Bracing system for a suspension system

Abstract

A bracing system 1 configured to brace a suspension system 200 for an elongate suspended support 210, comprises a first strut bracket 320 and a second strut bracket 360 which are configured to support

Description

FIELD OF THE INVENTION Embodiments of the present invention relate to a bracing system for a suspension system. In particular, they relate to a bracing system configured to brace a suspension system for an elongate suspended support. BACKGROUND TO THE INVENTION Overhead utilities include electrical or fluid (liquid / gas) conduits which are suspended from overhead structures in buildings, such as ceilings or beams. The overhead utilities rest on elongate suspended supports, such as cable trays, and are secured to overhead structures by a series of spaced suspension systems. In some implementations, lateral and vertical loads may be encountered which can cause unwanted swaying of the suspension system. Such loads may be encountered by buildings in seismic regions, or by ships, for example. To prevent swaying, suspension systems may be braced. The bracing comprises wires, or square or rectangular hollow sections which are bolted to the suspension system via gusset plates. Bracing systems are often sold as a retrofit for trapeze systems. The bracing system may be fitted by a ‘seismic team’ of workers, after the suspension system has been fitted by a team of workers for fitting suspension systems. BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION According to various, but not necessarily all, embodiments of the invention there is provided a bracing system configured to brace a suspension system for an elongate suspended support, the bracing system comprising: a first strut bracket; and a second strut bracket, wherein the first and second strut brackets are configured to support a bracing strut such that the bracing strut extends between the first and second strut brackets, wherein at least one of the first and second strut brackets comprises a protrusion having a curved side in cross-section, and wherein the respective strut bracket comprises a fixing point enabling connection of the respective strut bracket to the bracing strut such that the curved side of the protrusion faces a surface of the bracing strut to resist buckling of the bracing strut. This provides the advantage of improving structural rigidity. If the bracing strut starts to deflect or buckle under compressive load, the surface of the bracing strut moves laterally to abut the curved side of the protrusion, causing the connection to behave more like a fixed joint and less like a pin joint, to resist further deflection or buckling. The curved side of the protrusion is optimised for bracing struts which have a correspondingly curved surface in cross-section, creating a minimal average gap width or tight fit between the curved side of the protrusion and the curved surface of the bracing strut. Therefore, a curved bracing strut such as a circular hollow section can be used, having isotropic stiffness in cross-section, and rigid end connections resistant to buckling. In some examples, the respective bracket is also compatible with non-rounded bracing struts such as square or rectangular hollow sections. However, a benefit of the side of the protrusion being curved is optimisation for use with curved hollow sections. According to various, but not necessarily all, embodiments of the invention there is provided a bracing system comprising: a first strut bracket comprising an anchor connector securable to an external structure; and a second strut bracket comprising an interface connector securable to an upright strut or support beam, wherein the first and second strut brackets are configured to support a bracing strut such that the bracing strut extends between the first and second strut brackets, wherein at least one of the first and second strut brackets comprises a protrusion having a curved side in cross-section, and wherein the respective strut bracket comprises a fixing point enabling connection of the respective strut bracket to the bracing strut such that the curved side of the protrusion faces a surface of the bracing strut to resist buckling of the bracing strut. Optionally, the bracing system further comprises the bracing strut. However, it would be appreciated that seismic teams of workers may purchase lengths of strut of standardised cross-section dimension separately from the brackets, and cut the struts to the required lengths. Therefore, the bracing system could be supplied with just the brackets, and optionally fixings. Optionally, the curved side of the protrusion is convexly curved in cross-section. Optionally, the surface of the bracing strut is concavely curved in cross-section. Therefore, the convexly curved side of the protrusion and the concavely curved surface of the bracing strut are curved in a same direction as each other, and facing each other. An advantage is that the curved side of the protrusion is optimised for insertion of the protrusion into a hollow interior of a bracing strut with a rounded hollow section shape such as a circular hollow section. The gap between the curved surfaces may be of a near-constant width. Optionally, the protrusion is in the form of a prong. Optionally, the protrusion is cantilevered from a root of the respective strut bracket. Optionally, the protrusion is insertable into the bracing strut through an end hole of the bracing strut. Optionally, the protrusion is securable via the fixing point to a hollow interior of the bracing strut. An advantage is ease of assembly. Optionally, the curved side of the protrusion has a cantilever length of at least several centimetres, providing a reaction surface to react against the surface of the bracing strut when the bracing strut deflects sufficiently for the surface of the bracing strut to meet the reaction surface. An advantage is a more rigid connection because the maximum deflection of the bracing strut occurs closer to its span centre, so a longer protrusion reduces the amount of strut deflection that is possible before contact is made with the curved side of the protrusion. Optionally, the protrusion has a gross cross-sectional area less than half or less than a third of a hollow interior cross-sectional area of the bracing strut. Optionally, when the respective strut bracket is connected to the bracing strut, a centroid of the protrusion is offset to a first side of a centroid of the bracing strut, the first side being proximal to the fixing point. Optionally, when so connected, a cross-section perimeter of the protrusion is offset to the first side of the centroid of the bracing strut. An advantage is optimising material use and mass. The protrusion may be wholly located to one side of the bracing strut when the bracing strut is connected to the respective strut bracket. Optionally, the first and second strut brackets are connectable to the bracing strut such that the protrusion faces parallel to an elongate axis of the bracing strut. Optionally, one of the curved side of the protrusion and the surface of the bracing strut follows a convex arc and the other follows a concave arc, and wherein the convex arc is about a radius smaller than a radius of the concave arc. Optionally, the radius of the convex arc is greater than 85% or greater than 90% of the radius of the concave arc. Optionally, the curved side of the protrusion follows the convex arc and the surface of the bracing strut follows the concave arc. An advantage is improved fitment, because the bracing struts can be made to wide manufacturing tolerances, and with a variety of tube material thicknesses. Furthermore, a range of nominal diameters of the bracing strut can be accommodated. Optionally, the curved side of the protrusion has an arc length defined by a central angle of at least 25 degrees. Optionally, the curved side and the curved surface each have an arc length defined by a central angle of at least 25 degrees. An advantage is a rigid connection because the curved side and the curved surface are contactable with each other for at least the above arc length, notwithstanding any tolerance differences. Optionally, the fixing point is a hole configured to receive a fixing (fastener). The bracing system may further comprise the fixing. Optionally, the hole is a through-hole. Optionally, the fixing comprises a self-tapping screw configured to create a threaded hole in the bracing strut. Optionally, the fixing point is located on a second protrusion of the respective bracket which is adjacent to the (first) protrusion and separated from the first protrusion. Optionally, the second protrusion is separated from the first protrusion such that a wall of the bracing strut is receivable between the first and second protrusions. Optionally, the fixing point and corresponding fixing enable the wall of the bracing strut to be fixed between the first and second protrusions. Optionally, the fixing point is a hole through the second protrusion and facing the first protrusion. An advantage is convenience, because when a hollow section strut is inserted over one of the protrusions, the fixing can be pushed through the hole of the other external protrusion outside the hollow interior of the strut, until the tip of the fixing touches the exterior surface of the wall of the bracing strut, and then the fixing can be drilled in a self-tapping manner through the wall of the bracing strut. The hole of the external protrusion acts as a guide for where the fixing should be drilled, and supports the fixing during drilling. The internal protrusion holds the bracing strut in place during drilling. Optionally, the first protrusion and second protrusion define a pair of protrusions spaced laterally from each other and extending parallel to each other. Optionally, the pair of protrusions are spaced laterally from each other and separated from each other by a slit gap for receiving a wall of the bracing strut. A minimum width along the slit gap may be greater than a wall material thickness of the bracing strut. Optionally, the pair of protrusions are connected to a same root, the root and pair of protrusions collectively defining a fork structure. Optionally, each of the pair of protrusions comprises an inner side and an opposite outer side, wherein the inner sides of the pair of protrusions face each other and are each a curved side, curved oppositely than each other. Optionally, the minimum width of the slit gap is defined between apexes of the curved inner sides of the pair of protrusions. Optionally, each of the pair of protrusions comprises one or more of the fixing points. Optionally, the pair of protrusions provide a pair of selectable connection positions for the bracing strut, wherein in a first connection position, a fixing connects the bracing strut to the second protrusion, and wherein in a second connection position, the fixing connects the bracing strut to the first protrusion. Optionally, a fixing insertion direction for the first connection position is opposite a fixing insertion direction for the second connection position. An advantage is an adjustable connection because if the worker does not have space to position their tool (e.g., screwdriver / impact driver) to one side of the strut bracket and bracing strut, the worker can use the other connection position and position their tool to the opposite side. The worker can choose whichever connection position gives them the most space to manoeuvre their tools. Optionally, in the first connection position, the first protrusion is inside a hollow interior of the bracing strut and the second protrusion is external to the bracing strut, and the curved side of the first protrusion faces an interior surface of the bracing strut. Optionally, in the second connection position, the second protrusion is inside the hollow interior of the bracing strut and the first protrusion is external to the bracing strut, and the curved side of the second protrusion faces the interior surface of the bracing strut. Optionally, each protrusion of the pair of protrusions comprises at least one of the earlier-defined holes, and wherein the holes of the pair of protrusions are through-holes each extending from the outer side to the inner side (curved side) of the respective protrusion, wherein the outer side of each of the pair of protrusions comprises a mating surface (e.g., flat mating surface) to receive the head of the fixing. Optionally, the respective strut bracket comprises a plurality of the fixing points, enabling fixings to be secured at different span lengths along the bracing strut. An advantage is a rigid connection because the use of multiple spaced fixings provides a fixed joint. Optionally, each of the strut brackets comprises at least one protrusion as defined above. Optionally, the protrusions of the first and second strut brackets are connectable to opposite end regions of the bracing strut. An advantage is a rigid connection. Optionally, the first strut bracket comprises a strut connector securable to the bracing strut, and an anchor connector securable to an external structure, wherein the strut connector comprises one or more of the protrusions, and wherein the anchor connector comprises an anchoring point enabling the anchor connector to be connected to the external structure. An advantage is rigidity because the suspension system can be braced against an external rigid structure such as a building ceiling, or even a wall or floor in some cases. Optionally, the first and second strut brackets are configured to support the bracing strut such that the bracing strut extends from the first strut bracket to the second strut bracket. Optionally, the first strut bracket is operable to position the bracing strut extending diagonally down from the first strut bracket, towards the second strut bracket. Optionally, the strut connector and anchor connector of the first strut bracket are connected to each other by a pivot joint allowing a vertical angle between the strut connector and anchor connector to be varied. Optionally, the pivot joint has freedom of rotation of more than 90 degrees. Optionally, the pivot joint has freedom of rotation of more than 180 degrees. Optionally, the pivot joint is lockable. An advantage is adaptability because a single bracket design can accommodate a wide variety of use cases, such as bracing the suspension system against any of a ceiling, wall, or floor. Optionally, the second strut bracket comprises a strut connector securable to the bracing strut, and an interface connector securable to a part of the suspension system, wherein the strut connector comprises one or more of the protrusions, and wherein the interface connector comprises an adjustable securing device securable to the part of the suspension system. An advantage is adaptability because the suspension system can be adjustably connected or retrofitted to the suspension system. Optionally, the second strut bracket is operable to position the bracing strut extending diagonally up from the second strut bracket, towards the first strut bracket. Optionally, the strut connector and interface connector of the second strut bracket are connected to each other by a pivot joint allowing a vertical angle between the strut connector and anchor connector to be varied. 9 Optionally, the pivot joint has freedom of rotation of more than 90 degrees. Optionally, the pivot joint is lockable. An advantage is adaptability because a single bracket design can accommodate a wide variety of use cases. Optionally, the adjustable securing device of the interface connector of the second strut bracket comprises a clamp, the clamp comprising a seat for receiving the part of the suspension system, and a locking device configured to urge the part of the suspension system against the seat. Optionally, the seat comprises a hook. Optionally, the second strut bracket is configured to allow rotation of the part of the suspension system about a horizontal plane (rotation when viewed in plan view). An advantage is adaptability because the horizontal angle between the bracing system and the suspension system can vary. Along with the pivot joint(s), the bracing system can provide multiple degrees of rotational freedom, allowing the second strut bracket to be positioned almost anywhere on a virtual sphere around the first strut bracket, defined mostly by the length of the bracing strut. Furthermore, the interface connector can face a same direction regardless of where the second strut bracket is on the virtual sphere. Optionally, the locking device of the adjustable securing device of the interface connector of the second strut bracket comprises a mechanical fastener having a tip configured to press the part of the suspension system against the seat when tightened. Optionally, the mechanical fastener comprises an adjustment head allowing the threaded mechanical fastener to be tightened and loosened against the part with a tool and / or by hand. An advantage is adjustability during initial fitment and for adjustments. According to various, but not necessarily all, embodiments of the invention there is provided a system comprising the bracing system and the suspension system. Optionally, the suspension system comprises a support beam. Optionally, the suspension system comprises a horizontal support beam. Optionally, the support beam comprises an upper surface configured for the elongate suspended support to rest on. For example, the upper surface may be flat and / or horizontal, and the support beam may comprise fixing points for securing the elongate suspended support on the upper surface of the support beam. Optionally, the elongate suspended support comprises a tray for supporting suspended services such as cables or pipes. Optionally, the support beam of the suspension system is supported by at least one upright strut. Optionally, the upright strut comprises a vertical strut. Optionally, the suspension system comprises a pair of the upright struts, secured to opposite end regions of the support beam, the pair of upright struts and support beam collectively defining a trapeze. Optionally, the bracing system is securable to the upright strut, or if there are multiple upright struts, any one of the upright struts. The upright strut is the “part” of the suspension system referred to earlier. Optionally, in use, a first one of the bracing system is connected to one of the upright struts, and a second one of the bracing system is connected to the other one of the upright struts, wherein the first and second bracing systems are located to opposite lateral sides of the suspension system and face generally opposite directions than each other. An advantage is highly improved rigidity of the suspension system (such as a trapeze) against side-to-side swaying. Furthermore, the bracing system can also help to prevent forwards / backwards swaying due to its stiffness, and in 11 some examples by the plan view angle between the bracing system and the suspension system, in a horizontal plane. Optionally, more than one of the bracing system is connectable to the same part (e.g., upright strut) of the suspension system, and their bracing struts may extend at different angles relative to each other in a horizontal plane and in plan view. An advantage is even more rigidity against forwards / backwards swaying of the suspension system in the direction of the elongate suspended support. Optionally, the support beam is supported by the at least one upright strut at an adjustable height. Therefore, the support beam or each end region of the support beam is movable up and down the corresponding upright strut to a different secured heights. Optionally, the bracing system has one or more degrees of positional freedom between the first and second strut brackets, for preventing interference between the support beam and the bracing system. An advantage is adjustability, allowing the bracing system to find a location to connect to the upright strut, regardless of the height of the support beam. Optionally, the bracing strut has a higher material cross-sectional area than the upright strut. Optionally, the bracing strut has a higher second moment of area in both major and minor axes, than the upright strut. An advantage is that the bracing system is rigid and prevents longitudinal sway and side-to-side sway of the suspension system. Optionally, the upright strut comprises a rounded cross-section, and the earlier-described interface connector of the second strut bracket allows rotation of the interface connector relative to the upright strut of the suspension system, until the locking device is tightened. Optionally, the system further comprises the elongate suspended support, extending in a longitudinal direction. Optionally, the elongate suspended support is a tray (e.g., solid or basket type), extending in a longitudinal direction. Optionally, the bracing system is configured to face transverse to the longitudinal direction of the elongate suspended support, in plan view. Optionally, the suspension system is configured to face perpendicular to the longitudinal direction of the elongate suspended support, in plan view. Optionally, the bracing system is configured to face a variable transverse direction to the longitudinal direction of the elongate suspended support, in plan view. Optionally, the variable transverse direction is enabled by the horizontal rotation allowed by the second strut bracket, as defined above. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: FIG. 1 illustrates a perspective view of a system; FIG. 2 illustrates a perspective view of a bracing system; FIG. 3 illustrates a perspective view of a strut connector; FIG. 4 illustrates a top view of a strut connector connected to a bracing strut; FIG. 5 illustrates a cross-section view of a strut connector connected to a bracing strut in one connection position; and FIG. 6 illustrates a cross-section view of the strut connector connected to the bracing strut in another connection position. DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION FIG. 1 illustrates a system 1. The system 1 is an overhead utility support system 1, for supporting cables or pipes for example. The system 1 comprises an elongate suspended support 100 in the form of a cable tray. The cable tray 110 comprises a base 112 and a pair of side walls 114. In use, utilities such as pipes or cables run along the base 112. In other examples, the elongate suspended support 100 is a net or basket different than the rigid tray shown. The cable tray 110 extends in a longitudinal axis, and may have a length of many metres in a building or installation. The cable tray 110 is suspended above floor level by a plurality of suspension systems 200, spaced at intervals. FIG. 1 illustrates one such suspension system 200 in the form of a trapeze frame, comprising a pair of upright struts 220 supporting a support beam 210. The upright struts 220 are vertical or mostly vertical, and the support beam 210 is horizontal or mostly horizontal. The cable tray 110 rests on an upper surface 212 of the support beam 210, and may be secured to optional fixing points 214 on the upper surface 212 of the support beam 210. FIG. 1 shows the support beam 210 comprising fixing points 214 in the form of holes / slotted holes, allowing cable ties or other connectors to secure the cable tray 110 to the upper surface 212 of the support beam 210. The illustrated upright struts 220 and the support beam 210 are each elongate members. In examples, the upright struts 220 are threaded bars. The illustrated support beam 210 is a horizontal strut. In examples, the support beam 210 has an angled cross-section shape. The support beam 210 has openings (concealed in FIG. 1) for the upright struts 220 towards each of its ends. Each upright strut 220 extends through one of the openings in the support beam 210. If the upright strut 220 is a threaded bar, a pair of nuts can be fastened to each upright strut 220, one being above the support beam 210 and the other being below the support beam 210. The support beam 210 can be raised and lowered and correspondingly tilted by adjusting the nuts along each upright strut 220. The illustrated upright struts 220 are slender, being strong in tension but with low stiffness in bending or compression. The suspension system 200 may sway from side to side, or forwards and backwards during a seismic event, or due to the rocking effect of waves on a seaborne structure. In extreme cases, this can lead to buckling or failure of the suspension system 200. To prevent excessive deflection, FIG. 1 illustrates a bracing system 300 for the suspension system 200. The bracing system 300 may be supplied together, or separately from the suspension system 200. The bracing system 300 may be included when the suspension system 200 is being installed in countries or regions where seismic activity is higher, or on seaborne structures. The bracing system 300 comprises a first strut bracket 320, a second strut bracket 360, and a bracing strut 310 connectable therebetween to provide diagonal bracing of the suspension system 200. The bracing system 300 is securable to an upright strut 220 of the suspension system 200. The first strut bracket 320 couples a first end portion of the bracing strut 310 to an external structure such as a ceiling wall, concrete anchor, beam clamp, etc. The second strut bracket 360 connects a second opposite end portion of the bracing strut 310 to the suspension system 200, specifically to the upright strut 220. Advantageously, a plurality of such bracing systems 300 can be connected to the same suspension system 200. For example, FIG. 1 shows a separate bracing system 300 connected to each upright strut 220 of the suspension system 200. Each bracing system 300 is located to an opposite lateral (left / right) side of the suspension system 200 and elongate suspended support 100, and they face generally opposite directions. In some implementations (not shown), a pair of bracing systems 300 may be connected to the same upright strut 220, with one extending at least partially forwardly in plan view and the other extending at least partially rearwardly in plan view, to brace against forwards / backwards swaying of the suspension system 200. If replicated for the other upright strut 220, a quadrupod is defined by the bracing struts 300, in which the bracing struts 310 are triangulated when viewed in all three orthogonal planes. The illustrated bracing strut 310 is a straight strut having a closed cross-section shape such as a circular hollow tube. The illustrated bracing strut 310 is tubular along its whole length, with the first and second strut brackets 320, 360 connecting directly to the tube. In other examples, the bracing strut 310 may comprise a tube having end extensions to which the first and second strut brackets 320, 360 connect. The bracing strut 310 has a higher material cross-sectional area than the upright strut 220, for example at least 25% greater or at least 33% greater. 16 Furthermore, due to being a hollow tube, the bracing strut’s mass is distributed away from its centroid, giving it a second moment of area several times greater than that of the upright strut 220. The brackets are even more rigid than the bracing strut 310. FIG. 2 illustrates a bracing system 300 in more detail, showing the bracing strut 310 and the first and second strut brackets 320, 360. The first strut bracket 320 is shown to the left of FIG. 2. The first strut bracket 320 comprises a strut connector 340 and an anchor connector 330. The strut connector 340 is securable to one end region of the bracing strut 310 by fixings 390, and is pivotally connected to the anchor connector 330. The anchor connector 330 is securable to the external structure such as the ceiling or wall. The second strut bracket 360 is shown to the right of FIG. 2. The second strut bracket 360 comprises an identical or similar strut connector 340 securable to an opposite end region of the bracing strut 310 by fixings 390. The strut connector 340 is pivotally connected to an interface connector 370, the latter being securable to the upright strut 220 of the suspension system 200. The strut connectors 340 are partially hidden in FIG. 2 so are described later. The first strut bracket 320 comprises any appropriate anchor connector 330 for connecting to the external structure. In the illustrated example, the anchor connector 330 comprises a body 332 such as a metal plate assembly, and a plurality of anchoring points 336 in the form of fixing holes formed in the body 332, enabling the anchor connector 330 to be bolted or otherwise connected to the external structure. The first strut bracket 320 further comprises a pivot joint 334 mounted to the body 332 of the anchor connector 330, and wherein the strut connector 340 is mounted to the pivot joint 334. The pivot joint 334 is vertically rotatable by at 17 least 180 degrees, allowing the bracing strut 310 to extend in any direction along an arc of at least 180 degrees around the pivot joint 334. In some cases, the pivot joint 334 is vertically rotatable by greater than 180 degrees or greater than 185 degrees. Optionally, the pivot joint 334 is lockable, for example by tightening a locking fastener for the pivot joint 334. In the configuration shown in FIGS. 1 and 2, the bracing strut 310 extends downwardly from the first strut bracket 320, by an angle selected from the range 0 to 90 or 30 to 60 degrees. This is what may be expected when suspended services are hung from a ceiling. The second strut bracket 360 has an interface connector 370 instead of an anchor connector 330. The interface connector 370 interfaces with the upright strut 220 of the suspension system 200, or another part of the suspension system 200 such as an edge or hole of the support beam 210. The illustrated interface connector 370 comprises a body 372 comprising an adjustable securing device 376 in the form of a clamp 378. The clamp 378 comprises a curved seat 380 and a locking device 382 for clamping the upright strut 220 against the seat 380. The curved seat 380 may be G-shaped or C-shaped, for example. The locking device 382 comprises a mechanical fastener such as a bolt having an adjustment head 386 and a threaded shank 392 ending at a tip 384, wherein as the bolt is tightened, the tip 384 moves towards the seat 380 to press the upright strut 220 against the seat 380. The adjustment head 386 may be in the form of a bolt head, for example, to allow a worker to tighten and loosen the clamp 378 during assembly and adjustment. The second strut bracket 360 further comprises a pivot joint 374 mounted to the body 372 of the interface connector 370, and wherein the strut connector 340 is mounted to the pivot joint 374. The pivot joint 374 is vertically rotatable by at 18 least 90 degrees, allowing the bracing strut 310 to extend in any direction along an arc of at least 90 degrees around the pivot joint 374. Optionally, the pivot joint 374 is lockable, for example by tightening a locking fastener for the pivot joint 374. The pivot joints 334, 374 of both the first and second strut brackets 320, 360 allow the vertical angles of the anchor connector 330, the bracing strut 310, and the interface connector 370 to be varied independently from each other. Therefore, the interface connector 370 can always remain at a suitable angle for clamping the upright strut 220. Furthermore, the clamp 378 can rotate in a horizontal plane (plan view) about the upright strut 220 as long as the locking device 382 is not fully tightened. This is due to the circular cross-section shape of the upright strut 220, and the curvature of the seat 380 of the clamp 378. This combination of degrees of freedom allows the interface connector 370 to be positioned anywhere on a virtual sphere extending around the anchor connector 330 of the first strut bracket 320, the virtual sphere having a radius corresponding to the fixed length of the bracing strut 310, plus the extra radii of the first and second strut brackets 320, 360. Therefore, the angles of the bracing systems 300 are not restricted to what is shown in FIG. 1. In other examples, one or more of the pivot joints 334, 374 are replaced with fixed-angle joints. FIGS. 3-6 illustrate the strut connector 340 of each of the first and second strut brackets 320, 360 in more detail. The strut connector 340 comprises a fork structure 342, comprising a root 344 and a pair of elongate prong-like protrusions 346 cantilevered from the root 344. 19 The protrusions 346 are straight and parallel to each other and separated from each other by a slit gap 351. In cross-section, each protrusion 346 comprises an inner side 348 facing the gap 351, an outer side 350 opposite the inner side 348, and top and bottom sides 352, 354 connecting the inner and outer sides 348, 350. The inner side 348 may be an inner surface. The outer side 350 may be an outer surface. The top and bottom sides 352, 354 may be top and bottom surfaces. The inner side 348 of each protrusion 346 may be a curved side and the outer side 350 of a relatively flat side, in cross-section. In some examples, each protrusion 346 is generally D-shaped in cross-section. The protrusions 346 are mirrored so that their curved inner sides 348 face each other and their flat outer sides 350 face away from each other. The curved inner side 348 of the protrusion 346 has an arc length defined by a central angle of at least 25 degrees. Where the bracing strut 310 is a circular hollow tube, its curved surface 312 may have an arc length of 360 degrees. The arc length of the curved inner side 348 of the protrusion 346 provides a tighter and more snug connection to the curved inner side 348 of the protrusion 346. The slit gap 351 between the protrusions 346 may be formed at the metal casting stage of the bracket, rather than by post-machining such as sawing. This allows the slit gap 351 to have curved sides defined by the curved inner sides 348 of the protrusions 346. The curved inner side 348 of the protrusion 346 defines a reaction surface configured to react against the generally parallel curved surface 312 of the bracing strut 310 when the bracing strut 310 deflects sufficiently for the curved surface 312 of the bracing strut 310 to collide with the reaction surface. Each protrusion 346 comprises a pair of fixing points in the form of nonthreaded through-holes 356. The pair of holes 356 are longitudinally separated from each other along the axis of the protrusion 346. Each hole 356 may extend from the outer side 350 to the curved inner side 348. The holes 356 along each protrusion 346 may be separated from each other by several centimetres. The nearest hole 356 to the root 344 may be at least one centimetre away from the root 344. The pair of holes 356 of one of the protrusions 346 is aligned with the pair of holes 356 of the other protrusion 346. The slit gap 351 between the protrusions 346 has a width greater than a material thickness of the wall of the tubular bracing strut 310. In use, one side of the bracing strut 310 is end-fed into the slit gap 351, so that one of the protrusions 346 of the strut connector 340 enters the end hole 314 of the bracing strut 310 into the interior hollow space 316 of the bracing strut 310, while the other protrusion 346 remains external to the bracing strut 310. These are then referred to as interior and exterior protrusions 346. A threaded fixing 390 such as a self-tapping screw is then inserted through a hole 356 in the external protrusion 346, its threaded shank 392 extending through the through-hole 356 of the external protrusion 346, and drills a threaded hole 318 in the side of the bracing strut 310. The self-tapping screw fixing 390 creates the threaded hole 318 in the wall of the bracing strut 310 and therefore rigidly connects the bracing strut 310 to the external protrusion 346, without holes needing to be pre-drilled. The tip of the fixing 390 finally extends into an aligned through-hole 356 of the internal protrusion 346. In other examples, the threaded hole 318 in the bracing strut 310 is pre-drilled, so that a different fixing 390 can be used. As the fixing 390 is tightened, the head 394 of the fixing 390 mates (directly or indirectly) against a flat mating surface 358 on the outer side 350 of the external protrusion 346, and pulls the threaded hole 318 of the bracing strut 310 towards 21 the external protrusion 346. This pulls the bracing strut 310 away from the internal protrusion 346, creating a small gap 359 between the parallel curved surfaces 348, 312. At full tightness, the exterior surface of the wall of the bracing strut 310 may contact the curved inner side 348 of the external protrusion 346. Due to the similar curvature of the surfaces 348, 312, the gap 359 may be approximately constant width along its height. The width of the gap 359 depends on the wall thickness of the bracing strut 310. The gap 359 is wide for a thin-walled bracing strut 310, and narrow or non-existent for a thick-walled bracing strut 310. During operation, if buckling of the bracing strut 310 starts to occur, the gap 359 will shrink until the interior curved surface 312 of the bracing strut 310 abuts the curved inner side 348 of the internal protrusion 346, preventing further buckling. The curved inner side 348 may have a radius substantially equal to but less than the radius of the curved surface 312 of the bracing strut 310, allowing for some manufacturing tolerance and different sizes / thicknesses of the bracing strut 310. The protrusions 346 may have a cantilever length of at least several centimetres, which also defines the depth of the slit 351, and therefore the maximum overlap distance of an end region of the bracing strut 310 and the protrusions 346. The lengths of the protrusions 346 may also define the length of the curved inner sides 348. Longer protrusions 346 and further fixings 390 from the root 344 reduce the effective free span length of the bracing strut 310, making it stiffer. If the bracing strut 310 is non-circular in cross-section, the curved surface 312 of the bracing strut 310 may follow a non-circular shape. As shown by FIGS. 5 and 6, the strut connector 340 is ambidextrous, meaning that the bracing strut 310 can be inserted onto the other protrusion 346 such that the direction of the fixing 390 is reversed. Therefore, a worker can use an impact driver or similar tool from either side of the strut connector 340, by changing which protrusion 346 the bracing strut 310 is fixed to. FIGS. 5 and 6 represent first and second connection positions. In other implementations, the strut connector 340 is not ambidextrous, such that only one of the protrusions 346 may have a curved inner surface. Furthermore, one of the protrusions 346 may be omitted so that only the external protrusion 346 is used. FIGS. 5-6 also show that the protrusions 346 may be formed from solid material rather than hollow material, and therefore can have a smaller cross-sectional area than the interior hollow space 316 of the bracing strut 310 while being stiff. In fact, the illustrated protrusion 346 is laterally offset from the centroid of the bracing strut 310 in FIGS. 5-6, the protrusion 346 being located wholly to one side of the interior hollow space 316 of the bracing strut 310. In the illustrations, the curved inner sides 348 of the protrusions 346 are convex surfaces, to conform with the concave curved surface 312 of the bracing strut 310. In other examples, the bracing strut 310 may be provided with convex curved surfaces 312, and the protrusions 346 may instead comprise concave inner sides 348. As used here, the term ‘cross-section’ refers to a cross-section taken perpendicular to the elongate axis / direction of the part or collection of parts being described. For example, FIGS. 5-6 show a cross-section perpendicular to the elongate axis of the bracing strut 310, which is used to describe the crosssection shape of the bracing strut 310 as well as the generally parallel protrusions 346 of the strut connector 340. 23 Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, the suspension system 200 may be other than a trapeze frame. For example, a single upright strut 220 may connect to a support beam 210 or other type of support. Furthermore, the curved side of the protrusion 346 may be concavely curved, for connection to the outer surface of the bracing strut 310. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A bracing system configured to brace a suspension system for an elongate suspended support, the bracing system comprising:a first strut bracket; anda second strut bracket,wherein the first and second strut brackets are configured to support a bracing strut such that the bracing strut extends between the first and second strut brackets,wherein at least one of the first and second strut brackets comprises a protrusion having a curved side in cross-section, andwherein the respective strut bracket comprises a fixing point enabling connection of the respective strut bracket to the bracing strut such that the curved side of the protrusion faces a surface of the bracing strut to resist buckling of the bracing strut.

2. The bracing system of claim 1, wherein the curved side of the protrusion is convexly curved in cross section.

3. The bracing system of any preceding claim, wherein the protrusion is in the form of a prong, and wherein the protrusion is cantilevered from a root of the respective strut bracket.

4. The bracing system of any preceding claim, wherein the protrusion is insertable into the bracing strut through an end hole of the bracing strut.

5. The bracing system of any preceding claim, wherein the protrusion is a first protrusion, wherein the fixing point is located on a second protrusion of the respective bracket which is adjacent to the first protrusion and separated from the first protrusion.

6. The bracing system of claim 5, wherein the second protrusion is separated from the first protrusion such that a wall of the bracing strut is receivable between the first and second protrusions.

7. The bracing system of any of claims 5 or 6, wherein the first protrusion and second protrusion define a pair of protrusions spaced laterally from each other and extending parallel to each other.

8. The bracing system of claim 7, wherein the pair of protrusions are connected to a same root, the root and the pair of protrusions collectively defining a fork structure.

9. The bracing system of any of claims 7 or 8, wherein each of the pair of protrusions comprises an inner side and an opposite outer side, wherein the inner sides of the pair of protrusions face each other and are each a curved side, curved oppositely than each other.

10. The bracing system of any of claims 8 or 9, wherein the pair of protrusions provide a pair of selectable connection positions for the bracing strut, wherein in a first connection position, a fixing connects the bracing strut to the second protrusion, and wherein in a second connection position, the fixing connects the bracing strut to the first protrusion.

11. The bracing system of claims 9 and 10, wherein in the first connection position, the first protrusion is inside a hollow interior of the bracing strut and the second protrusion is external to the bracing strut, and the curved side of the first protrusion faces an interior surface of the bracing strut, and wherein in the second connection position, the second protrusion is inside the hollow interior of the bracing strut and the first protrusion is external to the bracing strut, and the curved side of the second protrusion faces the interior surface of the bracing strut.

12. The bracing system of any preceding claim, wherein the respective strut bracket comprises a plurality of the fixing points, enabling fixings to be secured at different span lengths along the bracing strut.

13. The bracing system of any preceding claim, wherein the first strut bracket comprises a strut connector securable to the bracing strut, and an anchor connector securable to an external structure, wherein the strut connector comprises one or more of the protrusion, and wherein the anchor connector comprises an anchoring point enabling the anchor connector to be connected to the external structure.

14. The bracing system of claim 13, wherein the strut connector and anchor connector of the first strut bracket are connected to each other by a pivot joint allowing a vertical angle between the strut connector and anchor connector to be varied.

15. The bracing system of any preceding claim, wherein the first and second strut brackets are configured to support the bracing strut such that the bracing strut extends from the first strut bracket to the second strut bracket.

16. The bracing system of any preceding claim, wherein the second strut bracket comprises a strut connector securable to the bracing strut, and an interface connector securable to a part of the suspension system, wherein the strut connector of the second strut bracket comprises one or more of the protrusion, and wherein the interface connector comprises an adjustable securing device securable to the part of the suspension system.

17. The bracing system of claim 16, wherein the adjustable securing device of the interface connector of the second strut bracket comprises a clamp, the clamp comprising a seat for receiving the part of the suspension system, and a 27locking device configured to urge the part of the suspension system against the seat.

18. The bracing system of claim 17, wherein the locking device of the adjustable securing device of the interface connector of the second strut bracket comprises a mechanical fastener having a tip configured to press the part of the suspension system against the seat when tightened.

19. The bracing system of claim 16, 17, or 18, wherein the strut connector and interface connector of the second strut bracket are connected to each other by a pivot joint allowing a vertical angle between the strut connector and interface connector to be varied.

20. The bracing system of claim 19, wherein the second strut bracket is configured to allow rotation of the part of the suspension system about a horizontal plane.

21. The bracing system of any preceding claim, wherein the suspension system comprises a support beam, wherein the support beam of the suspension system is supported by at least one upright strut, and wherein the bracing system is securable to the upright strut.

22. The bracing system of claim 21, wherein the bracing strut has a higher second moment of area in both major and minor axes, than the upright strut.

23. The bracing system of claim 21 or 22 as dependent through claim 16, wherein the upright strut comprises a rounded cross-section, and wherein the second strut bracket comprises the interface connector, and wherein the interface connector allows rotation of the interface connector relative to the upright strut of the suspension system, until the locking device is tightened.

24. The bracing system of any preceding claim, wherein the bracing system further comprises an elongate suspended support, extending in a longitudinal direction, and wherein the elongate suspended support is a tray extending in a longitudinal direction.

25. The bracing system of claim 24, wherein the bracing system is configured to face transverse to the longitudinal direction of the elongate suspended support, in plan view.T +44(0)30 0300 2000A

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