masonry, and plaster even though the use of concrete decreases. For the same number of repetition, the cost will be less if the period of completion is longer. This is because for a shorter completion period, the area of formwork is more than required for longer completion period. Cost of formwork is illustrated in Table no.3.8.2.
The aluminium formwork provides an integrated scaffolding system which reduces the cost of scaffolding requirements. The mechanical and electrical installation is simplified as conduits are embedded in the structure by precise engineering of outlets and service ducts.
Thus, we can conclude that the overall cost of the project is lesser when compared to project using traditional methods of formwork.
High quality Formwork panels ensure consistency of dimensions. On the removal of the formwork mould a high quality concrete finish is produced to accurate tolerances and verticality. The high tolerance of the finish means that no further plastering is required. Typically a 3mm to 4mm skin coat is applied internally prior to finishing and a 6mm build up coat prior to laying tiles. Care must be taken so that the concert and in particular the enforcement does not become contaminated due to excessive or negligent application of the releasing agent.
The Advantages of this system are:-
The MIVAN formwork is specifically designed to allow rapid construction of all types of architectural layouts.
1) Total system forms the complete concrete structure.
2) Custom designed to suit project requirements.
3) Unsurpassed construction speed.
4) High quality finish.
5) Cost effective.
6) Panels can be reused up to 250 times.
7) Erected using unskilled labor.
Quality and speed must be given due consideration along with economy. Good quality construction will never deter to projects speed nor should it be uneconomical. In fact, time consuming repairs and modifications due to poor quality work generally delay the job and cause additional financial impact on the project. Some experts feel that housing alternatives with low maintenance requirements may be preferred even if the initial cost is high.
LIMITATION OF MIVAN FORMWORK:
Even though there are so many advantages of MIVAN formwork the limitations cannot be ignored. However the limitations do not pose any serious problems. They are as follows: -
1) Because of small sizes finishing lines are seen on the concrete surfaces.
2) Concealed services become difficult due to small thickness of components.
3) It requires uniform planning as well as uniform elevations to be cost effective.
4) Modifications are not possible as all members are caste in RCC.
5) Large volume of work is necessary to be cost effective i.e. at least 200 repetitions of the forms should be possible at work.
6) The formwork requires number of spacer, wall ties etc. which are placed @ 2 feet c/c; these create problems such as seepage, leakages during monsoon.
7) Due to box-type construction shrinkage cracks are likely to appear.
8) Heat of Hydration is high due to shear walls.
In external walls, ties used in shutter connection create holes in wall after deshuttering. These may become a source of leakage if care is not taken to grout the holes. Due to box-type construction shrinkage cracks are likely to appear around door and window openings in the walls. It is possible to minimize these cracks by providing control strips in the structure which could be concreted after a delay of about 3 to 7 days after major concreting. The problem of cracking can be avoided by minimizing the heat of hydration by using fly ash.
50 INTERNAL BEAM CORNER
75 INTERNAL BEAM CORNER
100 INTERNAL BEAM CORNER
125 INTERNAL BEAM CORNER
150 INTERNAL BEAM CORNER
175 INTERNAL BEAM CORNER
50 EXTERNAL BEAM CORNER
75 EXTERNAL BEAM CORNER
100 EXTERNAL BEAM CORNER
125 EXTERNAL BEAM CORNER
150 EXTERNAL BEAM CORNER
175 EXTERNAL BEAM CORNER
VERTICAL BEAM FILLER
VERTICAL BULK HEAD
HORIZONTAL BULK HEAD
BEAM PROP WITH 2 PROPS
BEAM SOFFIT PANEL
50 HIGH THREE SIDED BEAM CORNER WITH 100mm ON ONE END
75 HIGH THREE SIDED BEAM CORNER WITH 100mm ON ONE END
100 HIGH THREE SIDED BEAM CORNER WITH 100mm ON ONE END
125 HIGH THREE SIDED BEAM CORNER WITH 100mm ON ONE END
150 HIGH THREE SIDED BEAM CORNER WITH 100mm ON ONE END
175 HIGH THREE SIDED BEAM CORNER WITH 100mm ON ONE END
COLUMN COLLAR-125 HIGH *100 WIDE
COLUMN COLLAR-125 HIGH *125 WIDE
COLUMN COLLAR-150 HIGH *150 WIDE
INTERNAL-100 ON LEFT LEG (FOR25mm ROCKER)
INTERNAL-100 ON LEFT LEG (FOR50mm ROCKER)
INTERNAL-100 ON LEFT LEG (FOR75mm ROCKER)
INTERNAL-100 ON LEFT LEG (FOR100mm ROCKER)
CHANNEL PROP HEAD
CHANNEL PROP HEAD WITH 2 PROPS
INTERNAL CORNER-100 ON RIGHT LEG (FOR 25mm ROCKER)
INTERNAL CORNER-100 ON RIGHT LEG (FOR 50mm ROCKER)
INTERNAL CORNER-100 ON RIGHT LEG (FOR 75mm ROCKER)
INTERNAL CORNER-100 ON RIGHT LEG (FOR 100mm ROCKER)
DECK PROP HEAD
HORIZONTAL EXTERNAL CORNER
END PROP HEAD
INTERNAL CORNER-(FOR 25mm ROCKER)
INTERNAL CORNER-(FOR 50mm ROCKER)
INTERNAL CORNER-(FOR 75mm ROCKER)
INTERNAL CORNER-(FOR 100mm ROCKER)
INTERNAL CORNER-100 ON LEFT LEG
INTERNAL CORNER-100 ON RIGHT LEG
100 INTERNAL KICKER CORNER
100 EXTERNAL KICKER CORNER
125 INTERNAL KICKER CORNER
125 EXTERNAL KICKER CORNER
150 INTERNAL KICKER CORNER
150 EXTERNAL ICKER CORNER
175 EXTERNAL KICKER CORNER
175 INTERNAL KICKER CORNER
SOFFIT LENGTH-100 HEIGHT ON VERTICAL FACE(INVERTED)
AS ABOVE WITH 100*100mm END PLATES ON EITHER END
AS ITEM 63 WITH 100*100mm END PLATE ON L.H.S ONLY
AS ITEM 63 WITH 100*100mm END PLATE ON R.H.S ONLY
PLATE COVER TO WINDOW SILL
PROP LENGTH BASE
SOFFIT BEAM (ACCOMODATES UPTO A MAXIMUM BEAM WIDTH 300mm)
100 HIGH*100 WIDE SOFFIT CORNER EXTERNAL
100 HIGH*100 WIDE SOFFIT CORNER INTERNAL
100 SOFFIT CORNER WITH RIGHT LEG MITRED
100 SOFFIT CORNER WITH LEFT LEG MITRED
125 HIGH *100 WIDE SOFFIT CORNER
125 HIGH *100 WIDE EXTERNAL CORNER
125 SOFFIT CORNER WITH RIGHT LEG MITRED
125 SOFFIT CORNER WITH LEFT LEG MITRED
150 SOFFIT CORNER
150 HIGH*100 WIDE SOFFIT CORNER EXTERNAL
150 SOFFIT CORNER WITH RIGHT LEG MITRED
150 SOFFIT CORNER WITH LEFT LEG MITRED
125 HIGH *100 WIDE SOFFIT LENGTH
SOFFIT LENGTH WITH 100 RETURN ON BOTH ENDS
SOFFIT LENGTH WITHOUT LIP
125 HIGH *125 WIDE SOFFIT LENGTH
125 HIGH *125 WIDE SOFFIT LENGTH WITH 125 RETURN ON BOTH ENDS
125 HIGH *125 WIDE SOFFIT CORNER
125 HIGH *125 WIDE SOFFIT CORNER EXTERNAL
125 HIGH *125 WIDE SOFFIT CORNER WITHOUT LIP
125 HIGH *150 WIDE SOFFIT LENGTH
125 HIGH *150 WIDE SOFFIT LENGTH WITH 150 RETURN ON BOTH ENDS
125 HIGH *150 WIDE SOFFIT CORNER
125 HIGH *150 WIDE SOFFIT CORNER EXTERNAL
125 HIGH *150 WIDE SOFFIT LENGTH WITHOUT LIP
25/50 SOFFIT BEAM CORNER
25/50 SOFFIT BEAM CORNER WITH 125/150 RETURN ON BOTH ENDS
25/50 SOFFIT BEAM CORNER WITH 125/150 RETURN ON LEFT END
25/50 SOFFIT BEAM CORNER WITH 125/150 RETURN ON RIGHT END
TOP PANEL(ABOVE STANDARD WALL PANEL)
HORIZONTAL WALL FILLER
VETICAL WALL FILLER WITH BOTTOM MITRED (FOR 25 mm ROCKER)
VETICAL WALL FILLER WITH BOTTOM MITRED (FOR 50 mm ROCKER)
VETICAL WALL FILLER WITH BOTTOM MITRED (FOR 75 mm ROCKER)
VETICAL WALL FILLER WITH BOTTOM MITRED (FOR 100 mm ROCKER)
WX-PANEL OR WX- FILLER
WX-FILLER WITH BOTTOM MITRED
The Bombay municipal corporation (BMC) are responsible for the development of Mumbai. It has undertaken massive projects to achieve this goal and has encouraged use of latest technologies to complete these projects. In recent years it has undertaken large – scale constructions of houses in Mumbai.
completed Project with mivan FORMWORK:-
SRA AT MAHUL
Location: MAHULVILLAGE KURLA
Client: DB REALITY
Scope: 7 Storey, 68 Apts.
Design: Load Bearing wall & slab.
Cycle: 11 days per floor.
System formwork: 51.76 laks sq.mt.
Contract Start Date: July 2007.
Project Type (s): High rise, residential building having 68 buildings in all.
Architect: SHAH & DUMASIA CONSULTANCY PVT LTD.
The task of housing due to the rising population of the country is becoming increasingly monumental. In terms of technical capabilities to face this challenge, the potential is enormous; it only needs to be judiciously exploited.
Civil engineers not only build but also enhance the quality of life. Their creativity and technical skill help to plan, design, construct and operate the facilities essential to life. It is important for civil engineers to gain and harness the potent and versatile construction tools.
Traditionally, construction firms all over the world have been slow to adopt the innovation and changes. Contractors are a conservative lot. It is the need of time to analyze the depth of the problem and find effective solutions. MIVAN serves as a cost effective and efficient tool to solve the problems of the mega housing project all over the world. MIVAN aims to maximize the use of modern construction techniques and equipments on its entire project.
We have tried to cover each and every aspect related to aluminium (MIVAN) form construction. We thus infer that MIVAN form construction is able to provide high quality construction at unbelievable speed and at reasonable cost. This technology has great potential for application in India to provide affordable housing to its rising population.
Thus it can be concluded that quality and speed must be given due consideration with regards to economy. Good quality construction will never deter to projects speed nor will it be uneconomical. In fact time consuming repairs and modification due to poor quality work generally delay the job and cause additional financial impact on the project. Some experts feel that housing alternatives with low maintenance requirements may be preferred even if at the slightly may preferred even if at the higher initial cost.