GB2363620A

GB2363620A - Reinforced timber structural member

Info

Publication number: GB2363620A
Application number: GB0109086A
Authority: GB
Inventors: Gordon Smith
Original assignee: Roof Profiles Ltd
Current assignee: Roof Profiles Ltd
Priority date: 2000-04-11
Filing date: 2001-04-11
Publication date: 2002-01-02
Also published as: GB0008738D0; GB0109086D0

Abstract

A timber structural member 2 is reinforced at the site of a localised load 9 by the application of a metal plate 5b having a plurality of nail portions, e.g. a nail plate made by cutting and bending V- shaped portions out of the plane of the plate. The structural member may be a roof truss as shown, a beam or a lintel.

Description

2363620 METHOD AND APPARATUS FOR REINFORCEMENT OF STRUCTURAL MEMBERS 1 The

present invention relates to a method of 2 reinforcement of structural members and a composite 3 building member for use therewith.

4 Timber structural members have been used in building 6 and construction for hundreds of years, and although 7 many structural members for large buildings are now 8 manufactured from steel, timber is still used in the 9 bulk of house-building projects However, although timber has several considerable advantages over 11 other materials with its lower production costs and 12 ease of fabrication, it is not as stiff as steel.

13 At present, in order to provide local stiffening of 14 timber members such as, for example, roof trusses, it is often necessary to provide additional 16 structural members or to increase the size of the 17 timber members, thereby increasing manufacturing and 18 construction costs.

1 In the areas of the building and construction field

2 which utilise timber, it is known to use connector 3 plates or nail plates to secure joints between 4 individual timber members These connector plates are commonly fabricated from metal and have V-shaped 6 cuts made in them during the fabrication process.

7 The cut portions are bent through 900 so as to 8 produce a large number of serrated portions or tangs 9 in the plates The serrated portions then effectively act as nails so that the connector 11 plates can be attached by pressure to a pair of 12 timber roof members to secure the joint between 13 them Examples of such plates can be seen in 14 U 54659604 and U 55560177 However, such plates are solely concerned with achieving a robust join 16 between two timber members, rather than reinforcing 17 either of the members being co-joined.

19 An attempted solution to the problem of reinforcing of timber members has been proposed in U 54274241, 21 where metal reinforcing strips are provided along 22 the entire length of each timber member However, 23 this solution is both expensive and impractical when 24 it is desired to only provide localised reinforcement of the member Another solution was 26 proposed in U 54586550, wherein metal reinforcing 27 plates are provided on either or both top and bottom 28 faces of the timber member However, such 29 reinforcement is only appropriate for addressing tension and compression forces in the member, rather 31 than improving rigidity and reducing deflection, 32 which is an aim of the present invention A yet 1 further solution was offered by U 55809735, in which 2 a number of reinforcing members are fitted to a 3 timber member As with '241, however, the cost- 4 effectiveness of this solution is reduced by applying the reinforcing members along the entire 6 length of the timber member None of the 7 aforementioned prior art solutions addresses the

8 problem of providing localised reinforcement of 9 timber members against local loadings.

11 It is therefore an aim of the present invention to 12 provide a method of locally stiffening structural 13 timber members without requiring larger timber 14 sections or additional structural members It is a further aim of the present invention to provide an 16 apparatus for use in such a method It is a yet 17 further aim of the present invention to provide a 18 stiffening arrangement which is more cost effective 19 than existing arrangements.

21 According to a first aspect of the present invention 22 there is provided a structural member reinforced 23 against at least one localised load, said member 24 comprising:

an elongate beam member having two 26 substantially planar side faces; and 27 at least one elongate plate of metal attached 28 to at least one of said planar side faces of said 29 beam member proximate the at least one localised load; 31 said elongate plate having a plurality of nail 32 portions extending into said beam member.

2 Preferably, said metal is steel.

4 Preferably, said nail portions on said elongate plate are a plurality of shaped cut portions, said 6 cut portions being bent away from said elongate 7 plate so as to be substantially perpendicular to the 8 horizontal plane of said elongate plate.

9 Preferably, said shaped cut portions are V-shaped.

11 Preferably, said elongate plate is attached to said 12 planar side face of said beam member by application 13 of pressure.

Preferably, said elongate beam member is adapted to 16 be connected to a plurality of similar elongate beam 17 members Preferably, said elongate beam member is 18 manufactured from timber.

Preferably, said elongate beam member is a member 21 selected from the group consisting of rafters, 22 joists, purlins, and lintels.

24 Preferably, said elongate plate is shorter than the beam member.

27 Preferably, the beam member has a plate on each of 28 said two side faces.

According to a second aspect of the present 31 invention, there is provided a roof truss comprising 1 a structural member in accordance with the first 2 aspect of the present invention.

4 According to a third aspect of the present invention, there is provided a method of reinforcing 6 a structural timber member against at least one 7 localised load, comprising the steps of:

8 selecting at least one point along the length 9 of the member where the at least one localised load is to be applied; 11 attaching an elongate metal plate to at least 12 one portion of a planar side face of said member 13 over an intermediate length of the member, the 14 intermediate length including said one point where said load is to be applied; 16 wherein said elongate plate has a plurality of 17 nail portions extending into said timber member.

18 19 Preferably, said elongate metal plate is attached to said planar face of said timber member by 21 application of pressure.

22 23 Preferably, the structural timber member is a 24 structural member in accordance with the first aspect of the present invention.

27 Preferred embodiments of the present invention will 28 now be described, by way of example only, with 29 reference to the following drawings, in which:

31 Figure 1 shows a reinforced timber floor joist 32 of an attic truss; 2 Figure 2 shows a reinforced timber rafter of 3 the attic truss shown in Fig 1; Figure 3 shows a projected view of a reinforced 6 timber beam; and 8 Figure 4 shows a projected view of a reinforced 9 structural door lintel.

11 Figure 1 shows an attic roof truss 1 manufactured 12 from timber The roof truss 1 is made up of a pair 13 of rafters 2,3 and a floor joist 4 A number of 14 auxiliary support members 6,7,8 also provide support between the rafters 2,3 and floor joist 4 In the 16 particular example shown in Fig 1, it is a portion 17 of the floor joist 4 which is to be strengthened 18 against localised loadings Thus, a metal plate 5 a 19 has been cut to a rectangular shape similar to the side face of the floor joist 4 The plate 5 a is 21 attached to the floor joist 4 by way of a large 22 number of serrated portions on the plate 5 a which 23 act as nails or hooks which embed themselves in the 24 timber joist 4 when the joist 4 and plate Sa are squeezed together under pressure Thus, with the 26 plate 5 a embedded in the joist 4, the joist 4 is 27 reinforced against localised loadings occurring at 28 points along the joist 4 between the support members 29 6,8 Thus, a relatively small deflection of the joist 4 occurs thanks to the reinforcement provided 31 by the metal plate 5 a As the deflection of the 32 joist 4 under localised loadings is reduced, the 1 number of trusses 1 required in the roof space may 2 also be reduced, to the benefit of cost and space 3 considerations.

4 In each of the examples given herein, an initial 6 step is undertaken prior to the attachment of the 7 plate to the timber member In this initial step, a 8 point or points are selected on the timber member 9 where it is anticipated that the localised loadings will occur Following this selection, one or more 11 of the plates may be located at the points or areas 12 of localised load to provide the reinforcement.

13 14 Figure 2 shows the same roof truss 1 as Fig 1, but with a metal plate 5 b now attached to a rafter 2.

16 Again, as in Fig 1, the plate 5 b is manufactured to 17 closely follow the surface dimensions of the side 18 face of the member to be strengthened in this 19 case, the rafter 2 The rafter 2 has the plate 5 b embedded in it in the same manner as in Fig 1, and 21 is being subjected to two localised point loads 9 22 which are acting at two distinct points on the 23 rafter 2 Once more, the embodiment of Figure 2 24 shows how points on a structural member where localised loadings are anticipated can be 26 strengthened by use of the reinforced member.

27 Deflection of the rafter 2 is again reduced thanks 28 to the added rigidity of the plate 5 b.

29 Figure 3 shows a projected view of a reinforced 31 timber member produced in the same manner as the 32 members of Figures 1 and 2 In this instance, the 1 timber member is a purlin joist 10 The purlin 2 joist 10 is shown being acted on by local point 3 loads 11,12,13 and by reactionary forces 14,15.

4 These loads 11,12,13 and reactionary forces 14,15 cause deflection of the joist 10 The reinforcement 6 provided by the plate 5 either reduces or eliminates 7 the deflection of the joist 10.

9 Figure 4 shows a final example of a reinforced member in use In this example, the plate 5 is 11 embedded in a door lintel 17 which forms part of a 12 door frame 16 Again, three localised point loads 13 18,19,20 (representing the wall loads) act downwards 14 on the door lintel 17 which is reinforced by the plate 5 The plate 5 could also be used in a 16 similar manner with a window lintel or the like.

18 It should be noted that the examples shown in 19 Figures 3 and 4 have the plate 5 extending along the whole length of the structural member for 21 illustrative purposes only In use, it is intended 22 that the plate 5 is only used on sections of members 23 where localised loadings are anticipated Thus the 24 plate will usually be shorter than the member.

26 The addition of reinforcing plates to joists and 27 trusses gives a number of benefits over conventional 28 timber members While the main benefit of the 29 present invention will be the increased rigidity of structural members at points where localised 31 loadings are anticipated, another benefit is that 1 the plates give additional protection to the timber 2 in the event of a fire.

4 The metal plates can be produced in varying lengths and widths so that they can be fitted to a wide 6 variety of timber members Members such as chords 7 for attic trusses, purlin beams, girder and bolted 8 trusses, floor joists, structural lintels, and 9 bridles are all examples of timber members which can all have specific areas reinforced with the metal 11 plates.

12 13 Modifications and improvements can be incorporated 14 without departing from the scope of the invention.

For example, a plate may be attached to both side 16 faces of the member to further reinforce the member.

Claims

1 1 A structural member reinforced against at least 2 one localised load, said member comprising:

3 an elongate beam member having two 4 substantially planar side faces; and at least one elongate plate of metal attached 6 to at least one of said planar side faces of said 7 beam member proximate the at least one localised 8 load; 9 said elongate plate having a plurality of nail portions extending into said beam member.

12 2 A structural member as claimed in Claim 1 13 wherein said metal comprises steel.

14 3 A structural member as claimed in either Claim 16 1 or Claim 2 wherein said nail portions on said 17 elongate plate comprise a plurality of shaped cut 18 portions.

4 A structural member as claimed in Claim 3 21 wherein the cut portions are bent away from said 22 elongate plate so as to be substantially 23 perpendicular to the horizontal plane of said 24 elongate plate.

26 5 A structural member as claimed in either Claim 27 3 or Claim 4 wherein said shaped cut portions are V- 28 shaped.

1 6 A structural member as claimed in any preceding claim wherein said elongate plate' is attached to 3 said planar side face of said beam member by 4 application of pressure.

6 7 A structural member as claimed in any preceding 7 claim wherein said elongate beam member is adapted 8 to be connected to a plurality of similar elongate 9 beam members.

11 8 A structural member as claimed in any preceding 12 claim, wherein said structural member is 13 manufactured from timber.

14 9 A structural member as claimed in any preceding 16 claim wherein said elongate beam member is a member 17 selected from the group consisting of rafters, 18 joists, purlins, and lintels.

19 10 A structural member as claimed in any preceding 21 claim wherein said elongate plate is shorter than 22 the beam member.

23 24 11 A structural member as claimed in any preceding claim wherein the beam member has a plate on each of 26 said two side faces.

27 28 12 A roof truss comprising a structural member 29 according to any of claims 1 to 11.

1 13 A method of reinforcing a structural timber 2 member against at least one localised load, 3 comprising the steps of:

4 selecting at least one point along the length of the member where the at least one localised load 6 is to be applied; 7 attaching an elongate metal plate to at least 8 one portion of a planar side face of said member 9 over an intermediate length of the member, the intermediate length including said one point where 11 said load is to be applied; 12 wherein said elongate plate has a plurality of 13 nail portions extending into said timber member.

14 The method of Claim 13 wherein said elongate 16 metal plate is attached to said planar face of said 17 timber member by application of pressure.

18 19 15 The method of either Claim 13 or Claim 14 wherein the structural timber member is a structural 21 member according to any of Claims 1 to 12.

23 16 A structural member reinforced against at least 24 one localised load substantially as hereinbefore described with reference to the accompanying 26 drawings.

28 17 A roof truss substantially as hereinbefore 29 described with reference to the accompanying drawings.

1 18 A method of reinforcing a structural timber 2 member against at least one localised load 3 substantially as hereinbefore described with 4 reference to the accompanying drawings.