FLOATING CONNECTION BETWEEN A STRUCTURAL MEMBER AND A WALL MEMBER IN A BUILDING STRUCTURE
[0001] This international application claims priority to and the benefit of Australian Provisional Patent Application No. 2015902273, which was filed on June 15, 2015, the entire contents of which are incorporated herein by reference.
[0002] The present invention relates to a method of forming a connection between a structural member, such as a roof frame member, and a wall member, such as a wall frame top plate, such that vertical movement of/in the structural member is permitted but horizontal movement of/in the structural member and/or wall member is precluded. The invention also relates to the connection formed via the method.
[0003] The invention has particular, though not exclusive, application to the transfer of racking loads from ceiling diaphragms to non-loadbearing bracing walls in buildings, in a manner which permits vertical movement, such as that resulting from roof truss camber dissipation, of a structural member forming part of a ceiling plane/diaphragm. The invention also has particular, though not exclusive, application to the lateral stabilisation of the top edge of an internal non-load bearing wall that acts as a partition and does not contribute to the transfer of bracing forces from the ceiling plane to the foundation in a building.
[0004] According to a first aspect of the present invention, there is provided a method of forming a floating connection between a structural member and a wall member, the method comprising securing a rigid connecting element to one of the members such that it projects from that member, along a substantially upright axis, into the other member, whereby there is formed, between the element and said other member, a sliding fit which permits relative movement between the element and said other member parallel to the axis but precludes relative movement between said element and said other member perpendicular to said axis, thereby allowing the structural member to move parallel to the axis but transferring, from the wall member into the structural member or from the structural member into the wall member, loads perpendicular to the axis so as to brace the member from which it transfers the loads.
[0005] In an embodiment of the invention, the wall member is a top plate of a wall frame.
[0006] In an embodiment of the invention, said element is introduced through a surface of said other member which faces away from said one member, so as to extend through said other member, and thence driven into said one member. Preferably, said element is defined by a fastener. Preferably, the fastener is elongate along said axis. Preferably, the fastener is threaded. Preferably, the fastener is self-tapping and driven through said other member so as to form therethrough a passage in which it extends in said connection. Preferably, the fastener has a threaded portion and a threadless portion between the threaded portion and a trailing end of the fastener, and is driven through said one member such that in the connection, the threaded portion is disengaged from said one member and the threadless portion extends in the passage so as to be able to slide axially therein. Preferably, the fastener comprises a reaming portion, between the threaded portion and the threadless portion, which reams said one member during driving of the fastener and is passed through said one member so as to be spaced therefrom in said connection. Preferably, the reaming portion is not smaller in cross-section than the threadless portion. Preferably, the reaming portion is larger in cross section than the threadless portion. Preferably, the reaming portion is not smaller in cross-section than the trailing end, and the fastener is driven through said one member such that the trailing end is contained in said passage. Preferably, the reaming portion is larger in cross section than the trailing end.
[0007] Preferably, the trailing end is not larger in cross-section than the threadless portion, and the fastener is driven through said one member such that the trailing end is contained in said passage. Preferably, the trailing end and threadless portion are equally sized in cross section.
[0008] Preferably, the trailing end is configured with at least one formation engageable by a tool to effect the driving of the fastener. Preferably, the or each formation is defined by a recess formed through a trailing face of the trailing end.
[0009] Preferably, said one member is said structural member.
[0010] Preferably, the structural member is arranged above the wall member.
[0011] Preferably, said surface is an underside surface of said wall member. Preferably, said element is both introduced through said surface and driven into said one
member by an installer standing directly on an installed floor structure of a building of which said connection is to form a part.
[0012] In a preferred embodiment of the invention, the structural member forms part of a truss. The structural member may be a bottom chord of the truss.
[0013] In a preferred embodiment of the invention, the structural member is a roof frame member.
[0014] In a preferred embodiment of the invention, the truss is a roof truss or floor truss.
[0015] In a preferred embodiment of the invention, the structural member is a trimmer. The trimmer may extend between two trusses.
[0016] Preferably, the wall member is a member in a frame for an internal wall.
[0017] According to a second aspect of the present invention, there is provided the floating connection formed via said method.
[0018] The present invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings in which:
[0019] Figure 1 is a schematic elevation view showing a floating connection between a trimmer and wall frame top plate formed in accordance with a preferred embodiment of the present invention;
[0020] Figure 2 is a schematic elevation view showing a floating connection between a truss bottom chord and wall frame top plate formed in accordance with another preferred embodiment of the invention;
[0021] Figure 3 A is a schematic elevation view showing a floating connection between a truss bottom chord and wall frame top plate formed in accordance with yet another preferred embodiment of the invention, as seen side-on to the top plate;
[0022] Figure 3B is a schematic elevation view of the connection shown in Figure 3A as seen side-on to the truss;
[0023] Figure 4 shows positioning of a fastener immediately before it is driven through a wall frame top plate to establish a floating connection between that top plate and a bottom chord of a truss in accordance with an embodiment of the invention;
[0024] Figure 5 shows details of a threaded portion, reamer portion and threadless portion of the fastener; and
[0025] Figures 6A to 6C show varying extents to which the fastener may be passed through the top plate in formation of the connection according to any one of the preferred embodiments of the invention.
[0026] Each of the floating connections shown in Figures 1, 2, 3 A and 3B is between a roof frame member, positioned so as to lie in a ceiling plane/diaphragm of a building, and a top plate of a wall frame, which may be the frame of a non-load bearing wall - typically an internal wall.
[0027] Shown in Figure 1 is a timber wall frame 20, which includes a top plate 21, a timber roof frame 30, which includes parallel trusses 31, the planes of which are parallel to the wall/top plate 21, and a trimmer 32 extending horizontally between the trusses 31 so as to interconnect them, the trimmer 32 being arranged to form part of the ceiling diaphragm. Either or each of the top plate 21 and trimmer 32 is to be exploited to brace the other against horizontal loading/movement - being, in the case of the trimmer 32 being braced, axial or transverse loading/ movement in the trimmer 32, and, in the case of the top plate 21 being braced, lateral loading against the wall of which wall frame 20 is to form a part - but the trimmer 32 must remain permitted to move vertically relative to the top plate 21, including in particular when a camber with which each of the trusses 31 is preformed dissipates under the weight of a roof covering when applied over the roof frame 30. To this end, a screw 40 is driven vertically upwards through the top plate 21 and into the trimmer 32 such that it is movable vertically/ axially in the former (and slidable in the former should it come into contact therewith) but is fixed to the latter. The screw 40 is self- tapping and has a sharp tip 41 and, referring to Figure 5 (which shows parts of the screw 40 in further detail), a shank 42 configured with a threaded portion 43 including at least one thread 44, a reamer portion 45 comprising helical threads 46 regularly spaced around the shank circumference, and a threadless portion 47, the diameter of which is smaller than the (maximum) diameter of the reaming portion (being a distance between radially outermost extents of diametrically opposed ones of the threads 46) and the (maximum) diameter of the threaded portion 43 (being the outer diameter of the thread(s) 44).
[0028] Referring again to Figure 1, the screw 40 is headless, whereby a trailing end 48 thereof has a diameter equal to the diameter of the threadless portion 47 of the shank 42. Formed through a trailing face of the trailing portion 48 is a cavity 49 having a
configuration (e.g. hexagonal or cross-shaped) which is such that a complementarily shaped head of a driving tool can be received therein whereby the screw 40 can be driven up through the top plate 21, as shown in Figure 1, by the tool. The screw 40 is driven through the top plate 21 such that the threaded portion 43 and the reamer portion 45 which follows it pass fully through the top plate 21, the reamer portion thus cleaning out the hole created by the threaded portion 43, whereby the threadless portion 47, which extends in the hole/passage once the screw 40 has been driven fully home, can be displaced axially in the hole/passage (when the trimmer 32 moves vertically) but will contact the cylindrical face bounding the passage if displaced horizontally to even a very small extent (on average, half the difference between the smooth shaft diameter of the screw and the diameter of the reamer portion) as a result of horizontal loads on/ in the trimmer 32. Advantageously, owing to the screw 40 being headless, its being able to float with respect to the top plate 21 is assured, including when the screw 40 is driven so far that the trailing end 48 thereof enters the passage formed through the top plate 21, as shown in Figures 6B and 6C (there being no screw head to foul against the top plate 21). In fact, owing to the headless configuration of the trailing end 48, the position of the trailing face of that end relative to the bottom face of the top plate 21 can serve as an indicator, to the installer, of whether the degree to which the screw 40 has been passed through the top plate 21 is insufficient, excessive or appropriate. More specifically, the lengths of the threaded portion 43, reamer portion 45 and threadless portion 47 may be set such that the trailing face of the trailing end 48 becoming flush with the lower surface of the top plate 21, as shown in Figure 6A, indicates that the screw 40 has been passed through the top plate 21 and driven into the trimmer 32 to an appropriate extent, whereas the trailing face being proud of the top plate lower surface, as shown in Figure 6B, indicates that the screw 40 has been under driven, and the trailing face being countersunk with respect to the top plate lower surface, as shown in Figure 6C, indicates that the screw 40 has been overdriven.
[0029] The screw could, without departure from the invention, be configured with a head and installed such that the head is sufficiently clear of the underside of the top plate 21 so as not to preclude upward displacement of the trimmer 32.
[0030] Also, without departure from the invention, the screw could lack a reamer portion, whereby the threadless portion would lie immediately adjacent the threaded
portion, especially if the threadless portion were to have a diameter slightly less than that of the shank of the threaded portion.
[0031] In the embodiment described with respect to Figure 1, the floating connection is between the top plate 21 and a trimmer 32 which extends perpendicular to the top plate 21 and interconnects trusses 31 planes of which are parallel to the plane of the wall frame 20/wall. Referring to Figure 2, a floating connection formed in accordance with an alternative preferred embodiment of the invention can be between the top plate 21 and a bottom chord 31A of a truss 31 itself, the truss 31 including webs 3 IB and a nail plate 31C connecting the webs 3 IB to the bottom chord 31 A, the plane of the truss 31, like that of each of the trusses 31 shown in Figure 1, being parallel to the plane of the wall frame 20/wall. Referring to Figures 3A and 3B, the truss 31 may, instead of being arranged such that the plane thereof is parallel to and coplanar with the plane of the wall frame 20/wall, be arranged such that its plane is perpendicular to the plane of the wall frame 20/wall without departure from the invention, the screw 40, again, being introduced through the underside of the top plate 21 as shown in Figure 4.
[0032] In an alternative embodiment of the invention, the fastener 40 is, instead of being driven upwardly through the top plate 21, whereby it is fixed in the trimmer or bottom chord overlying that top plate 21, driven downwardly, through the trimmer or bottom chord such that it becomes fixed in the top plate 21, whereby the hole/passage is instead formed in the trimmer/bottom chord and the trimmer/bottom chord can thus float up and down with respect to the fastener (which remains stationary owing to it being secured to the top plate 21). Such an embodiment might be invoked, for example, where a stud or other member obscures the top plate from below, precluding driving of the fastener upwardly through it, or where the trimmer or bottom chord is steel (and the wall member is timber).
[0033] That said, the driving of the fastener upwardly through the top plate 21, where possible, is particularly advantageous because of ease of installer access beneath the top pate 21 and ease of siting of the appropriateness of the degree to which the fastener has been driven (as described above). The upward driving of the fastener from below can also, particularly given that there is a common availability of extended-length screw tools, eliminate the need for the installer to use a ladder to install the screw(s) to form the
each/connection embodying the invention, perhaps even permitting installer to stand on the floor to install the screw(s).
[0034] The strength of the load transfer element defined by a given screw 40 can be varied by varying the gauge of the screw. Also, the spacings of screws 40, forming respective connections embodying the invention, along the wall member can vary according to the degree of shear transfer required at particular positions along the wall member.
[0035] The formation of connections embodying the invention as described above with reference to the drawings, advantageously, is far more rapid than formation of conventional connections, requires only a single part/element (defined by the fastener) to form the connection (there being no bracket and nails to this end), and is practically foolproof, given in particular that an appropriate degree of driving of the fastener can be visually determined, as described above, and that function of the connection is not compromised if the fastener is overdriven or underdriven, as also described above.
[0036] Also, it is conceivable (though less common) that, without departure from the invention, the structural member, from which horizontal loads are to be transferred into the wall or into which horizontal loads are to be transferred from the wall, will pass through the wall, in which case that member will be arranged below the top plate 21.
[0037] The invention is thus embodied in a floating connection between a structural member and a wall member. It is to be appreciated that, without departure from the invention, the structural member, though commonly a roof truss member or trimmer, could be another member, e.g. a hanging beam, ceiling joist, ceiling batten, intermediate ceiling joist or floor truss. It is also to be appreciated that, without departure from the invention, the wall member, though commonly a wall frame top plate, could likewise be another member, e.g. a lintel, stud or nog.
[0038] The invention is not limited to interconnection of timber members; either or each of the two members between which a connection embodying the invention is formed may be formed of other material - e.g. metal, such as steel.
[0039] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit
and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.
[0040] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
[0041] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.