WO2003006760A1

WO2003006760A1 - Formwork connecting member

Info

Publication number: WO2003006760A1
Application number: PCT/CA2002/001059
Authority: WO
Inventors: Francesco Piccone
Original assignee: Francesco Piccone
Priority date: 2001-07-10
Filing date: 2002-07-10
Publication date: 2003-01-23
Also published as: CA2352819A1

Abstract

A connecting member for use in a stay-in-place modular concrete formwork assembly that includes at least one brace and that is suitably perforated to permit the placement of reinforcement rods at or near the optimal placement position for a given structure. The connecting member includes terminal connectors at either longitudinal edge adapted for mating engagement with at least one wall element of a modular formwork assembly and at least one elongate brace connected to and depending from its central portion (from a point of connection offset from the terminal connectors) for engagement with the supplementary engagement means present on the inner surface of a wall element. The central portion and brace of the connecting member are perforated within a zone of perforation that extends through the point of connection of the brace and the flat central portion to permit the cross-flow of concrete and the cross-placement of reinforcement rods.

Description

FORMWORK CONNECTING MEMBER

FIELD OF THE INVENTION

This invention relates generally to stay-in-place modular formwork for creating concrete structures, and more particularly to connecting members for use with such formwork.

BACKGROUND OF THE INVENTION

The use of modular formwork elements and members that interconnect to create a stay-in-place formwork assembly or structure into which concrete may be poured is well known in the prior art. Typically, such modular formwork is manufactured from lightweight plastic (such as PVC) or other lightweight materials in order to minimize transportation costs and to facilitate the assembly of a comparatively large section of formwork structure prior to the pouring of the concrete. Examples of such modular formwork, and of the methods for its use and application, are provided in Canadian patent nos. 2215939, 2226497, and 2218600 to Piccone. In formwork structures constructed of prior-known modular formwork of this type, discrete inner and outer wall elements are assembled together in end-to-end relationship and interconnected by connecting members to create cells via the sliding engagement of complementary terminal connectors that are present along the longitudinal edges of the wall elements and connecting members. The engagement between the connecting members and the wall elements normally extends along the entire elongate (height) dimension of the formwork.

Internal braces that extend between the connecting members and supplementary engagement means on the inner surfaces of the wall elements may also be present. Such braces may similarly be interconnected with the elements and members via a contiguous sliding engagement of compatible engagement means. Since the formwork is preferably thin (relative to the thickness of the concrete structure) in order primarily to conserve material, internal braces are particularly important in applications where it is desired to prevent or limit outward distension of the central portions of the wall elements (known as "pillowing") under the weight of the concrete that is poured into the formwork assembly. Thin sections of lightweight materials are (as is well known) inherently susceptible to bending or flexing, but are generally less susceptible to deformation under axial tension. The internal braces of prior known formwork are themselves preferably manufactured of thin, lightweight materials; accordingly, such braces must generally extend at a relatively shallow angle relative to the connecting member to which they are connected so as to avoid excessive bending (such as might otherwise result from the outward distension of the wall element to which the given brace is also connected).

It is also well known that concrete withstands compressive forces well, but without reinforcement is not well suited to withstand tensile forces. Accordingly, reinforcement rods are conventionally set within concrete structures (whether or not stay-in-place formwork is used in the construction of the concrete structure) for strengthening purposes. To maximize the effect that reinforcement rods of a given diameter and cluster density may have on the prevention of excessive flexing in a concrete structure (such as may be caused, for example, by wind loading of the structure), it is generally preferable to set the reinforcement rods relatively close to at least one surface of the structure. If the rods cannot be located at or near the optimal position for a given structure, then more rods or thicker rods (or both) need to be used; this, of course, increases overall cost.

Prior-known formwork connecting members and braces are typically perforated to permit the placement of reinforcement rods and to permit the cross-flow of concrete (between cells of the formwork assembly) that is poured into the formwork assembly. However, the attachment points between prior-known braces and connecting members (which, as noted above, typically comprise a sliding engagement of compatible engagement means) obstruct the contiguity of such perforations. This makes it difficult or impossible to place reinforcement rods at or near the optimal placement position for a given structure. The attachment points also limit the maximal overall dimensions of the perforations, thereby limiting the maximal cross-flow of concrete from one discrete cell of formwork assembly to another during the pouring of concrete into the formwork assembly. Inadequacy in the cross-flow of concrete may result in the bulging of one cell of formwork assembly relative to another, which in turn may lead to undesirable distortion in the concrete structure.

It is therefore an object of one aspect of the present invention to provide a formwork connecting member that includes at least one brace, but that is nevertheless suitably perforated to permit the placement of reinforcement rods at or near the optimal placement position for a given structure and to facilitate the cross-flow of concrete.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a formwork connecting member that includes an elongate central portion that has terminal connectors located at both longitudinal edges. The terminal connectors of the connecting member are adapted to mate slidingly with the complementary terminal connectors that are present on the longitudinal edges of the wall elements of known stay-in-place modular formwork, and different terminal connectors may be selected to suit a given modular formwork application. Preferably, the terminal connectors of the connecting member (and the complementary terminal connectors of the wall element) are selected so that the connectors of the connecting member do not protrude, such that the connecting members are not visible between the wall elements once they are assembled in end-to-end relationship. This permits the entire connecting member to be constructed of recycled material (or other lower-cost materials) without adversely affecting the external aesthetic quality of the resulting structure or wall.

The connecting member also includes at least one associated elongate brace that depends from a point of connection on the central portion that is offset from the terminal connectors. The connection between the brace and the central portion may be permanent (such that the brace at the point of connection is integral with the central portion) or releasable (employing known types of complimentary engagement means) depending, in part, upon the physical characteristics of the material from which the connecting member is constructed. In the preferred embodiments described below that are manufactured of PVC plastic material, the brace(s) at the point of connection is integral with the central portion. The extent of the offset is dependent primarily upon the particular application (relative to the size of the resulting concrete structure, and relative to the position or function of the connecting member within a given modular formwork system and as between different formwork systems), and upon the material or materials from which the connecting member is manufactured. In the preferred embodiments described below that are manufactured of PVC plastic material, the point of connection is offset far enough away from the nearest terminal connector to permit the brace to depend at a comparatively shallow angle (preferably no more than about 60°, and most preferably about 45°) from the central portion so as to limit flexing of the brace. In a typical commercial and residential wall building application, the point of connection is offset more than one inch from the nearest terminal connector.

The brace includes engagement means at its distal longitudinal edge that are adapted to mate slidingly with the supplementary engagement means that are present on the inner surface of known wall elements. As noted previously, bracing limits the "pillowing" of the central portion of the wall element under the weight of the poured concrete. Both the central portion and the associated brace (or braces) of the inventive connecting member are perforated in a selected zone of perforation that extends through the point of connection of the brace (or braces) to facilitate the cross-flow of concrete and to permit the placement of reinforcement rods at or near the optimal placement position for a given structure. The ability to place the reinforcement rods at or near the optimal placement position results not only in lower material costs (due to the reduced need for reinforcement rods), but also in a reduction in construction time because fewer or thinner reinforcement rods need to be placed and those rods that do need to be placed can be placed more easily. Placement of reinforcement rods within a formwork structure generally involves the insertion and tying in place of the rods to the formwork structure before each given cell of formwork is completely closed off. After the reinforcement rods are in place, a cell of formwork assembly is closed off (usually by the sliding into place of a wall element), and that cell of formwork assembly is then ready for the pouring of concrete.

In typical commercial and residential wall building applications, the optimal position for reinforcement rods is about one inch from at least one of the inner and outer surfaces of the wall. This definition of optimal positioning is, in part, determined with reference to government building regulations that typically require a minimum of about % to one inch of concrete cover over any reinforcement rods that may be present in order to ensure that the reinforcing rods do not corrode as a result of moisture seeping into the wall through minute cracks that may be present in the concrete. It is noted that the government minimum cover regulation to which reference is made is selected with reference to traditional building practices (not involving the use of stay-in-place formwork) and that concrete structures built using stay-in-place formwork are inherently less susceptible to the development of minute surface cracks because the formwork wall elements at least partially protect the concrete from moisture, temperature fluctuations, and other environmental variations. It may accordingly be possible, for a typical commercial or residential wall that is built using stay-in-place formwork, to select an optimal position for the reinforcement rods that is closer to the surface than one inch. However, current building regulations would generally not allow for such positioning in a typical commercial or residential wall.

In one embodiment of the invention, the connecting member is configured to connect together two generally parallel rows of wall elements of a known formwork assembly of the sort in which the concrete (when poured) will communicate with the inner surface of the wall elements of both of the parallel rows. In this embodiment, at least one brace depends from a point of connection on a first side of the central portion (relative to the longitudinal mid-line of the central portion), and at least one other brace depends from a point of connection on the other side of the mid-line of the central portion. The braces of this embodiment do not extend across the mid-line of the central portion, but instead each brace extends generally towards the supplementary engagement means of the nearest wall element. The resulting structure provides for the bracing of both of the parallel rows of wall elements against the weight of the poured concrete (so as to limit the distension of the central portions of the wall elements of both rows). At the same time, excess use of materials (such as would result from the extension of the braces across the mid-line) is avoided.

In a similar embodiment of the invention, at least two braces depend from at least two points of connection on each side of the central portion (for a total of at least four braces associated at at least four points of connection with the central portion of the connecting member). Each braces extends towards the supplementary engagement means of a different wall element, two of which elements are associated in end-to-end relationship about each of the terminal connectors of the connecting member. As in the embodiment discussed immediately above, the braces of this embodiment preferably do not extend across the mid-line of the central portion so as to avoid the excess use of materials.

In another embodiment, two braces depend from each of two points of connection, with one point of connection being on each side of the mid-line (for a total of four braces associated at two points of connection). As in the embodiment discussed above, each of the four associated braces extend towards the supplementary engagement means of a different wall element. This configuration of braces into opposing pairs is preferable to the configuration in which each brace has its own point of connection (as discussed immediately above) in cases where the connecting member is made of a comparatively flexible material (such as thin PVC) because the tensile forces exerted upon the braces by the weight of the concrete on the wall elements will tend to balance out and limit the distortion of the central portion. Distortions of the central portion may lead to variations in the thickness of the resultant wall or other concrete structure.

Embodiments of the inventive connecting member also have application in the connection of two parallel rows of wall elements of a known formwork assembly of the sort in which the concrete (when poured) will communicate with the inner surface of the wall elements of only one row, and in which a layer of insulating or other material communicates with or sits adjacent the inner surface of the wall elements of the other row. Since the insulation layer of wall structures of this sort offers at least some measure of resistance against distension under the weight of the poured concrete of the central portion of the wall elements that are adjacent the insulation layer (i.e. pillowing), it is not usually necessary to brace these wall elements of the formork assembly. Accordingly, inventive connecting members adapted for use with known formwork assemblies of this type will typically include no braces that extend to the wall elements on the insulation layer side of the wall or structure. The various embodiments discussed above (for use in non-insulated formwork assemblies) can be readily adapted for use in insulated formwork assemblies by a person skilled in the art. In order to conserve material from which the inventive connecting member is made, the central portion may include auxiliary perforations (in addition to the primary zone of perforation) near the terminal connector that is adjacent the insulation side of the formwork assembly. Such auxiliary perforations are generally not intended for the placement of reinforcement rods.

A suitable length and point of connection for the at least one brace of any of the aforesaid embodiments may, of course, also be selected by a person skilled in the art having regard to the discussion above so as to co-operate with convex or concave wall elements, or wall elements having any other simple or complex shape. Such wall elements may be used in situations where it is desired to create a concrete structure having a scalloped appearance (in the case of concave or convex wall elements) or some other ornamental appearance.

Nibs, grooves, or other indentations or protrusions that aid in holding a reinforcing rod in position during the tying of the rod into place on the connecting member may be included within individual perforations in the zone of perforation. The overall elongate (height) dimension of individual perforations is selected in part with reference to the material from which the connecting member is manufactured, but in any event is selected to be sufficiently large to permit the placement of reinforcement rods that are of suitable dimension relative to the structure being constructed. The longitudinal (width) dimension of individual perforations may also be made discontinuous along their elongate (height) dimension, especially in cases where the elongate (height) dimension of individual perforations is relatively large, by the inclusion of inward puckers that provide additional thickness to the connecting member in regions that are adjacent the individual perforations. This additional thickness limits possible vertical pillowing along the elongate (height) dimension of the formwork.

Other forms and aspects of the invention will be appreciated by those skilled in the art having reference to the following detailed description of the preferred embodiments and to the claims. BRIEF DESCRIPTION OF THE DRAWINGS

In drawings that illustrate embodiments of the invention:

Figure 1 is a plan view of stay-in-place formwork in accordance with the prior art;

Figure 2 is a frontal elevation of a connecting member in accordance with the prior art;

Figure 3 is a plan view of a connecting member in accordance with one embodiment of the invention;

Figure 4 is a frontal elevation of the connecting member of Figure 3;

Figure 5 is a plan view of a connecting member in accordance with another embodiment of the invention;

Figure 6 is a frontal elevation of the connecting member of Figure 5;

Figure 7 is a plan view of stay-in-place formwork including connecting members in accordance with embodiments of the invention.

Figure 8 is a plan view of stay-in-place formwork including connecting members in accordance with embodiments of the invention, and showing the location of placed reinforcement rods.

Figure 9 is a plan view of a connecting member in accordance with one embodiment of the invention;

Figure 10 is a plan view of stay-in-place formwork including connecting members in accordance with the embodiment of Figure 9.

Figure 11 is a frontal elevation of a connecting member in accordance with an embodiment of the invention;

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to Figure 1 , there is illustrated one completed cell of a PVC formwork assembly in accordance with the prior art. The formwork assembly includes discrete wall elements 10 that are assembled in end-to-end relationship to define a segment of an inner or outer wall surface (12, 14) of the resulting structure. The wall elements 10 are interconnected and held in spaced-apart relationship by connecting members 16 via complementary terminal connectors 18, 20 that are present respectively along the longitudinal edges of the wall elements and connecting members. Internal braces 22 extending between connecting members 16 and the inner surface of wall elements 10 are similarly interconnected via compatible attachment points and engagement means 24, 26 and 28,30 extending along the elongate dimension (height) of the braces, members, and elements. As noted above, since the formwork is constructed of thin PVC material, the attachment points 24 for the braces 22 must be sufficiently offset from the nearest terminal connector to limit bending of the brace 22 under the weight of the poured concrete. In the prior art embodiment illustrated in Figure 1, the attachment points 24 are offset a sufficient distance from terminal connectors 18, 20 to permit the braces 22 to depend at a 45° angle from the connecting member 16.

As seen in Figure 2, prior art connecting member 16 includes central perforations 32 to permit the cross-flow of concrete between cells of the formwork assembly, and to permit the placement of reinforcement rods (not shown). Auxiliary perforations 34 are also present; these permit the cross-flow of concrete, but are not suitably large to allow for the placement of of reinforcement rods. The presence of engagement means 24 along the elongate dimension (height) of connecting member 16 limits the longitudinal dimension (width) of the central perforations 32. As discussed previously, this in turn makes it difficult or impossible to place reinforcement rods at or near the optimal placement position for a given structure. It also limits the maximal cross-flow of concrete from one cell of formwork to another. Figures 3 and 4 illustrate a connecting member 36 in accordance with an embodiment of the present invention that is suitable for connecting together two generally parallel rows of wall elements of a known formwork assembly of the sort in which the concrete (when poured) will communicate with the inner surface of the wall elements of both of the parallel rows. Figures 5 and 6 illustrate a connecting member 38 in accordance with another embodiment of the present invention that is suitable for connecting together two parallel rows of wall elements of a known formwork assembly of the sort in which the concrete (when poured) will communicate with the inner surface of the wall elements of only one row, and in which a layer of insulating or other material communicates with or sits adjacent the inner surface of the wall elements of the other row.

Connecting members 36 and 38 are manufactured of PVC material and, as is best seen in Figures 3 and 5, the central portions 40 and 42 (of connecting members 36 and 38 respectively) are accordingly (given the relatively pliable nature of PVC material) integral with braces 44 and 46 (of connecting members 36 and 38 respectively) at their points of connection 45 and 47 (of connecting members 36 and 38 respectively). As noted previously, the connection between the braces and the central portion of a connecting member in accordance with the invention may be integral or releasable depending upon the physical characteristics of the material from which the connecting member is constructed.

As best seen in Figures 4 and 6, the zones of perforation 48 and 50 (of connecting members 36 and 38 respectively) extend through points of connection 45 and 47. As outlined previously, this facilitates the cross-flow of poured concrete and permits the placement of reinforcement rods at or near the optimal placement position for a given structure.

A representative reinforcement rod 51 is shown cradled by optional nib 52 in Figures 4 and 6. Auxiliary perforations 54 (intended primarily to conserve material) are shown in Figure 6, as are ridges 56 that serve to locate the insulating material

(shown in Figure 7) adjacent one of the outer and inner wall surfaces. Terminal connectors 20 and engagement means 30 of the sort discussed above in relation to the prior art formwork assembly of Figures 1 and 2 are also present on connecting members 36 and 38. These connectors and engagement means cooperate with the formwork system of Canadian patent no. 2218600. However, as previously noted, different terminal connectors and engagement means may be selected to suit other modular formwork systems or applications.

Figure 7 shows a segment of formwork assembly utilizing connecting member 38, and Figure 8 shows a segment of formwork assembly utilizing connecting member 36. The wall elements and other formwork elements shown in Figures 7 and 8 correspond to the prior art formwork system of Canadian patent no. 2218600. Figure 8 also illustrates the placement of reinforcement rods 51 at or near the optimal placement position for a typical commercial or residential wall structure.

Figures 9 and 10 illustrate a connecting member 58 having shortened braces 60 dimensioned to cooperate with concave wall elements 62 that permit the construction of a wall structure having a scalloped appearance. Apart from the presence of shortened braces 60, connecting member 58 is otherwise the same as connecting member 36.

Figure 11 illustrates a connecting member 64 in which the longitudinal

(width) dimension of perforations 66 is discontinuous along their elongate (height) dimension due to the inclusion of inward puckers 68 that provide additional thickness to one side of the connecting member in regions adjacent the perforations. Although the embodiment of Figure 11 shows puckers 68 on only one side of connecting member 64, such puckers may of course be included on both sides of a connecting member in accordance with the invention.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A connecting member for use in a stay-in-place modular formwork assembly comprising:

an elongate central portion having terminal connectors at either longitudinal edge, each terminal connector being adapted for the mating engagement of a complementary terminal connector at a selected longitudinal edge of at least one wall element of the modular formwork assembly;

at least one elongate brace connected to and depending from the central portion from a point of connection offset from the terminal connectors, the brace having engagement means at its distal end adapted for the mating engagement of supplementary engagement means on the inner surface of at least one wall element of the modular formwork assembly;

the central portion and the brace being perforated within a zone of perforation to permit the cross-flow of fluids (e.g., concrete) and the cross-placement of solids (e.g., reinforcement rods), said zone of perforation extending through the point of connection of the brace and the flat central portion.

2. The connecting member of claim 1 wherein the brace at the point of connection is integral with the central portion.

3. The connecting member of claim 1 wherein the point of connection of the at least one brace is offset more than one inch from the nearest terminal connector, and wherein the zone of perforation extends between at least the mid-point of the central portion, through the point of connection, to about one inch from the nearest terminal connector.

4. The connecting member of one of claims 1 and 2 wherein plural braces depend from a single point of connection.

5. The connecting member of one of claims 1 and 2 wherein plural braces depend from plural points of connection.

6. The connecting member of claim 5 wherein at least one point of connection is located on either side of the longitudinal mid-point of the central portion.

7. The connecting member of claim 1 wherein the brace does not extend across the longitudinal mid-point of the central portion.

8. The connecting member of claim 1 wherein the elongate central portion and the at least one brace are perforated across at least 60% of the elongate surface area of the central portion and the at least one brace.

9. The connecting member of claim 1 wherein the dimension of the perforations is of a selected suitable size to permit the placement of a reinforcement rod.

10. The connecting member of claim 9 wherein the perforations include at least one nib to facilitate the placement of a reinforcement rod.

11. The connecting member of claim 11 wherein the perforations include inward puckers along the elongate dimension of the connecting member.