AYRES, Ryan, Charles (14 Vickery Street, Kaiapoi, Canterbury 7630, NZ)
ALLINGTON, Christopher, James (313 Dunsandel Brookside Road, RD 2 Leeston, Canterbury 7682, NZ)
DIEHL, Andrew, Karl (10 Ashton Mews, Redwood, Christchurch 8051, NZ)
AYRES, Ryan, Charles (14 Vickery Street, Kaiapoi, Canterbury 7630, NZ)
ALLINGTON, Christopher, James (313 Dunsandel Brookside Road, RD 2 Leeston, Canterbury 7682, NZ)
| CLAIMS: 1 A bearing member for incorporation in a first structural member, said first structural member in use being in slideable, load-bearing contact with a second structural member along a structural member interface between the first and second structural members, said bearing member including: - a first bearing layer having: • a sliding surface, and • an opposing contact surface, orientated in use to face said first structural member, and characterised in that the first bearing layer is connectable to a second bearing layer having: • a sliding surface, and • an opposing contact surface, orientated in use to face said second structural member, such that when connected said first and second bearing layer sliding surfaces share a mutual sliding interface such that under relative sliding movement of the first and second structural members the first and second bearing layers are capable of sliding relative to each other. A bearing member as claimed in claim 1 , wherein said bearing member includes said first and second bearing layers. A bearing member as claimed in claim 2, wherein said first and second bearing layers are connected together via a resilient and/or deformable connection(s). A bearing member as claimed in claim 2, wherein said first and second bearing layers are releasably connected together. A bearing member as claimed in claim 4, wherein said first and second bearing layers are configured to at least partially disconnect on said relative sliding movement of the first and second structural members. A bearing member as claimed in claim 4 or claim 5, wherein the first and second bearing layers are releasably connected together via a resilient 'snap-fit' connection. A bearing member as claimed in any one of claims 4-6, wherein the first and second bearing layers are releasably connected together via at least one of: a frangible joint, breakable adhesive, interlocking slots, rails, connectors, clasps, retainers, deformable fittings. A bearing member as claimed in any one of the preceding claims, wherein in use the bearing member is fixed to the first structural member. A bearing member as claimed in any one of the preceding claims, wherein the first bearing layer contact surface is a 'high-friction' surface such that the coefficient of friction at the interface (hereinafter "first interface") with the first structural member has a higher coefficient of friction than said sliding interface. A bearing member as claimed in any one of the preceding claims, wherein the second bearing layer contact surface is a 'high-friction' surface such that the coefficient of friction at the interface (hereinafter "second interface") with the second structural member is higher than the sliding interface. A bearing member as claimed in any one of the preceding claims, wherein the first bearing layer includes a deformable portion to provide a cushion and/or recess when deformed. A bearing member as claimed in any one of the preceding claims, wherein said first bearing layer sliding surface includes a recess. A bearing member as claimed in claim 12, wherein said recess is formed as an elongate slot or channel with a concave transverse cross-section. A bearing member as claimed in any one of the preceding claims, wherein said second bearing layer sliding surface includes a recess. A bearing member as claimed in claim 14, wherein said recess is formed as an elongate slot or channel with a concave transverse cross-section. A bearing member as claimed in any one of claims 12-15, wherein said recess is substantially curved and/or arcuate. A bearing member as claimed in any one of claims 12-16, wherein the bearing layers are releasably connected together adjacent a said recess. A bearing member as claimed in any one of claims 12-17, wherein the bearing layers are resiliently connected together adjacent a said recess. A bearing member as claimed in any one of the preceding claims, wherein said second bearing layer sliding surface includes a convex portion. A bearing member as claimed in claim 19, wherein said convex portion is formed in the second bearing layer sliding surface at a location such that in use, said convex portion will cover or replace a second structural member apex at the structural member interface. A bearing member as claimed in any one of the preceding claims, wherein said first bearing layer sliding surface includes a convex portion. A bearing member as claimed in claim 2 , wherein said convex portion is formed in the first bearing layer sliding surface at a location such that in use, said convex portion will cover or replace a first structural member apex at the structural member interface. A bearing member as claimed in any one of claims 19-22, wherein said convex portion is substantially curved and/or arcuate. A bearing member as claimed in any one of claims 19-23, wherein the bearing layers are releasably connected together adjacent a said convex portion. A bearing member as claimed in any one of claims 19-23, wherein the bearing layers are resiliently connected together adjacent a said convex portion. A bearing member as claimed in any one of the preceding claims, wherein the first bearing layer includes one or more protrusions extending from the contact surface for attachment, insertion or embedding in said first structural member. A bearing member as claimed in any one of the preceding claims, wherein the second bearing layer is constructed as a single unitary extrusion. A bearing member as claimed in any one of the preceding claims, wherein the first and/or second bearing layer sliding surfaces are formed from one or more materials selected from the group comprising: Polyamides, Polyethylenes, Polytertafluroethylene, Polymers, Polypropylene and combinations thereof. A bearing member as claimed in any one of the preceding claims, wherein the first and second bearing layers are constructed from steel with one said bearing layer sliding surface formed as a hardened steel surface and the other bearing layer sliding surface with a steel plate with protrusions. A bearing member as claimed in any one of the preceding claims, wherein the first bearing layer is provided as an elongate strip for extending along a peripheral portion of the first structural member. A bearing member as claimed in any one of the preceding claims, wherein the first and/or second bearing layers are extrusions. A bearing member as claimed in claim 4 or claim 17, wherein the bearing member is constructed from two extruded bearing layers which can be releasably connected together and the first bearing layer fixed to the first structural member. A bearing member as claimed in any one of the preceding claims, wherein said first structural member is a precast concrete panel. A bearing member as claimed in any one of the preceding claims, wherein said first structural member is a concrete support. A bearing member as claimed in any one of the preceding claims, wherein one of more intermediate layers are located between said first and second bearing layers. A structural member incorporating a first bearing layer of a bearing member as claimed in any one of the preceding claims. A structural member as claimed in claim 36, wherein the first bearing layer is fixed to said structural member by the embedding of protrusions of the first bearing layer contact surface in said structural member. A structural member as claimed in claim 37, wherein the first bearing layer protrusions are embedded during manufacture of said structural member. . . . .. . A first and a second structural member, said first structural member in use being in a slideable load-bearing contact with said second structural member along a structural member interface between the first and second structural members, wherein said second structural member incorporates a second bearing layer of a bearing member as claimed in any one of claims 1 -35. A structure including a structural member as claimed in any one of claims 36-38, said first structural member including said bearing member. A structure as claimed in claim 40, incorporating multiple said structural members, at least one said structural member incorporating a bearing member as claimed in any one of claims 1 -35. A method of making a structural member as claimed in any one of claims 36-38, said structural member being constructed from a liquid or flowable solid material capable of setting as a solid, the method including: - placing of said bearing member in a formwork; - insertion of said flowable material in said formwork to immerse a first bearing layer of said bearing member, thereby embedding said first bearing layer in said flowable material. A method of forming a structural member interface between first and second structural members, said first structural member in use being in slideable load-bearing contact with said second structural member, said first structural member being a structural member as claimed in any one of claims 36-38, said method including: - connecting a said second bearing layer to the first bearing layer, and - positioning said first structural member in said slideable load bearing contact with said second structural member with said bearing member therebetween, and wherein said second bearing layer is not fixed to said second structural member. |
TECHNICAL FIELD
The present invention relates to improvements in and relating to bearing members and more particularly to an improved bearing member for placement at an interface between two structural members.
BACKGROUND ART
Many structures contain load-bearing supports that support a load. In building construction for example, vertical struts, beams or 'uprights' are load-bearing supports for 'loads' provided in the form of horizontal beams, slabs, girders, panels or floor units. Reference hereinafter will be made to the 'load' being a 'floor unit' supported by a support. However, such reference is purely exemplary and should not be seen to be limiting as the principles are also applicable to any combination of structural members where a load is applied therebetween.
The use of pre-fabricated components such as pre-cast concrete floor units (also known as concrete 'slabs' or 'panels') has become increasingly prevalent as the use of pre-fabricated components can reduce the construction time and complexity of construction on-site. Such floor units are used in a diverse variety of structures, e.g. many buildings and bridges. Such floor units are typically supported by resting on a ledge or other supporting surface of a support such as a wall or beam. The supporting surface is also often constructed from concrete.
An exemplary pre-cast concrete floor unit will typically span 8 - 18 metres between supports with a 1.2 - 2.4 metre width. Typically only a small interface portion (herein referred to as a structural member interface) of the floor unit's ends (typically 75 - 125 millimetres in depth) is supported. Thus, given the size and weight of the floor units and this relatively small structural member interface, the portions of the support and floor unit at this structural member interface are subjected to high gravity loads and large bearing stresses. "Bearing stress" is defined as the load (weight force) divided by the supported area.
When such floor units are subjected to thermal variations they may expand and contract and thus change length, width and/or thickness. In order to avoid damage to the structure from these thermal fluctuations, the floor units are designed to incorporate movement relative to the supporting surface at the structural member interface. During relative movement a friction force is generated at the structural member interface and opposes this movement. If these friction forces exceed the tensile strength of the concrete (either in the floor unit or the support surface) then damage can occur to either. Any damage to the supporting surface or floor unit may reduce the integrity of the connection between the support and floor units and increase the likelihood of structural collapse.
Relative movement between support and floor unit may also occur when structures are subjected to earthquakes or other seismic events. The structure may deform laterally, causing relative rotations between the floor unit and the corresponding supporting surface. An exaggerated example of this rotation is shown in Figure 1b. Furthermore, in a seismic event, inelastic deformation of lateral load-resisting components (e.g. beams running parallel with edges of the floor units) can cause an increase in the component's length and therefore the structure's length parallel to the span of the floor units. This effect is known as "beam elongation". Such beam elongation will tend to 'stretch' the structure and may move the support away from the floor unit. In addition, other environmental static and dynamic forces on the structure itself may cause deformation or relative movement of structural elements. For example, bridges are subject to substantial dynamic forces from traffic, wind etc.
Thus, multiple forces (e.g. friction, tension and bearing forces) may occur and relative movements acting at the structural member interface between two structural members such as a floor unit and a corresponding support.
Attempts have been made to ameliorate the damaging effects of these relative movements, with varying success.
For example, one method of reducing the friction force at the structural member interface is to insert a plastic or low-friction 'bearing strip' or 'pad' between the floor unit and supporting surface. These bearing strips are a piece of plastic that provide a horizontal sliding surface with a reduced coefficient of friction relative to direct contact between the floor unit and support, i.e. concrete on plastic normally has a lower coefficient of friction than concrete on concrete.
To a limited extent these bearing strips accommodate the effects of seismic activity, thermal fluctuations and vertical deflections, both under applied weight of dead and live loads. The bearing strips reduce the high static and dynamic friction usually generated between the floor unit and the support, in turn reducing the likelihood of damage such as cracking and spalling. The typical coefficient of friction for concrete/plastic interface is approximately 0.6 or greater. This friction co-efficient is not fixed however as it is directly related to the friction generated between the plastic surface and the supporting surface or floor unit and therefore by the materials used. Thus, for example, if the surfaces of the floor unit or supporting surface are relatively 'rough', the coefficient of friction will be higher.
During construction these existing bearing strips are manually placed on top of the support before the floor units are installed. As the strips are installed manually, there is a significant risk of the bearing strips being installed incorrectly or even not installed at all. Furthermore, these existing bearing strips do not sufficiently reduce the damage described previously resulting from relative rotation at the structural member interface.
There are many known bearings and bearing mechanisms between supports and loads and examples are described in United States Patent Nos. 3,105,252; 3,243,236; 3,301 ,609; 3,329,472; 3,349,418; 3,484,882; 3,924,907; 3,971 ,598; 4,070,836; 4,187,573; 4,553,792; 5,303,524; 5,597,240 and 7,547,142. US Patent Publication No. 2004-0131287 also describes a bearing mechanism that uses a roller at the structural member interface, thus allowing relative rotation and sliding movement.
Many of these documents describe seismic isolation devices, dampeners or bearing pads designed to address the aforementioned problems. However, the devices described in these documents are often large, cumbersome, expensive, complicated or may not fully address all of the potential relative movements at the structural member interface, i.e. relative rotation and sliding movement. All of the devices described in the prior art also require manual installation on-site and therefore may be installed incorrectly.
It would therefore be advantageous to provide a bearing friction strip that:
• is economical; and/or
· is simple to construct; and/or
• does not require onsite manual installation; and/or
• addresses relative sliding movement at the structural member interface; and/or
• addresses relative rotation at the structural member interface; or
• any and/or all of the above. It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
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.
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 a first aspect of the present invention there is provided a bearing member for incorporation in a first structural member, said first structural member in use being in a slideable load-bearing contact with a second structural member along a structural member interface between the first and second structural members, said bearing member including:
- a first bearing layer having:
o a sliding surface, and
o an opposing contact surface, orientated in use to face said first structural member, and characterised in that the first bearing layer is connectable to a second bearing layer having:
- a sliding surface, and
- an opposing contact surface, orientated in use to face said second structural
member, such that when connected said first and second bearing layer sliding surfaces share a mutual sliding interface such that under relative sliding movement of the first and second structural members the first and second bearing layers are capable of sliding relative to each other.
As used herein the term "slideable load-bearing contact" refers to any load-bearing interaction between two structural members which allows relative sliding movement of the two structural members. It should be appreciated that "slideable load-bearing contact" does not refer solely to direct physical contact between two structural members but also includes indirect contact, i.e. with intermediate objects such as the aforementioned bearing member between the structural members. Preferably, said first and second bearing layers are connectable together via a releasable connection.
Preferably, said bearing member may include both said bearing layers.
Preferably, said first and second bearing layers are configured to at least partially disconnect on said relative sliding movement of the first and second structural members. in one preferred embodiment the first and second bearing layers are releasably connected together via a resilient 'snap-fit' connection. However, it will be appreciated that there are numerous other methods and mechanisms for releasably connecting the two bearing layers together and by way of example, the releasable connection may be via one or more of: a frangible joint, breakable adhesive, interlocking slots, rails, connectors, clasps, retainers, deformable fittings or the like.
In use the bearing member is preferably fixed to the first structural member such that when the first structural member is transported or installed, the bearing member is also automatically installed correctly in the correct position without risk of misplacement or omission by workers onsite. Axiomatically, the second bearing layer will also be installed correctly as it is connected to the first bearing layer. However, as the first and second bearing layers are releasably connected together they are still able to slide relative to each other and therefore still function as a bearing allowing relative movement between the structural members. In one alternative embodiment, the first bearing layer contact surface is a 'high-friction' surface such that the coefficient of friction at the interface (hereinafter "first interface") with the first structural member has a higher coefficient of friction than said sliding interface. The first bearing layer contact surface may by way of example have a pattern of protrusions, ridges or the like to increase the coefficient of friction with the first structural member. Alternatively, a high-friction surface coating may be applied to the bearing layer contact surface. ..
According to another aspect, there is provided a bearing member for incorporation in a first structural member, said first structural member in use being in a slideable load-bearing contact with a second structural member along a structural member interface between the first and.second structural members, said bearing member including:
- a first bearing layer having:
o a sliding surface, and o an opposing contact surface, orientated in use to face said first structural member, and
- a second bearing layer having:
o a sliding surface, and
o an opposing contact surface, orientated in use to face said second structural member, characterised in that the first and second bearing layers are connected together via a resilient and/or deformable connection(s) and said first and second bearing layer sliding surfaces share a mutual sliding interface such that under relative sliding movement of the first and second structural members the first and second bearing layers are capable of sliding relative to each other. The bearing layers may thus be joined together while still being slideable relative to each other with deformation of the connection(s) therebetween.
Preferably, the second bearing layer contact surface is a 'high-friction' surface such that the coefficient of friction at the interface (hereinafter "second interface") with the second structural member is higher than the sliding interface. For example, in one embodiment, a bearing layer contact surface may be formed with surface protrusions or may be constructed from a relatively high-friction material. Alternatively, a high-friction surface coating may be applied to the bearing layer contact surface.
Preferably, said first bearing layer sliding surface includes a recess. This recess is preferably formed as an elongate slot or channel with a concave transverse cross-section, though it will be appreciated that the recess could also be may be formed as any indentation, void, concave portion, slot, channel or the like. As previously described, in existing construction where there is relative rotation of the two structural members, e.g. a vertical support and a supported floor unit, the contact between a second structural member corner and first structural member can cause damage to the structural members, as the area of contact, and therefore load, between structural members is concentrated at the corner. Often this damage will include spalling of the corner which will reduce the overall area of support surface available. The aforementioned embodiment reduces the likelihood of such damage as, when rotation occurs, movement of the corner apex may pass through, or be accommodated in, the recess and thereby reduce the likelihood of damage to that corner.
In an alternative embodiment, the first bearing layer includes a deformable portion.
Preferably, said deformable portion is compressible to provide a cushion and/or recess when compressed. When the corner apex is pressed against the deformable portion (e.g. during said rotation) the deformable portion will deform to act as a cushion or may compress to provide a recess through which the corner apex may pass or be accommodated in;
In another embodiment, said second bearing layer sliding surface includes a convex portion. Preferably, the convex portion is formed in the second bearing layer sliding surface at a location such that in use, said convex portion will cover or replace a second structural member apex, e.g. a corner, edge or other protrusion of the second structural member at the structural member interface. Thus, the corner, edge or protrusion may be convex, e.g. a bevelled, radiused or rounded corner, and be covered or replaced with the convex sliding surface such that on relative rotation, a 'sharp' edge is not presented in contact with the other structural member and thus the likelihood of damage is reduced. As used herein the term "convex" should be understood to mean a shape having all interior angles less than 180 degrees and need not be arcuate or curved. The convex portion may, for example, be a bevelled corner or multi-faceted.
Similarly, reference herein to the term "concave" should be understood to mean a shape having at least one interior angle greater than 180 degrees and also need not be arcuate or curved.
It will be appreciated that the two aforementioned embodiments may be used in conjunction with each other, i.e. the first bearing layer sliding surface may include the recess AND the second bearing layer sliding surface may include the convex portion.
It will also be appreciated that the converse configuration is also possible, i.e. the first structural member may also have an apex such as a corner, edge or protrusion that will receive a point load upon relative rotation of the structural members. Thus, preferably, said second bearing layer sliding surface includes a recess. This recess is preferably formed as an elongate slot or channel with a concave transverse cross-section, though it will be appreciated that the recess could also be formed as any indentation, void, concave portion, slot, channel or the like.
In another embodiment, said first bearing layer sliding surface includes a convex portion. Preferably, the convex portion is formed in the first bearing layer sliding surface at a location such that in use, said convex portion will cover or replace a first structural member apex, e.g. a corner, edge or other protrusion of the first structural member at the structural member interface.
It will be appreciated that the bearing member may be provided with any combination of recesses and convex portions on the first and second bearing layers. Preferably, said convex portion is substantially curved and/or arcuate. Preferably, said recess is substantially curved and/or arcuate.
Having curved and/or arcuate concave and/or convex portions may reduce the likelihood of damage to 'sharp' or pointed edges. Preferably, the bearing layers are releasably connected together adjacent a said recess.
Preferably, the bearing layers are releasably connected together adjacent a said convex portion.
Preferably, the bearing layers are releasably and/or resiliently connected together.
Preferably, the first bearing layer includes one or more protrusions extending from the contact surface for attachment, insertion or embedding in said first structural member.
The present invention may also be embodied in a structural member incorporating the aforementioned bearing member, thus, according to another aspect of the present invention there is provided a first structural member in use being in a slideable load-bearing contact with a second structural member along a structural member interface between the first and second structural members, and wherein said first structural member incorporates a bearing member including:
- a first bearing layer fixed to said first structural member and having:
o a sliding surface, and
o an opposing contact surface orientated in use to face said first structural member, and
characterised in that the first bearing layer is connectable to a second bearing layer having:
o a sliding surface, and
6 an opposing contact surface, orientated in use to face said second structural member, such that when connected said first and second bearing layer sliding surfaces share a mutual sliding interface such that under relative sliding movement of the first and second structural members the first and second bearing layers are capable of sliding relative to each other.
Preferably, said first and second bearing layers are releasably connected together and configured such that under the relative movement of the first and second structural members the first and second bearing layers will slide relative to each other to at least partially disconnect.
In one preferred embodiment the first and second bearing layers are releasably connected together via a snap-fit connection. However, it will be appreciated that there are numerous other methods and mechanisms for releasably connecting the two bearing layers together and by way of example, the releasable connection may be via one or more of: a frangible joint, breakable adhesive, interlocking slots, rails, connectors, clasps, retainers, deformable fittings or the like. In an alternative embodiment, the first and second bearing layers are connected together via a resilient and/or deformable connection(s). The bearing layers may thus be joined together while still being slideable relative to each other with deformation of the connection(s) therebetween.
According to another aspect, there is provided a first and a second structural member, said first structural member in use being in a slideable load-bearing contact with a second structural member along a structural member interface between the first and second structural members, wherein said first structural member incorporates a first bearing layer having: o a sliding surface, and
o an opposing contact surface orientated in use to face said first structural member, and wherein said second structural member incorporates a second bearing layer having:
o a sliding surface, and
o an opposing contact surface orientated in use to face said second structural member, wherein use " the first and second bearing layer sliding surfaces share a mutual sliding interface such that said first and second bearing layers are capable of sliding relative to each other under relative sliding movement of said first and second structural members.
Thus, the bearing member may be formed by incorporating each bearing layer in a corresponding structural member. When the structural members are positioned in use together, the bearing layer sliding surfaces will come into contact to form the sliding interface of the bearing member.
According to yet another aspect of the present invention there is provided a first structural member in use being in a slideable load-bearing contact with a second structural member along a structural member interface between the first and second structural members, and wherein said first structural member incorporates a bearing member including:
- a first bearing layer fixed to said first structural member and having:
o a sliding surface, and
o an opposing contact surface orientated in use to face said first structural member, and
- a second bearing layer having:
o a sliding surface, and
o an opposing contact surface orientated in use to face said second structural member, characterised in that the first and second bearing layer sliding surfaces share a mutual sliding interface such that said first and second bearing layers are capable of sliding relative to each other under relative sliding movement of said first and second structural members and said first and/or second bearing layer sliding surface includes a recess.
Preferably, said recess is formed as an elongate slot or channel with a concave transverse cross-section, though it will be appreciated that the recess could also be may be formed as any indentation, void, concave portion, slot, channel or the like.
According to yet another aspect of the present invention there is provided a first structural member configured for use in a slideable load-bearing contact with a second structural member along a structural member interface between the first and second structural members, and wherein said first structural member incorporates a bearing member including:
- a first bearing layer fixed to said first structural member and having:
o a sliding surface, and
o an opposing contact surface orientated in use to face said first structural member, and
- a second bearing layer having:
o a sliding surface, and
o an opposing contact surface orientated in use to face said second structural member, characterised in that the first and second bearing layer sliding surfaces share a mutual sliding interface such that said first and second bearing layers are capable of sliding relative to each other under relative movement of said first and second structural members and said first and/or second bearing layer sliding surface includes a convex portion. Preferably, the convex portion is formed in the second bearing layer sliding surface at a location such that in use, said convex portion will cover or replace a second bearing member apex, e.g. a corner, edge or other protrusion of the second structural member at the structural member interface.
It will be appreciated that the aforementioned embodiments may be used in conjunction with each other, i.e. the bearing member may include any combination of the aforementioned recesses and/or convex portions, e.g.:
• first bearing layer sliding surface with:
o recess and/or
o convex portion, and/or
· second bearing layer sliding surface with:
o recess and/or
o convex portion.
Preferably, a said convex portion is substantially curved and/or arcuate.
Preferably, a said recess is substantially curved and/or arcuate. Preferably, the bearing layers are releasably connected together adjacent a said recess.
Preferably, the bearing layers are releasably connected together adjacent a said convex portion.
In an alternative embodiment, the first bearing layer may include a deformable portion instead of the recess. Preferably, said deformable portion is compressible to provide a . cushion and/or recess when compressed. When the corner apex is pressed against the deformable portion (e.g. during said rotation) the deformable portion will deform to act as a cushion or may compress to provide a recess through which the corner apex may pass or be accommodated in.
Preferably, the first bearing layer is fixed to the first structural member by the embedding of protrusions of the first bearing layer contact surface in said first structural member. However, it will be appreciated that alternative methods of fixing the first bearing layer to the first structural member are also possible and in an alternative embodiment the first bearing layer may be fixed to the first structural member by an attachment selected from the group comprising: adhesion, interlocking portions, slots, catches, mating portions. Preferably, the first bearing layer protrusions are embedded during manufacture of the first structural member. Where the first structural member is a precast concrete panel or support for example, the first bearing layer is preferably placed in the 'mould' or 'formwork' and the concrete placed therein to set, the protrusions of the first bearing layer thus being embedded in the concrete at manufacture. Fixing of the first bearing layer to the first structural member ensures that the first structural member is constructed with an integral bearing member and thus eliminates the possibility of the bearing member being omitted altogether or incorrectly installed onsite when the first structural member is installed. The fixing of the first bearing layer to the first structural member also ensures the first bearing layer will not move relative to the first structural member.
While reference herein has been made to the bearing member including two bearing layers it should be appreciated that further intermediate bearing layers may be included if required for a particular application. The further bearing layers may be interleaved between the first and second bearing layer sliding surfaces or alternatively may be located facing the first or second bearing layer contact surfaces. Such an additional layer(s) may provide a
convenient way to alter the friction characteristics of the sliding interface to suit a particular application. It will be appreciated that the additional bearing layer(s) may be formed as an independent bearing layer(s) or may be adhered or otherwise connected to the first or second bearing layers. It should be appreciated that even with intermediate layers provided, there still remains a sliding interface between the first and second bearing layer sliding surfaces and thus reference herein to the first and second bearing layer sliding surfaces forming a sliding interface should not be interpreted to exclude the inclusion of intermediate layers between those sliding surfaces. The interface between the first bearing layer contact surface and first structural member will hereinafter be referred to as the first interface.
The interface between the second bearing layer contact surface and second structural member will hereinafter be referred to as the second interface. Preferably, the first and second bearing layers are constructed such that the sliding interface has a lower coefficient of friction than the second interface.
The second bearing layer may be constructed as a single unitary extrusion or similar and thus the contact surface may be constructed from the same material as the second bearing layer sliding surface.
Preferably, the second bearing layer contact surface is a 'high-friction' surface such that the coefficient of friction at the second interface is higher than the sliding interface. For example, in one embodiment, the second bearing layer contact surface is formed with surface protrusions or may be constructed from a relatively high-friction material. Alternatively, a high-friction surface coating may be applied to the second bearing layer contact surface.
As the coefficient of friction at the sliding interface is preferably lower than at the second interface, and where the first bearing layer is fixed to the first structural member, the first and second bearing layers will slide relative to each other without (or with minimal) sliding of the bearing layers relative to the structural members. Thus, the structural member interface will effectively have a coefficient of friction equal to that at the sliding interface.
It will be appreciated that the coefficient of friction at a structural member interface may be controlled by using a bearing member with a sliding interface of a particular coefficient of friction. Such a bearing member can be manufactured relatively inexpensively (compared to concrete panels) to have a particular coefficient of friction to suit the particular application. It will also be appreciated that in a building there may be multiple bearing members provided that need not necessarily have sliding interfaces with the same coefficient of friction, i.e. some joints between structural members may suffer more movement than others and require sliding interfaces with lower coefficients of friction than others.
Preferably, the first and/or second bearing layer sliding surfaces are formed from one or more materials selected from the group comprising: Polyamides, Polyethylenes,
Polytertafiuroethylene, Polymers, Polypropylene or combinations thereof.
The first and second bearing layers may also be constructed from steel by providing one bearing layer sliding surface as a hardened steel surface and the other bearing layer sliding surface with a steel plate with dimples, domes or the like, the steel surface thus slideable over the steel dimples/domes. It will be appreciated that the first and/or second bearing layers may be constructed from such materials or alternatively a surface coating applied to the first and/or second bearing layers to form respective sliding surfaces. Preferably, the bearing layers are provided as elongate strips for extending along a peripheral portion of the first structural member. It will be appreciated that multiple bearing members may be provided to extend along the peripheral portion and the bearing layers may be shaped or configured to suit any particular structural member. Preferably, the first and/or second bearing layers are extrusions.
The bearing member is preferably constructed from two extruded bearing layers which can then be releasably connected together and the first bearing layer fixed to the first structural member.
Preferably, the bearing layers are resiliently connected together. Preferably, the bearing layers are resiliently connected together adjacent a said concave portion.
Preferably, the bearing layers are resiliently connected together adjacent a said convex portion.
Preferably, said first structural member may be a precast concrete panel, floor unit or the like.
In an alternative embodiment, said first structural member may be a concrete support, pillar or the like.
According to another aspect, the present invention may be embodied in a structure including said first and second structural members, said first structural member including said bearing member.
According to another aspect, there is provided a method of forming a structural member interface between first and second structural members, said first structural member in use being in siideabie load-bearing contact with said second structural member, said first structural member being including:
· a first bearing layer fixed to said first structural member and having:
• a sliding surface, and
• an opposing contact surface orientated in use to face said first structural
member, and wherein the first bearing layer is connectable to a second bearing layer having:
• a sliding surface, and
• an opposing contact surface, orientated in use to face said second structural member, such that when connected said first and second bearing layer sliding surfaces share a mutual sliding interface such that under relative sliding movement of the first and second structural members the first and second bearing layers are capable of sliding relative to each other, said method including:
- connecting a said second bearing layer to the first bearing layer, and
- positioning said first structural member in said slideable load bearing contact with said second structural member with said bearing member therebetween, and wherein said second bearing layer is not fixed to said second structural member.
According to yet another aspect of the present invention there is provided a method of making a first structural member as aforementioned, said first structural member incorporating a bearing member as aforementioned and being constructed from a liquid or flowable solid material capable of setting as a solid, the method including:
• placing of said bearing member in a formwork;
• insertion of said flowable material in said formwork to immerse a first bearing layer of said bearing member, thereby embedding said bearing member in said flowable material.
In a further embodiment, steel rods, or other reinforcing may also be placed in the formwork. It will be appreciated that the concrete may be manufactured according to known techniques with reinforcing, pre-stressing or any other manufacturing techniques. According to yet another aspect, there is provided a structure incorporating multiple structural members, at least one said structural member incorporating a bearing member substantially as aforementioned.
According to yet another aspect, there is provided a structure incorporating multiple structural members, at least one said structural member incorporating a bearing layer substantially as aforementioned. The present invention may thus provide a bearing member and/or structural member that may reduce at least one of:
• risk of incorrect instalment of the bearing member;
• friction generated between structural members on relative sliding movement;
· damage or spalling occurring on relative rotation of the structural members.
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 1a shows a partial end elevation of a support and floor unit;
Figure 1 b shows a partial end elevation of relative rotation of the support and floor unit shown in figure 1a;
Figure 2a shows a partial isometric view of an elongate bearing member according to one preferred embodiment of the present invention; Figure 2b shows a transverse cross-section through the elongate bearing member of figure 2a;
Figure 2c shows a partial isometric view of the first bearing layer of the bearing member shown in figures 2a and 2b;
Figure 2b shows a partial isometric view of the second bearing layer of the bearing member shown in figures 2a - 2c;
Figure 3 shows a transverse cross-section through a structural member interface between a first structural member incorporating the elongate bearing member of figure 2 and a second structural member;
Figure 4 shows the structural member interface of figure 3 with topping concrete; Figure 5 shows the structural member interface of figure 3 during relative sliding movement of the first and second structural members;
Figure 6 shows a transverse cross-section through a structural member interface between a first structural member and a second structural member, the first structural member incorporating the bearing member of figures 2-5; shows the structural member interface of figure 6 during relative rotation of the first and second structural members in the opposite direction to that shown in figure 6; shows a graph of coefficient of friction vs. displacement for a concrete-on- concrete interface and the structural member interface shown in figures 3-7; shows a transverse cross-section through a bearing member according to another embodiment of the present invention; shows a transverse cross-section through a bearing member according to yet another embodiment of the present invention; shows a transverse cross-section through a bearing member according to yet another embodiment of the present invention;
Figure 12 shows a transverse cross-section through a structural member interface between a first structural member and a second structural member, the first structural member incorporating a bearing member according to yet another embodiment of the present invention;
BEST MODES FOR CARRYING OUT THE INVENTION
Figure 1a shows a typical supporting arrangement between two structural members provided in the form of a horizontal precast concrete floor unit (1 ) and concrete support (2) respectively. The horizontal precast concrete floor unit (1 ) is supported at one end (4) on a ledge (3) of a concrete support (2) such as a wall or beam. The other end is similarly supported, though not shown in the figures. The support (2) and floor unit (1 ) are used as part of a building or other structure. Such a pre-cast concrete floor unit (1 ) will normally span between 8 - 18 metres between supports and have a 1.2 - 2.4 metre width. Typically only a small portion (4) of the floor unit (typically 75 - 125 millimetres in depth) is supported. Thus, given the size and weight of the floor unit (1 ) and the small portion (4) supported, the portions of the support (2) and floor unit (1 ) at this structural member interface (5) are subjected to high loads and large bearing stresses.
When the floor unit (1 ) is subjected to thermal variations it may expand and contract and thus change length, width and/or thickness. In order to avoid damage to the structure from these thermal fluctuations, the floor unit (1) is designed to move relative to the support (2) at the structural member interface (5). An example of horizontal movement is indicated by arrows (6) from an original position indicated by the floor unit (1 ) shown in broken lines, to new position with the floor unit (1 ') shown in solid lines. During this relative movement a friction force is generated at the structural member interface (5) and opposes this movement. If these friction forces exceed the tensile strength of the concrete (either in the floor unit (1 ) or the support ledge (3)) then damage can occur to either. Any damage to the support (2) or floor unit (1 ) may reduce the integrity of the connection and increase the likelihood of structural collapse.
Relative rotation (11 ) between the support (2) and floor unit (1) may also occur when structures are subjected to earthquakes or other seismic events. An exaggerated example of this rotation is shown in Figure 1 b. This rotation (11 ) can also cause damage, including spalling of the support and/or floor unit corners (8, 7).
With reference to figures 2-7, there is provided a bearing member (100) according to one preferred embodiment of the present invention. As shown most clearly in figure 3-7, the bearing member (100) is employed in a first structural member provided in the form of a precast concrete floor unit (1 ). The floor unit (1 ) is slideably connected to a second structural member provided in the form of a concrete support (2).
Only one end of the floor unit (1) and a corresponding support (2) is shown for clarity and it will be appreciated that the other end of the floor unit (1 ) is normally supported in a complimentary manner.
It should be appreciated that a reverse configuration is possible with the bearing member ( 00) incorporated in the support (2) rather than the floor unit (1 ). However, for clarity and to avoid prolixity, reference herein will be made to the first structural member being the floor unit (1) with the bearing member (100) incorporated in same.
The floor unit (1 ) and support (2) are connected along a structural member interface (5) and in use the floor unit (1 ) applies a load to the support (2). It should also be appreciated that other applications are possible where the load is applied non-vertically.
In most applications the connection between the support (2) and floor unit (1 ) is covered with concrete (9) or similar, as is shown in figure 4. This concrete cover (9) also acts to limit the movement of the floor unit (1 ) and initial sliding movement is limited to movement away from the concrete cover (9) as indicated by arrow (6). As shown most clearly in figures 2-5, the bearing member (100) has:
- a first bearing layer (101) fixed to the floor unit (1 ), the first bearing layer (101 )
having:
o a sliding surface (102), and
o an opposing contact surface (103) orientated in use to face the floor unit (1 ), and
- a second bearing layer (104) having:
o a sliding surface (105), and
o an opposing contact surface (106) orientated in use to face the support (2). The first bearing layer (101 ) is connectable to the second bearing layer (104) by a releasable connection and the first and second bearing layer sliding surfaces (102, 105) are in sliding contact and share a mutual sliding interface (107). Thus, under relative sliding movement of the floor unit (1 ) and support (2) the first and second bearing layers (101 , 104) will also slide relative to each other. The bearing layers (101 , 104) are provided as extrusions forming elongate strips which are connected together at their respective lateral edges (108a, 108b and 109a, 109b) via snap fit connections (110a, 110b).The first (101 ) and second (104) bearing layers are formed from High Density polyethylene (HDPE) or other low-friction material such as Nylon,
polytetrafluoroethylene (PTFE) or other plastics. As shown in figures 3-5, the first bearing layer (101 ) is fixed to the floor unit (1) by the embedding of protrusions (111 ) of the first bearing layer contact surface (103) into the floor unit (1) during casting of the floor unit (1 ). The interface (116) between the first bearing layer contact surface (103) and floor unit (1) is referred to as the "first interface".
During casting, the first bearing layer (101 ) is placed in a formwork and the concrete poured therein to set, the protrusions (111 ) of the first bearing layer (101 ) are- thus embedded in the concrete floor unit (1) once set. The second bearing layer (104) is also preferably connected to the first bearing layer (101 ) when placed in the formwork, with the second bearing layer ( 04) lying against the base of the formwork. This positioning ensures the contact surface (106) of the second bearing layer (104) is coplanar with the lower surface of the floor unit
(1 )-
The floor unit (1 ) is thereby constructed with an integral bearing member (100) and thus , eliminates the possibility of the bearing member (100) being incorrectly installed onsite when the floor unit (1) is installed, i.e. as long as the floor unit (1 ) is installed correctly, so will the bearing member (100).
It follows therefore that the second bearing layer (104) will also be installed correctly as it is connected to the first bearing layer (101 ). However, as the first ( 01 ) and second (104) bearing layers are releasably connected together they are still able to slide relative to each other and therefore still function as a slidable bearing surface allowing relative movement between the structural members (1 , 2).
The fixing of the first bearing layer (101 ) to the floor unit (1 ) also ensures the first bearing layer (101 ) will not move relative to the floor unit (1 ) along the first interface (1 16).
The second bearing layer contact surface (106) is a 'high-friction' surface provided with a series of parallel ridges (112) running the length of the second bearing layer (104). . The coefficient of friction at the interface (referred to as the "second interface" (1 17)) with the support (2) is thus higher than at the sliding interface (107) and prevents the second bearing layer (104) sliding in concert with the first bearing layer (101) on relative sliding movement of the structural members (1 , 2). Other types of surface protrusions could be provided instead of ridges (112) to increase the friction at the second interface.
The snap fit connections (110a, 110b) at either edge of the bearing member (100) are configured to require a lower force to disconnect than the friction force at the second interface (117). The first (101 ) and second (104) bearing layers are able to slide relative to each other along the sliding interface (107) without causing sliding of the bearing layers (101 , 104) relative to the structural members (1 , 2) as the coefficient of friction at the sliding interface (107) is lower than at the second interface (117) and the first bearing layer (101 ) is fixed to the floor unit (1 ). The structural member interface (5) will also thereby effectively have a coefficient of friction equal to that of the sliding interface (107).
The coefficient of friction at the sliding interface (107) is typically between 0.1 and 0.4 (depending on the load profile) for HDPE bearing layers (101 , 104). In comparison, a concrete-on-concrete interface can exceed 2.0 and a concrete on plastic interface has a coefficient of friction of approximately 0.6 or greater. The bearing member (100) thus provides for a structural member interface (5) with a much lower coefficient of friction by utilising an HDPE-on-HDPE sliding interface (107). Figure 8 shows an approximate graph showing general friction characteristics of a concrete- on-concrete interface in comparison to general friction characteristics of the HDPE sliding interface (107) shown in figures 2-5 during relative sliding movement. As shown in figures 2-5, the first (101 ) and second (104) bearing layers are releasably connected together via resilient 'snap-fit' connections (1 10a, 1 10b) at their respective edges (108a, 109a and 108b, 109b). As shown in figure 5, on relative sliding movement of the structural members (1 , 2), the first bearing layer (101 ) will also slide relative to the second bearing layer (104) at the sliding interface (107) and then when movement is sufficient, the snap-fit connections (110a, 110b) may disconnect. Figure 5 shows the connection (110b) disconnected as the floor unit (1 ) moves away from the support (2).
The snap-fit connection (1 10a) adjacent the floor unit corner (7) is formed between a resilient edge portion (113) of the first bearing layer (101 ) and the corresponding second bearing layer edge (109a). This resilient portion (113) effectively acts as a biased hinge, applying a bias against the relative sliding movement between the bearing layers (101 , 104).
The resilient 'hinge' portion (1 13) also acts as a support for when the floor unit is cast, i.e. the resilient hinge (113) is placed against a wall of a formwork to hold the bearing member (100) in position while the concrete is poured. The first bearing layer sliding surface (102) also includes a recess provided in the form of elongate slot (114) which has a curved concave transverse cross-section. As shown in figures 3-4, the slot (114) is capable of receiving a corner apex (8) of the support (2). Thus on relative rotation of the floor unit (1 ) and support (2), as is shown in figure 6, the corner apex (8) may pass through, or be accommodated in, the slot (114). The adjacent edge (109b) of the second bearing layer (104) is also pushed into the slot (114) by the support corner (8). The support corner (8) is thus not pressed against the floor unit (1 ) which may otherwise cause spalling of the corner (8) or otherwise damage the integrity of the support (2)·
As the slot (114) is part of the first bearing layer (101 ), when the floor unit (1) is
manufactured, the slot (114) will inherently form a corresponding slot (10) in the floor unit (1 ).
However, it will be appreciated that in alternative embodiments the floor unit (1 ) need not include such a corresponding slot, e.g. in an alternative embodiment (shown in figure 12) the bearing member (500 has a first bearing layer (501) that is much thicker than that of the first embodiment (101 ) and has an essentially planar contact surface (503) adjacent slot (514), the slot (514) thereby formed only in the bearing layer (501 ) and not first structural member (1 ).
It will also be appreciated that in another alternative embodiment (not shown), a. slot or recess may be formed only in the floor unit (1 ) and the first bearing layer may include a deformable compressible material adjacent the floor unit recess. Thus, on relative rotation of the structural members (1 , 2) the corner apex (8) may compress the deformable portion in the floor unit recess and be accommodated therein. Such a compressible material may also act as a cushion.
Referring again to figures 2-5 the at the edge (108a) of the first bearing layer (101 ), the first bearing layer sliding surface (102) includes a convex portion (115) corresponding to an apex (i.e. corner (7)) of the floor unit (1 ) so that the corner (7) is formed with a curved plastic-on- plastic interface rather than a sharp concrete-on-concrete corner. This convex portion (115) reduces the likelihood of damage to the floor unit corner (7) as a result of the relative rotation as shown in figure 7. Thus, both the floor unit corner (7) and support comer (8) are protected by the first bearing layer convex portion (115) and slot (114) respectively.
It will be appreciated that a reverse configuration is also possible where the support (2) incorporates the bearing member (100). In this embodiment (not shown), the bearing member (100) would effectively be turned upside down so that the concave portion (114) would be in the support (2) opposing the floor unit corner (7) and the support corner (8) would be covered by the convex portion (115). Furthermore, it should be appreciated that in another embodiment both the support (2) and floor unit (1 ) may be constructed with corresponding recesses (1 14) and convex portions (115). Forming the recess (114) and convex portion (1 5) in the bearing member (100) may also ensure that the floor unit (1 ) is formed during casting with a corresponding recess and curved corner (7) without requiring additional moulding or modification of the floor unit (1 ).
Figures 9 to 11 show alternative bearing members (200, 300, 400) with different snap-fit connections (210a, 310a, 410a) to that of the bearing member (100) shown in figure 2-7. It will be appreciated that in all other respects the bearing members (200, 300, 400) are the same as bearing member (100) and like parts have been referenced correspondingly. Thus, the preceding description may also be applied to the bearing members (200, 300, 400) in respect of all aspects bar the snap-fit connection (1 10a) and resilient hinge (1 13).
The bearing members (200, 300, 400) shown in figures 9 and 10 do not have the resilient hinge (113) of the first mentioned bearing member (100) and instead are formed with walls (213, 313, 413) respectively. The snap-fit connections (210a, 310a, 410a) and wall profiles (213, 313, 413) offer alternative manufacturing options to the resilient hinge (113) while still functioning similarly in most respects. Throughout the aforementioned description reference has been made to the first structural member being a concrete "floor unit" (1) and the second structural member being a concrete "support (2). However, such reference is purely exemplary only and should not be seen to be limiting. Embodiments of the present invention may be utilised in any application where two structural members are connected, a load is applied therebetween and relative movement is required. It should thus be appreciated that this description is not limited to supporting vertical loads and should be interpreted to include horizontal loads. It should also be appreciated that the bearing members (100, 200, 300, 400) may also be used with structural members constructed from other building materials, e.g. mud, brick, stone, hempcrete, steel, wood or any other material where the friction at the structural interface needs to be controlled.
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.