GB2470797A

GB2470797A - Restraining strap

Info

Publication number: GB2470797A
Application number: GB0920208A
Authority: GB
Inventors: Ian Harrison; Paul Clayton
Original assignee: Simpson Strong Tie International Inc
Current assignee: Simpson Strong Tie International Inc
Priority date: 2005-02-23
Filing date: 2005-02-23
Publication date: 2010-12-08
Anticipated expiration: 2025-02-23
Also published as: GB2470797B; GB2423532A; GB0503715D0; GB2423532B; GB0920208D0

Abstract

A retraining strap1for tying a joist or beam to a wall comprises an elongate member2and a down stand member4. The elongate member2has a plurality of fixing apertures5for securing it to a joist or beam. The down stand member4extends perpendicular to the elongate member2. At adjoining ends of the elongate member2and the down stand member4a channel shaped bend3is formed. The elongate member2and the down stand member4may be planar. The strap1may be formed from a single piece of metal sheet which may be less than 3mm thick. The down stand member4may have a plurality of fixing apertures. The sides of the channel3may be tapered.

Description

1 2423532

RESTRAINING STRAP

The present invention relates to a restraining strap for use in the building industry.

Definitions Within the context of this specification the word "comprises" is taken to mean "includes, among other things". It is not intended to be construed as "consists of only".

Within the context of this specification "a developed channel shaped bend" is taken to mean a bend at a join between members wherein the members have raised or down turned edges forming a channel having a base and sides. The sides of the channel stiffen the bend and resist straightening forces.

Background *1**

In building it is conventional to use restraining straps to tie horizontal or...* substantially horizontal structures such as floors and roofs to the vertical walls of the building in order to withstand pressures separating them caused, for example, by wind.

Conventionally such straps comprise a planar strip of metal material formed at * spaced intervals with holes by which it can be secured to the floor or a joist, trussed rafter, pitched roof, flat roof, masonry wall or roof beam. One end of the strip of metal is bent over through about 90 degrees to provide a bent over portion and the bent over portion engages the outer surface of a wall to resist pressures separating the wall and floor or roof. The strip of metal adjacent the bent over portion passes through the wall and may be twisted so that it can pass through a vertical mortar joint between two brIcks of the wall. This mortar joint is generally no more than 10mm wide while the width of the strip is greater, commonly greater than 25mm.

Because the bent over portion is simply turned through about 90 degrees and in use it is generally subject to large forces, there is a risk that the conventional strap experience failure at the bend.

GB2301604 (Caradon Catnic Limited) discloses a strengthened restraining strap comprising a longitudinally extending body and stiffening elements formed of longitudinally extending integrally formed cylindrical parts at or adjacent each longitudinal edge, the centre of the cylindrical parts being substantially aligned with the central transverse axis of the body. The stiffening elements are present over the complete length of the longitudinally extending body and it has been found that this increases the cost of production of the strap and surprisingly, if the length of the stiffening element Is significantly greater than about one quarter of the wall thickness i.e. about 25mm of the 100mm wall thickness, the capacity of the strap is reduced.

The present invention addresses or reduces at least one of the problems set out above.

Summary Of Invention S

S

Accordingly, in one aspect the present invention provides a restraIning strap comprising an elongate member and an adjoining down stand member wherein the elongate member defines a plurality of fixing apertures and is adapted to be secured along its length to a joist/beam or the like and, the down stand member extends generally perpendicular to the elongate member, and at adjoining ends of the * elongate member and the down stand member is positioned a developed channel * .*S*S * S shaped bend.

* .5.5' * * Advantageously, an embodiment of a restraining strap according to the invention * resists straightening of the bend where the down stand member adjoins the * elongate member.

Preferably, the elongate member and the down stand member are generally planar.

This provides the advantage that they can be produced from sheet materIal.

Preferably, the developed channel shaped bend comprises a bend in a continuous channel having a base and sides defined in the elongate member and the down stand member adjacent their adjoining ends. Preferably the base and the sides of the channel meet at an angle which tends to perpendicular. More preferably, they meet at an angle of about 90 degrees to about 130 degrees, more preferably about 118 degrees. This provides the advantage that superior resistance to straightening is provided at the bend where the down stand member adjoins the elongate member.

It has been found that the length of the sides of the channel to be positioned within a horizontal mortar joint in a wall is critical. In this regard, the sides of the channel to be positioned within a horizontal mortar joint (ie the sides of the channel defined In the elongate member) are about one quarter of the wall thickness. If their length Is significantly greater the mode of failure is different when pulled out of the wall and the capacity of the restraining strap is reduced. In addition, the sides of the channel taper from full height to zero height.

S S-S.

Therefore, preferably, the length of the sides of the channel at full height defined in * the elongate member extend along the elongate member about 15mm to about *.* 50mm. More preferably they extend about 20mm to about 40mm, more preferably they extend about 25mm to about 30mm, even more preferably they extend about 25mm. * S * S.,., S *.I

*5** .5k In addition, the tapering length of the sides of the channel defined in the elongate member are about 25mm to about 65mm. More preferably they are about 30mm to * * S **S * 1 about 60mm, more preferably they are about 40mm to about 50mm, even more preferably they are about 45mm S...

Preferably, the height of the sides of the channel defined in the elongate member are about 70% to about 80% of the approximate 10mm mortarjolrit thickness.

Therefore, preferably, the height of the sides of the channel defined in the elongate member is about 6.5 mm to about 8mm; more preferably about 7.0mm to about 7.4mm; even more preferably about 7.1mm measured from the upper surface of the base of the channel.

Preferably, the elongate member defines a mortar key slot. Preferably, the mortar key slot is provided by an elongate aperture In the elongate member. Preferably the elongate aperture and the elongate member share a longitudinal axis. Preferably, the elongate aperture has a length of about 30mm to about 60mm, more preferably 40mm to about 50mm, even more preferably about 45mm. In addition, preferably, the centre of the elongate aperture defined in the elongate member is positioned about 40mm to about 55mm, more preferably about 45mm to about 50mm, even more preferably, about 48mm from the end of the elongate member.

Preferably, the down stand member defines a plurality of fixing apertures. ThIs provides the advantage that the down stand member can be secured to a face of a masonry wall.

Preferably, fixing apertures defined in the down stand member are spaced an "a.

unequal distance from each other. This provides the advantage of minimlslng the.. *

risk of cracking caused by placement of fixings. a

The sides of the channel defined in the down stand member can vary between about * a! 25mm and the full length of the down stand member. However, preferably, they taper from full height to zero height. In this regard, preferably, the length of the * * S sf1 sides of the channel at full height defined in the down stand member are about y *** 15mm to about 50mm. More preferably they are about 20mm to about 40mm, * more preferably they are about 25mm to about 30mm, even more preferably they S.....

are about 25mm.

S..... * .

*:::: In addition, the tapering length of the sides of the channel defined in the down stand member are about 25mm to about 65mm. More preferably they are about 30mm to *SS..S * about 60mm, more preferably they are about 40mm to about 50mm, even more preferably they are about 45mm.

A strap according to an embodiment of the invention is preferably made from relatively thin sheet material (less than 3mm thick and preferably no more than 2mm thick).

WIth the conventional flat metal straps having a bent over end, the weakest point of the strap, against pulling forces, is the bend. In order to obtain sufficient strength the conventional straps, particularly for horizontal use, are made from 5mm thick sheet material and usually have a width of about 15mm. Advantageously, the invention enables thinner sheet material to be used.

It is another object of the present Invention in a different aspect to provide a restraining elongate strap made from a single piece of sheet metal material but of thinner gauge than conventional.

Accordingly in another aspect the present invention provides a restraining strap formed from a single piece of metal sheet material of a thickness less than 3mm comprising an elongate member and a down stand member wherein the elongate member is adapted to be secured along its length to a joist/beam or the like and * defines a plurality of fixing apertures, the down stand member extends generally in a plane substantially at right angles to the plane of the elongate member and defines a plurality of fixing apertures, and between the elongate member and the * down stand member is positioned a developed channel shaped bend. tI

**** S * aI' Preferably, a restraining strap according to an embodiment of the invention is formed from a single piece of metal sheet material of a thickness less than 2mm. *

S... SS * Such a section is stronger which allows the strap to be made of thinner material and *.*.** * to pass through a mortar joint without any need for twisting. ***. * S S

S

With advantage the majority of the length of the elongate member remains substantially flat although It may be formed with a rib or ribs. Therefore, advantageously, the elongate member does not interfere unduly with a flat deck or boards placed over the joists and the elongate member to provide a floor surface.

Detailed Description

For the purposes of clarity and a concise description features are described herein as part of the same or separate embodiments, however it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

Embodiments of a restraining strap will now be described, by way of example only, with reference to the accompanying drawings of which:-FIgure 1 is a cross sectional view of an embodiment of a restraining strap according to the invention.

Figure 2 is a perspective view of an embodiment of a restraining strap according to the Invention.

Figure 3 shows plan, side, front and sectional views of a restraining strap according to the invention (Example 2).

Figure 4 shows plan, side, front and sectional views of a restraining strap of Example *:::: 1. ; *:::: Figure 5 shows a restraining strap of Example 1. S *

* * ..

S.. Figure 6 shows location of a restraining according to Example 1. **..

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* Figure 7 shows location of a restraining according to Example 1. ..

S. ***S * S *: Figure 8 shows load deflection curves for the results described in Example 1.

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* Figure 9 shows load deflectIon curves for the results described In Example 1.

Figure 10 shows a restraining strap of Example 2.

Figure 11 shows location of a restraining according to Example 2.

Figure 12 shows location of a restraining according to Example 2.

Figure 13 shows load deflection curves for the results described in Example 2.

Figure 14 shows load deflection curves for the results described in Example 2.

Referring to Figures 1, and 2 an embodiment of a restraining strap 1 can be used horizontally or vertically to restrain structural elements within the building such as securing Joists, trussed rafters, pitched roofs, flat roofs or wall plates to masonry walls and comprises an elongate member 2 and a down stand member 4.

The elongate member 2 is planar and formed from sheet metal material of about 1.5mm thickness and about 35mm width. The sheet thickness is with advantage less than 2.5mm, preferably less than 2mm and may be less than 1.5mm. The elongate member 2 defines a plurality of fixing apertures 5 for receiving fixings 9 (eg nails or screws) by which it may be connected to a substrate such as a beam or joist.

Figure 1 shows the elongate member 2 secured by fixings 9 (eg nails or the like) to timber noggins 8 or joists 7 of a building. The fixings 9 extend through fixing apertures 5 defined by the elongate member 2. The elongate member 2 extends in.:.

* the mortar joint of a masonry wall 11 between two blocks or bricks so that the down S... . . stand member4 bears on the outer face of the blocks or bricks of this masonry wall. S... *.. S..

* Figure 2 shows that the fixing apertures 5 defined by the elongate member are *: *.*.*a * positioned adjacent the sides of the elongate member 2 and they are staggered with the advantage that this avoids splitting of the substrate to which the restraining strap 1 is fixed.

S..... * *

The down stand member 4 Is also formed from sheet metal about 1.5mm thick and defines fixing apertures 5.

As seen in Figure 1, the down stand member abuts the outer face of the masonry wall of a building.

As seen in Figure 2, the down stand member preferably defines three fixing apertures.

The developed channel shaped bend 3 comprises a bend In a continuous channel having a base and sides defined in the elongate member 2 and the down stand member 4 adjacent their adjoining ends. The base and the sides of the channel meet at an angle tending to about 118 degrees.

The sides of the channel to be positioned within the horizontal mortar joint in the masonry waIl 11 (ie the sides of the channel defined In the elongate member 2) are about one quarter of the wall thickness ie the length of the sides of the channel defined in the elongate member 2 are about 25mm.

he height of the sides of the channel defined in the elongate member 2 are about 70% to about 80% of the approximate 10mm mortar joint thickness. Therefore, preferably, the height of the sides of the channel is about 7.1mm measured from the upper surface of the base of the channel. *S..

The elongate member 2 defines an elongate mortar key slot 6 provided by an * elongate aperture in the elongate member 2. The elongate aperture and the..

elongate member share a longitudinal axis and the elongate aperture has a length of. : : about 30mm to about 60mm. In addition, the centre of the mortar key slot 6 is * S. S positioned about 50mm from the end of the elongate member 2. 5.... S... * S S

S..... S. S * Referring to Figure 3, preferred dimensions of an embodiment of a restraining strap according to the Invention are shown.

S * S

The invention will now be described with reference to the following examples:

Example 1

A design of horizontal masonry restraint strap was tested in accordance with BS EN846-4:2001.

TEST PROGRAMME

Two sets of five samples of straps were tested in each of the following test modes (a) Built into MC blockwork and tested in tension (b) Fixed to a timber joist construction tested in tension -tested with 8 No. fixings

SAM PLES

The design of strap is a single piece strap of dimensions 38x1.Smm, as shown in Figures 4 and 5.

METHOD OF CONSTRUCTION

a) Horizontal Restraint Strap Built into AAC Blockwork The tength of the straps was cut down to approximately 235mm. This incorporated 125mm, whIch Is built into the wallette and leaves 110mm projecting from the face of the wallette to enable the strap to be gripped in the vice jaws of the test rig.

Using autoclaved aerated concrete blocks (MC) blocks, the properties of which are given in Table 1, and designation (iii) mortar, the straps were built into the centre of.:.

a wallette 2 blocks long by 5 hIgh, as shown in Figure 6. The samples were covered In polythene and allowed to cure for 28 days prior to testing. *fl.

* Samples of mortar were taken and mortar prisms prepared. These were cured under * **..S. *. * * water and tested for compressive strength In accordance with 85 EN1O15-11.

Furthersamples were taken to determine its flow value in accordance with 8545511:

* 1998. A summary of these is given in Table 1.

*..�**

I

Table 1 Blockwork and Mortar Properties Mortar (28 days AAC Blocks Cured) I Corn presshie 3. 07N/mm2 I 3.75N/mm2 Strength L Flow 29.55 b) Horizontal Restraint StraD Fixed to a Timber Joist Construction The bent section of the straps was cut off to allow the straps to be gripped in the vice Jaws of the test rig. Using 8 no. 3.75mm x 30mm square twist sheradised nails, each strap was fixed to a 1.2m long timber member which itself was built Into a joist construction incorporating 3 joIsts, as shown in Figure 7. The joist had a cross sectional area of 150mm x 50mm and grade C16. The strap was fixed such that It projected 100mm from the end of the timber. This overhang represented a block width.

METHOD OF TEST

a)ilorizontal Restraint Strap Built into Blockwork The sample was placed flush with the bearing plates of the testing rig such that any reaction would be taken at a distance of 450mm away from the centre of the strap.

The strap was then clamped in the vice Jaws of the rig with sufficient force to prevent slipping of the strap during the test.

*. S S S... * S.5

A precompression of 4OkN/m was applied to the top of the wallette which was held **IS for the duration of the test. A tensile load of approximately 250N was applied to the,...

* strap in the line of the strap. This was held for 1 minute then released. The load and **.

***.*S *0 S * S deflections were zeroed and the load was applied at a rate adjusted so that failure of *: the specimen occurred between 2 and 3 minutes test duration.

*..*.* * The load was measured using a load cell and deflection was measured using two transducers. The transducers measured movement of the moveable loading frame and were located either side of, and parallel to the strap.

The load cell and transducer output was measured using a data logger which was programmed to print out readings every 3 seconds.

b) Horizontal Restraint Strap Fixed to Timber Joist Construction The sample was placed flush with the front plate of the rig. The strap projected into the vice jaws and was clamped with sufficient force to prevent slipping of the strap during the test.

The timber joist construction was securely held down and prevented from lifting and twisting with an anti-rotation device.

A tensile load was then applied to the strap in the line of the strap. The loading rate was adjusted so that failure occurred between 1 and 3 mInutes test duration.

The load was measured using a load cell and deflection was measured using two transducers. The transducers measured movement of the moveable loading frame and were located either side of, and parallel to the strap.

The load cell and transducer outputs were measured using a data logger which was programmed to print out readings every 3 seconds. *.,

RESULTS

The loads at 1 mm, 2mm and the ultimate loads and modes of failure of the.:.

** * S horizontal restraint strap built into blockwork wallettes is given in Table 2. . 5% 5 S...

S S... * .

S S * S

S * . * . S

S

S S.

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Table 2 Strap Tested in Tension Built into AAC Wailettes __________ Load (kN1 ___________ Failure Test Deflection _________________ 1mm 2mm Failure mm 1 1.49 3.36 7.66 4.91 2 2.54 4.13 5.31 10.00 3 1.68 2.73 1.55 10.00 4 3.06 5.06 5.46 10.00 - 2.59 5.68 3.56 4.90 mean 2.27 4.19 6.71 -standard 0.66 1.20 1.52 deviation lowest 1.49 2.73 4.55 _____________-The loads at 1 mm, 2mm and the ultimate loads and modes of failure of the horizontal restraint straps tested in tension fixed to a timber joist Is given in Table 3.

Table 3 FRS REV 02 Strap Fixed to Timber Joist Construction Using 8 No. 3.75 x 30mm Square Twist Sheradised Nails _________ Failure Test Failure Deflection _________________ 1mm 2mm _________ mm 1 2.74 -5.25 _9.86 10.00 2 2.71 5.20 -10.89 10.00 3 -2.74 6.09 12.62 10.00 .. : 4 2.71 5.20 11.41 10.00 2.77 4.23 12.27 10.00: * * -___________ Mean 2.73 5.19 11.41 --Standard S...

0.03 0.66 1.10 -* . * Deviation ___________ ___________ __________ _____________.. : ***.aS __________ __________ * * Lowest Value 2.71 -. 9.86 -____________ Load deflection curves for all results with both sets of tests are given in Figures 8 and 9.

COMPLIANCE WITH B5 EN 845-1:2003 This example of a restraint strap built into MC blockwork, tested in tension, has a mean failure load of 6.71 kN. Tested In tension whilst fixed to timber joists the restraint strap achieved a mean failure of 11.41 kN.

When measured in accordance with EN846-4 the displacement of any Individual strap at one third of the declared value of tensile load capacity shall not exceed 1 mm and no individual specimen load shall be less than 9O0Io of the declared value given by the manufacturer. The lowest value recorded for the strap tested in blockwork at 1 mm deflection was 1.49kN. The lowest value recorded for the strap tested fixed to a timber joist at 1 mm deflection was 2.71 kN. All Individual specimens achieved failure loads In excess of 90% of these values. However, the lower value of the two ends gives the declared value. The maximum declared value can therefore be calculated as 4.47kN.

Example 2

TEST PROGRAMME

Two sets of five samples of straps were tested in each of the following test modes (a) Built Into AAC blockwork and tested In tension (b) Fixed to a timber joist construction tested in tension -tested with 8 No. fixings .. : SAMPLES * *.*,* : The design of strap is a single piece strap of dimensions 38x1.Smm, as shown in Figures 3 and 10. S * S

* S.5 5

METHOD OF CONSTRUCTION

a) Horizontal Restraint Strap Built into MC Blockwork 5: The length of the straps was cut down to approximately 235mm. This incorporated 125mm, which was built into a wallette and left 110mm projecting from the face of the waHette to enable the strap to be gripped in the vice jaws of the test rig.

Using autoclaved aerated concrete blocks (MC) blocks, the properties of which are given in Table 4, and designation (Ill) mortar, the straps were built into the centre of a wallette 2 blocks long by 5 high, as shown in Figure 11. The samples were covered in polythene and allowed to cure for 28 days prior to testing.

Samples of mortar were taken and mortar prisms prepared. These were cured under water and tested for compressive strength in accordance with BS EN1O15-11.

Further samples were taken to determine their flow value in accordance with BS45511: 1998. A summary of these is given in Table 4.

Table 4 Blockwork and Mortar Properties AAC Blocks Mortar (28 days cured) Compressive 3. 75N/mm2 3, 15N/mm2 strength ______________ ______________ Flow -29.75 b) Horizontal Restraint Strap Fixed to a Timber Joist Construction The bent section of the straps was cut off to allow the straps to be gripped in the vice jaws of the test rig. Using 8 no. 3.75mm x 30mm square twist sheradised nails, each strap was fixed to a 1.2m long timber member which itself was built into a joist construction incorporating 3 joists, as shown in Figure 12. The joist had a cross sectional area of 150mm x 50mm and grade C16. The strap was fixed such that it * * . .s.

projected 100mm from the end of the timber. This overhang represented a block width. S S S... * S

* METHOD OFTEST.:. S. *

* aiHorizontal Restraint Strap Built into Biockwork *:::: The sample was placed flush with the bearing plates of the testing rig such that any reaction would be taken at a distance of 450mm away from the centre of the strap.

A precornpression of 4OkN/m was applied to the top of the wallette which was held for the duration of the test. A tensile load of approximately 250N was applied to the strap in the line of the strap. This was held for 1 minute then released. The load and deflections were zeroed and the load was applied at a rate adjusted so that failure of the specimen occurred between 2 and 3 mInutes test duration.

b) Horizontal Restraint StraD Fixed to Timber Joist Construction The sample was placed flush with the front plate of the rig. The strap projected Into the vice jaws and was clamped with sufficient force to prevent slipping of the strap during the test.

The timber joist construction was securely held down and prevented from lifting and twisting with an anti-rotation device. *a*.

S *5*S

* * . . . 50* The load was measured using a load cell and deflection was measured using two S *S..

transducers. The transducers measured movement of the moveable loading frame,...* and were located either side of, and parallel to the strap. *:::: 5S*5 , : The load cell and transducer outputs were measured using a data logger which was programmed to print out readings every 3 seconds.

RESU LTS

The loads at 1 mm, 2mm and the ultimate loads and modes of failure of the horizontal restraint strap built into blockwork wallettes is given in Table 5.

Table 5 FRS Strap Tested in Tension Built into MC Wallettes ___________ Load (kN) at ___________ Failure Test Deflection ___________________ 1mm 2mm Failure mm 1 3.69 6.39 9.73 10.00 2 3.67 6.60 8.25 10.00 3 2.71 5.45 9.14 10.00 - 4 3.26 5.84 8.38 10.00 4.18 6.35 9.74 10.00 mean 3.50 6.13 9.05 -standard deviation 0.55 0.47 0.71 _____________ lowest 2.71 -8.25 _____________ The loads at 1 mm, 2mm and the ultimate loads and modes of failure of the horizontal restraint straps tested in tension fixed to a timber joist is given in Table 6.

Table 6 FRS Strap Fixed to Timber Joist Construction Using 8 No. 3.75 x 30mm Square Twist Sheradised Nails _________ Load (kN) at _________ Failure Test Deflection ___________________ 1mm 2mm Failure mm *: 1 2.74 5.25 9.86 10.00 2 2.71 5.20 10.89 10.00 3 2.74 6.09 12.62 10.00 4 2.71 5.20 11.41 10.00 2.77 4.23 12.27 10.00 S... _______________ _______________ Mean 2.73 5.19 11.41 - : Standard 0.03 0.66 1.10:::: * * Deviation _____________ _____________ -. Lowest Value 2.71 _________ 9.86 ____________- * . ___________ ______________ *.** * 5' Load deflection curves for all results with both sets of tests are given in Figures 13 *.. 5*.

and 14.

COMPUANCE WITH BS EN845-1:2003 It is stated within BS EN 845-1:2003 that the traditional 3Ox5mm horizontal restraint strap, installed at 2 metre centres should achieve a declared load of 8kN.

This example of a restraint strap built into MC blockwork, tested in tension, has a mean failure load of 9.O5kN. Similarly, tested in tension whilst fixed to timber joists the restraint strap achieved a mean failure of 11.41 kN.

When measured in accordance with EN846-4 the displacement of any individual strap at one third of the declared value of tensile load capacity shall not exceed 1 mm and no individual specimen load shall be less than 90% of the declared value given by the manufacturer. The lowest value recorded for the strap tested both in blockwork and fixed to a timber joist at 1 mm deflection was 2.71 kN. The maximum declared value can therefore be calculated as 8.l3kN. All individual specimens achieved failure loads in excess of 90% of this value.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art.

Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications are covered by the *S.S appended claims. * * S S... t.t. S *

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Claims

Claims 1. A restraining strap comprising an elongate member and an adjoining down stand member wherein the elongate member defines a plurality of fixing apertures and is adapted to be secured along its length to a joist/beam or the like and, the down stand member extends generally perpendicular to the elongate member, and at adjoining ends of the elongate member and the down stand member is positioned a developed channel shaped bend.
2. A restraining strap according to claim 1 wherein the elongate member and the down stand member are generally planar.
3. A restraining strap according to claim 1 or 2 wherein the developed channel shaped bend comprises a bend in a continuous channel having a base and sides defined in the elongate member and the down stand member adjacent their adjoining ends; wherein the base and the sides of the channel meet at an angle of about 90 degrees to about 130 degrees.
4. A restraining strap according to claim 3 wherein the sides of the channel defined in the elongate member taper from full height to zero height. *1* * I.
5. A restraining strap according to claim 4 wherein the full height of the sides of * :. the of the channel defined in the elongate member are about 15mm to about * 50mm. * * * * **SS
6. A restraining strap according to claim 5 wherein the length of the sides of the *.: * .*S S. * channel at full height defined in the elongate member extend along the elongate member about 15mm to about 50mm.
7. A restraining strap according to claim 6 wherein the length of the sides of the *sSS * channel at full height defined in the elongate member extend along the elongate member about 25mm to about 30mm.
8. A restraining strap according to claim 7 wherein the length of the sides of the channel defined in the elongate member extend along the elongate member about 25mm.
9. A restraining strap according to any one of claims 4 to 8 wherein the taper in the sides of the channel defined in the elongate member has a length of about 25mm to about 65mm.
10. A restraining strap according to any one of claims 3 to 7 wherein the height of the sides of the channel defined in the elongate member Is about 6.5mm to about 8mm measured from the upper surface of the base of the channel.
11. A restraining strap according to claim 10 wherein the height of the sides of the channel defined in the elongate member is about 7.0mm to about 7.4mm measured from the upper surface of the base of the channel.
12. A restraining strap according to claim 10 or 11 wherein the height of the sides of the channel defined in the elongate member is about 7.1mm measured from the upper surface of the base of the channel. l1)13. A restraining strap according to any preceding claim wherein the elongate member defines a mortar key slot provided by an elongate aperture which * shares a longitudinal axis with the elongate member and the elongate *S.. ** aperture has a length of about 30mm to about 60mm and the centre of the * S elongate aperture defined in the elongate member is positioned about 48mm from the end of the elongate member. : * S 14. A restraining strap according to any preceding claim wherein the down stand member defines a plurality of fixing apertures.S.. SS* * 15. A restraining strap according to claim 14 wherein the fixing apertures are spaced an unequal distance from each other.16. A restraining strap according to any one of claims 3 to 15 wherein the length of the sides of the channel defined in the down stand member are between about 25mm and the full length of the down stand member.17. A restraining strap according to claim 16 wherein the sides of the channel defined in the down stand member taper from full height to zero height.18. A restraining strap according to claim 17 wherein the length of the sides of the channel at full height defined in the down stand member are about 15mm to about 50mm.19. A restraining strap according to any one of claims 17 to 18 whereIn the the taper in the sides of the channel defined in the down stand member are about 25mm to about 65mm.20. A restraining strap according to any preceding claim formed from thin sheet material less than 3mm thick.21. A restraining strap formed from a single piece of metal sheet material of a thickness less than 3mm comprising an elongate member and a down stand member wherein the elongate member is adapted to be secured along its length to a joist/beam or the like and defines a plurality of fixing apertures, * the down stand member extends generally at right angles to the elongate **** * member and defines a plurality of fixing apertures, and between the elongate * member and the down stand member is positioned a developed channel shaped bend.S..... S * . . 1 * I. 22. A restraining strap as described herein with reference to the accompanying examples or as shown in the accompanying drawings.S.....