Cantilevered expansion finger joint apparatus

A roadway expansion joint apparatus comprises at least one finger joint that extends across an expansion gap. Each finger joint comprises a base plate, a finger unit, a pivot and a cantilever support. The finger unit comprises a body and at least one unsupported finger extending longitudinally from a distal end of the body. The pivot pivotally couples the finger unit to the base plate about a vertical pivot axis. The cantilever support is located at or between the pivot and a proximal end of the finger unit; the cantilever support allows pivoting of the finger unit relative to the base plate about a vertical pivot axis and impedes pivoting of the finger unit relative to the base plate about a horizontal axis, thereby cantilevering the finger joint to the base plate at the cantilever support.

FIELD

This disclosure relates generally to an expansion finger joint apparatus for use in bridge and other roadway expansion gaps.

BACKGROUND

An expansion finger joint system known in the art typically comprises a pair of finger joints that face each other across an expansion gap of a bridge or other roadway components, each with longitudinally protruding fingers that intermesh across the expansion gap. The intermeshing fingers support vehicles that cross the expansion gap, yet allow the expansion gap to change e.g. due to a change in temperature. Known expansion finger joint systems are typically designed to accommodate a full range of movement of the bridge or roadway either in expansion or contraction while supporting traffic across the expansion gap. When the gap is at its largest, the opposing fingers move apart from each other but are prevented by the design length of the fingers from forming a continuous transverse gap between finger tips. When the gap is at its narrowest the fingers move towards each other but never fully engage such that there always remains a small gap between the male end of a finger on one side of the joint gap and its opposite female end of the finger on the other side of the expansion gap.

Prior art finger joint systems which have fingers rigidly attached to both sides of the joints cannot accommodate any or very little differential lateral movements and rotations about a vertical axis of the bridge. When these lateral movements and rotations occur, the fingers encounter each other and either jam up or break resulting in adverse effects to the bridge.

Some prior art finger joint systems have been proposed which provide finger joints that are rotatable about a vertical axis, thereby accommodating the movements and rotations of the bridge. These prior art joints remain structurally stable by being supported on both sides of the expansion gap. The finger tips rest and slide on the steel plates as the gap increases and decreases. However, these joints would be structurally unstable if support from either side of the gap was removed. Supporting the fingers on both sides of the expansion gap requires sliding surfaces which are exposed to debris, dirt and road grime and consequently susceptible to wear and tear. In addition unmaintained finger gaps jammed with debris and dirt will also result in limitation in joint performance and movement capacity. Examples of such prior art finger joint systems are: CA 3,014,382, JP 2018-119287 and KR 10-1951734.

It is therefore desirable to provide a solution to at least some of the existing challenges faced by prior art devices. In particular, it is desirable to provide an expansion finger joint apparatus that can support traffic across an expansion joint gap while accommodating an unrestricted range of deck movements including lateral, longitudinal, vertical and rotational about both the vertical and horizontal axes whilst not needing any support of the finger tips.

SUMMARY

According to one aspect of the invention, there is provided a roadway expansion joint apparatus comprising at least one finger joint for extending across an expansion gap. In some aspects, the apparatus comprises one or more pairs of finger joints, wherein for each pair, a first finger joint faces a second finger joint of the pair and are spaced apart across the expansion gap, and wherein fingers from the first and second finger joints of the pair intermesh over the expansion gap. Each finger joint comprises a support for anchoring to a surface of a supporting structure, a finger unit, a pivot mechanism and a cantilever mechanism. The finger unit comprises a body and at least one unsupported finger extending longitudinally from a distal end of the body. The pivot mechanism pivotally couples the finger unit to the support and allows rotation about a pivot axis on a sliding plane parallel to a top surface of the support. The cantilever mechanism contacts the finger unit to provide cantilever support to the one or more fingers, wherein rotation within the sliding plane is allowed but rotation out of the sliding plane is prevented.

The pivot mechanism can further comprise a pivot bore extending through the finger unit body along the pivot axis, and the cantilever mechanism can further comprise a rigid collar slidably seated in the pivot bore and fastened to the support such the finger unit is rotatable relative to the collar about the pivot axis but fixed relative to the collar about any other axis. The collar can be seated and the pivot mechanism can comprise a top sliding surface, a bottom sliding surface and a top anchor fastener. The top sliding surface is seated in the collar, and the bottom sliding surface is located between the finger unit and the support. The top anchor fastener is seated on the top sliding surface and extends through the top sliding surface, the collar, the bottom sliding surface and is fixed to the support. The top and bottom sliding surfaces have a low friction surface permitting the finger unit to slide relative to the collar and the support when the top anchor fastener is connected to the support.

Alternatively or additionally, the cantilever mechanism can comprise a flange fixed to the support and an extension fixed to the finger unit. The flange overlaps the extension in a plane parallel to the sliding plane, thereby impeding pivoting of the finger unit out of the sliding plane. The extension is laterally slidable relative to the flange thereby allowing pivoting of the finger unit in the sliding plane about the pivot axis only.

Alternatively or additionally, the cantilever mechanism can comprise a flange fixed to the support, wherein the flange overlaps the proximal end of the finger unit in a plane parallel to the sliding plane, thereby impeding pivoting of the finger unit out of the sliding plane. The proximal end of the finger unit is laterally slidable relative to the flange thereby allowing pivoting of the finger unit in the sliding plane about the pivot axis only. Further, the proximal end of the finger unit can comprise a cut out corresponding to a thickness of the flange, such that top surfaces of the flange and finger unit are flush.

The finger unit body can further comprise a top surface, a bottom surface and side surfaces that taper inwardly from the top surface to the bottom surface. When the apparatus comprises multiple pairs of the finger joints, wherein the first finger joint of each pair are positioned side-by-side on one side of an expansion gap and the second finger joint of each pair are positioned side-by-side on an opposite side of the expansion gap, the inwardly tapering side surfaces of adjacent finger units define a debris evacuation channel therebetween.

The pivot mechanism can further comprise a spring compressed along the pivot axis and expandable upon wear of the top or bottom sliding surface to maintain the pivot mechanism in contact with the finger unit. The spring can be composed of an elastic compressible material such as urethane or rubber.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments disclosed herein relate generally to a cantilevered expansion finger joint apparatus for supporting vehicles crossing a bridge or roadway expansion gap. In some embodiments, the expansion finger joint apparatus comprises a plurality of opposed pairs of finger joints each comprising fingers which intermesh across an expansion gap. Each finger joint comprises a support such as a base plate, a finger unit with a body and one or more unsupported fingers extending longitudinally outwards from a distal end of the body, and a pivot mechanism which pivotably couples the finger unit to the base plate to allow rotation about a pivot axis and on a sliding plane parallel to a top surface of the base plate. The finger joint also comprises a cantilever mechanism contacting the finger unit and which allows the finger unit to pivot relative to its base plate within the sliding plane, yet impedes the finger unit from pivoting out of the sliding plane. Consequently, the finger joint is cantilevered and pivotable relative to the base plate within the sliding plane, and the fingers can extend across the expansion gap without being supported at their proximal ends.

According to a first embodiment and referring toFIGS.1to4, a cantilevered expansion finger joint apparatus1comprises pairs of pivotable expansion joints10that are positioned side-by-side across an expansion gap G of a bridge or other roadway with fingers22from opposed expansion joints10in intermeshing engagement (seeFIGS.3and4). The required number of pairs of expansion joints10in the apparatus1will depend on the number required to span the width of the bridge or roadway.

A single expansion joint10is shown inFIG.1in exploded view. In this embodiment, the cantilevering mechanism is provided by a rigid collar in a pivot mechanism of the expansion joint10. In this embodiment, the pivot mechanism comprises a top anchor bolt12, a rigid collar14, a top sliding ring16, and a bottom sliding ring18. However, the top anchor bolt can be substituted by a suitable fastener known in the art, and the top and bottom sliding rings can be substituted by other sliding surfaces known in the art. A finger unit20of the expansion joint10comprises a body and a plurality of fingers22extending longitudinally from a distal end of the finger unit body. The finger unit body has a top surface, bottom surface, and side surfaces, and a pivot bore24which extends through the body from the top surface to the bottom surface. The pivot bore24has an annular seat25and the top sliding ring16is seated in the bore24with the rigid collar14seated on the top sliding ring16. The collar14also comprises an annular seat, and when a head of the top anchor bolt12sits on the collar seat, a threaded body of the top anchor bolt12extends through the collar14, top sliding ring16, bottom sliding ring18and threads into a base plate anchor26, which in turn is welded or otherwise affixed to a base plate28(not shown inFIG.1but shown inFIG.2). The top anchor bolt12is torqued tight onto the collar14, effectively anchoring the collar14to the base plate28via the base plate anchor26and preventing the pivot mechanism from vibrating.

The base plate anchor26forms the fulcrum about which the finger unit20rotates, and is designed to anchor to a supporting structure and resist lateral forces from traffic such as braking and centrifugal forces on curved bridges. Although a base plate is featured in this embodiment, other types of support for anchoring to a supporting structure can be provided.

The collar14prevents the top anchor bolt12from coming undone during normal operation of the apparatus1, while allowing the finger unit20to rotate relative to the collar14. The collar14has locating pins or key(s) on its face (not shown) which fixedly connect the collar14to the base plate anchor26, and locates the top sliding ring16between the collar14and the bore seat. Consequently, the collar14allows the finger unit20to rotate about the pivot axis in a sliding plane and freely from the top anchor bolt12, while impeding the finger unit20from rotating out of the sliding plane and causing the fingers22to sag when weight is applied to the finger unit20across the expansion gap. In other words, the collar is a cantilever mechanism that provides a cantilever support by way of the top anchor bolt12being tensioned against the collar14, which is seated in the bore of the finger unit20. The finger unit20in turn is seated on the bottom sliding ring18which is laying on top of the base plate28, thereby preventing the finger unit20from pivoting about the horizontal axis relative to the base plate28.

The top sliding ring16and bottom sliding ring18are composed of a low-friction high strength material that allows the finger unit20to slide freely with minimal restraint from the top anchor bolt12and the collar14and at the same time resist the loads from traffic. Such materials are readily available in the art and thus are not described in detail here.

A bottom anchor assembly can consist of any known type of device allowing anchoring into concrete; in the shown embodiment, the bottom anchor assembly consists of plate30(round or square) and a bottom anchor rod32connected to the base plate anchor26by any means and extending downwardly from the base plate28. The base plate anchor26is welded to the underside of the base plate28to prevent the base plate anchor26from rotating in the vertical axis. Base plate anchor26in combination with top anchor bolt12and bottom anchor rod32secure the entire apparatus to base plate28. Base plate28is in turn secured into the concrete bridge deck by Nelson studs (not shown). When secured, the bottom anchor assembly together with contributions from the base plate28resists uplift forces generated during tightening of the top anchor bolt12, as well as resisting uplift forces generated from the rotating finger unit20under traffic loads.

A back plate34extends upward from the base plate28and has a top surface that sits flush with the top surface of the finger unit20. The back plate34shown inFIG.1is configured with a pair of curved side surfaces which correspond to two side-by-side finger units (seeFIGS.3and4); alternatively, the back plate34can be configured with a single curved side surface to correspond to one finger unit, or with three or more curved side surfaces to correspond to three or more finger units (not shown).

Optionally and as shown inFIG.1, the finger joints10are provided with a debris evacuation channel wherein the sides of each finger unit20taper inwards from the top surface to the bottom surface of the finger unit body. When two finger joints10are positioned side-by-side, the evacuation channel has a small gap at the top surface of adjacent finger units20which increases towards the bottom surface of the adjacent finger units20. This tapering evacuation channel impedes larger sized debris from falling between finger joints10, while allowing smaller sized debris to fall into the channel and avoid being compacted by passing traffic. The debris that has fallen to the bottom of the channel can be flushed away from the apparatus1, e.g. by rainfall, through a drain in the expansion gap (not shown).

Optionally and as shown inFIG.1, the distal ends of the fingers22are sloped to allow for bridge/roadway deck rotation and to prevent the fingers from protruding into traffic or coming into contact with snow plough blades.

Referring now toFIGS.3and4, the finger joint apparatus1is shown in operation, supporting vehicular traffic across an expansion gap G while accommodating the full range of bridge deck movement, including lateral, longitudinal, and rotational about a vertical axis, and rotational about a horizontal axis. When the bridge is correctly aligned as shown inFIG.3, the fingers22of the finger units20extend along a normal direction relative to the apparatus1. When the bridge moves and the expansion gap shifts transversely as shown inFIG.4, the finger units10rotate about the vertical pivot axis, while the fingers22maintain contact with each other, resulting in no restraining force (apart from the effects of friction) that can be transferred to the bridge components on both sides of the expansion gap G.

It is expected that the finger joint apparatus1will be particularly useful in certain expansion gap locations that are challenging for prior art rigidly fixed finger joints, including:At abutments of very skew bridges—the normal forward rotation of these abutments results in a twisting effect or rotation of the deck in plan which would cause rigidly fixed fingers to jam up;Where differential lateral forces are felt by deck components on opposite sides of an expansion gap during a seismic event;Where differential settlement occurs across the width of abutments on very wide bridges and which could result in variations in lateral movement between the opposite components of bridges at an expansion joint;At expansion gaps on curved bridges (in plan)—the forces resulting from abutments or by other means can cause the bridge to rotate in plan and cause differential movement at an expansion gap between two opposite components of the bridge; andWhere there exist differences in temperature between two opposite sides of a gap which results in differential expansion and contraction along the length of the gap which could cause rigidly fixed fingers to jam up.

Referring now toFIGS.5to8and according to a second embodiment, a cantilevered expansion finger joint apparatus100is similar to the apparatus1shown inFIGS.1to4, with the notable exception that the cantilever mechanism further comprises a flanged back plate120and an extension on the finger unit120that slidably engages the flanged back plate120along a plane parallel to the sliding plane. When loaded by traffic over the gap, the finger unit120is prevented from rotating out of the sliding plane by means of the flanged back plate134and the extended finger unit120. More particularly, the back plate134is provided with a curved flange102that extends from the top surface of the back plate134towards the finger unit, and the finger unit120is provided with a curved extension104that extends from the bottom surface of the finger unit120towards the back plate134. A low-friction sliding layer106is affixed on the top surface of the extension104(or alternatively to the bottom surface of the flange102). When the apparatus100is assembled, the flange102and extension104vertically overlap and are in sliding contact via the sliding layer106. The curvature of the flange102conforms to the curvature of the proximal end of the finger unit120, and the curvature of the extension104conforms to the curvature of the side surface of the back plate134. The sliding layer106permits the extension104to slide relative to the flange102in a plane parallel to the sliding plane, thereby allowing the finger unit120to rotate relative to the base plate28/back plate134about the pivot axis on the sliding plane. However, the vertical overlap of the flange102and the extension104prevent the finger unit120from rotating relative to the base plate28/back plate134out of the sliding plane. In other words, the flange102and extension104serves as the cantilever mechanism to provide a cantilever support to the finger unit20and prevent the finger unit from uplifting when weight is applied on the finger ends across the expansion gap G.

The sliding layer106can be made of the same material as the top sliding ring16and bottom sliding ring18, or alternatively, with another low-friction sliding material as known in the art.

To provide additional uplift resistance, the finger joint apparatus100of the second embodiment can optionally be provided with the rigid collar of the first embodiment. Alternatively, the finger joint apparatus100of the second embodiment can be provided with a conventional pivot mechanism that does not include a rigid collar to provide cantilevering support.

Referring now toFIGS.9to12and according to a third embodiment, a cantilevered expansion finger joint apparatus200is similar to the apparatus100shown inFIGS.5to8, with the notable exception that the cantilever mechanism comprises a flanged back plate234and a cut out204on the finger unit220. That is, the finger unit220is cantilevered to the base plate28by means of a cantilever mechanism comprising the flanged back plate234and the cut-out finger unit220. More particularly, the back plate234is provided with a curved flange202that extends from the top surface of the back plate234and over a portion of the finger unit body, and the finger unit220comprises a cut-out204from its top surface that corresponds to the curved flange202. A low-friction sliding layer206is affixed over the cut-out204(or alternatively to the bottom surface of the flange202). When the apparatus200is assembled, the flange202and cut out204vertically overlap and are in sliding contact via the sliding layer206. The curvature of the flange202conforms of the curvature of the cut out206. The sliding layer206permits the finger unit body to slide relative to the flange202in a plane parallel to the sliding plane, thereby allowing the finger unit220to rotate relative to the base plate28/back plate234about the pivot axis on the sliding plane. However, the vertical overlap of the flange202and the cut out204prevent the finger unit220from rotating relative to the base plate28/back plate234out of the sliding plane. In other words, the flange202and cut-out204serve as a cantilever mechanism to provide a cantilever support to the finger unit220and prevents the finger unit220from uplifting when weight is applied on the finger ends across the expansion gap G.

Preferably, the cut-out204has a depth that corresponds to the thickness of the flange202, such that top surfaces of the flange202and finger unit220are flush.

The sliding layer206can be made of the same material as the top sliding ring16and bottom sliding ring18, or alternatively, with another low-friction sliding material as known in the art.

To provide additional uplift resistance, the finger joint apparatus200of the third embodiment can optionally be provided with the rigid collar of the first embodiment. Alternatively, the finger joint apparatus200of the third embodiment can be provided with a conventional pivot mechanism that does not comprise a rigid collar to provide cantilevering support.

Referring toFIGS.13and14and according to an alternative embodiment, a sprung pivot mechanism300can be used in any of the aforementioned cantilevered expansion finger joint apparatus embodiments.

Like the pivot mechanism shown inFIGS.1-9, the sprung pivot mechanism300comprises a top anchor bolt312, a rigid collar314, a top sliding ring316, a bottom sliding ring318and a base plate anchor26, permanently connected to the base plate, which serves to prevent the rigid collar314from rotating and further allows free downwards movement of collar314with wear of the top/or bottom sliding rings. Additionally, the rigid collar314comprises a lower section, through which all horizontal loads are transferred to the base plate and structure, extending through the annular seat25of the bore24, and the sprung pivot mechanism300further comprises a steel washer313and a spring319located in a gap in between the head of the top anchor bolt312and an annular seat of the rigid collar319. A rubber plug320or sealant (not shown) fills the open space between the top anchor bolt head313and the bore of the rigid collar314.

The spring319can be a ring made of an elastic compressible material such as urethane or rubber. The spring319is intended to reduce fatigue of the top anchor bolt312due to repetitive traffic loading. When the top anchor bolt312is tensioned, it compresses the spring319. If the top and/or bottom sliding rings316,318wear and become thinner, the compressed spring319will expand and the top anchor bolt312is expected to remain in sufficient tension to hold the rigid collar314in place and prevent the rigid collar314and therefore the finger unit20from becoming loose and/or rattling when traffic passes over. If there is any play in the finger joint apparatus due to fabrication intolerances or uneven wear, the finger joint apparatus is expected to still function. The cantilever mechanism is still expected to prevent the finger plate from rotating in a vertical plane.

All shear forces in the horizontal plane are resisted by the rigid collar314. The top anchor bolt312only experiences axial tension. The gap between the collar314and the top anchor bolt312ensures that the top anchor bolt312does not experience any bending.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Accordingly, as used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and “comprising,” when used in this specification, specify the presence of one or more stated features, integers, steps, operations, elements, and components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and groups. Directional terms such as “top”, “bottom”, “upwards”, “downwards”, “vertically”, and “laterally” are used in the following description for the purpose of providing relative reference only, and are not intended to suggest any limitations on how any article is to be positioned during use, or to be mounted in an assembly or relative to an environment. Additionally, the term “couple” and variants of it such as “coupled”, “couples”, and “coupling” as used in this description are intended to include indirect and direct connections unless otherwise indicated. For example, if a first device is coupled to a second device, that coupling may be through a direct connection or through an indirect connection via other devices and connections. Similarly, if the first device is communicatively coupled to the second device, communication may be through a direct connection or through an indirect connection via other devices and connections.

It is contemplated that any part of any aspect or embodiment discussed in this specification can be implemented or combined with any part of any other aspect or embodiment discussed in this specification.