GB2125475A

GB2125475A - Formwork

Info

Publication number: GB2125475A
Application number: GB08320315A
Authority: GB
Inventors: Kok Heng Anthony Lim
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-08-13
Filing date: 1983-07-28
Publication date: 1984-03-07
Also published as: GB8320315D0; GB2125475B

Abstract

A transportable table formwork unit for use in the construction of a reinforced concrete floor, comprising a substantially flat-topped structure having a pouring surface formed of suitable sheet material 2 secured upon and supported by an array of fixed joists 1, and a metal base structure 5 supporting said array of joists and adapted to be supported by adjustable jacks 10 to set the level of the pouring surface. <IMAGE>

Description

SPECIFICATION Construction of reinforced concrete floors This invention relates to the construction of reinforced concrete floors. The conventional manner of constructing such a floor is to erect a table formwork from timber joists overlaid with sheet material such as plywood and supported underneath by a suitable steel structure, and then to pour the concrete on top. Such an operation involves in situ assembly of all of the formwork structure to the precise dimensions required for each successive floor of the building, followed by its complete disassembly when the floor has become self-supporting. This procedure is timeconsuming and labour-intensive and therefore expensive.

Viewed from one aspect the present invention provides a transportable table formwork unit for use in the construction of a reinforced concrete floor, comprising a substantially flat-topped structure having a pouring surface formed of suitable sheet material secured upon and supported by an array of fixed joists, and a metal base structure supporting said array of joists and adapted to be supported by adjustable jacks to set the level of the pouring surface.

Preferably such a unit is provided in combination with a chair unit adapted to support the same at a desired level and incorporating jacks for setting the level of the supporting surfaces of the said unit.

Preferably the said base structure includes additional support means extending along at least one side thereof for supporting removable joists for providing an intermediate formwork extending between the said unit and another similar unit in use.

The use of such transportable table formwork units enables the complete formwork for a floor to be erected and subsequently removed much more quickly and efficiently than in the past. The preferred provision for supporting removable joists between two such units enables a pouring surface of desired dimensions to be built up, despite the fixed dimensions of the units themselves.

The said additional support means may be arranged to support the said removable joists at the same level as the joists of the formwork unit, to provide one continuous flat pouring surface spanning two or more such units. Alternatively such support means may be located at a lower level to support a pouring surface for an integrally poured beam of a floor.

Viewed from a further aspect the invention provides a table formwork unit for use in the construction of a reinforced concrete floor, in combination with a chair unit adapted to support the same at a desired level and incorporating jacks for adjusting the level of the supporting surfaces of the said chair unit. Such a formwork unit may or may not be in accordance with the said one aspect of the invention already set forth above. The provision of such a chair unit removes the necessity for the level of the formwork unit itself to be individually adjusted, and the formwork unit need not therefore incorporate jacks or adjustable legs, and indeed can be made without legs as such, which makes it much easier to handle.

Viewed from yet another aspect the invention provides a method of locating a transportable table formwork unit for use in forming a reinforced concrete floor, wherein a chair unit for supporting the said formwork unit is first placed in position and the level of its supporting surfaces adjusted by means of jacks incorporated in the chair unit, and the formwork unit is then placed in its operative position on the said chair unit without any individual levelling of the formwork unit. Such a formwork unit may or may not be a unit according to the other aspects of the invention already set forth above.

Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a view in side elevation of a table formwork unit according to the invention; Figure 2 is a plan view of the unit; Figure 3 is an end elevation of three units in a lined-up position; Figure 4 illustrates the sequence of removing and flying the unit onto the next floor, in use of the unit; Figure 5 is an end elevation of a modified unit; and Figure 6 is a detail of the unit of Figure 5.

Referring first to Figures 1 to 3, the table formwork unit comprises a top array of parallel timber joists 1 having secured thereto plywood boards 2 providing a flat pouring surface 3. The timber joists are secured by angle brackets to 5"x2" mild steel hollow section bearers 4 extending between opposed vertical parallel trusses 5 of a base structure. Each said truss comprises a top member 6 and a bottom member 7 in the form of 5"x2" mild steel hollow sections welded together via 2" diameter mild steel pipes 8, and the trusses are interconnected by cross bracings in the form of 2" diameter pipes 9 at suitable spacings from one another.

The bottom members 7 of the substantially inverted-U-shaped unit are adapted to seat on a supporting chair 10 made up of 2" diameter pipes attached together by clamps and incorporating jacks 11 which are set at the required level prior to the placing of the unit. Additional supports 12 with a jack base to facilitate dismantling are placed under the bottom members 7 prior to the pouring of concrete floor slab 1 3.

At each side of the unit there is provided support means for removable joists 14 (Figure 3), in the form of 22 "x2-" mild steel angles 15 welded to the hollow section bearers 4. This enables the space between two table units to be filled to form a continuous flat pouring surface.

The angles 1 5 may be secured at a lower level to the pipes 8 as shown at 1 spa in Figure 3, to support removable joists 1 6 and a reinforced plywood board structure 17 for forming an integral beam 18. If desired the angles 1 5a could be set away from the horizontal to form a tapered beam.

In use, table formwork units according to the invention will usually be hoisted up by a tower crane to sit on a supporting chair 10, which has already been adjusted by means of its jacks 11 to a required level. This means that the table formwork system can be adapted to a building with floors of different heights.

After the table units have been placed on the supporting chairs 10, the units have to be adjusted for alignment only, since their level is already predetermined by the supporting chairs.

This means that valuable time would not be wasted in adjusting the levels of the table units.

When all the table units have been aligned properly, the spaces between the units are then filled up with detachabie pieces of timber formwork as shown in Figure 3. When all the spaces have been filled up and any required beam formwork placed in position, the surface is then ready for placing of steel reinforcement. Before pouring concrete the additional supports 12 are placed under the table units.

After the concrete has been poured.and become self-supporting the table units are lowered by means of four garage jacks onto 2" diameter pipe rollers 19 (Figure 4) ready for flying onto the next floor.

The method of flying the table unit is illustrated in Figure 4. Step (i) shows the table unit resting on three 2" diameter pipe rollers 1 9 ready for rolling out. Step (ii) shows the unit in the rolled out position and being secured at point P by two wire ropes 20 from the tower crane. The table is then slowly pulled out by the tower crane and lowered as shown in step (iii). Two detachable steel props 21 inserted into steel sleeves 22 (see also Figure 2) will engage the concrete ceiling, thus preventing the table unit from moving. Another two wire ropes 23 are then tied at point Q. Then the tower crane lifts up the table unit again, this time with four wire ropes properly hooked on the unit, and gently moves the unit outwards. Before this movement of the unit the two steel props 21 are removed for use on the next unit.Step (iv) shows the unit being pulled out and ready for flying onto the next floor as indicated in step (v).

Before the unit is hoisted onto the next floor, the supporting chair 10 has already been located there at the required.level, and all that remains is to place the table unit on the chair 10 without any levelling of the table unit itself being necessary.

In the modification illustrated in Figures 5 and 6 the fixed timber joists 1 extend transversely of the length of the unit and are received at their shaped ends in 6"x3" mild steel channels 24 constituting the top members of the opposite parallel trusses of the unit. The bottom members 25 of the trusses are 4"x3" mild steel angles, the intermediate members 8 are again 2" diameter pipes, and the cross bracings 26 are +" diameter steel bars. Additional support means for removable joists comprise 3"x3" mild steel angles 27 welded back to back to the top members 24 of the trusses.

The use of mild steel angles, channels, rectangular hollow sections and pipes held together by welding is in itself a substantial improvement over prior art table formwork systems which are held together by nuts and bolts. This means that a table formwork system can be easily made from cheap and common materials instead of expensive aluminium alloy and other high quality materials which would otherwise put this time and labour saving device beyond the reach of small construction companies.

Claims

1. A transportable table formwork unit for use in the construction of a reinforced concrete floor, comprising a substantially flat-topped structure having a pouring surface formed of suitable sheet material secured upon and supported by an array of fixed joists, and a metal base structure supporting said array of joists and adapted to be supported by adjustable jacks to set the level of the pouring surface.

2. A unit as claimed claim 1, in combination with a chair adapted to support the same at a desired level and incorporating jacks for setting the level of the supporting surfaces of the said chair unit.

3. A unit as claimed in claim 1 or 2, which is of substantially inverted U-shape in vertical crosssection transverse to its length.

4. A unit as claimed in any of claims 1 to 3, wherein the said base structure includes additional support means extending along at least one side thereof for supporting removable joists for providing an intermediate formwork extending between the said unit and another similar unit in use.

5. A unit as claimed in claim 4, wherein the said additional support means is arranged to support said removable joists at the same level as the said fixed joists of the said unit and a said similar unit, to permit the formation of a continuous flat pouring surface spanning said units in use.

6. A unit as claimed in claim 4, wherein the said additional support means is arranged to support said removable joists at a level below that of the said fixed joists of the said unit and a said similar unit, to permit the formation of an integral beam between such units.

7. A unit as claimed in claim 6, wherein the said additional support means is offset from the horizontal, to form a tapered beam.

8. A unit as claimed in any of the preceding claims, wherein the said base structure comprises two opposite parallel trusses each formed of steel pipes extending as struts in a common vertical plane between top and bottom horizontal members, and diagonal ties formed by steel pipes extending between the said top and bottom members of the respective opposite trusses to interconnect the latter.

9. A unit as claimed in any of the preceding claims, wherein the said base structure is formed entirely of elongate steel members interconnected by welding.

10. A table formwork unit for use in the construction of a reinforced concrete floor, in combination with a chair unit adapted to support the same at a desired level and incorporating jacks for adjusting the level of the supporting surfaces of the said chair unit.

11. Table formwork units substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of locating a transportable table formwork unit for use in forming a reinforced concrete floor, wherein a chair unit for supporting the said formwork unit is first placed in position and the level of its supporting surfaces adjusted by means of jacks incorporated in the chair unit, and the formwork unit is then placed in its operative position on the said chair unit without any individual levelling of the formwork unit.

13. A method as claimed in claim 12, substantially as hereinbefore described with reference to the accompanying drawings,