GB2127474A

GB2127474A - Improvements in or relating to concrete formwork systems

Info

Publication number: GB2127474A
Application number: GB08323053A
Authority: GB
Inventors: George Bernard Arthur Young
Original assignee: Acrow Ltd UK
Current assignee: Acrow Ltd UK
Priority date: 1982-09-21
Filing date: 1983-08-26
Publication date: 1984-04-11
Also published as: GB2127474B; GB8323053D0

Abstract

Formwork (16) on which the outer edges of a building structure are to be cast comprises primary beams (26), secondary beams (40), formwork panels (42), a platform (44) at the outer end thereof beyond the outer edge of the building structure two props (28 and 30) for supporting each primary beam, one prop (30) for supporting the inner end thereof and the other prop (28) supporting the approximate centre point (see 39) thereof, and means (34) to secure the formwork (16) to either the rest of the formwork (12) or the building structure itself. <IMAGE>

Description

SPECIFICATION Improvements in or relating to concrete formwork systems The invention relates to concrete formwork systems.

Formwork for supporting concrete (or other suitable material) during setting usually comprises a number of props and primary beams and formwork panels supported by the props. For the edges of a building structure, however, specialised formwork has to be used so that either a perimeter beam or a flat slab may be cast.

Known formwork for supporting cast concrete for the edge of building structure are either difficult to dismantle and/or to erect, are not versatile, are complicated in structure and design, or do not provide a platform for workmen outside the edges of the building.

It is an object of the invention to mitigate or overcome one or more of the above problems.

In accordance with the invention a formwork on which the outer edges of a building structure are to be cast comprises a plurality of substantially horizontal primary beams for supporting a plurality of secondary beams and/or formwork panels and a platform at the outer end thereof beyond the outer edge of the building structure, at least two substantially upright support props for supporting each primary beam, one prop supporting the inner end thereof and the other prop supporting the approximate centre point thereof, means being provided for securing the formwork to either the formwork for the main part of the building structure or the building structure itself.

Preferably the upright support props are adjustable so that the vertical position of the primary beams can be varied to provide the required level of casting surface. For example, the height of the props may be adjustable so that either a perimeter beam or flat slab can be cast.

Preferably, the primary beam can be swung about the longitudinal axis of the prop supporting the approximate centre point thereof, so that, for example, the primary beams may be hoisted in a position parallel to a pavement above which the building is to extend, and then be swung when positioned above the pavement.

A platform for the outer edges of the formwork in accordance with a further feature of the invention, comprises a plurality of primary beams, a plurality of formwork panels supported by and spanning between the primary beams, a keep plate extending over the top of a primary beam and at least one formwork panel, and means for securing the keep plate to the primary beam so that the formwork panels are securely held down.

The keep plates will then act to hold down the formwork panels during any updraft of air or accidental displacement by a workman.

Preferably, beams are supported by and span between the primary beams, to support the formwork panels. The means for securing the keep plate is preferably fixed to the primary beam.

A method of erecting formwork on which the outer edges of a building structure are to be cast in accordance with the invention, comprises placing secondary beams and/or formwork panels on the casting surface of the formwork for the main part of the building structure, hoisting formwork onto the outer edge of the building structure, and transferring the secondary beams and/or formwork panels onto the formwork on the outer edge of the building to span and be supported by the formwork.

Preferably, the formwork used in the method is the formwork in accordance with the invention.

The primary beams may be hoisted in a position parallel to a pavement above which the building is to extend, and then when positioned above the pavement swung out transverse thereto. The vertical position of the primary beam is then adjusted by means of the upright props to provide the required level of casting surface, i.e., for casting of a perimeter beam or flat slab. Finally, the formwork is secured to either the formwork for the main part of the building or the building structure itself.

To dismantle the formwork the secondary beams and/or formwork panels are stripped, the vertical position of the primary beams lowered, the primary beams swung out about the approximate centre point thereof and removed from the building structure.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of one embodiment of formwork structure in accordance with the invention; Figure 2 is a plan view of the formwork of Figure 1 Figure 3 is a side view of the formwork of Figure 1 in an alternative position, and Figure 4 is a view of a portion of the formwork of Figure 1 along line IV--IV of Figure 1.

The formwork shown in Figures 1,2 and 3, comprises formwork 12 on which the central part of the building structure 14 is cast, and formwork 1 6 on which the outer edges of the building structure 14 is cast.

The formwork 12 is conventional and comprises a number of primary beams 1 8 supporting a number of secondary beams 1 9 and a casting surface 20. The primary beams 1 8 are themselves supported by drop heads 22 on vertical props 24. An example of such formwork 12 is described in British Application No. 8216474.

The formwork 1 6 comprises a number of substantially horizontal primary beams 26, each beam being supported by two substantially upright props 28 and 30. The prop 28 supports the primary beam 26 approximately at the centre point thereof while the prop 30 supports the primary beam 26 at the inner end 32 thereof. The height of both props 28 and 30 is adjustable such that the height of the primary beam 26 can be raised or lowered relative to the height of the casting panels supported by the formwork 12. A securing cross-member 34 is attached at one end to the upper portion of the prop 30, and at the other end to either the prop 24 of the formwork 12, or (in an arrangement which is not illustrated) to the building structure 36.The member 34 acts to secure the formwork 1 6 to the building structure 36 and prevents overbalancing of the formwork 1 6 which could occur if excess weight is placed on the outer end 38 of the primary beam 26. The beam 26 can swivel about the longitudinal axis of the prop 28 by means of a swivel pin 39 (see below).

The formwork 1 6 also includes a number of secondary beams 40 supported by and spanning between two primary beams 26 (see Figure 2). A formwork panel(s) 42 is supported over the secondary beams 40 and forms, a casting surface over the central and inner end 32 portions of the primary beam 26 and an access platform area 44 for workmen at the outer end 38 portion of the beam 26.

The outer end 38 of the beams 26 and accordingly the platform area 44, are outside the building structure as seen in Figure 2 where the outer edge of the building structure is represented by the line 46. Figure 2 shows the formwork 10 before casting, for simplification showing the secondary beams 19 and 40 on the left-hand side only, although in use secondary beams are used to span all the primary beams 18 and 26 in the formwork 10.

The formwork 1 6 can be used for two main applications. Firstly, in Figure 1 the formwork 16 is shown with its casting surface 42 below the casting surface 20 of the formwork 12. This is such that with other formwork members 48 a perimeter beam 50 can be formed integral with the floor 14 of the building structure. Secondly in Figure 3, the formwork 1 6 is shown with its casting surface 42 flush with the casting surface 20 of the formwork 12. This is so that a flat slab 14 can be formed. To raise or lower the height of the beam 26 the prop height of props 28 and 30 are simply adjusted.

In order to obtain a flat outer face of a building structure 14, vertical formwork 52 is provided comprising a vertical panel 54, the position of which is adjustable by a turnbuckle strut 56 attached to a U-shaped bracket 58 at one end by means of a bolt 60 (see Figure 4). The arrangement is such that by adjusting the length of the strut 56, the panel 54 can be moved forward or backwards along the beam 26 until the appropriate position for casting is reached and maintained in an upright position.

The bracket 58 is securely fixed, for example by welding, to the upper surface of the beam 26 at a distance from the handrail 62 of the platform 44 which is such that there is ample space for a workman to pass without being obstructed by the turnbuckle strut 56.

To prevent an updraught of air from lifting up the formwork panels 42 of the platform 44 or alternatively to prevent accidental displacement of the panels 42 by workmen on the platform 44, a keep plate 64 is placed around the U-shaped bracket 58 and over the edges of the formwork panels 42 (see Figure 4) so that after the bolt 60 is positioned in the U-shaped bracket, the head and nut of the bolt 60 hold down the keep plate 64 which in turn holds down the panels 42 and secondary beams 40.

To position and erect the whole formwork 1 6 on the building structure 36, at least beams 26 and props 28 and 30 are hoisted one by one, up the side of the building. The longitudinal axis of the beams 26 is positioned generally parallel to the outer edge of the building when being hoisted.

The beam 26 and prop 30 are then swung around the swivel pin 39 so that the longitudinal axis of the beam 26 is at right angles to the edge of the building 36.

Secondary beams 40 and formwork panels 42 previously placed on the casting surface 20 of the formwork 2, are then transferred from this surface 20 to the beams 26 so that they span and thus are supported by the primary beams.

The formwork 1 6 is then secured to the building structure 36 by means of the crossmember 34 which secures the prop 30 to the prop 24 on the formwork 12. Before or after any of these steps the vertical height of the upright props 28 and 30 are adjusted so as to provide when the formwork 1 6 is in position, the required level of the casting surface 42 relative the casting surface 20.

To dismantle the formwork 16, the vertical height of the upright props 28 and 30 is adjusted to lower the beams 26 and 40 from the now cast structure 14. The secondary beams 40 and casting panels 42 are then stripped from the beams 26 and the cross-member 34 removed from its attachment to props 24 and 30.

The advantage of raising and lowering the beams 26 generally parallel to the outer edge of building structure is that the primary beam will not extend out across a pavement into any adjacent road, and for example, is useful where there is little space between any adjacent building.

Claims

1. A formwork on which the outer edges of a building structure are to be cast comprising a plurality of substantially horizontal primary beams for supporting a plurality of secondary beams and/or formwork panels and a platform at the outer end thereof beyond the outer edge of the building structure, at least two substantially upright support props for supporting each primary beam, one prop supporting the inner end thereof and the other prop supporting the approximate centre point thereof, and means being provided for securing the formwork to either the formwork for the main part of the building structure or the building structure itself.

2. A formwork as claimed in Claim 1, wherein the upright support props are adjustable so that the vertical position of the primary beams can be varied to provide the required level of casting surface.

3. A formwork as claimed in Claim 2, wherein the height of the props are adjustable so that either a perimeter beam or flat slab can be cast.

4. A formwork as claimed in any preceding claim wherein the primary beam is pivotal about the longitudinal axis of the prop supporting the approximate centre point thereof.

5. A formwork as claimed in any preceding claim wherein the securing means is a crossmember attached to the rest of the formwork by the prop supporting the inner end.

6. A platform for the outer edges of formwork comprising a plurality of primary beams, a plurality of formwork panels supported by and spanning between the primary beams, a keep plate extending over the top of a primary beam and at least one formwork panel, and means for securing the keep plate to the primary beam so that the formwork panels are securely held down.

7. A platform as claimed in Claim 6 wherein secondary beams are supported by and span between the primary beams, to support the formwork panels.

8. A platform as claimed in either Claim 6 and 7 wherein the means for securing the keep plate is fixed to the primary beam.

9. A method of erecting formwork on which the outer edges of a building structure are to be cast, comprising placing secondary beams and/or formwork panels on the casting surface of formwork for the main part of the building structure, hoisting formwork onto the outer edge of the building structure, and transferring the secondary beams and/or formwork panels onto the formwork on the outer edge of the building to span and be supported by the formwork.

10. A method as claimed in Claim 9 wherein the formwork is hoisted in a position parallel to a pavement above which the building is to extend, and then when positioned above the pavement swung out transverse thereto.

1 1. A method as claimed in either Claim 9 or 10 wherein the vertical position of the formwork is adjusted by means of the upright props to provide the required level of casting surface.

12. A method as claimed in any one of Claims 9 to 11 wherein the formwork is secured to either the formwork for the main part of the building or the building structure itself.

13. A method as claimed in either Claim 11 or 12 wherein the formwork is swung out about the approximate centre point thereof when positioned above the pavement.

14. A formwork on which the outer edges of a building structure are to be cast substantially as described herein with reference to the accompanying drawings.

1 5. A platform for the outer edges of formwork substantially as described herein with reference to the accompanying drawing.

1 6. A method of erecting formwork on which the outer edges of a building structure are to be cast substantially as described herein with reference to the accompanying drawings.