BRACING MEMBERS FOR BUILDINGS

In the construction of steel framed buildings and other structures formed from structural steel work, such as warehouses, factory units, portal buildings or other commercial or industrial premises in the form of buildings, bracing members typically comprise tubular body members having spade end connectors. Such connectors may comprise a tongue welded to a plate itself welded across the end of tubular member and, because of the welded construction, are time-consuming and costly to manufacture. Alternatively, the connectors may comprise a tongue formed by flattening an end portion of the tubular member. Since this causes substantial deformation of the tubular member in the transitional area between the tubular member and flattened tongue significant stress is caused to the metal tubular member that often results in the appearance of cracks in the bracing member, thus weakening the bracing member. Bracing members are required primarily to reinforce the sides, floors and roofs of steel framed buildings.

According to a first aspect of the present invention there is provided a bracing member for buildings in accordance with the appended claims.

An embodiment of the present invention is described below by way of illustrative example only, with reference to the accompanying figures, of which:

Figure 1 is a side elevation of one end of a tubular bracing member according to an embodiment of the present invention;

Figure 2 is a side elevation at 90° to the view shown in Figure 1 ;

Figure 3 is a side elevation of a tubular bracing member as shown in Figures 1 and 2 in combination with a portion of a steel building frame;

Figure 4A is a side elevation of a tubular bracing member as shown in Figures 1 and 2 during the podging process in assembly to a steel building frame;

Figure 4B is a side elevation of a tubular bracing member known from the prior art during the podging process in assembly to a steel building frame;

Figure 5 is a side elevation of a tubular bracing member according to a embodiment of the present invention at an intermediate point of its manufacture; and

Figure 6 is a side elevation of a tubular member according to an alternative embodiment of the present invention at an intermediate point in its manufacture.

With reference to Figures 1 and 2, a tubular bracing member 1 according to an embodiment of the present invention has an end connector comprising parallel connecting plates 3, 5 formed with respective co-axial through-holes 7, 8. In the particular embodiment shown in Figures 1 and 2 each connector plate 3, 5 comprises a pair of through-holes. However, it will be appreciated that any number of through-holes may be provided according to the intended use. Figure 3 illustrates a tubular bracing member 1 according to an embodiment of the present invention in its intended final spatial relationship with a portion of a steel framed building 10. The building frame portion 10 includes an anchoring cleat 12 that includes a further through-hole 14. In use, the tubular bracing member 1 of the present invention is placed to one side of the anchoring cleat 12 such that the through-holes 7, 8 within the connecting plates 3, 5 of the bracing member 1 are aligned with the through-hole 14 in the cleat 12 of the building frame portion 10. A securing bolt can then be passed through the respective holes and secured with a nut.

An advantage of bracing members according to embodiments of the present invention, which is shared with the traditional welded end plate design, is that it is relatively easy to align the through holes in the connector plates with the through hole in the frame cleat when the connector plates are placed to one side of the cleat only, hi practice this is done using a tool known as a podger, which is a tapered metal spike. The podger 15 can be passed through the through holes in the connector plates and cleat even if they are not exactly aligned, as shown in Figure 4A, and used to subsequently align the holes. Since the connector plates 3,5 of embodiments of the present invention are so close together they can be viewed as a single plate during the. podging process. This is in marked contrast to the situation where the connector plates are spaced apart so as to allow the cleat to be

threaded between them, as in the bracing member discussed in UK Patent No GB2369629.

In this instance it is significantly more difficult to align the through holes by podging, since the upper and lower connector plates are effectively mis-aligned to the cleat in opposite directions, as illustrated in Figure 4B. By avoiding the need to assemble the bracing member and building frame with the anchoring cleat 12 interposed in between the connecting plates 3, 5 of the bracing member the construction process is greatly simplified and speeded up, since it is far easier to align the respective co-axial through-holes of the bracing member and anchoring cleat by simply placing the bracing member to one side of the anchoring cleat. Furthermore, none of the previously discussed disadvantages in the production of the welded plate type braces are experienced, as is discussed in more detail below.

In preferred embodiments the connecting plates 3, 5 are spaced apart by a distance of approximately 2mm so as to allow both sides of the respective connecting plates to be fully galvanised during their manufacture. In this instance the two separate connecting plates 3, 5 are pulled together into connect with one another at the time of assembly by the tightening of the securing nut and bolt. However, in other embodiments of the present invention the connecting plates 3, 5 of the bracing member may be manufactured such that the two separate connecting plates 3, 5 are in connect with one another, i.e. there is no gap in between at all.

With reference to Figures 1,2 & 5, the connecting plates 3, 5 of the tubular bracing member are formed by firstly taking a plain tubular member 40 and forming a pair of co-planar slots 16 in the walls of the plain tube 40. The slots 16 may be formed by a punching operation, in which case the interior of the tube 40 may be supported by a slotted die complementary to the punch which forms the corresponding slots in the walls of the tube. Alternatively, the slot 16 may be formed by a cutting operation, preferably a thermal cutting operation such as plasma cutting. The two tongues 30, 50 defined by the slots 16 are then pressed together, as indicated by the twin arrows A, A in Figure 5, to flatten the tongues. The through-holes 7, 8 are formed by a further punching or cutting operation, either at the same time as the slots are formed or after the tongues have been flattened. In one method of manufacture, a thin rectangular die is inserted in the slots 16 prior to a first flattening operation to force the tongues 30, 50 to flatten evenly without their respective edges

obstructing one another. The rectangular die is preferably removed and a second flattening operation performed to close any resultant gap between the tongues 30, 50. In an alternative method of manufacture the rectangular die is omitted and the tongues are pressed together in a single operation.

The advantage in forming the connector plates 3, 5 by first cutting the co-planar slots 16 is that the tube 40 undergoes reduced deformation during the subsequent flattening process of the tongues than would be the case if the corresponding end portion of a plain tube were to be simply flattened, as occurs in the known prior art. The reduced stress experienced by the tube during the formation of the connecting plates improves the operational strength of the bracing member and reduces the risk of cracking in the metal occurring, which significantly weakens the resultant structure. The stress is most significantly reduced around the closed end portion of the co-planar slots 16. To reduce cracking of the prior art flattened tubes special ductile steels can be used. However, in embodiments of the present invention normal grades of steel as used in steel buildings can be used whilst achieving the same advantages. This stress can be reduced further by enlarging the closed end of the slot 16, as indicated in Figure 6. By enlarging the closed end of the slot 16 the amount of deformation of the corresponding part of the formed tongue during the punching process is correspondingly reduced.