AU2015201724B2 - Armoured Joints Including Load Transfer Means - Google Patents

Abstract

An armoured joint for transferring loads across a controlled joint between concrete slab edges includes two series of embedded anchors fused to either side of an elongate metal structure. An edge of afirst slab has a metal-coated tongue that may be pressed by an applied load onto a lower border of a metal groove attached to an edge of the second slab, the lower border having one or many support foot/dowel members, the load isthen transferred into the second slab. A load on the second slab istransferred to the first slab by downward pressure on the tongue f rom an upper border of the groove. 108 109 110 B 7 '7$ v17v 7 14'" 112 > *[7 F 7 F7 -0 11411 717 7 7 <1 77 77 77 114 11. - 107 10B- 7715 77117114 1l3B11I3 13 F g

Description

TITLE: Improvements In Armoured Joints Including Load Transfer Means 2015201724 05 Dec 2016 FIELD: 5 The invention relates to armoured joints for use in poured concrete slab floors. In particular the invention relates to armoured joints capable of transferring loads across the joints in either direction, and the armoured joints are compatible with floors that include prestressed concrete slabs.

BACKGROUND 0 In this specification we shall assume that the armoured joint is used on a flat horizontal floor, so terms like “horizontal”, “up” and “down” as used in this specification have a directional meaning accordingly. Joints of this type are not limited to a horizontal orientation, they might be used on a sloping ramp or on a wall of a building or of a tunnel.

Joints are used to separate a large concrete floor into sections which can shrink or expand 5 relative to each other while the adjacent edges are protected from damage caused by locally applied forces. Concrete floors on ground are generally designed as a continuous concrete membrane, supported by a continuous base material, which is frequently a layer of compacted hard fill over natural ground. Support is provided for discontinuous loads such as point loads or line loads by spreading the load though the slab on to a general 0 larger area of ground around the load. The underlying design assumption is that the concrete membrane is continuous in all directions. However, concrete is a material which shrinks as it sets and hardens (known as curing, during which the polycrystalline nature of the concrete becomes reorganised). Concrete also expands and contracts slightly with temperature variation. The concrete of some floors is placed in pre-compression by the 25 inclusion of steel cables within the concrete which are stressed against the concrete. The resulting compressive stresses in the concrete help to counter the tension stresses which arise as a result of gravity loads from weights placed on the floor. However, the compression in the concrete causes strain shortening in the concrete. The overall effect on concrete floors on ground is that there is inevitably dimensional movement in a horizontal 30 plane within the concrete relative to the ground below.

Unless provision for directed cracking is made within the floor, random cracking of the concrete will occur as a result of contraction. The cracks are unsightly and undesirable. Provision for the movement of the concrete is usually made by creating joints or straight 1 line breaks in the concrete membrane. Once a joint is created in the concrete floor or membrane, the membrane then becomes discontinuous, and it is unable to adequately distribute gravity loads which occur near the joint. A slab forming a working surface in a 5 factory for example is provided with an array of joints that separate one part of the slab from another, and which joints allow for inevitable shrinkage during curing or later expansion owing to thermal changes. Amounts of movement inevitably grow when a larger area of concrete shrinks during curing. The separated edges are preferably covered with an armour comprising a flat or a bent steel strip. 2015201724 06 Apr 2015

0 DOWELS

The most common prior-art method of providing load-carrying continuity across joints in concrete floors is to install a series of steel sections across the joint which are usually called dowels. They are embedded into the concrete on both sides of the joint, and pass across the joint. Dowels may be round steel bars, or square steel bars, or sections of steel 5 plate. Dowels are inserted into the concrete of each floor slab, so that the force of a weight placed on the concrete presses on to the steel dowel, which transfers the load across the joint and then transfers the load into the concrete on the other side of the joint. Dowels are usually designed so that they can slip within the concrete on at least one side of the joint relative to the concrete on the other side of the joint, thereby allowing for horizontal 0 movement of the concrete perpendicular to the dowel. They must be oriented with care, to be parallel to each other.

The traditional location for dowels in concrete floor joints is in the centre of the concrete, half way between the upper and lower surfaces of the concrete. In most circumstances, one level of dowels is used, but on some occasions, two levels of dowels are used, one above 55 the other, so that one level of dowels is above the central plane of the concrete, and the other level of dowels is below the central plane. It is of course desirable that the prior-art dowels, located at the central plane of the concrete, or in two or more layers while remaining well within the body of the concrete, can transfer loads in both directions across the joint. 60 It is known that dowels can be located at the lower surface of a concrete floor, and also at the upper surface of the concrete. Lower-surface dowels need a vertical connecting piece on one side of the joint to transfer the load up into the concrete. These dowels can usually transfer loads in only one direction across a joint and this requires a second set of dowels 2 to transfer loads in the other direction. Thus the total number of dowels is increased and may be doubled, which is a less efficient use of material. 2015201724 05 Dec 2016

It is also known and is common industry practice that the concrete edges of joints at the upper floor surface benefit by being protected beneath sections of steel or even epoxy resin 0 mortar, since these edges can be and usually are relatively brittle. Where steel protection is used, and in particular where the width of gap which develops at a joint may be quite wide, sections of horizontal steel plate which are anchored into the concrete on one side of the joint are seated on sections of steel on the other side of the joint in an arrangement so that the upper steel plate can slide over the lower steel section and allow for relative movement 5 of the concrete floor on the two sides of the joint, while still protecting the concrete from the loads which may damage the edges of the concrete. Often, the steel edge protection systems with or without cover plates, are part of an assemblage which also forms the vertical edge concrete at the joint, and includes the steel members which become the dowels. It is beneficial if these steel assemblages have steel supporting sections at the 0 lowest edge, commonly known as feet, which assist in holding the steel assemblages in location upon the substrate while the concrete is being cast.

PRE-STRESSED FLOORS

The present application is optimised, though not exclusively so, for use with floors having pre-stressed concrete slabs. One of the common uses of these steel assemblages is in the 5 joints in concrete floors which have steel stressing cables cast into them, since the joints in these floors can become relatively wide. The steel stressing cables are usually located in the central plane within the concrete floor. At the joints which form each end of a section of floor, there are anchoring mechanisms for the cables that need to be cast into the concrete. Because these anchoring mechanisms are located in or about the same plane as 90 the prior-art load transfer dowels, there can often be clashes between dowel locations and stressing cable anchoring mechanism locations.

Nothing above should be read as necessarily falling within the common general knowledge.

PROBLEM TO BE SOLVED 95 Installation of prior-art load-transferring dowels requires an extra step to be taken during pouring, when the installer should ensure that the dowels are mounted to be perpendicular and parallel to the joint, and transfix the joint, and be immovable during the flow and 3 settling of wet concrete. Separated dowels cause a focus of applied forces at the spacing interval of the dowels, which may cause failure if the floor is not inherently strong enough 0 to withstand applied loads. They must lie sufficiently far beneath the top surface to prevent any risk of “punching shear” in which a spalling type of fracture occurs if a dowel is lifted so as to exceed the strength under tension of the covering concrete by motion of the adjoining slab. It would be desirable if the function of prior-art dowels could be provided by a structural portion of the armoured joint. 2015201724 05 Dec 2016

5 DESIRABLE OUTCOMES A desirable outcome of the present application is to provide an armoured joint for slab floors that provides for load transfer between the joined slabs in both directions and without use of mid-thickness transfixing dowels; and further, to provide an armoured joint allowing clear spaces for the installation of cable anchors and ancillary equipment for use 0 with prestressed cables, or at least to provide the public with a useful choice.

These are merely desirable outcomes that may or may not be met by the present invention. These are not intended to be read as objects of the present invention.

SUMMARY OF INVENTION

Throughout this specification - the word "comprise", or variations such as "comprises" or 5 "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

In a first aspect, the present invention provides an armoured, load-transferring expansion joint apparatus for providing a slidable joint of the tongue and groove type having a 120 longitudinal axis along a joint between adjacent concrete slabs in order to maintain an edge of a first slab in proximity to a parallel and adjoining edge of a second slab and provide bidirectional load-transferring between the slabs; the joint including a tongue comprised of moulded concrete encased in a metal sheath and forming part of the first slab characterised in that the tongue and sheath have a maximised height equal to a thickness of any one 125 concrete slab minus a thickness of a second upper longitudinal metal strip; a lower surface of which defines an upper interior surface of the corresponding groove of the joint and which may slide against an upper side of the tongue, and minus a thickness of at least one 4 lower metal foot or dowel an upper side of which may slide against a lower side of the tongue. 2015201724 05 Dec 2016 0 Preferably, a base of the metal sheath of the tongue bears an affixed first longitudinal metal strip sharing an upper, exposed surface with an upper surface of the first slab and with the second upper affixed longitudinal metal strip sharing an upper, exposed surface with an upper surface of the second slab wherein a floor of an exposed gap of variable width between the first strip and the second strip comprises part of an upper aspect of the metal 5 sheath of the tongue; the exposed gap being displaced along an axis perpendicular to the longitudinal axis in relation to a variable concealed gap between the slabs thereby rendering the gap safe.

More preferably, the vertically maximised tongue and groove joint of the apparatus provides a plurality of sites at a height half way between an upper surface and a lower 0 surface of each slab for installation and use of at least one pre-stressing cable anchor while also providing armoured, load-transferring expansion joint apparatus.

It is preferred, that a crack-inducing function is provided by the joint, by providing a metal sheet as a continuous sheet extending between upper tongue edge and lower tongue edge.

Preferably, the anchors are installed as a series along the length of the armoured joint with 5 placement or deletions of anchors arranged along the length of the joint in order to provide at least one site free of anchors where apparatus related to applying and maintaining tension on embedded cables is to be embedded within the slab.

More preferably, the components which comprise rigid vertical connectors within the groove assembly are discontinuous along the length of the armour joint so that, when in 150 use, devices including pre-stressing equipment related to imposition of stress using prestressing cables disposed within each slab may be placed in between the discontinuous components.

It is preferred, that the rigid foot or dowel of the load-transferring expansion joint is elongated as a continuous strip along the line of the joint. 4a 5 Preferably, that the rigid foot or dowel components or of the load-transferring expansion joint are discontinuous along the length of the armour joint. 2015201724 05 Dec 2016

More preferably, the variable-width space between the slabs is covered from above by strip anchored into one slab while a variable-width space open to the upper surface is bounded at each side by a metal strip, anchored into the other slab and by strip and at the base of the 0 space by a metal sheet.

It is preferred, that the strips and act as armour and protecting the edge of each concrete slab from damage from above.

Preferably, the strip and the bar are made as a single piece having an “L” shaped cross section. 5 Also described herein is an expansion joint between two slabs of concrete forming a floor (in which the two slabs may have been poured as a single pour or separately), an armour joint (100) comprising a load-transferring expansion joint connecting contiguous edges of a first floor slab (101) of concrete and a second floor slab (102) of concrete across a space between the contiguous edges, and horizontally elongated parallel to the contiguous edges; 0 the space having a variable width consequent on expansion or contraction of the slabs from time to time, causing a undergo a horizontal sliding motion relative to each other over a common substrate (114); the expansion joint to be included within poured concrete and hence anchored to each slab when the or each slab is formed; wherein the armour joint (100) comprises a load-transferring type of tongue-and-groove joint in which a tongue 175 assembly originating from an edge of the first slab (101) is at least partially encased in metal (105, 106, 108) and anchored by a plurality of anchors (107) located along the joint into the first slab (101) and is partially enclosed within a complementary groove assembly along an edge of the second slab (102) that is comprised of metal (113, 112, 110 and 109); the groove assembly being anchored by a plurality of anchors (111) into the second slab 180 (102); the sliding surfaces of metal for example as (109) over (105) and (106) over (113) thereby serving a function of transferring a load (A) or a load (B) applied on to either slab across the joint and to the other slab along the length of the load-transferring expansion joint while the joint protects the edges of the concrete slabs from local impact-related damage and also permits the width of the inter- 4b 5 slab space (103, 103A, 103B) to decrease or increase in event of any relative horizontal movement of the or each slab (101, 102). 2015201724 05 Dec 2016

Preferably a crack-inducing function is included by providing the metal sheet as a continuous sheet (104) extending between upper tongue edge (105) and lower tongue edge (106). 0 Further described herein is the load-transferring function comprising either a relative downward movement when imposed during use by a force (A) on to the slab (101) with respect to slab (102) to cause rigid foot or dowel (113) to move down and thereby pull rigid vertical connector (112) down, taking rigid bar (110) and rigid anchor (111) in the same direction, or a relative downward movement when imposed during use by a force (B) 5 on to the slab (102) with respect to slab (101) tending to lower the rigid elongated strip (109) covering an upper edge of the first slab (101) and depressing the sheath over the tongue (105) and depressing the rigid anchors (1107) in the same direction; meanwhile allowing expansion or contraction of the first and second slabs to occur.

In one option, the components (112a) which comprise vertical elements within the groove 0 assembly are discontinuous along the length of the armour joint so that, when in use, prestressing equipment selected from a range including prestress anchors and hydraulic jacks related to imposition of stress within prestressing cables disposed within each slab (101, 102) is placed in between the discontinuous components (112a).

The anchors may be installed as a series along the length of the armoured joint with 205 placement or deletions of anchors arranged along the length of the joint in order to provide one or more sites free of anchors where apparatus related to applying and maintaining tension on embedded cables is to be embedded within the slab.

The rigid foot (113) of the load-transferring expansion joint may be elongated as a continuous strip along the line of the joint. 210 Alternatively, the components (113a) or (113b) of the load-transferring expansion joint are discontinuous along the length of the armour joint. 5

Preferably the elongated bar (108), the elongated strip (109), and the metal sheet at (105) together comprise a joint having metal edges and an ability to open or close when the concrete slabs expand or contract, sliding over a substrate (114). Preferably the strips (108) and (109) act as armour and protecting the edge of each concrete slab from damage from 0 above. 2015201724 06 Apr 2015

Preferably the variable-width space (103a) between the slabs is always covered from above by the strip (109) anchored into one slab (102) while a variable-width space (103) open to the upper surface is bounded at each side by a metal strip (108), anchored into the other slab (101) and by strip (109) and at the base of the space (103) by a metal sheet (105); 5 strips (108) and (109) also protecting the concrete from damage.

Optionally the strip (109) and the bar (110) are made as a single piece having an “L” shaped cross section.

PREFERRED EMBODIMENT

The description of the invention to be provided herein is given purely by way of example 0 and is not to be taken in any way as limiting the scope or extent of the invention.

Throughout this specification unless the text requires otherwise, the word "comprise" and variations such as "comprising" or "comprises" 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. Each document, reference, patent application /5 or patent cited in this text is expressly incorporated herein in their entirety by reference. Reference to cited material or information cited in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in New Zealand or in any other country.

DRAWINGS 180 Fig 1: is a plan view through the closed joint, when the concrete is expanded.

Fig 2: is a plan view through the opened joint, when the concrete has contracted.

Fig 3: is a perspective view of the joint of Fig 1.

Fig 4: is a perspective view of a variant of the joint.

Fig 5: is a perspective view of a further variant of the joint. 6

5 INTRODUCTION 2015201724 06 Apr 2015

The improvement uses the feet or support mechanisms of the armoured joint-forming steel assemblages to perform an additional function as the load transfer mechanisms analogous to prior-art dowels required for the joints by appropriately connecting them to the sections of steel cover plate used at the upper plane of the concrete floor to fulfil the “armoured” 0 description. These feet (113) replace conventional transfixing dowels for load transfer.

This invention is intended firstly to provide the benefit of creating a free vertical plane of joint forming steel to which pre-stressing anchorage mechanisms can be attached without the compromise of having dowel steel sections in the same horizontal plane generally a mid-thickness plane, and secondly to more efficiently utilised the components of the steel 5 assemblage by creating a mechanism in which one set of components fulfils two functions, namely as the supporting feet and as the load transfer dowels. This in turn allows a more simple and efficient assembly process, which will further save cost in the manufacture of the product. EXAMPLE 1 0 See Fig 1, showing an elevation cross-sectional view (100) of one version of the invention. The drawing shows two concrete slabs (101) and (102) that meet at a vertical face, lined on one side (slab 101) by a continuous vertically oriented sheet (104) and on the other side (slab 102) by a continuous or discontinuous vertical support (112). As shown in Fig 2 there may be an actual space (103 A) in between, depending on the extent of slab contraction that __5 is present. The slabs lie on a substrate (114) and the invention provides for horizontal motion of one or both slabs over the substrate as a result of expansion and contraction. Movement is apparent at the armoured joint (100). Sheet (104) serves mainly as a crack inducer in situations where both slabs are poured at the same time, and is for example made of a rolled, 2 mm thick steel sheet having an upper flap (105) oriented horizontally 210 when in use, a vertical surface (104) and a lower flap (106). Sheet (104) is tied to the edge of slab (101) by the anchor (107). In Fig 1 a potential space at the joint runs between strips (108) and (109), is transmitted by relative sliding of strip (109) across the top of sheet (105), and down between (104); which is anchored to slab (101), and support (112) which is anchored to slab (102) by anchor (111) at an upper end and is welded at its base to the 215 foot and dowel (113). The potential space between now moved-apart slabs is shown in Fig 2 as (103) (at the upper surface), (103A) (between the slab edges) and (103B) beneath the 7 slab. The specific width of the space is dependent on conditions. From above, a person would see two continuous metal strips (108) and (109) running along the length of the armoured joint. In Fig 1 the space between (108) and (109) is closed, but in use, 2015201724 06 Apr 2015 0 contraction of either or both slabs would cause a gap (103) to appear at that space as shown in Fig 2. It is “a safe gap” since nothing can fall deep into the enclosed space (103A) between the slabs. Slab 101 is firmly attached to the sheet (104/105) and to the strip (108) by spaced-apart anchors (107), one of which is shown here as a ragged-end metal strip. (Anchors (111) are drawn differently to anchors (107), as metal rods with expanded ends, 5 but there is no functional difference for the purpose of the present invention between the two types drawn here). Parts (105), (107) and (108) are welded together, preferably before application of a corrosion-inhibiting coating such as zinc. As a result, the wider upper strip (109) slides over the upper flap of the sheet (105) during contraction (fig 2) and expansion (Fig 1), while at the base of the slab, the lower leg or flap (106) of the steel sheet slides 0 over the dowel or foot (113) and the underside of the concrete slab (101) slides over the surface of the dowel or foot (113). Both sliding joints are in contact and transfer a force between one sliding member and the other. Since the concrete is in its most expanded state just after pouring, a space such as (103B) will develop beside the left-hand edge of foot (114) (as referred to Fig 1) during the curing process; sufficient for taking up later thermal 5 expansion. Foot or dowel (113) is expected to exist in at least three versions as shown for example as (113) in Fig 3, (113a) in Fig 4, and (113b) in Fig 5. Each foot is attached such as by welding to the joint vertical support (112), and the slab (102) on the right of the drawing (Figs 1 and 2) is particularly attached to the hardware on the right-hand side of the joint by embedded anchors (111). Preferably, anchors are placed at about 250 mm centres 240 or up to 1 m apart, depending on thickness, concrete quality, and on load applied to the slab. Each anchor is welded to a strip or bar (110) which in turn is welded to the flat strip (109) and to the vertical support (112). An “L” - shaped metal strip combining 109 and 110 would be usable if available in straight lengths. The vertical support (112) may be intermittent as shown in Fig 3. While some weight may be carried by the edge of the slab, 245 it is preferable to provide alternative paths for transferring weights via the foot or dowel (113), which is conventionally seated upon the compacted substrate (114) beneath the slab and usually also on a damp course layer and, serving as a dowel, into the adjoining slab. Foot (113) may be continuous along the length of the joint as shown in Fig 3, or may be discontinuous as in Figs 4 or 5. In Fig 4 the foot is a short, stout strip (113a) and in fig 5 250 the foot is comprised of a pair of strips (113b). Selection of any one option may be dictated 8 in part by the firmness of the substrate (114). The function of any foot is at least in part to maintain the armoured joint at a required height during the pouring and settling process before the concrete hardens. The feet will then serve the function of prior-art dowels. After hardening the entire slab serves as a weight support means. 2015201724 06 Apr 2015 5 The “free vertical plane of joint -forming steel for each slab” is comprised on one adjoining slab (101) of sheet 104, but more particularly on the other adjoining slab edge as the side of vertical connector (112) and adjoining bar (110). There is some freedom to locate anchors such as (111).

Transfer of Loads Across the Joint. 0 The predominant load applied to a slab floor is always downward - arising from the weight of concrete or from masses placed on, or moving over, the top. The edge of slab (101) rests slidably on the top of foot (113) which, as shown in Fig 3 may be continuous, or as in Figs 4 and 5, may be discontinuous along the joint. A force “A” (triangle A, Fig 1) applied downwardly on to slab (101) is transmitted across a sliding surface between (101) and 5 (113) on to the dowel/foot (113) which is connected to, and slides together with slab (102).

Then, any tendency of foot (113) to move downwardly in relation to slab (102) as a result of force “A” will tend to apply tension along the width of vertical support (112); tending to pull down the bar (110) and the attached anchors (111) within slab (102). The anchors (111) tend to spread an applied force sideways. Bar (110) is welded to strip (109) or may 0 be a single component. A force “B” (triangle, Fig 1) if applied downwardly on to slab (102) will be transferred through anchors (111) on to bar (110) and then to the continuous (along the armoured joint) strip (109), which tends to push the edge of slab (101) downward through metal layer (105); the force also pushes anchors (107) downward, thereby distributing the force, if 275 localised, sideways along the armour joint.

Fig 3 is an oblique perspective view of the armour joint (100) of Fig 1. Here, dowel or foot (113) is shown as a continuous part. Anchor (111) is shown as a single dashed line here, because anchors may be displaced to one side or the other of the space between one vertical support (112) and the next, in order to allow space (shown here as dashed-line 280 aperture (301) made through sheet (104), for the installation and stretching of the cable or cables). A preferred site along the armoured joint is at about half-way through the thickness or height of the slab. Slabs of this type are often pre-stressed using an array of 9 cables laid horizontally within the thickness of the concrete, using a well-known technique. In the aperture a prestress anchor (not shown) may be installed for prestressing cables, on 5 the side to be poured first (slab (102)), and a temporarily placed hydraulic jack on the other side of the slab is used for tensioning the cables. Note that the bar (110) and the strip (109) form a continuous “bridge” over the aperture (301). Bars (109) and 110 also serve to spread the force resulting from the sideways tension arising from the transfixing base of the prestress anchor. Foot or dowel (113) will also distribute the force along the length of 0 the armour joint if is continuous along the armoured joint. 2015201724 06 Apr 2015

Fig 4 is an oblique perspective view of a version (400) in which strip (113a) is not continuous. In this example strip (113a) is extended at right angles to the axis of the armoured joint. Load transfer from an “A” type force (see in relation to Fig 1 above) would be applied from the slab (101) onto the left side of strip (113a), up through vertical support 5 (112) and along the joint through bar (110) which is welded to or is contiguous with strip (109), and through anchors (111) into slab (102).

Fig 5 is an oblique perspective view of another version (500) in which strip (113a) is replaced by a pair of bars (113b), more like the shapes of known dowels, but which are placed upon the substrate. This drawing shows a modified armour joint for lighter 0 demands, in which a crack inducer sheet (104) and the fixed strip (108) are not included, and an angle strip (501) carries possible tension loads across gaps between vertical supports (112).

ADVANTAGES

One advantage of this joint is to provide the benefit of creating a free vertical plane of joint 305 forming steel for each slab to which pre-stressing anchorage devices can be attached at any position without the compromise of having dowel steel sections in the same horizontal plane.

Another is to more efficiently utilise the components of the steel assemblage by creating a joint mechanism in which one set of components fulfils two functions, namely (1) 310 supporting feet for the armour joint components before the concrete has set, and (2) providing the novel load transfer dowels.

This in turn allows a more simple and efficient joint assembly process, which will further save cost in the manufacture of the product. 10

The invention provides a simpler and easier assembly process at the construction site by 5 not including separate dowel units which will further save cost at the time of installation. 2015201724 06 Apr 2015

An advantage is that by not including a parallel series of embedded dowels that pass straight across the expansion joint that movement between the slabs is not restricted to solely movements perpendicular to the joint.

Although the invention helps to distribute the loads imposed by prestressing cables, the 0 invention is applicable even if prestressed cables are not used.

This load transfer device is substantially free of any tendency to rotate.

This load transfer device provides a less localised transfer of forces than is obtained by dowels.

Finally it will be understood that the scope of this invention as described and/or illustrated 5 herein is not limited to the specified embodiments. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth in the following claims. 11

Claims (11)

1. WE CLAIM:

   1. An armoured, load-transferring expansion joint apparatus for providing a slidable joint of the tongue and groove type having a longitudinal axis along a joint between adjacent concrete slabs in order to maintain an edge of a first slab in proximity to a parallel and adjoining edge of a second slab and provide bi-directional loadtransferring between the slabs; the joint including a tongue comprised of moulded concrete encased in a metal sheath and forming part of the first slab, wherein the tongue and sheath have a maximised height equal to a thickness of any one concrete slab minus a thickness of a second upper longitudinal metal strip; a lower surface of which defines an upper interior surface of the corresponding groove of the joint and which may slide against an upper side of the tongue, and minus a thickness of at least one lower metal foot or dowel an upper side of which may slide against a lower side of the tongue.
2. 2. An armoured, load-transferring expansion joint apparatus as claimed in claim 1, wherein a base of the metal sheath of the tongue bears an affixed first longitudinal metal strip sharing an upper, exposed surface with an upper surface of the first slab and with the second upper affixed longitudinal metal strip sharing an upper, exposed surface with an upper surface of the second slab wherein a floor of an exposed gap of variable width between the first strip and the second strip comprises part of an upper aspect of the metal sheath of the tongue; the exposed gap being displaced along an axis perpendicular to the longitudinal axis in relation to a variable concealed gap between the slabs thereby rendering the gap safe.
3. 3. An armoured, load-transferring expansion joint apparatus as claimed in claim 1, wherein the vertically maximised tongue and groove joint of the apparatus provides a plurality of sites at a height half way between an upper surface and a lower surface of each slab for installation and use of at least one pre-stressing cable anchor while also providing armoured, load-transferring expansion joint apparatus.
4. 4. An armour joint as claimed in claim 1, wherein a crack-inducing function is provided by the joint, by providing a metal sheet as a continuous sheet extending between upper tongue edge and lower tongue edge.
5. 5. An armour joint as claimed in claim 1, wherein the anchors are installed as a series along the length of the armoured joint with placement or deletions of anchors arranged along the length of the joint in order to provide at least one site free of anchors where apparatus related to applying and maintaining tension on embedded cables is to be embedded within the slab.
6. 6. An armour joint as claimed in claim 1, wherein the components which comprise rigid vertical connectors within the groove assembly are discontinuous along the length of the armour joint so that, when in use, devices including pre-stressing equipment related to imposition of stress using prestressing cables disposed within each slab may be placed in between the discontinuous components.
7. 7. A dowel-free armour joint as claimed in claim 1, wherein the rigid foot or dowel of the load-transferring expansion joint is elongated as a continuous strip along the line of the joint.
8. 8. An armour joint as claimed in claim 1, wherein the rigid foot or dowel components or of the load-transferring expansion joint are discontinuous along the length of the armour joint.
9. 9. An armour joint as claimed in claim 1, wherein the variable-width space between the slabs is covered from above by strip anchored into one slab while a variable-width space open to the upper surface is bounded at each side by a metal strip, anchored into the other slab and by strip and at the base of the space by a metal sheet.
10. 10. An armour joint as claimed in claim 1, wherein the strips and act as armour and protecting the edge of each concrete slab from damage from above.
11. 11. A dowel-free armour joint as claimed in claim 1, wherein the strip and the bar are made as a single piece having an “L” shaped cross section.