GB2438854A

GB2438854A - Wall ties

Info

Publication number: GB2438854A
Application number: GB0611256A
Authority: GB
Inventors: Steven Mullineaux
Original assignee: WALLFAST Ltd
Current assignee: WALLFAST Ltd
Priority date: 2006-06-08
Filing date: 2006-06-08
Publication date: 2007-12-12
Also published as: GB0611256D0

Abstract

An elongate tie 10 has a leading end 16 and a grooved portion 20 disposed part-way along the length of the tie and extending over part of the length of the tie generally equal to the thickness of the structural member. The grooved portion has one or more grooves 18 so that the grooved portion has a smaller maximum cross-sectional diameter than that of a leading portion 22 of the tie adjacent the grooved portion and nearer the leading end and has a smaller maximum cross-sectional diameter than that of a trailing portion 24 of the tie adjacent the grooved portion and further from the leading end. The tie is inserted, leading end first, into a hole through the thickness of the structural member so that the grooved portion becomes generally aligned with the thickness of the structural member and so that after such insertion the hole has a non-circular cross-section and the leading and trailing portions having maximum cross-sectional diameters that are greater than the minimum cross-sectional diameter of the hole. The tie is then turned about its axis so that, as viewed in the longitudinal direction of the tie, the leading and trailing portions partly overlap the structural member around the hole and so that the structural member enters the groove or grooves.

Description

TITLE

Wall ties

DESCRIPTION

This invention relates to the tying of walls to structural members such as steel frames.

When a building is being constructed of a steel frame and masonry walls, it is often desirable to tie the walls to the frame. It is also sometimes necessary as part of remedial work to tie a existing masonry wall to a steel member, for example of box-section, I-section, channel-section or Z-section. A known tying method uses an elongate wall tie that is inserted through a hole in the wall and then forced into a pilot hole in the structural member so that the wall tie and structural member are deformed and become held together by friction and interference. Part of the tie remains in the hole though the wall, which is then filled and adhesive, mortar, resin or grout to lock the tie to the wall. Various designs of wall tie have been proposed and some examples are described in patent documents GB2262560A and W000/6 1 887A 1. Typically, the wall tie may have a star-shaped cross-section so it is fluted, and the flutes may be arranged in a helical fashion along the wall tie so as to form a very coarse-pitched screw thread.

The existing wall ties and fitting method rely on friction to prevent the wall tie sliding out of the hole in the steel member. Ensuring sufficient friction between the wall tie and the steel member is a problem. Also, the helically-fluted wall ties rely on the locking of the wall tie to the wall and the torsional yield strength of the tie to prevent the tie unscrewing itself from the steel member. Another problem is that if the wall tie and structural member are formed of electrochemically dissimilar metals (i.e. of different nobility), galvanic corrosion may occur between the wall tie and structural member which may serve to weaken them or the connection between them.

An aim of the present invention, or at least specific embodiments of it, is to overcome, at least to some extent, the problems mentioned above.

In accordance with a first aspect of the present invention, there is provided a method of fitting a wall tie to a structural member. The method uses a tie that is elongate and has a leading end and a grooved portion disposed part-way along the length of the tie and extending over part of the length of the tie generally equal to the thickness of the structural member. The grooved portion has one or more grooves so that the grooved portion has a smaller maximum cross-sectional diameter than that of a leading portion of the tie adjacent the grooved portion and nearer the leading end and has a smaller maximum cross-sectional diameter than that of a trailing portion of the tie adjacent the grooved portion and further from the leading end. The tie is inserted, leading end first, into a hole through the thickness of the structural member so that the grooved portion becomes generally aligned with the thickness of the structural member and so that after such insertion the hole has a non-circular cross-section and the leading and trailing portions having maximum cross-sectional diameters that are greater than the minimum cross-sectional diameter of the hole. The tie is then turned about its axis so that, as viewed in the longitudinal direction of the tie, the leading and trailing portions partly overlap the structural member around the hole and so that the structural member enters the groove or grooves.

The method of the first aspect of the invention therefore does not rely solely, or at all, on friction to prevent the tie simply being withdrawn from the hole. Instead, the leading and trailing portions of the tie partly overlap the structural member around the hole so as to provide positive locking against longitudinal movement between the tie and the structural member.

Furthermore, in the case of a helically formed wall tie, the method of the first aspect of the invention obviates any significant torsional loading occurring between the wall tie and the structural member once the wall tie has been fitted.

The tie is preferably covered, at least in the region of the groove or grooves, with a corrosion protection coating. In this case, immediately after the insertion step, the tie and the hole are preferably shaped and sized such that, after the turning step, a layer of the corrosion protection coating remains between the tie and the structural member. Although some of the corrosion protection coating may be scraped from the leading portion of the tie during the insertion step, because a layer of the corrosion protection coating remains between the tie and the structural member after the turning step, the tie and structural member can be protected against galvanic corrosion between them.

In one example of the method, the hole may be non-circular immediately before the insertion step takes place. in this case, immediately before the insertion step, the cross-sectional shape of the hole may be generally similar to the cross-sectional shape of the leading portion of the tie, and the cross-sectional size of the hole may be generally similar to, or a clearance fit for, the cross-sectional size of the leading portion of the tie. The tie can therefore be freely inserted into the hole, or may need to be lightly driven into the hole; however, there is no need for significant deformation of the tie or of the structural member around the hole during the insertion step. The hole may initially be formed to be circular, and the method may further include the steps, before the inserting step, of driving a punch tool or wedge tool into the circular hole to render it non-circular, and then removing the tool.

In another example of the method, the hole is generally circular immediately before the insertion step, and the tie acts during the insertion step to render the hole non-circular.

The tie may have one or more flutes, and the flute or flutes may be helical.

The method preferably further includes the step, after the turning step, of bonding the tie to a wall.

In accordance with a second aspect of the present invention, there is provided a wall tie per se for use in the method of the first aspect of the invention, the tie being elongate and having a leading end and a grooved portion disposed part-way along the length of the tie and extending over part of the length of the tie, the grooved portion having one or more grooves so that the grooved portion has a smaller maximum cross-sectional diameter than that of a leading portion of the tie adjacent the grooved portion and nearer the leading end and has a smaller maximum cross-sectional diameter than that of a trailing portion of the tie adjacent the grooved portion and further from the leading end. The tie is preferably covered, at least in the region of the groove or grooves, with a corrosion protection coating. The tie preferably has one or more flutes, which may be helical.

The invention also extends to a wall that is tied to a structural member by a wall tie fitted by the method of the first aspect of the invention, or by a wall tie per se of the second aspect of the invention.

Specific embodiments and examples of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1A is a side view of a first embodiment of wall tie; Figure lB is a cross-sectioned view of the wall tie, taken on the section line lB-lB shown in Figure 1A; Figure 2A & 2B are longitudinally-sectioned views of the wall tie as it begins to enter a hole in a structural member, taken on the section lines 2A-2A and 2B-2B, respectively, shown in Figure 2C; Figure 2C is a cross-sectioned view of the wall tie as it begins to enter the hole in the structural member, taken on the section line 2C-2C shown in Figure 2A; Figures 3A to 3C are similar to Figures 2A to 2C, respectively, but after the wall tie has started to engage the hole in the structural member; Figures 4A to 4C are similar to Figures 3A to 3C, respectively, but after the wall tie has been forced further into the hole in the structural member; Figures 5A to 5C are similar to Figures 4A to 4C, respectively, but once a groove in the wall tie has reached the structural member; Figures 6A to 6C are similar to Figures 5A to 5C, respectively, but after the wall tie has been turned through 45 ; Figure 7A to 7D are sectioned side elevations illustrating the tying of a wall under construction to a structural member; Figure 8A to 8D are sectioned side elevations illustrating the tying of an existing wall to a structural member; Figures 9A & 9B are similar to Figures 1A and lB. but showing a tool that may be used to pre-form the hole in the structural member before insertion of the wall tie; Figure 1OA is an isometric view of a second embodiment of wall tie; Figure lOB is a cross-sectional view of the wall tie of Figure 1OA in its grooved portion; Figure IOC shows the initial shape of a hole in a structural member to receive the wall tie of Figure 1OA; Figure 1OD shows the shape of the hole in a structural member after the wall tie has been inserted; Figure 1OE is a cross-sectional view of the wall tie and structural member after the wall tie has been inserted and turned; Figures hA to liD are similar to Figures lOB to 1OE, respectively, but showing a third embodiment of the wall tie and the corresponding holes in the structural member; Figures 12A to 12E are similar to Figures 1OA to 1OE, respectively, but showing a fourth embodiment of the wall tie and the corresponding holes in the structural member; Figures 13A to 13D are similar to Figures 12B to 12E, respectively, but showing a fifth embodiment of the wall tie and the corresponding holes in the structural member; Figures 14A to 14D are similar to Figures 12B to 12E, respectively, but showing a sixth embodiment of the wall tie and the corresponding holes in the structural member; Figure 15A to 15D are similar to Figures 12A, 12B, 12C and 12E, respectively, but showing a seventh embodiment of the wall tie and the corresponding holes in the structural member; Figure 16A to 16D are similar to Figures 15A to 15D, respectively, but showing an eighth embodiment of the wall tie and the corresponding holes in the structural member; Figure 17A to 17D are similar to Figures 15A to 15D, respectively, but showing a ninth embodiment of the wall tie and the corresponding holes in the structural member; and Figure 18A to 18C are similar to Figures 15B to 15D, respectively, but showing a tenth embodiment of the wall tie and the corresponding holes in the structural member.

Referring to Figures 1A and 1B, the wall tie 10 is an elongate member of stainless steel, for example of grade 304' or 316'. The wall tie 10 has the cross-sectional shape of a four-pointed star so that it has four longitudinal ribs 12 and four longitudinal flutes 14. A leading end 16 of the wall tie 10 is tapered to a point. Part-way along the wall tie 10, notches 18 are formed in the ribs 12 so that the four notches 18 can be considered to form a discontinuous grooved portion 20 around the wall tie 10. The leading portion 22 of the wall tie 10 between the leading end 16 and the grooved portion 20, the grooved portion 20, and at least part of a trailing portion 24 of the wall tie 10 behind the grooved portion 20 are all covered by an corrosion-resistant coating 26, for example by dipping. The coating 26 may be of paint applied by brushing, spraying or dipping, of a plastics material applied by hot-dipping, or of a metal applied by plating, the plating metal having an anodic value close to that of the metal of the structural member with which the wall tie 10 is to be used. The coated grooved portion 20 has a maximum cross-sectional diameter XG that is substantially less than the identical maximum cross-sectional diameters XL,XT of the coated leading and trailing portions 22,24, respectively, of the tie 10. After coating, the grooved portion 20 has a width G in the longitudinal direction ofthe tie 10.

Referring to Figures 2A to 2C, the tie 10 is intended to be secured to a mild-steel structural member 28 having a thickness T that is preferably equal to the groove width G. A pilot hole 30 is drilled through the structural member 28 having a diameter XH that is preferably equal to the groove diameter XG. However, the hole diameter XH may be slightly greater than the groove diameter XG, but is substantially less than the leading and trailing portion diameters XL,XT. The tie 10 is offered up to the hole 30 leading end 16 first.

The tie 10 is then forced into the hole 30 by any suitable method, for example using a manual hammer or a power hammer. As shown in Figures 3A to 3C, as the leading end 16 of the tie 10 is forced into the hole 30, the tapering ribs 12 at the leading end 16 of the tie 10 deform the structural member 28 so that four notches 32 are formed around the periphery of the hole 30. Also, the structural member 28 scrapes some of the corrosion resistant coating 26 off the tie 10 in the places 32 where the tie 10 engages the structural member 28.

Referring to Figures 4A to 4C, once the leading portion 22 of the tie 10 has entered the hole 30, the notches 32 in the hole 30 have become fully formed, and the tie 10 becomes easier to force further into the hole 30, it merely being required to overcome the friction between the tie 10 and the structural member 28 and to scrape more of the corrosion resistant coating 26 from the ribs 12.

Forcing of the tie 10 into the hole 30 continues until the grooved portion 20 becomes aligned with the structural member 28, as shown in Figures 5A to 5C, whereupon the tie 10 becomes relatively slack in the hole 30, depending on the difference between the original diameter XH of the hole 30 and the diameter XG of the grooved portion 20.

The tie 10 is then turned about its longitudinal axis through an angle of 450 relative to the structural member 28 to the position shown in Figures 6A to 6C. As the tie 10 is turned, the portions 34 of the structural member 28 between the notches 32 that have been formed around the hole 30 enter the notches 18 of the grooved portion 20 of the tie 10, so that the tie 10 becomes positively locked against longitudinal movement relative to the structural member 28.

It should be noted however that, because the width G of the coated grooved portion 20 of the tie is not less than the thickness T of the structural member 28, and because the initial diameter XH of the hole 30 is not less than the diameter XG of the coated grooved portion 20 of the tie 10, a Continuous portion 36 of the coating 26 remains between the tie 10 and the structural member 28. In the case where the coating 26 is of paint or plastics, it prevents direct electrical contact between the stainless steel of the tie 10 and the mild-steel of the structural member 28, so that, despite the different anodic values of the two metals, galvanic corrosion will not occur due to the lack of an electrical connection between the two metals. In the case where the coating 26 is of plated metal, the small difference in anodic value between the plating metal and the mild-steel of the structural member 28 prevents any significant galvanic corrosion occurring between the plating metal and the structural member 28.

Figures 7A to 7D illustrate how a single-skinned masonry waIl 38 under construction is tied to a steel frame 28, only one web 40 of which is shown in the drawings. Before the level of the wall 38 approaches the position where a tie 10 is to be used, a pilot hole 30 of diameter XH is drilled through the web 40, as shown in Figure 7B. The tie 10, as described above with reference to Figures 1A to 6C, is then driven into the hole 30 until the grooved portion 20 becomes aligned with the web 40, and then the tie 10 is turned about its longitudinal axis through 45 sO that the tie 10 becomes longitudinally locked relative to the web 40 and electrically insulated from it, as shown in Figure 7C. Building of the waIl 38 then continues above the tie 10 so that the tie becomes embedded in the mortar 42 between two courses of the blocks 44 of the wall 38, as shown in Figure 7D. Once the mortar 42 has hardened it bonds the tie 10 in place so that the tie 10 cannot move longitudinally, or turn, relative to the wall 38, and therefore so that the tie 10 cannot turn relative to the web 40, and accordingly so that the tie 10 cannot move longitudinally, or turn, relative to the frame 28.

When a similar method is used for tying a double-skinned cavity wall under construction to a steel frame, a tie 10 is preferably used that is sufficiently long to interconnect the two skins of the wall in addition to tying the wall to the steel frame.

Figures 8A to 8D illustrate how an existing single-skinned masonry wall 38 is tied to a steel frame 28, only one web 40 of which is shown in the drawings. A hole 46 of a diameter XW is drilled through a block 44 of the wall, the diameter XW being greater than (or equal to) the leading and trailing portion diameters XL,XT of the tie 10. A pilot hole 30 is drilled through the web 40, as shown in Figure 8B. The tie 10, as described above with reference to Figures 1A to 6C, is then passed through the hole 46 and driven into the hole 30 until the grooved portion becomes aligned with the web 40, and then the tie 10 is turned about its longitudinal axis through 45 so that the tie 10 becomes longitudinally locked relative to the web 40 and electrically insulated from it, as shown in Figure 8C. The hole 46 is then filled by injecting an adhesive material 48 such as resin or grout into it. Once the adhesive material 48 has hardened it bonds the tie 10 in place so that the tie 10 cannot move longitudinally, or turn, relative to the wall 38, and therefore so that the tie 10 cannot turn relative to the web 40, and accordingly so that the tie 10 cannot move longitudinally, or turn, relative to the frame 28.

When a similar method is used for tying an existing double-skinned cavity wall to a steel frame, a tie 10 is used that is sufficiently long to bridge the two skins of the wall in addition to tying the wall to the steel frame, and the tie 10 is bonded to the skin of the wall that is further from the steel frame.

In the methods described above with reference to Figures 1A to 8D, the tie 10 is driven into a circular pilot hole 30 that is drilled through the steel frame 28, and the steel frame 28 becomes deformed around the hole 30, as can be seem particularly with reference to Figures 2C to 6C so that the hole 30 has notches 32 produced by the ribs 12 of the tie 10. The tie 10 therefore needs to be sufficiently strong and tough to produce the notches 32. In order to enable a less strong and tough tie 10 to be employed, once the circular pilot hole 30 has been drilled, it can then be deformed using a tool 50 as shown in Figures 9A and 9B. The tool 50 is made from hardened tool steel. As shown in the drawings, the tool 50 may have a somewhat similar shape to the uncoated core of the tie 10, but with a more shallowly tapered leading end 52 and without a grooved portion corresponding to the grooved portion 20 of the tie 10. In use, the tool 50 is driven into the pilot hole 30 as far as its parallel, ribbed portion 54, and is then removed before insertion of the tie 10. The tool 50 may be modified so that it has a somewhat similar shape to the coated tie 10, but again with a more shallowly tapered leading end and without a grooved portion corresponding to the grooved portion 20 of the tie 10. The modified tool will therefore deform the steel frame 28 around the hole 30 sufficiently that no significant amount of the coating 26 will be scraped off the tie 10 when it is subsequently inserted into the hole 30.

Further embodiments of the invention will now be described with reference to the remaining drawings. In the further description, it is to be taken that these embodiments have similar features to the first embodiment described above, except where otherwise stated.

In the second embodiment of Figures 1OA to bE, the tie 10 has the cross-section of a three-pointed star, as seen in Figure lOB. Furthermore, the ribs 12 and flutes 14 are helically formed so that the tie 10 acts as a screw. This modification may also be applied to the first embodiments of the invention described above, and to the further embodiments of the invention described below. As the tie 10 is driven into the hole 30 in the steel member 28 it forms three notches 32 as shown particularly in Figure 1 OD.

In the third embodiment of Figures 1 1A to 1 1D, the tie 10 has a cross-section that is circular but with two opposed generally- triangular ribs 12.

In the fourth embodiment of Figures 12A to 12E, the tie 10 has a cross-section that is circular but with equiangularly spaced generally-square ribs 12.

In the fifth embodiment of Figures 13A to 12D, the tie 10 has a cross-section that is circular but with only one generally-square rib 12.

In the sixth embodiment of Figures 14A to 14D, the tie 10 has a cross-section that is circular but with two opposed generally-square ribs 12.

In the seventh embodiment of Figures 15A to 15D, the tie 10 has a cross-section of an equilateral triangle, and the cross-section of the notched portion 22 is circular. The hole 30 in the steel member 28 is formed by a triangular punch so as to be the same size as the triangular cross-section of the tie 10. The tie 10 does not therefore need to deform the structural member 28 around the hole 30 as the tie 10 is driven into the hole 30. After insertion, the tie 10 is turned through 600.

In the eighth embodiment of Figures 16A to 16D, the tie 10 has a cross-section of an equilateral triangle, and the cross-section of the notched portion 22 is like a circle with three flats, as seen in Figure 16B. The hole 30 in the steel member 28 is formed by a triangular punch so as to be larger than the triangular cross-section of the tie 10 but with an inscribing circle 56 that is slightly smaller than the generating circle 58 for the notched portion 22. The tie does not therefore need to deform the structural member 28 around the hole 30 as the tie 10 is driven into the hole 30. After insertion, the tie 10 is turned through until it jams as shown in Figure 16D.

-10 -In the ninth embodiment of Figures 17A to 17D, the tie 10 has a square cross-section, and the cross-section of the notched portion 22 is like a circle with four flats, as seen in Figure 17B. The hole 30 in the steel member 28 is formed by a square punch so as to be larger than the square cross-section of the tie 10 but with an inscribing circle 56 that is slightly smaller than the generating circle 58 for the notched portion 22. Again, the tie 10 does not therefore need to deform the structural member 28 around the hole 30 as the tie 10 is driven into the hole 30.

After insertion, the tie 10 is turned through until it jams as shown in Figure 17D.

The tenth embodiment of Figures 18A to 18C is similar to the eighth and ninth embodiments, except that the cross-section of the tie 10 and hole 30 are pentagonal.

It is desirable that the wall ties 10 described above should not facilitate the passage of water between the steel member 28 and the wall 38 or between the two leaves of the wall 38 in the case of a cavity wall. In the case where the wall tie 10 is helically formed, for example as described above with reference to Figures 7A to 8D and 1OA to bE, the vertically undulating lowermost surface of the wall tie 10 may serve to prevent water passage along the wall tie 10.

In the case where the wall tie 10 is not helically formed, it may be provided with a water stop part-way along its length, such as an annular notch in the surface of the wall tie 10, or a rubber ring that tightly encircles the wall tie 10.

It should be noted that the embodiments of the invention have been described above purely by way of example and that many other modifications and developments may be made thereto within the scope of the present invention.

Claims

CLAIMS

1. A method of fitting a wall tie to a structural member having a thickness, the method comprising the steps of: (i) using such a tie that is elongate and has a leading end and a grooved portion disposed part-way along the length of the tie and extending over part of the length of the tie generally equal to the thickness of the structural member, the grooved portion having one or more grooves so that the grooved portion has a smaller maximum cross-sectional diameter than that of a leading portion of the tie adjacent the grooved portion and nearer the leading end and has a smaller maximum cross-sectional diameter than that of a trailing portion of the tie adjacent the grooved portion and further from the leading end; (ii) inserting the tie, leading end first, into a hole through the thickness of the structural member so that the grooved portion becomes generally aligned with the thickness of the structural member, after such insertion the hole having a non-circular cross-section and the leading and trailing portions having maximum cross-sectional diameters that are greater than the minimum cross-sectional diameter of the hole; and (iii) turning the tie about its axis so that, as viewed in the longitudinal direction of the tie, the leading and trailing portions partly overlap the structural member around the hole and so that the structural member enters the groove or grooves.

2. A method as claimed in any preceding claim, wherein the tie is covered, at least in the region of the groove or grooves, with a corrosion protection coating.

3. A method as claimed in claim 2, wherein, immediately after the insertion step, the tie and the hole are shaped and sized such that, after the turning step, a layer of the corrosion protection coating remains between the tie and the structural member.

4. A method as claimed in any preceding claim, wherein the hole is non-circular immediately before the insertion step.

5. A method as claimed in claim 4, wherein, immediately before the insertion step, the cross-sectional shape of the hole is generally similar to the cross-sectional shape of the leading portion of the tie, and the cross-sectional size of the hole is generally similar to, or a clearance fit for, the cross-sectional size of the leading portion of the tie.

-12 - 6. A method as claimed in claim 5, wherein the hole is initially formed to be circular, and further including the steps, before the inserting step, of driving a punch tool or wedge tool into the circular hole to render it non-circular, and then removing the tool.

7. A method as claimed in any of claims 1 to 3, wherein the hole is generally circular immediately before the insertion step, and the tie acts during the insertion step to render the hole non-circular.

8. A method as claimed in any preceding claim, wherein the tie has one or more flutes.

9. A method as claimed in claim 8, wherein the flute is, or flutes are, helical.

10. A method as claimed in any preceding claim, further including the step, after the turning step, of bonding the tie to a wall.

11. A method of fitting a wall tie to a structural member, substantially as described with reference to the drawings.

12. A wall that is tied to a structural member by a wall tie fitted by a method as claimed in claim 10 or 11.

13. A wall tie for use in a method as claimed in any of claims 1 to 11, the tie being elongate and having a leading end and a grooved portion disposed part-way along the length of the tie and extending over part of the length of the tie, the grooved portion having one or more grooves so that the grooved portion has a smaller maximum cross-sectional diameter than that of a leading portion of the tie adjacent the grooved portion and nearer the leading end and has a smaller maximum cross-sectional diameter than that of a trailing portion of the tie adjacent the grooved portion and further from the leading end; 14. A wall tie as claimed in claim 13, wherein the tie is covered, at least in the region of the groove or grooves, with a corrosion protection coating.

15. A wall tie as claimed in claim 14, wherein the tie has one or more flutes.

16. A wall tie as claimed in claim 15, wherein flute is, or flutes are, helical.

17. A wall tie substantially as described with reference to the drawings.

18. A wall that is tied to a structural member by a wall tie as claimed in any of claims 13 to 17.