GB2044330A - Methods and Devices for Securing or Bracing Structural Members - Google Patents

Abstract

This invention relates to methods and devices for securing or bracing a system or framework of structural members, such as rafters or joists. Such a device may be constituted by strip 10 having regularly spaced slots 11 formed axially herein and associated nail receiving holes 12, which allow the strip 10 to be secured to structural members. The slots 11 can receive the blade of a screwdriver or other such tool to allow tensioning of the strip. The device may include an anchor 21 which can be secured in a mortar bed of a building to provide a loop 24 to which the strip 10 can be secured. The strip 10 can be used in a system of trussed rafters and in laterally braced ceiling or floor joist systems. <IMAGE>

Description

SPECIFICATION Methods and Devices for Securing or Bracing Structural Members This invention relates to methods and devices for securing or bracing a system or framework of structural members, such as rafters or joists.

Roof rafters, ceiling joists and floor joists must support a considerable load in buildings and, if the load limit is exceeded, there is the serious danger of the system of rafters or joists collapsing, possibly causing collapse of the building itself.

It is possible to strengthen floor and ceiling joists, for example by using heavy support cross members, but this is expensive and time consuming.

It is an object of the present invention to provide simple and inexpensive devices and methods for securing or bracing a system or framework of structural members so as to reduce the danger of the system collapsing.

Broadly stated, the invention consists in a device for securing or bracing a system or framework of ixed structural members such as rafters or joists, comprising a strip of strong, flexible material having spaced slots along its length for receiving a strip-tensioning device, and spaced holes for receiving nails or the like to secure the strip to the structural members.

Preferably, the longitudinal extent of each slot has a directional component parallel to the longitudinal extent of the strip.

The slots are preferably aligned parallel to the longitudinal extent of the strip, are preferably collinear and may be spaced equidistant along the strip.

The holes may be arranged in two rows parallel to the strip, each row being outside the confines of the slot.

Preferably at least one hole is positioned between each slot and an edge of the strip.

In another aspect the invention consists in a load-carrying device designed to be secured to a load-support medium such as timber or brickwork, comprising a substantially planar body having an inclined part at one end and means for receiving and retaining a tensioning or bracing strap at the other end, the device being designed so that the inclined part can bear against the support medium when a load is applied to the other end.

Preferably, the device is in the form of substantially U-shaped element, the closed end of the U being designed to receive the tensioning or bracing strap, and the free ends of the legs of the U being inclined to the body of the U.

Preferably, the end of the device for receiving the tensioning or bracing strap is inclined to the body of the device.

The two ends of the device may be oppositely inclined on opposite sides of the body of the U.

Preferably the inclined part which can bear against the support medium is at right angles to the body of the device.

The length of the planar body is preferably substantially equal to or slightly greater than the thickness of a standard building or construction block or member.

In a further aspect, the invention consists in a system of framework of fixed structural members, such as rafters or joists, which are secure or braced by means of a device as defined above, optionally with a load-carrying device as defined above.

Preferably the securing or bracing device is under an adjustable tension, and the tension is transmitted to a support medium for the structural members, such as brickwork or timberwork, via one or more load-carrying devices as defined above.

The invention also consists in a method of laterally bracing a system or framework of fixed structural members, such as floor or ceiling joists, in which a securing or bracing device as defined above is secured to each member so as to extend transversely across the members, the device being tensioned until the required degree of bracing is obtained.

Preferably two strips of flexible material are interlaced alternately over and under the structural members so that the strips cross each other between each pair of adjacent members.

In yet a further aspect the invention consists in a method of bracing or securing a system or framework of fixed roof rafters in which bracing or tensioning straps are secured to the rafters so that each strap extends diagonally across the rafters, the straps being tensioned until the required degree of bracing is obtained.

Preferably the bracing or tensioning strap is a flexible strip as defined above.

The lower ends of the straps may be secured to structual parts of a building such as brickwork.

Preferably, the straps are secured with the aid of a load-carrying device as defined above.

The straps may extend from substantially the bottom corners of the rafter system to substantially the mid-point of the ridge of the system to form a cross-shaped bracing arrangement.

The invention may be performed in various ways and some preferred embodiments, with .several modifications, will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a tensioning or bracing strap, Figure 2 is a plan view of an alternative construction of the strap, Figure 3 is a plan view of a further construction of the strap, Figure 4A is a side elevation of a load-carrying device in the form of a strap anchor, Figure 4B is a plan view of the device, Figure 5 shows the load-carrying device'of Figure 4A and 48 secured to brickwork, Figure 6 is a plan view of a trussed rafter system in a building, strengthened with tensioning straps, Figure 7 is a side elevation of the rafter system of Figure 6, Figure 8 is a plan view of a trussed rafter system with diagonal bracing and additional lateral bracing of ceiling joists, and Figure 9 is a side elevation of floor or ceiling joists laterally braced with tensioning straps.

In the described embodiments, a device for securing or bracing fixed structural members is a tensioning or bracing strap in the form of a strip of metal or plastics material which is secured to the members by, for example, nails. Three preferred forms of strip are shown in Figures 1 to 3.

In Figure 1 the strip 10, which may be cut to any desired length from a roll, has regularly spaced slots 11 formed therein. Two parallel rows of regularly spaced holes 12 are also formed in the strip 10 to receive nails in order to secure the strip to beams, rafters or joists. Each hole 1 2 is equidistant from each of its four adjacent holes, and this arrangement provides a minimum number of fixing points within a given area of beam, rafter or joist to which the strip is secured.

A fixing hole 1 3 is also provided between each slot and the edge of the strip so that the strip can be fixed to a beam, rafter or joist close to the slot.

This is particularly useful in the case of, for example, a narrow beam, rafter or joist. The slots 11 permit a screwdriver or other tensioning device to be inserted and used as a lever to tension the strip between fixing points. In this way the fixing and tensioning operation can be carried out successively along the length of the strip. The width of the strip is preferably about 25 mm and its thickness about 1 mm, the length of each slot about 12 mm, and the distance between adjacent holes about 20 mm. The distance between the mid-points of the slots is about 40 mm.

The strip shown in Figure 2 has a group of three diagonally oriented holes 12 between adjacent pairs of slots 11, and this gives a greater density of fixing points than in the Figure 1 embodiment.

The strip shown in Figure 3 has additional fixing holes so as to give an even greater density of fixing points in a given area. The lateral distance between holes is about 20 mm, as in the Figure 1 embodiment. In this embodiment there are two fixing holes 14 on a line at right angles to the length of the strip. This helps to provide strong, evenly distributed fixing points close to each slot.

It will be appreciated that the number and distribution of the fixing holes can be varied within extremely wide ranges. However, too many fixing holes tend to weaken the strip so that it cannot be tensioned successfully without the danger of snapping. The embodiment of Figures 1 to 3 provides the optimum number and distribution of fixing holes.

Referring now to Figures 4A and 4B, an anchor for the tensioning or bracing strap consists of a Ushaped bracket 20 fabricated from about 4 mm diameter metal rod, preferably galvanised mild steel. The closed end 21 of the U is inclined to the body of the U at a small acute angle of about 90 as shown in Figure 4A, and the ends 22 of the legs 24 of the U are turned out at right angles to the body of the U. The ends 22 are formed with sharp points 23 to aid the gripping of the bracket 20 on a support surface. Other inclinations of the closed end 21 and the ends 22 may be chosen according to the intended use of the anchor. The overall length of the bracket is about 100 mm and its width about 35 mm, the length of the flat body of the U being about the same as the thickness of a standard building brick.

In use, the legs 24 of the brackets 20 are secured to a support surface, such as brickwork or timber, and the tensioning or bracing strap is passed through the closed end 21. When a tension is applied to the strap, the anchor takes up the tension and retains the strap in position.

An example of the use of the anchor is shown in Figure 5. The legs 24 can be laid flat on a single skin of brickwork 30 so that the ends 22 hook over an edge of a brick and the closed end 21 projects from the opposite edge of the brick. A further layer of bricks can be laid on top of the anchor, thereby sandwiching it between two rows of bricks. If the closed end 21 is inclined upwards, as shown in Figure 5, and an upward load is applied to the end by, for example, a tensioned strap 10 connected to the anchor and extending upwardly from it, the ends 22 of the legs 24 will tend to bite into the brickwork and so resist any tendency for the anchor to work loose. The length of the legs of the anchor can be chosen for use with any standard building blocks, such as brieze blocks, wood battens etc.

The tensioning strap and the strap anchor can be used together in a variety of situations to provide strengthening or bracing of structural members, and an example of this is shown in Figures 6 and 7.

In Figures 6 and 7, a system of trussed rafters 40 in the roof of a building is braced or strengthened by means of tensioning straps 1 0.

The straps 10 are secured to each rafter 40 by means of nails at points 41 and extend diagonally across the rafters. It has been found that this type of diagonal fixing provides the strongest lateral bracing to the roof structure. The bottom ends of the straps 10 are secured at or near the bottom corners of the trussed rafter system and may be guided through appropriately positioned strap anchors 20. In Figure 6, a strap anchor 20 is secured to the top of a wallplate 42 by means of U-shaped nails or straps, the pointed ends 22 of the anchor 20 biting into the wallplate 42 and the inclined closed end 21 extending upwardly. The anchor is positioned about 30 cm from the rafter 44 adjacent the left-hand gable wall 45 so that the strap can be looped round the rafter 44 and then round the anchor 20, and finally secured to a structural part of the building by nailing.

Alternatively, the strap may be looped through the anchor 20 and secured to itself by appropriate means.

The anchors 20 can also be built into the brickwork, as shown on the right-hand side of Figure 7, and the strap can be looped through and finally secured to the wallplate at 46.

When using the straps and anchors to brace a rafter structure, the strap should first be secured at or near the bottom ends of the rafter structure, as described above, and guided diagonally across the rafters towards the ridge of the structure. In this way the strap can be secured and tensioned successively from rafter to rafter. The tensioning can be carried out by inserting a screwdriver into a slot in the strap and turning it through an angle of about 450. The strap can then be secured by nailing when in a tensioned condition.

Not only can the tensioning strap be used to tension the rafters, it can also be used to fix the wallplate 42 to the supporting brickwork, as shown in Figure 7. Straps 50 can be sandwiched in the brickwork at 51 and then tightened round the wallplate 42 to hold the wallplate 42 down on the brickwork.

In the arrangement shown in Figures 6 and 7, a separate strap 10 is secured at or near each bottom corner of the rafter structure and then guided diagonally across the rafters to the ridge of the structure. The straps can be guided to the same point on the ridge, and this produces a bracing pattern as shown in Figure 8 which is found to have the best lateral bracing effect. In addition to bracing the rafters in this fashion the ceiling joists can be laterally braced with straps 60, as shown in Figure 8. The straps 60 can be secured at their ends to structural parts of the building, such as gable walls.

A preferred form of lateral bracing for ceiling or floor joists is shown in Figure 9. The same lateral bracing can, of course, be used for any other system of parallel stuctural members.

In Figure 9 two straps 60 are interlaced over and under floor or ceiling joists 61 and are firmly secured at their ends to structural parts of a building (not shown). As in the previous examples, the straps 60 can be tensioned between fixing points as desired, by using a screw-driver.

It will be appreciated that many other tensioning or bracing functions can be carried out with the tensioning or bracing strap of the invention, with or without the help of the fixing anchors. For example, wall partitions can be strengthened or braced by stretching the strap laterally across the structural supports of the partitions.

The tensioning or bracing strap can also be used for hanging suspended ceilings, reinforcing fencing and as retaining clips.

Claims (24)

Claims

1. A device for securing or bracing a system or framework of fixed structural members such as rafters or joists, comprising a strip of strong, flexible material having spaced slots along its length for receiving a strip-tensioning device, and spaced holes for receiving nails or the like to secure the strip to the structural members.

2. A device according to claim 1, in which the longitudinal extent of each slot has a directional component parallel to the longitudinal extent of the strip.

3. A device according to claim 1 or claim 2, in which the slots are aligned parallel to the longitudinal extent of the strip.

4. A device according to any of the preceding claims, in which the slots are collinear and are spaced equidistant along the strip.

5. A device according to any of the preceding claims, in which the holes are arranged in two rows parallel to the strip, each row being outside the confines of the slots.

6. A device according to any of the preceding claims, in which at least one hole is positioned between each slot and an edge of the strip.

7. A load-carrying device designed to be secured to a load-support medium such as timber or brickwork, comprising a substantially planar body having an inclined part at one end and means for receiving and retaining a tensioning or bracing strap at the other end, the device being designed so that the inclined part can bear against the support medium when a load is applied to the other end.

8. A load-carrying device according to claim 7, in the form of a substantially U-shaped element, the closed end of the U being designed to receive the tensioning or bracing strap, and the free ends of the legs of the U being inclined to the body of the U.

9. A load-carrying device according to claim 7 or 8, in which the end of the device for receiving the tensioning or bracing strap is inclined to the body of the device.

10. A load-carrying device according to claim 9, in which the two ends of the device are oppositely inclined on opposite sides of the body of the U.

11. A load-carrying device according to any one of claims 7 to 10, in which the inclined part which can bear against the support medium is at right angles to the body of the device.

12. A load-carrying device according to any one of claims 7 to 11, in which the length of the planar body is substantially equal to, or slightly greater than, the thickness of a standard building or construction block or member.

13. A system or framework of fixed structural members, such as rafters or joists, which are secured or braced by means of a device according to any one of claims 1 to 6, optionally with a loadcarrying device according to any one of claims 7 to 12.

14. A system according to claim 12, in which the securing or bracing device is under an adjustable tension, and the tension is transmitted to a support medium for the structural members, such as brickwork or timberwork, via one or more load-carrying devices as defined in any one of claims 7 to 12.

1 5. A method of laterally bracing a system or framework of fixed structural members, such as floor or ceiling joists, in which a device as defined in any one of claims 1 to 6, is secured to each member so as to extend transversely across the members, the device being tensioned until the required degree of bracing is obtained.

1 6. A method according to claim 15, in which two strips of flexible material are interlaced alternately over and under the structural members so that the strips cross each other between each pair of adjacent members.

1 7. A method of bracing or securing a system or framework of fixed roof rafters in which bracing or tensioning straps are secured to the rafters so that each strap extends diagonally across the rafters, the straps being tensioned until the required degree of bracing is obtained.

1 8. A method according to claim 17, in which the bracing or tensioning strap is a flexible strip as defined in any one of claims 1 to 6.

19. A method according to claim 17 or claim 18, in which the lower ends of the straps are secured to structural parts of a building, such as brickwork.

20. A method according to claim 19, in which the straps are secured with the aid of loadcarrying devices according to any one of claims 7 to 17.

21. A method according to any one of claims 1 7 to 20, in which the straps extend from substantially the bottom corners of the rafter system to substantially the mid-point of the ridge of the system to form a cross-shaped bracing arrangement.

22. An anchorage for securing the end of a flexible tension member to a wall, frame, roofing components or other part of a building, comprising a substantially rigid flat metal body of appropriate dimensions to fit within a mortar bed between building bricks or blocks, the body having a loop or other means at one end for connection to the tension element, and adjacent the other end a limb displaced out of the plane of the body.

23. An anchorage according to claim 22, in which the limb or limbs have pointed ends to be driven into timber, if required.

24. A method of tensioning and fixing a device according to any of claims 1 to 6, in which a screwdriver or like tool with a flattened blade end is inserted in one of the slots and used as a lever to tension the strip, and one or more nails or like fastenings are driven through adjacent holes.