AU2019100937A4

AU2019100937A4 - Joint for concrete slabs

Info

Publication number: AU2019100937A4
Application number: AU2019100937A
Authority: AU
Inventors: Andrew Keen; Abbots MEAD
Original assignee: Rcr Flooring Products Ltd
Current assignee: Rcr Flooring Products Ltd
Priority date: 2019-08-21
Filing date: 2019-08-21
Publication date: 2019-10-10
Anticipated expiration: 2027-08-21

Abstract

Abstract JOINT FOR CONCRETE SLABS A concrete slab joint has a first and a second galvanised steel strip 2, 3. At the top of each strip there is an anchor 4 that provides support for top plates on the first and second strips 5, 6. The anchor projects horizontally outward with a subsequent downward bend at an angle. It has several regularly spaced cut-outs 7 along its length. The supporting beams 8 on either side of the cut-outs provide strength. The strips are connected via frangible screws 9, placed at regular intervals along the strips, such that the strip faces mate. Both the first and second strips have top plates 5, 6 respectively, fast with their horizontal projections. Both sides of the plates are sinusoidal in shape. Figure 1 <2 7/~"A (3

Description

JOINT FOR CONCRETE SLABS

FIELD

The present disclosure relates to a joint system for concrete slabs.

BACKGROUND

The reference to prior art in this specification is not and should not be taken as an acknowledgment or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia or in any other country.

Use of concrete slabs as flooring material for warehouses and other large-scale buildings is commonplace. However, impact damage at slab joints is a problem. As is well known, concrete is strong in compression, but less strong in tension and shear. Sharp edges between a horizontal face of a concrete slab and its vertical face are known as “arrises”. Application of vertical load to a horizontal concrete slab face close to its free vertical face results in shear stress at the respective arris, where stress can be higher than the concrete is able to withstand. The result is the cracking and crumbling of the arris, a process known as “spalling”.

In this regard, much of the stress in unprotected arrises arises due to vehicle wheels dropping slightly into the gaps between the slabs and suddenly impacting the arris towards which the wheel is rolling. The individual wheels drop a little, but the cumulative fatigue stressing at the arris can result in comparatively rapid spalling, in particular where tyres are solid as opposed to pneumatic.

The object of the present disclosure is to describe a joint for concrete slabs that in some aspects may provide an improvement over known joints or provide the public with a useful or commercial choice.

DEFINITION

In the specification the term “comprising” shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

SUMMARY

According to the disclosure there is provided a joint for concrete slabs, the system comprising:

• a first strip and a second strip adapted for concrete to be cast against on respective sides of the joint, • frangible means for connecting the first and second strips to each other, • at least one top plate on each of the strips for armouring of the joint, • at least one anchor on each strip, oppositely extending therefrom for continuous anchorage in the concrete, the at least one anchor subsequently extending at a downwards angle, • at least one dowel extending through, and outwardly from, the strips for load transfer across the joint, wherein the top plates are shaped as complementary waves, the peaks of which extend over opposite strips at least prior to joint opening.

Whilst it is envisaged that complementary mating inner edges of the top plates could form any regular shape, such as trapezoidal, triangular or rectangular, it is preferred that the shape formed is sinusoidal for improved load transfer.

It is possible that there is only one strip in the joint, from which the other joint elements extend. Conceivably, the single strip is of regular wave shape or equivalent regular shape along its length. Nonetheless, it is preferable that there are two strips with inner mating faces.

It is imagined that outer edges of the top plates could be straight, extending parallel to the edges of the concrete slab. Possibly, the outside edges of the top plates are of equivalent sinusoidal wave shape as the inside edges. It is preferable however that the outside edges are of a wider wave shape to the inside edges to reduce localised impact.

Normally the strips are of steel. In cases where water ingress is likely, the strips could be of galvanised steel. Alternatively, they can also be of stainless steel or mild steel.

The joint will normally include dowels for improved load transfer across the joint, extending into the two sections of two adjacent concrete slabs, for improved vertical load transfer in use. The dowels may be any type of dowels, but it is preferred that the dowels are plate dowels.

The strips may have dowels connected to the strip faces, extending outwardly therefrom, but it is preferred that the dowels extend through both of the strips, a length of dowel oppositely extending from each strip face.

To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of the joint;

Figure 2 is a plan view of the underside of the joint;

Figure 3 is a plan view of the top of the joint;

Figure 4 is a side view of the joint;

Figure 5 is the other side view of the joint;

Figure 6 is an end view of the joint;

Figure 7 is the other end view of the joint; and

Figure 8 is a perspective view of the joint in use.

Referring to the Figures, there is a joint for reinforcement of concrete slabs 1 having a first and a second galvanised steel strip 2, 3 respectively. At the top of each strip there is an anchor 4 that provides support for top plates on the first and second strips 5, 6. The anchor projects horizontally outward with a subsequent downward bend at an angle, such that it is located within the concrete when it is poured against the strips, and anchored therein once the concrete hardens.

The anchor has several regularly spaced cut-outs 7 along its length, as clearly shown in Figures 1 to 5. The supporting beams 8 on either side of the cut-outs provide sufficient rigidity and strength to the joint system, whilst the presence of the cut-outs allows for an overall reduction in weight.

The first and second strips are connected via screws 9, placed at regular intervals along the strips, such that the strip faces mate. This type of attachment mechanism allows for easy assembly and disassembly of the joint system, allowing any excess part of the system to be removed and kept for a subsequent installation. The screws 9 are frangible for breaking when the concrete cures and shrinks, opening the joint. They are of nylon with a failure force of approximately 2,250 Newtons.

A separate extension plate 10 is attached to the lower part of the first strip 2, along its entire length. The plate has an outwardly projecting lip 11 at the bottom end of the plate for anchoring of the first strip within the concrete slab. This extension plate can be set to various heights on the strip to be suitable for slab depths between 150-200mm, thus allowing a variety of slab depths to be accommodated, as shown in Figure 4.

The extension plate is connected to the strip via a screw 12 that passes through the plate at a slot 13, and through the first strip to be locked in place by a nut 14 on the far side of the second strip. The second strip 3 has a lip 15 that is outwardly projecting from its base, extending the entire length of the strip and projecting oppositely to the lip on the first strip.

As shown in Figures 6 and 7, there are dowels 16 extending horizontally through both the first and second strips, and outwards therefrom into the concrete for load transfer across the joints. These are situated at regular intervals along the strips. The dowel extends further from the first strip face 2 than from the second strip 3. The dowel extending from the first strip is covered with a plate dowel sleeve (not shown) to debond the dowel.

The joint as described above is essentially conventional. In conventional joints, the strips 5,6 have straight edges.

In accordance with the present disclosure, both the first and second strips have top plates 5, 6 respectively, fast with their horizontal projections. Both sides of the plates are sinusoidal in shape. The plates act as armouring for the joint and the concrete arrises, whilst providing a pleasing finish at the joint. The sinusoidal shape of the plate also allows it to be easily trowelled into place by the installer and accommodates small variances in floor level between two adjoining concrete slabs.

The sinusoidal wave-shape is significantly more pronounced on the inner edges 17 of the top plates. The first and second strips are aligned in a staggered manner such that the peak of one top plate mates with a complementary trough of the other. In this way, as shown in Figure 8, a visible sinusoidal shape is formed at the meeting point of the concrete slabs.

When the concrete hardens, it shrinks which the present joint accommodates. As the first and second strips are securely attached to the two slabs of concrete (one strip in each slab), the shrinking action of the concrete pulls the first and second strips in opposing directions. Usually, this would cause a linear gap to form between the top plates of the joint, creating an area of impact likely to cause spalling. However, due to the sinusoidal wave shape of the joint, the gap created as a result of the shrinking concrete is almost completely covered by the steel of the top plates; the peak of a wave on one plate, mate with the trough of the other, and vice versa. This interconnection of plates prevents localised areas of high impact and dramatically reduces the likelihood of spalling concrete.

Claims

CLAIMS:

1. A joint for concrete slabs comprising:

• a first strip and a second strip adapted for concrete to be cast against on respective sides of the joint, • frangible means for connecting the first and second strips to each other, • at least one top plate on each of the strips for armouring of the joint, • at least one anchor on each strip, oppositely extending therefrom for continuous anchorage in the concrete, • at least one dowel extending through, and outwardly from, the strips for load transfer across the joint, wherein the top plates are shaped as complementary waves, the peaks of which extend over opposite strips at least prior to joint opening.
2. A joint as claimed in claim 1, wherein the first and second strips are interconnected by means of a frangible screw, extending through the first strip and locked on the far side of the second strip.
3. A joint as claimed in claim 1 or claim 2, wherein the first and second strips each have a top plate visible in use, with inner and outer edges.
4. A joint as claimed in claim 1, claim 2 or claim 3, wherein the strips are arranged in a staggered manner such that the inner edges of the first and second top plates mate complementarily.
5. A joint as claimed in claim 3 or claim 4, wherein the mated inner edges of top plates form a visible sinusoidal wave.
6. A joint as claimed in claim 5, wherein the visible outer edges of the top plate are sinusoidal in shape, less pronounced than the inner edge wave.
7. A joint as claimed in any preceding claim, wherein the anchor extends substantially horizontally from the strips for top plate support, subsequently turning downwards at an angle into the concrete slabs on either side of the joint.
8. A joint as claimed in claim 7, wherein the anchor has cut-outs regularly spaced along its length.
9. A joint as claimed in any preceding claim, wherein a plurality of plate dowels are regularly situated along the lengths of the strips, projecting oppositely and horizontally therefrom.
10. A joint as claimed in claim 9, wherein the plate dowels extend through the first and second strips, extending oppositely and horizontally therefrom.
11. A joint as claimed in claim 9 or claim 10, wherein at least one plate dowel has a dowel sleeve to debond the dowel.
12. A joint as claimed in any preceding claim, wherein a lip extends from the bottom edge of the second strip for anchoring within the concrete slab.
13. A joint as claimed in claim 1, wherein an extension plate is connected to the first strip by means of a height adjustable screw.
14. A joint as claimed in claim 13, wherein the extension plate has an outwardly projecting lip running its length, extending oppositely to the lip of the second strip.