The purpose of this document is to describe the work procedure to be adopted for
erection of System Form Work in building Project. This Procedure will ensure that the erection process of the same, which directly affects the quality should be planned and controlled.
Form work drawings will indicate the Followings: –
- Plans, elevations and sections drawings to show the general arrangement of the form work and to identify and locate all members and components including bracing where necessary.
- Components types and spacing.
- The prop sizes and location.
- Location of weep holes. inspection opening, form work opening for transfer of form work etc.
ON SITE PLANNING
All parties involved at the project site shall coordinate and cooperate with each
other during the planning and preparation stage to determine and safeguard the
system of work based on risk assessment and control process. An effective quality
control system must be implemented for the construction of form work.
The common defects which are likely to occur in form work system is illustrated
- failure to check tightness of bolts, wedges. etc.
- failure to check adequacy of pin and wedges.
- failure to control vertical rate of placement of concrete.
- failure to control placement of concrete, causing uneven loading of forms.
Materials and components that are damaged or excessively worn must not he used.
SITE COORDINATION & ADMINISTRATION
Ensuring mechanical aids are used to handle loads wherever possible. Storing loads on trolleys to minimize double handling or on raised platforms to minimize manual lifting from ground level. Having adequate storage space or lay down area to safely store materials and equipment and to minimize double handling.
SETTING OF LEVEL & POSITION MARKING
Based on the approved construction drawings. the project surveyor shall ensure that the grid lines and foundation level is properly set up. marked and peg for walls.
column etc. Leveling must be checked prior to commencement of form work
installation to ensure accurate positioning.
- Structural Line :- After checking verifying the leveling of slab , structural line must be indicated as per architectural and section drawings.
- Off-set Line :- This is the setting out line that is “snapped” onto the concrete surface and offset normally 300 mm from the internal face of external wall.
- Concrete Level Survey :- Leveling must be checked prior commencement of form-work installation to ensure accurate positioning. Concrete Level survey will be done on all sides and remedial work carried out prior to the erection of form work. All level survey will be taken from TBM. High spots along the wall line will be chipped off to the proper level. Low spots along the wall line will be packed to the required level using plywood or timber. Packing the corner and the center of the wall length to the required level will be normally be adequate 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 center line can be on a – level kicker. This in turn means the form work is not in plumb. Kickers are manufactured with a 26 mm slotted hole on the face to allow for adjustment after concreting. As with the concrete level survey, proper records of the kicker survey should be kept on file by the allocated supervisor. As with the concrete level survey, proper records of the kicker survey should be kept on file by the allocated supervisor.
- Setting out lines should continue through openings, external corners etc, by a minimum of 150 mm. This makes it easier to fix form work in position prior to concreting. It is very important that the reference points and the setting out points are protected against accidental movement or damage. 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 form work erection. It is suggested a theodolite be used for transferring the points through openings provided in the slab.
METHOD OF ERECTING SYSTEM FORM WORK
- 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:-
- 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.
- If steel reinforcement is likely to interfere with the placement of the ties, it can be seen and corrected without delaying the pane erection.
- Enables fast start up of deck teams as the first rooms can be closed quickly.
- Continuous steel reinforcement for the walls, creates a barrier between the two sides of the form work, 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 form work 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.
- Other Trades – Vertical Rebar , M&E and Plumbing :- The support work such as vertical rebar , mechanical , electrical and plumbing are to commence immediately once the setup is completed and confirmed by the project Surveyor.
- Wall Panel Positioning ( I / C + Wall ) :- All setting must start with the positioning of I / C and Wall . At least first setting , it is extremely important to apply sufficient quantity of form oil in order to maintain Panel’s Coating.
- Beam and Slab Soffit Length :- Starting from the one side of the beam , fix the beam soffits inserting the pins through the bottom rail of the beam side into the beam soffit.
- Staircase and Elev-Pit :- All form-work begins at a corner and proceeds from there. This is to provide temporary lateral stability.
- Deck Form-work :- In most cases the deck beam to support the deck form-work , can be assembled on the concrete slab. Components are held together by pinning join bar through two adjoining beam with a Deck Prop located between using the long pin.
- Other Trades – Bottom and Top Rebar , M&E and Plumbing :- In most cases the Deck beams to support the Deck form-work , can be assembled o the concrete slab. Components are held together by pinning join bar through two adjoining with a Deck Prop located between using the long pin.
- Kicker Form-work :- Where these is continuous vertical wall , e.g. lift shaft , external face of beam etc. , a Kicker Forms he perimeter of the slab and also acts the connecting component for the vertical wall form-work.
- Marking and Control / Correction of Deviations :- The vertical form-work is fixed in position , the external corners should be checked for plumpness. This will determine if further action is required to control the deviations.
- Concreting :- Ensure site Coordinators are available during concreting progress and concrete pouring is distributed evenly throughout the wall section before commencing to cast the slab level areas.
- Wall Mounted Working Platform :- Initial set-up of the form-work and when using the wall mounted scaffold bracket drill 20 mm diameter holes to position the PVC sleeves, which, when cast in concrete, should be used for fixing the scaffold bracket t the building.
- Striping Wall/Column Form work :- The first panel to be struck will be the most difficult as it is sandwiched between two components. Normally one man inserts the spigol on the panel puler into the bottom hole in the side rail of the panel to be struck.
- Striping beam Form work :- Remove all the pins wedges from the section of beam side to be struck. Using a panel puler, insert the spigot into one of holes in the top or bottom rails of the beam side.
- Striping Deck form work :- As the first deck panel in a row rests on the lip of the soffit length, the adjacent deck panel should be struck first. After removing all the pins and wedges from the panel to be struck, a panel puller can be used break the bond from the adjacent form work.
- Flat tie and tie bar shields (PVC Sleeve) :- Flat tie used for ensuring the thickness of the wall/ Column the tie bar sleeve to protect the flat tie and to remove by using special tools.
- Striping Kicker Form work :- The wall panel are removed, disconnected the lover kicker from the adjacent form work. Remove the cast in bolt by turning anti-clockwise. The leaves the kicker free to be taken of an prepared of reuse.
- Striping Wall and Slab mounted working platform :- Once the subsequent level of the external form work panels are fixed, the external working brackets of bottom level are removed and moved to the subsequent level.
- Cleaning form work :- All component should be cleaned with paint scrappers as soon as they are struck and longer the cleaning is delayed the more difficult the task will be.
- Transferring Form work :- the heaviest and larger the area are the full height wall panel and standards making them difficult to handle. Raised to through slots have served there propose they are closed by casting in a concrete filler.
To be continued…..