AU2016210740B2

AU2016210740B2 - An Improved Cast-In Member

Info

Publication number: AU2016210740B2
Application number: AU2016210740A
Authority: AU
Inventors: Derek Trent Lawley
Original assignee: ITW New Zealand Ltd
Current assignee: ITW New Zealand Ltd
Priority date: 2007-09-05
Filing date: 2016-08-05
Publication date: 2018-07-12
Anticipated expiration: 2028-09-05
Also published as: AU2016210740A1; NZ561172A; AU2008212012A1

Abstract

232478AUDIV2/91 The present invention relates to a cast-in member for joining cementitious building elements such as pre-fabricated segments of a building. The cast-in member is adapted to receive a connection element comprising a shaft and a head formed on at least one end of the shaft and is characterised in that it defines an internal volume comprising an insertion zone and a retention zone in communication with the insertion zone, the insertion zone being adapted to receive the head of the connection element, and the retention zone being adapted to receive and retain the head of the connection element.

Description

AN IMPROVED CAST-IN MEMBER Technical Field

The present invention relates to a cast-in member for cementitious building elements. In particular, this invention relates to a member for joining cementitious building elements such as pre-fabricated segments of a building. These pre-fabricated segments could be floor, wall or roof segments, or other building elements.

Background Art

Pre-fabricated building elements are commonly used in the construction industry.

They are advantageous because they can be prepared off-site to pre-determined dimensions. They are then able to be easily assembled on-site allowing quick and simple construction of buildings and other structures.

Commonly these pre-fabricated building elements are manufactured from concrete or Engineered Cementitious Composite (ECC) material and are used as floor, roof and wall sections in building methods known in the art as “tilt up construction” and/or “precast construction”. These sections are usually manufactured in a flat concrete/cementitious casting mould. Once the section has set there is a need to move them in-situ and, in the case of a wall section, this predominately involves tilting upwards and connecting to the foundation of the building. Additional levels may be created by joining floor elements to those wall sections, and further wall sections to the floor elements in known fashion.

Pre-fabricated wall sections and floor sections are commonly joined together using “Starter Bars” or “Reo Bars”. These bars are usually formed from a length of steel rod which is bent at one end to form a hook. They are embedded into the pre-fabricated section during the casting process with part of the bar exposed. Building sections pre-fabricated in this way can thus be aligned during construction and the exposed part of the bars sealed to the adjacent section(s) via a topping pad of concrete (where a wall section is joined to a floor or ceiling section) or an infill (between adjacent wall sections) to provide a ductile joint between adjacent sections. A topping pad is typically a layer of concrete 75 to 100mm thick.

However, there are a number of problems associated with this method. Firstly, the bars (which are embedded into the pre-fabricated element as aforesaid) protrude from the sections which can cause difficulties when aligning and manoeuvring the sections into place during the ‘tilt up’ phase of construction, and with aligning floor sections to wall sections when adding additional levels to a building. To alleviate this problem, the bars are often bent out of the way until they are required. However, when the bars are re-straightened it is not uncommon for many (typically at least one third) to break owing to stress fractures in the metal caused by this bending and re-bending.

To address this problem Reid Construction Systems Limited of New Zealand developed the “Reid Bar System” in 1990. The Reid Bar System comprises an internally threaded insert and corresponding externally threaded bar (known as a “Reid Bar”). The threaded inserts are cast into the section during manufacture. Once the section is manoeuvred into the place the Reid Bar can be wound into the threaded insert prior to pouring the final infill concrete section/topping pad.

It is desirable for any such system of joining sections to provide a flexible or ductile joint to allow movement, for example the natural movement of a building with the wind or in an earthquake. If the connection point between the sections is not sufficiently flexible, this can be mirrored in cracks which can develop in the topping pad / infill. A disadvantage of the Reid Bar system is that the smallest diameter Reid Bar is 12mm. These bars are considered too strong for the desired application, in that at least 5 tonnes of force must be applied to yield (or bend) that diameter bar. Thus in a typical application (using 4 bars to attach a floor section to a wall section) 20 tonnes of force must be applied before the Reid Bars will fail in a ductile manner. For this reason, the Reid Bar System does not provide appropriate yield during a building’s natural movement in wind or in the event of an earthquake. This can lead to topping pads cracking through the pre-stressed floor, infills between adjacent wall sections cracking and, in extreme cases, destruction of the floor and wall sections themselves.

The applicant has observed that it would be advantageous to have a cast-in member to connect pre-fabricated concrete building elements which addresses the foregoing problems.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or 'comprising' is used in relation to one or more steps in a method or process.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

Disclosure of Invention

According to one aspect of the present invention there is provided a cast-in connection member for pre-fabricated cementitious building elements the connection member being adapted to receive a connection element comprising a shaft and a head formed on at least one end of the shaft; characterised in that: • the connection member defines an internal volume comprising an insertion zone and a retention zone in communication with the insertion zone; • the insertion zone is adapted to receive the head of the connection element; and • the retention zone is adapted to receive and retain the head of the connection element.

Preferably, the pre-fabricated building elements may be wall and floor segments of a building.

Preferably, the cast-in connection member may incorporate means to engage with reinforcing steel bars or rods. Still more preferably, the means to engage may be exterior protrusions adapted to substantially encircle and engage with the reinforcing steel bars or rods.

Preferably, the cast-in connection member may include a body with at least one exterior projection configured both to stiffen the side walls of the body and provide a means by which cementitious material can key to the body once set into the building element.

Preferably, the connection member may include a means for sealing the internal volume so as to prevent cementitious material entering the internal volume of the cast-in connection member during the casting mould process.

Preferably, an interior rib extends into the retention zone of the internal volume to act against the head of the connection element inserted into the retention zone.

Preferably, a bonding agent may be inserted into the insertion and retention zones to provide an additional securing means for the connection element.

In preferred embodiments the cast-in connection member may be manufactured from injection moulded plastic.

Brief Description of Drawings

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1: shows a diagrammatic representation of a preferred embodiment of the cast-in member of the present invention comprising a main body, a base portion and a sealing cap;

Figure 2: shows a diagrammatic representation of the base element of the cast-in member of Figure 1;

Figure 3: shows a diagrammatic representation of the sealing cap element of the cast-in member of Figure 1;

Figure 4: shows a diagrammatic representation of the body element of the cast-in member of Figure 1;

Figure 4A: shows a diagrammatic representation of the opposite end of the body element viewed in Figure 4;

Figure 5: shows a diagrammatic representation of an application of the cast-in member of the present invention in which it has been used for the connection of a pre-fabricated wall element to a pre-fabricated floor element;

Figure 6: shows a diagrammatic representation of another application of the present invention in which the cast-in member has been used for the structural connection of in-situ wall to wall elements;

Figure 7 shows a diagrammatic representation of a further application of the present invention in which the cast-in member has been used for a shear beam connection; and

Figure 8 shows a side profile view of the same application of the present invention depicted in Figure 7.

Detailed Description Including Best Modes A preferred embodiment of the present invention is depicted in Figures 1 -4.

Throughout the present specification the term “cast-in connection member” should be understood to mean a component part of building or construction configured to be placed into a casting mould of cementitious material (such as concrete, Engineered Cementitious Composite (ECC) or other such materials) and cast into those materials during the process of manufacturing a building element from those materials.

Throughout the present specification the term ‘connection element’ should be understood to mean an implement shaped so as to include at least one elongated shaft portion and at least one head portion formed on at least one end of the shaft of greater diameter than the diameter of the shaft. Such ‘connection elements’ will be well known to either those skilled in the art. For example, a common connection element, known as a ‘foot anchor1, comprises a circular shaft with a head at one end of the shaft and a foot at the other end of the shaft, the head and foot being of a greater diameter than the diameter of the shaft (i.e. similar in appearance to a dumb bell). For ease of reference throughout the specification, a connection element may now simply be referred to as a foot anchor.

Throughout the current specification the term pre-fabricated should be understood to mean any process of fabrication in which the building element is substantially preformed prior to its use in the construction application. As will be apparent to those skilled in the art this may occur on or off site.

In preferred embodiments the connection member is manufactured out of injection moulded plastic. However, this should not be seen as a limitation on the embodiments envisaged for this invention as any type of material (such as resin, ABS plastic, galvanised steel, aluminium, composite material or any other such material) could conceivably be used for this invention.

Figures 1 - 4 depict a preferred embodiment of the cast-in connection member of the present invention. With reference to Figure 1 the connection member (generally indicated by arrow 1) comprises body (2) base (3) and (optional) cap (4).

Body

The body (seen best in Figures 4 and 4A) is substantially “key hole” shaped and comprises side walls (2A) joined to base wall (2B) via a curved top section (2C) so as to define an internal volume (5). Body (2) also features flanged portions (6) on each of the side walls (2A) which create two distinct zones of internal volume (5): an insertion zone (5A) corresponding to the interior of curved top wall (2C) and adapted to receive the head of a foot anchor (not shown) and a retention zone (5B) formed by the internal surfaces of flanged portions (6) of body (2) and adapted to retain the head of the foot anchor within the internal volume in the manner described below.

Retention zone (5B) is best seen in Figure 4A which depicts an opposite end view of the body element to that shown in Figure 4.

Body (2) also preferably includes at least one exterior projection (7) configured both to stiffen the side walls of body (2) so as to prevent flexure during the casting process and to provide a means by which the concrete or cementitious material can key to the body (2) once set into the building element (not shown).

Base

Figure 2 depicts the base (3) of Figure 1 in further detail. Base (3) is adapted to be clip fit engaged on the corresponding end of body (2) via recesses 8 adapted to receive corresponding projections (8A) on the body (2) (best seen in Figure 4) so as to seal one end of body (2) and substantially seal internal volume (5) at that corresponding end. Base (3) also features interior rib (9) and (optionally) external projections (10). As will be apparent to those skilled in the art, when base (3) is clip fit engaged to body (2) interior rib (9) will extend into the retention zone (5B) of internal volume (5) and act against the head of a foot anchor inserted into that retention zone (5B) in a manner described in more detail below.

Exterior projections (10) of base (3) are shaped and dimensioned so as to receive reinforcing bars (not shown) which may also be cast in to the concrete building element in known fashion so as to provide additional strength to that building element. As these reinforcing bars are predominantly lengths of circular bar, projections (10) are similarly depicted defining a substantially circular area between them. Flowever, it will be appreciated by those skilled in the art that any manner of shape can be defined by protrusions (10) depending on the corresponding shape of the reinforcing material they are adapted to receive. A further advantage of exterior projections (10) is that, by anchoring the base (3) (and in turn the body (2) and cap (4)) to the reinforcing members prior to casting of the building element, they provide a means by which the connection member (1) can be located within the casting mould (not shown).

Cap

Figure 3 depicts a cap (4) comprising end wall (4A) and continuous side wall (4B) shaped so as to correspond to the cross section of internal volume (5) of body (2) and dimensioned so that side wall (4A) can be received in close fit but removable engagement with the interior surface of side walls (2A and 2B) and curved top wall (2C) of body (2) so as to substantially seal one end of internal volume (5) of body (2) opposite the base (3). As will be appreciated by those skilled in the art sealing the internal volume (5) in this manner will prevent cementitious material or other such material filling the insertion (5A) and retention (5B) zones during the casting process. The cap (4) may be removed once the cementitious material has set or prior to insertion of a foot anchor in the manner described below.

Applications

The present invention is designed to be used as follows: • The cast-in member (1) is first assembled by attaching base (3) and cap (4) to body (2) as shown in Figure 1. • The cast-in member is then placed within a casting mould of a concrete element prior to pouring. If the cast-in member includes protrusions (10) then it may optionally be attached to reinforcing steel also within the casting mould in the manner previously described. The location of the cast-in member within the mould will depend on the building element being manufactured and the location at which it will need to be connected to an adjacent element. Some variations are depicted in the applications shown in Figures 5 - 8 of this specification. Further variations will be apparent to those skilled in the art. However in all such variations it is important that the cap end of the body remains exposed following casting of the building element. • Following positioning of the cast-in member within the casting mould a cementitious material is then poured into the casting mould and allowed to cure. In preferred embodiments the pre-fabricated building elements may be manufactured from Engineered Cementitious Composite (ECC) material. However, this should not be seen as a limitation on the current invention. Other materials envisaged for the pre-fabricated building element include concrete, plaster or other suitable cementitious materials as will be apparent to those skilled in the art. • Once the cementitious material has cured, the cast-in member (1) will be embedded into the pre-fabricated building element. The cap member (4) may be removed at this point, or after the building element has been removed from the mould, moved into position and aligned with a further building element for connection. • As will be appreciated by those skilled in the art, removal of the cap (4) will expose the insertion (5A) and retention (5B) zones. This allows the cast-in member (1) to receive the head or foot of a foot anchor once the building elements have been aligned. Specifically, one end (either head or foot) of the foot anchor is inserted into the insertion zone (5A) corresponding to the interior of curved top wall (2C, best seen in Figure 4) formed by the body (2) of the cast-in member (1) until it abuts the base (3). The foot anchor is then slid laterally (i.e. towards end wall (2B)) so that the head moves through the retention zone (5B) formed by the internal surfaces of flanged portions (6) of body (2). In this manner, the head or foot of the foot anchor (14) engages with both the interior rib (9, best seen in Figure 2) of base (3) and the internal surfaces of flanges (6) (best seen in Figure 4A) of body (2) thereby retaining (or capturing) the foot anchor within the internal volume (5) of body (2). It should be appreciated by those skilled in the art that the insertion (5A) and retention (5B) zones can communicate with either the head or foot portion of any suitable connection element. • In addition, a bonding agent (such as a cementitious material, epoxy resin or acrylic grout) may be inserted into insertion (5A) and retention (5B) zones during the course of inserting the foot anchor so as to (at least partially) fill the internal volume (5) of body (2) and provide an additional securing means for the foot anchor (14).

Three specific applications of the present invention are now described with reference to Figures 5 -8.

Figure 5: Wall to floor connection

Figure 5 depicts use of the cast-in member (1) to join a pre-fabricated wall element (11) to a pre-fabricated floor element (12). It should be appreciated by those skilled in the art that the number of cast-in members (1) shown in this (and subsequent) example(s) is non-limiting.

Referring to Figure 5, the cast-in members (1) are positioned in the casting mould (not shown) such that the cap ends of the cast-in members (1) are located flush with the front face of the wall element (11) and at a suitable height so that, when the foot anchors (14) are inserted into the cast-in members, they rest on top of the corresponding floor section to be joined in the manner depicted in Figure 5. In preferred applications, the cast-in members (1) are also configured within the mould so that the insertion zones (5A) of the cast-in members (1) are at the top when the wall element (11) is in-situ as depicted.

Following casting of the wall element and removal from the mould the wall (11) and floor (12) sections (Dycore floor or equivalent) must be aligned, for example by crane and/or skilled construction personnel. It should be appreciated that the Dycore floor (12) may be secured perpendicular to the pre-fabricated wall (11) by any method apparent to ‘those skilled in the art’. For example, Dycore sections are typically delivered to a site and set on a bearing angle of corbel (13) which has been bolted to the pre-fabricated wall (11) below the row of cast-in members (1).

Following alignment with the wall element (11) the pre-fabricated floor element (12) is structurally connected to the pre-fabricated wall element (11) by insertion of the foot anchors (14) into the cast-in members (1) of the wall element (11) in the manner previously described.

The distal end of the foot anchor (14) which is not retained within the internal volume (5) of the body (2) may also be tied to reinforcement bars (not shown) which are laid in a specified grid over the top of the Dycore floor (12) sections.

Finally, a further cementitious floor layer (15) known as a “topping layer” is poured over the Dycore floor (12) at a thickness as thin as 25 mm. This layer (15) covers the foot anchor (14) which provides a ductile joint between the connected pre-fabricated building elements (11 and 12). Also, the final overlay of cementitious material creates a continuous wall to floor fully reinforced and connected membrane. A structural connection prepared as described above allows for development of shear friction. The advantage of this invention is that the floor can perform as a shear diaphragm and create a structural load path distributed between the wall and floor. For example, the structural connection between the wall and floor will give adequate forgiveness during a building’s natural movement in wind or in the event of an earthquake.

Figure 6: wall to wall connection

Figure 6 shows use of the cast-in member (1) to join two corresponding pre-fabricated wall elements (12A and 12B). This type of structural connection is known in the industry as a ‘stitch joint’.

The cast-in member (1) is embedded into opposite side faces of pre-fabricated wall elements (12A and 12B) in the manner described previously. The wall elements (12A and 12B) are positioned and aligned adjacent to each other in known fashion.

As described previously, one end (either head or foot) of the foot anchor (14) is slid into the insertion zone (5A) and securely retained in the retention zone (5B) of each of the cast-in members (1).

The foot anchors (14) are held substantially horizontal in the retention zone (5B) of the cast-in member (1) by the interior rib (9) acting against either head or foot of the foot anchor (14) and capturing it between the rib (9) and internal surfaces of flanges (6) as described previously.

Following the insertion of the foot anchors (14) into the cast-in member (1), the gap between the wall sections (12A and 12B) is suitably boxed and filled with cementitious material (not shown) in a manner known to those skilled in the art. The cementitious material covers the foot anchors (14) and is allowed to cure. The boxing is removed to reveal a ductile joint between the wall elements (12A and 12B).

Figures 7 and 8: Shear beam connection

Figures 7 and 8 show use of the cast-in member (1) in a pre-fabricated wall element (11A) to provide a shear beam connection.

The cast-in member (1) is embedded into the front face of a pre-fabricated wall element (11A) as previously described. In this example, the connection element (16) contains an external thread on the shaft (ie in similar fashion to a bolt). As described previously, the head of the connection element (16) is slid into the insertion zone (5A) of the cast-in member (1) which is embedded into the side of the pre-fabricated wall element (11A). The head of the connection element (16) engages with the interior rib (9) and flanges (6) and is held securely in the retention zone (5B) of the cast-in member (1). A plate (17) with aperture is inserted on to the distal end of the connection element (16) (the end which is not retained within the internal volume (5) of the body (2)). Typically, the plate (17) provides an attachment point for another structure. For example, a steel beam or equivalent (not shown) can be welded to the plate (17). A washer (18) with larger external diameter than the aperture of plate (17) is also inserted onto the distal end of the connection element (16) against the aperture of plate (17). A nut (19) is then threaded onto the distal end of the connection element (16) to secure the plate (17) to the pre-fabricated wall element (11 A).

There are many advantages associated with this invention: • The cast-in connection member is pre-cast and embedded flush within the prefabricated building element to provide a simple method for making structural connections to these building elements.

Embedding the member flush into the pre-fabricated element not only ensures that the connection member is immediately available for use following alignment of building elements, but also means that it does not have any exterior protrusions that can cause difficulties when aligning and/or manoeuvring the building element into position on a construction site. • As the foot anchor is not inserted until after alignment, there is no longer the requirement to bend the foot anchor to facilitate manoeuvring the building elements into position. This will avoid weakening or breakage. • The cast-in member leads to a more ductile connection or joint as the hollow body of the cast-in connection member allows for additional movement or ‘play’ between the engaging portion and the connection element (foot anchor).

The ductilability of this connection is advantageous in situations of natural building movement such as high winds or extreme forces of nature such as earthquakes. A building which has connections with greater flexibility will typically have reduced structural damage following such event. • The use of the cast-in member in combination with ECC material will act as a load sharing diaphragm. This allows for a thinner topping pad to be applied to the reinforced concrete floor as there is no longer a requirement to cover the starter bars or other reinforcing components used in prior art systems after the floor element is located in-situ. A thinner screed of concrete also leads to greater ductilability of the pre-stressed building elements. • The cast-in connection member provides a convenient method of connecting pre-fabricated building elements as connection can be accomplished by simply aligning and inserting the connection element into the respective cast-in member.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims. For example: • It will be appreciated by those skilled in the art that the base (3) and body (2) may be separately formed, as depicted in the preferred embodiment, or form part of the same product in a unitary construction. • Similarly the base may be formed with or without projections (10). • The body of the cast-in connection member need not necessarily be of a “keyhole” shape. As will be appreciated by those skilled in the art it may be of any shape, dimension and volume to accommodate any type of connection element known to persons skilled in the art or industry. Furthermore, the cast-in connection member may be of a continuous extruded length embedded into the prefabricated building element. • In preferred embodiments of the present invention the pre-fabricated building elements may be wall and floor segments of a building. However, again this should not be seen as a limitation on the embodiments for this invention. Other embodiments envisaged include pre-fabricated roof segments, footings of a building, or any other aspect of a building or other structure employing cementitious materials.

Other variations will be apparent to those skilled in the art.

Claims

WHAT WE CLAIM IS:

1. A cast-in connection member for pre-fabricated cementitious building elements the connection member being adapted to receive a connection element comprising a shaft and a head formed on at least one end of the shaft; characterised in that: • the connection member defines an internal volume comprising an insertion zone and a retention zone in communication with the insertion zone; • the insertion zone is adapted to, in use, receive the head of the connection element in a first inserted position from a first direction; • the retention zone is adapted to, in use, receive and retain the head of the connection element within the retention zone in a second retained position by movement of the head and shaft in a second direction from the first inserted position to the second retained position, the second direction differing from the first direction.
2. A cast-in connection member as claimed in claim 1, wherein the pre-fabricated building elements are wall and floor segments of a building.
3. A cast-in connection member as claimed in claim 1 or claim 2, wherein the cast-in connection member includes means to engage with reinforcing steel bars or rods.
4. A cast-in connection member as claimed in claim 3, wherein the means to engage are exterior protrusions adapted to substantially encircle and engage with the reinforcing steel bars or rods.
5. A cast-in connection member as claimed in any one of claims 1 to 4, wherein the connection member includes at least one exterior projection configured to stiffen the side walls of the body.
6. A cast-in connection member as claimed in any one of claims 1 to 5, wherein the connection member includes at least one exterior projection configured to provide a means by which cementitious material can key to the member once set into the building element.
7. A cast-in connection member as claimed in any one of claims 1 to 6, wherein the connection member includes means for sealing the internal volume.
8. The cast-in connection member as claimed in any one of claims 1 to 7, wherein the one or more surfaces include at least one projection configured to bear against the head of the connection element inserted into the retention zone.
9. The cast-in connection member as claimed in any one of claims 1 to 7, wherein the one or more surfaces include at least one flange configured to bear against the head of the connection element inserted into the retention zone.
10. A cast-in connection member as claimed in any one of claims 1 to 9, wherein the connection member is manufactured from injection moulded plastic.