GB2374643A

GB2374643A - A butt joint between the end of a timber I-beam and a transverse closure

Info

Publication number: GB2374643A
Application number: GB0109966A
Authority: GB
Inventors: Roger Smith
Original assignee: Marlow & Co Ltd
Current assignee: Marlow & Co Ltd
Priority date: 2001-04-21
Filing date: 2001-04-21
Publication date: 2002-10-23
Anticipated expiration: 2021-04-21
Also published as: EP1251213A3; GB0109966D0; EP1251213A2; GB2374643B; US20020152706A1

Abstract

A butt joint between the end of a timber I-beam (10) and a transverse closure such as a rim joist (28) is formed by there being a hole (30) in each of an upper (14) and a lower flange (16) of the I-beam (10) and two further holes (44, 46) through the closure (28) and into the end of the I-beam (10), each further hole (44, 46) being generally perpendicular and intersecting one of the holes (30) in the flanges (14, 16) of the I-beam (10). A cross dowel (32, 33) having a threaded opening (34, 35) is inserted in each of the holes (30) in the flanges (14, 16) of the I-beam (10) and a threaded bolt (40, 42) is introduced into each of the further holes (44, 46) such that the threaded bolts (40, 42) engage the threaded opening (34, 35) in the dowels (32, 33) to secure the I beam (10) and the closure (28) together.

Description

Title: Structural timber floor assembly Field of invention

This invention concerns structural assemblies of timber which serve as prefabricated roofs or floors (often referred to as decks) for buildings, particularly but not exclusively, timber framed buildings.

Backgrgund to the invention Prefabricated timber buildings are generally delivered to site in the form of prefabricated wall panels and roof trusses. The ground floor wall panels, when erected, provide load-

bearing supports for f rst-floor flooring, the peripheral regions of which will in general provide a bearing for the first floor load bearing wall panels.

Timber I-beams are now used in the construction industry as an alternative to solid timber beams, and comprise a thin vertical web, typically made from oriental strand board, and top and bottom chord members (rails or flanges) made from solid or laminated timber. The I- beam section is more structurally efficient than a solid rectangular section and can be made to larger dimensions than is available in solid timber.

Originating in the USA more than 20 years ago, they are now gaining acceptance in the UK and other European countries.

In most applications, these beams are used as a direct replacement for solid timber and are supplied to site as individual components for assembly by site carpenters.

T The assembly details are very similar to those used for solid timber comprising mainly nails or screws for fixing members together with the use of metal joist hangers for load bearing construction.

Thus each flooring-panel or deck is constructed on site inter alla from a plurality of parallel spaced-apart fabricated timber I-beam joists each formed from a narrow web of timber and upper and lower rails or flanges formed from laminated veneer lumber, routed to accommodate the upper and lower edges of the web material. The I-beam joists are butt-

jointed to the joists (sometimes called rim-beams) which extend orthogonally to the rims of the I-beam joists, with the rim joists crossnailed on site to the ends of the I-beams.

Bracing between the I-beam joists resists lateral movement or tilting of the I-beam joists, and where appropriate the flooring panel or deck may include areas in which I-beam joists run perpendicularly to other I-beam joists, and are buttjointed at their ends to a rimjoist or another I-beam joist.

Such a structure is generally satisfactory when constructed on site as a first floor deck, sandwiched between ground floor and first floor wall panels. However the handling of such flooring panels or decks, after prefabrication, during storage, shipping from factory to site, and when lifted (usually by crane) into position at first floor level, can result in twisting and distortion of the panels, generating significant bending and shearing forces on the joints between the component parts. The result is that the flooring panel can become weakened and in particular joints between the ends of the I-beam joists and rimjoists can open-up. It is an object of the present invention to provide an improved method of connecting I-

beam joists to orthogonal timber components such as rim joists, to reduce the tendency for mix-handling and bending of the panel to open-up the joints between the joists.

Summary of He invention

According to the present invention a method of forming a joint between the end of a timber I-beam joist and a transverse rimjoist comprises the steps of: 1) forming two holes a short distance from the end of the I- beam to be buttjointed to the rirnjoist, one in each of the upper and lower rails (or flanges) of the I-beam section, the two holes being coaxial and generally aligned with and parallel to the web of the I-

beam section, 2) locating the rimjoist in place and forming two further holes through the rirnjoist and into the ends of the upper and lower rails (flanges) of the I-beam joist, generally perpendicular to and intersecting the first two holes, 3) inserting two cross-dowels into the two first holes, each having a transverse threaded opening, and aligning the openings with the holes which intersect the holes containing the cross-dowels, 4) inserting threaded bolts into the intersecting holes to engage in the threaded openings in the cross-dowels, and tightening the bolts so as to draw the rirnjoist towards the abutting end of the I-beam joist, and thereby clamp the rimjoist thereto.

Where a roofing or flooring panel is comprised of two or more such I-beam joists in a parallel spaced apart array, with ends of the I-beam joists abutting a perpendicular closure or rimjoist, a similar joint made up of two cross-dowels and co-operating bolts, is provided between the ends of each said I-beam joist and the rimjoists.

The cross-dowels may be formed from metal, or from a rigid plastics material or from a composite material.

The bolts are typically formed from metal or a rigid plastics material.

A load spreading washer may be located between the head of each bolt and the rimjoist, or each bolt head may include an integral load spreading flange for increasing the area of the bolt head which is to make contact with the rimjoist.

The ends of the holes through the rimboist through which the bolts pass into the rimjoist may be enlarged to accommodate the heads of the bolts, so that the latter are wholly contained within the rimjoist.

Where the upper and lower rails (flanges) of the I-beam joist are laminated, the holes which are to receive the cross-dowels preferably extend generally perpendicular to the laminations. The invention also lies in a prefabricated timber roofing or flooring panel or deck, constructed inter alla from parallel spaced apart laminated timber I-beam joists buttjointed to the side faces of perpendicularly extending rimjoists at opposite ends of the I-beam joists, wherein the joints between the ends of the I-beam joists and the rimjoists are formed by bolts and cross-dowels, wherein the latter extend perpendicularly to the laminations forming the upper and lower rails (flanges) of the I-beam joists and the bolts extend transversely through the rimjoists and are threadedly engaged in the cross-dowels.

The invention also lies in a laminated timber I-beam joist having crossdowels located transverse to the direction of the laminations forming the upper and lower rails (flanges) of the I-beam section, close to at least one end thereof, to enable the I-beam to be buttjointed to a transversely extending rimjoist by means of bolts which in use extend through the rimjoist for threaded engagement in the cross-dowels in the I-beam joist.

The invention also lies in a cross-dowel adapted to be secured in a laminated flange of a timber I-beam joist, wherein the dowel is generally cylindrical in configuration and is formed an external screw thread profile the external diameter of which increases from the end of the dowel which is to be first introduced into the hole in the laminated flange, towards the other end thereof, and the said other end includes a screwdriver slot or other

s tool engaging means, to enable it to be screwed into the hole in the laminated flange of the I-beam joist.

The screw thread may be of the self-tapping variety.

The invention also lies in a cross-dowel adapted to be secured in a laminated flange of a timber I-beam joist, wherein the external surface of the dowel is formed with at least one annular barb, and preferably a plurality of such annular barbs, in the form of a fir tree, the external diameter of the barbs increasing from the end which is first intruded into the hole in the laminations, towards the other end thereof, whereby in use the dowel may be secured in the laminated rail by introducing the barbed end into a pre-formed hole in the laminated flange and driving the dowel into the hole using a hammer or mallet or a power driver. Preferably the end of the dowel which is visible even after it has been driven into the flange of the I-beam joist, is formed with a screwdriver slot or other means whereby it can be rotated whilst embedded in the flange, to enable the transverse threaded opening therein to be aligned to receive a rimjoist securing bolt.

It has been found in practice that a roof or flooring panel constructed in accordance with the invention is less susceptible to distortion damage during handling, storage and/or shipment, than are similar flooring panels when constructed using conventional cross-

nailing techniques.

A cross-dowel connection may be formed between the end of one rimjoist and an abutting face of an adjoining rimjoist at a corner of a roof or flooring panel embodying the invention. The invention thus allows timber I-beams to be constructed into larger building sections.

Thus for example, beams and sheeting can be made up into larger prefabricated floor decks or roofing panels and delivered to site for lifting into position by crane.

Site assembly techniques using nails, screws and metal joist hangers do not provide the strength and rigidity suitable for large prefabricated components subject to the loads imposed during handling and lifting. These loads are different from those encountered on site and in situ and require joints with additional rigidity and strength.

The invention provides a solution to these problems for use at the junction of I-beams with supporting rimboards or rimjoists and for the first time it is now possible to industrialise the assembly process of roofing and flooring decks etc. The invention will now be described by way of example with reference to the accompanying drawing in which: Fig 1 is an exploded perpendicular view of a joint between the end of a timber I-beam joist and a rimjoist, embodying the invention; Fig 2 illustrates a cross-dowel, suitable for use in the joint of Fig 1; Fig 3 shows the initial stages of making the joint of Fig 1; and Fig 4 shows the completed joint.

Detailed description of the illustrated embodiment.

In Fig 1 a timber I-beam joist 10 is shown formed from a relatively thin vertical web of timber/timber composite material 12, the upper and lower longer edges of which are adhesively bonded into routed grooves in the upper and lower flanges or rails 14, 16 each of which is formed by laminating a larger number of thin strips of timber, the laminations running parallel to the length dimension of the beam (as shown) and the stack being orientated generally at right angles to the web 12. The laminations are denoted by

The end of the beam is cut square so that the cut ends 22, 24 of the upper and lower rails occupy the same plane as does the cut end 26 of the web 12.

A timber rim joist 28 is to be buttjoined to the end faces 22, 24, 26 of the I-beam joist 10.

In accordance with the invention holes are formed in the upper and lower rails (only the upper one 30 being visible in Fig 1) and cross-dowels such as 32, 33 are located in each of the two holes, with a threaded transverse openings 34, 35 in the dowels aligned with orthogonal holes 36 and 38 which intersect the holes in the upper and lower flanges.

The joint is completed by inserting two threaded bolts 40, 42 through two pre-drilled holes 44, 46 in the rimjoist 38, so as to enter and pass through the holes 36 and 38 respectively, to engage in the threaded transverse openings (such as 34 in the case of dowel 32) in the dowels. Tightening the bolts into the dowels draws the rimjoist into a tight fit on the ends 22, 24, 26 of the I-beam joist 10.

A typical cross-dowel cast and machined from metal, is shown at 48 in Fig 2.

Figs 3 and 4 show in cross section how the bolt 42 and dowel 33 fit into the orthogonal holes 38 and39 respectively.

Both holes 38 and 38 are conveniently formed by drilling and both are drilled beyond the region in which the two holes intersect, so as to accommodate the driven ends of the dowel and bolt respectively.

It is to be understood that the head of the bolt may be more like a flat nail head, to reduce the need for undercutting the hole 38. In this event a screwdriver slot (which may to advantage be a crossed slot to receive a cross-headed screwdriver) is formed in the end face of the head of the bolt.

Although not shown the dowel may be tapered and/or formed with annular rims to create a barbed or f rtree connection win the tunber joist.

Claims

1. A method of forming a butt joint between the end of a timber I-beam joist and a transverse closure such as a rimjoist comprising the steps of: I) forming two holes a short distance from the end of the I-beam to be buttjointed to the closure, one in each of the upper and lower flanges of the I-beam section, 2) locating the closure in place and forming two further holes therethrough and into the ends of the upper and lower flanges of the I-beam joist, generally perpendicular to and intersecting the first two holes, 3) inserting two cross-dowels into the two first holes, each having a transverse threaded opening, and aligning the threaded openings with the intersecting holes, and 4) inserting threaded bolts into the intersecting holes to engage in the threaded openings in the cross-dowels, and screwing the bolts into the dowels so as to draw the abutting end of the I-beam joist towards the closure, and thereby clamp it to the closure.

2. A roofing or flooring panel comprised of two or more I-beam joists joined as claimed in claim 1 to at least one perpendicular closure, the Ibeam joists forming a parallel spaced apart array, with ends of the Ibeam joists abutting the perpendicular closure, wherein a joint made up of two cross-dowels and co-operating bolts is provided between the end of each of the I-beam joists and the closure.

3. A roofing or flooring panel as claiTned in claim 2 wherein the crossdowels are formed from metal, or from a rigid plastics material or from a composite material.

In he

4. A roofing or flooring panel as claimed in claim 2 or 3 wherein the bolts are formed from metal or a rigid plastics material or a composite material

5. A roofing or flooring panel as claimed in claim 2, 3 or 4 wherein a load spreading washer is located between the head of each bolt and the closure.

6. A roofing or flooring panel as claimed in claim 2, 3 or 4 wherein each bolt head includes an integral load spreading flange for increasing the area of the bolt head which is to make contact with the closure.

7. A roofing or flooring panel as claimed in claim 2, 3 or 4 wherein the ends of the holes through the closure through which the bolts pass into the I-beam are enlarged to accommodate the heads of the bolts, so that the latter are at least partly contained within the thickness of the closure.

8. A roofing or flooring panel as claimed in any of claims 2 - 7 wherein the upper and lower flanges of the I-beam joist are laminated, and the holes which are to receive the cross-dowels extend generally perpendicular to the laminations.

9. A roofing or flooring panel as claimed in claim 8 wherein the holes in the upper and lower flanges are generally aligned with the web of the Ibeam section.

10. A roofing or flooring panel as claimed in claim 8 or 9 wherein the holes in the flanges are co-axial.

11. A prefabricated timber roofing or flooring panel or deck, constructed from parallel spaced apart laminated timber I-beam joists buttjointed to the side faces of perpendicularly extending rimjoists at opposite ends of the I-beam joists, wherein the joints between the ends of the I-beam joists and the rimjoists are formed by bolts and cross-dowels, wherein the latter extend perpendicularly to the laminations forming the upper and lower flanges of

t the I-beam joists, and the bolts extend transversely through the rimjoists and are threadedly engaged in the cross-dowels.

12. A laminated timber I-beam joist having cross-dowels located therein transverse to the direction of the laminations forming the upper and lower flanges of the I-beam section, close to at least one end thereof, to enable the I-beam to be buttjointed to a transversely extending closure by means of bolts which in use extend through the closure for threaded engagement in the cross-dowels in the I-beam joist.

13. A cross-dowel adapted to be secured in a laminated flange of a timber I-beam joist to enable the I-beam joist to be secured to a closure in accordance with the method of claim 1, wherein the dowel is generally cylindrical in configuration and is formed with an external screw thread profile and one end of the dowel includes tool engaging means (such as a screwdriver slot), to enable it to be screwed into a hole in the laminated flange of the I-beam joist.

14. A cross-dowel as claimed in claim 13 wherein the screw thread is of the so-called self tapping variety.

15. A cross-dowel as claimed in claim 13, wherein the external diameter of the screw thread profile increase from the end of the dowel which is to be first introduced into the hole in the laminated flange, towards the other end which includes the tool engaging means.

16. A cross-dowel adapted to be secured in a laminated flange of a timber I-beam joist to enable the I-beam joist to be secured to a closure in accordance with the method of claim 1, wherein the external surface of the dowel is formed with at least one annular barb for retaining the dowel in a hole in the laminated flange.

17. A cross-dowel as claimed in claim 16 wherein the dowel includes a plurality of annular barbs.

18. A cross-dowel as claimed in claim 17 wherein the external diameter of the barbs increases from the end which is to be first introduced into the hole in the I-beam laminations, towards the other end thereof to form a so-called fir-tree connection.

19. A method of securing a cross-dowel as claimed in claim 18 wherein the dowel is driven in using a hammer, or mallet or power driver.

20. A cross dowel as claimed in any of claims 16-19 wherein the end of the dowel which will be visible after it has been driven into the flange of the I-beam joist, is formed with a tool engaging means such as a screwdriver slot whereby it can be rotated whilst embedded in the flange, to erasable the transverse threaded opening therein to be aligned to receive a securing bolt.

21. A flooring or roofing panel as claimed in any of claims 2 to 11 wherein a cross-dowel connection is formed between the end of one closure and an abutting face of an adjoining closure at a corner of the panel.

22. A dowel for receiving a bolt to form a joint between an I-beam joist and a perpendicular closure, or between two perpendicular closures, constructed substantially as described herein with reference to and as illustrated in the accompanying drawings.

23. A method of joining an I-beam joist to a perpendicular closure such as a rimjoist or rim-beam substantially as herein described with reference to and as illustrated in the accompanying drawings.

24. A flooring or roofing panel formed from I-beams and rim-beam closures, a cross dowel, or a laminated I-beam joist fitted with at least one cross dowel constructed

1Q substantially as herein described with reference to and as illustrated in the accompanying drawings.

24. A flooring or roofing panel formed from I-beams and rim-beam closures, a cross dowel, or a laminated I-beam joist fitted with at least one cross dowel constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A method of forming a butt joint between one end of a timber, flanged I-beam joist and a transverse closure such as a rimjoist, wherein the I-beam joist is arranged so that the web of the joist is generally vertical and the flanges of the I-beam section are above and below the web, comprising the steps of: 1) forming two holes a short distance from the end of the Ibeam which is to be butt-

jointed to the closure, one hole in each of upper and lower flanges of the flanged I-beam section, 2) locating the closure in place and forming two further holes therethrough and into the abutting ends of the upper and lower flanges of the I-beam joist, the two further holes being generally perpendicular to, and intersecting, the first two holes, 3) inserting two cross-dowels into the two first holes, each having a transverse threaded opening, and aligning the threaded openings with the intersecting holes, and 4) inserting threaded bolts into the intersecting holes to engage in the threaded openings in the cross-dowels, and screwing the bolts into the dowels so as to draw the abutting end of the I-beam joist towards the closure, and thereby clamp it to the closure.

3. A roofing or flooring panel as claimed in claim 2 wherein the crossdowels are formed from metal, or from a rigid plastics material or from a composite material.

4. A rooting or flooring panel as claimed in claim 2 or 3 wherein the bolts are formed from metal or a rigid plastics material or a composite material 5. A roofing or flooring panel as claimed in claim 2, 3 or 4 wherein a load spreading washer is located between the head of each bolt and the closure.

7. A roofing or flooring panel as claimed in claim 2, 3 or 4 wherein the holes through the closure through which the bolts pass into the I-beam are enlarged at one end to accommodate the heads of the bolts, so that the latter are at least partly contained within the thickness of the closure.

11. A prefabricated timber roofing or flooring panel or deck, constructed from parallel spaced apart laminated timber I-beam joists buttjointed to the side faces of perpendicularly extending rimtoists at opposite ends of the I-beam joists, wherein the joints between the

l-G ends of the I-beam joists and the rimboists are formed by bolts and cross-dowels, wherein the latter extend perpendicularly to the laminations forming the upper and lower flanges of the I-beam joists, and the bolts extend transversely through the rimjoists and are threadedly engaged in the cross-dowels.

12. A laminated timber I-beam joist comprising a web between upper and lower laiminated flanges, having cross-dowels located therein transverse to the direction of the laminations forming the upper and lower flanges of the I-beam section, close to at least one end thereof, to enable the Ibeam to be buttjointed to a transversely extending closure by means of bolts which in use extend through the closure for threaded engagement in the cross-dowels in the I-beam joist.

14. A cross-dowel as claimed in claim 13 wherein the external screw thread profile is a self-tapping thread.

15. A cross-dowel as claimed in claim 13, wherein the external diameter of the screw thread profile increases from the end of the dowel which is to be first introduced into the hole in the laminated flange, towards the other end which includes the tool engaging means. 16. A cross-dowel adapted to be secured in a laminated flange of a timber I-beam joist to enable the I-beam joist to be secured to a closure in accordance with the method of claim 1, wherein the external surface of the dowel is formed with at least one annular barb for retaining the dowel in a hole in the laminated flange.

-1 ERIC

17. A cross-dowel as claimed in claim 16 wherein the dowel includes a plurality of annular barbs. 18. A cross-dowel as claimed in claim 17 wherein the external diameter of the barbs increases from the end of the dowel which is to be first introduced into the hole in the I-

beam laminations, towards the other end of the dowel, whereby to form a so-called fr-tree connection. 19. A method of securing a cross-dowel as claimed in claim 18 wherein the dowel is driven in using a hammer, or mallet or power driver.

20. A cross dowel as claimed in any of claims 16-19 wherein the dowel is formed at one end with a tool engaging means such as a screwdriver slot whereby it can be rotated whilst embedded in the flange, to enable the transverse threaded opening therein to be aligned to receive a securing bolt.

23. A method of joining an I-beam joist to a perpendicular closure such as a rim-joist or rim-beam substantially as herein described with reference to and as illustrated in the accompanying drawings.