This invention relates to composite beams and especially to beams
for construction of walls, floors, ceilings and roofing panels in particular for
use in buildings.
Background of the Invention
The present invention relates to building construction and in particular
to the construction of dwellings formed from spaced apart inner and outer walls
in which the inner wall provides a load bearing structure which support the upper
floors and roof structure etc., and the outer wall is formed of a weather resistant
material e.g brickwork, timber cladding etc. A known construction of building is
the Canadian timber frame house.
The present invention relates to composite beams which can be particularly,
but not exclusively, used in the construction of the above buildings.
The present invention may be utilised in building panels disclosed
in applicant's co-pending patent application GB-A-2391 027.
Many attempts have been made to produce composite beams which do not
bend under their own weight. Composite beans are described in US Patent 4191,000
in which the top and bottom timber flanges are connected by a plywood web. In a
further development shown in US Patent 6460,310, the flanges are formed from laminated
wood and include a fibre reinforcement. The flanges may be interconnected by two
spaced apart webs of plywood or OSB(oriented strand board). French patent application
FR-A-2691,993 again describes a composite beam having laminated wood flanges including
reinforcing layers and a web comprising two spaced apart wooden or metal panels.
Statements of Invention
According to the present invention there is provided a wooden Composite
beam having a central cavity surrounded by walls and filled with a core of corrugated
paper or cardboard, the core being adhered to the walls surrounding the cavity.
Preferably the beam is an I beam comprising upper and lower plywood
flanges interconnected by a web comprising a pair of widely spaced apart planar
side walls formed from wood or wood derivative material, the cavity being formed
within the web.
The flanges are made from plywood having a suitable thickness and
width depending upon the size of the beam, for example a 100mm deep X 75mm wide(
4" x 3"), 150mm deep X 70mm wide(6" x 2¾)") or 160mm deep X 100mm wide(6.5"
x 4") beam may use plywood about 6mm in thickness. Deeper beams for use with longer
spans may use thicker plywood. The 6mm ply may comprise at least three plies and
preferably 5 plies.
The mutually perpendicular adjacent plies produce an extremely rigid
material in directions within the plane of the wood.
The side walls may be made from hardboard, plywood, or cardboard,
preferably between 2-5mm in thickness.
The core comprises a plurality of layers of corrugated paper or corrugated
cardboard which are each coated in a suitable adhesive resin and laminated together.
The adhesive subsequently cures or dries after assembly of the core. The corrugations
may run between the flanges or substantially parallel thereto, and in the preferred
arrangement the corrugations in adjacent layers are normal to each other. The corrugations
in one layer may be smaller in dimensions than the corrugations in an adjacent layer.
The sidewalls are adhered to the core using a suitable adhesive resin
and the assembled web including the core is adhered to the flanges also using a
suitable adhesive resin. Suitable adhesive resins may be selected from any suitable
liquid glue which dries or cures to a water resistant form, such glues include polymeric
resins e.g. an epoxy resin, a polyester resin, acrylate resins, water based PVA(polyvinylacetate),
and two part phenolic based resins.
The width of the flanges on each side extend beyond the supporting
web by about 1/3 of their total width.
Composite beams according to the present invention are structurally
very rigid and don not bend under their own weight having an extremely high bending
moment per unit mass. A typical 75mm X 75mm I beam weighs about 400-500 gms/metre
I Beams of the above type may be used in the construction of building
panels having a rectangular frame having the two faces covered in board material,
the frame comprising top and bottom rails, preferably formed from "U" or "H" section
water resistant composite, with the two rails being joined together by a plurality
of spaced apart wood composite "I" beams extending therebetween.
The term "board" includes various boards derived from timber including
hardboard, cardboard,plywood, plaster board, OSB ( oriented strand board.
Such a panel may form a modular load bearing panel which can be used
for the construction of an inner wall, floor, ceiling or roof of a building.
When constructing an internal wall for a building, in particular a
load bearing wall, adjacent wall panels are linked together by posts having side
portions which are engagable within the recessed sides of the I beams. The posts
are a slide fit within the recessed sides of the I beams between the flanges on
the respective I-beams, as is described in GB 2391 027.
Preferably the posts are hollow having plywood sidewalls and a central
cavity filled with corrugated paper or cardboard. The posts may be fixed to the
panels by means of shouldered dowels secured to the web of a respective I-beam engaging
in clips secured on the post, preferably within the hollow post.
Description of the Drawings
The invention will be described by way of example and with reference
to the following drawings in which:
Detailed Description of the Invention
- is an isometric view of an I beam according to the present invention,
- is an enlarged portion of the isometric view of Fig.1,
- Fig. 3
- is a cross section of the I beam shown in Fig.1,
- Fig. 4
- is an isometric view of a second I beam also in accordance with the present
- Fig. 5
- is a cross-section through the beam shown in Fig.4,and
- Fig. 6
- is an isometric exploded view of a wall panel and including I beams according
to the present invention.
Referring to Figs. 1 to 3 there is shown an I beam 10 which is a composite
beam having plywood flanges 11,12 linked by a composite central web 13 so that recesses
30 are formed either side of the web 13. The overall depth D and width W of the
beam 10 will be determined by the end use of the beam and material used for its
construction. The present Examples shown in Figs 1-5 relate to 162mm x 100mm beam
but it will be understood that other I beams, for example, 100mm X 75mm or 150mm
x 70mm can be made in accordance with the invention.
The flanges 11,12 are formed from plywood having a thickness of about
6.0mm with the grain of the outer veneers extending longitudinally of the beam 10.
The flanges 11,12 have awidth W of about 100 mm and have a central groove 16 on
their inner surface to accommodate the web 13. The groove has a width to suit the
particular web, in this case 38mm and a depth of about 3.0mm.
The web 13 is composite structure comprising two spaced apart sidewalls
25,26 with a light weight cellular material core 17 filling the cavity therebetween.
The two side walls 25,26 may be formed from one of plywood, hardboard, or card board
and preferably have thickness of between 2-6mm depending upon the material chosen,
in this case 3mm plywood.
The core 17 filling the cavity comprises corrugated paper or cardboard,
preferably comprising a plurality of layers thereof laminated together. The corrugations
may run between the flanges 11,12 or substantially parallel thereto, and in the
preferred arrangement the corrugations in adjacent layers are normal to each other.
In another arrangement, the corrugations in pairs of adjacent layers may be arranged
so that the corrugations in one layer are smaller than the corrugations in the other
layer with the corrugations extending in the same direction.
The core is made from sheets of corrugated paper which are each coated
in an adhesive, preferably PVA and laminated together, the resin then being dried
and cured. The core is then cut from the dried/cured resin impregnated laminate.
The sidewalls 25,26 are then laminated with the core using a suitable water resistant
adhesive, which again may be PVA, to form the web. The web is then adhered to the
flanges 11 & 12 also using a suitable water resistant adhesive, for example
a two part phenolic resin adhesive available from Borden Chemicals, with the web
being secured in the opposed grooves 16 in the flanges.
The two flanges extend beyond the web 13 on each side thereof by about
1/3 of their total width, in this example 21mm.
Composite beams according to the present invention are structurally
very rigid and do not bend under their own weight. Bending tests were carried out
on 150mm X 70mm beam having 5.5 mm plywood flanges 11,12, with a web 13 comprising
two 4.5mm plywood sidewalls 25,26 with a 15mm corrugated paper core 17 with the
corrugations extending between the flanges. The tests were carried out using the
method specified in EN 408:1995E but using limited samples.
The results may be summarised as follows:
Load to Failure
approx 6050 kN
approx 15.7 N/mm2
approx 3920 N/mm2
Immersion tests on composite beams according to the present invention
were carried out. The results are given in Table 1. below and compared with a dry
sample which is given value of 100.
A second embodiment 41 of the I beam is shown in Figs. 4 & 5.
The I beam 41 is substantially similar The dowels 31 may each be attached to a support
plate 32 which bears on the opposite sidewall 26. A plurality of such dowels 31
are spaced along the side wall 25 and are used for assembly of adjacent panels as
will be described later.
With reference to Fig 6, there is shown a wall panel 110 which is
a module for building the internal load bearing wall of a dwelling or other building.,
The panel 110 has predetermined standard dimensions for matching with and assembly
to other modular panels, for example width W of 1200mm, thickness T of 150mm, and
height H of 2400mm. Other panels according the present invention may have difference
to at least some of the above dimensions.
Each panel 110 has a rectangular frame 111, having top and bottom
rails 112,113 interconnected by a plurality of I Beams 41 & 10 which form the
sides and vertical struts of the frame 111 and are spaced at predetermined distances
apart across the width of the panel. A preferred spacing between I beams 41 &
10 is 400mm. The frame 111 is covered on one face, which is use faces externally
of the building, with water resistant board 116 and its other face which in use
faces inwardly of the building with a second board 117. The externally facing board
16 is preferably 8-9mm plywood or OSB and the internally facing board is a laminated
board which may comprise plywood, plasterboard, fibre board, calcium board, or magnesium
oxide board laminated with a layer of melamine on its exposed surface. The laminated
layer may be provided with a finished decorative surface or may be suitable for
painting or wall papering. The internal and external boards 17 & 16 respectively
are bonded to the beams 14.
The top rail 112 comprise a "H" shaped section channel formed from
water resistant wood composite, preferably 12mm plywood and the bottom rail 113
is a substantially "U" section rail. The H shaped rail 112 has open sided recesses
43 which face both inwardly and outwardly of the frame 111. The inwardly facing
recess 43 received stepped end portions of the I beams 41, 10 and the outwardly
facing recess receives a strip 102 used for fixing panels 110 to an upper panel
during construction. The bottom rail 113 is orientated with its recess downwards
and the wall panel 110 is mounted to a floor or base by use of a sole plate 101.
The sole plate 101 has a height or thickness slightly in excess of the depth of
the recess 43 in the bottom rail. The recess within the bottom rail 113 of each
panel can be slidably located over the sole plate 101 which has previously been
secured to the floor. Nails or other fixings can then be used to secure the panel
to the floor strip.
A fire test according to BS 476:20:1987 was conducted on a building
panel with composite I beams according to the invention, OSB on one face and Magnesium
oxide board on the other face. The OSB unexposed face remained unaffected during
The beams 41 are arranged with the dowels projecting outwardly of
the panels 110 and adjacent panels 110 may be linked together using a jointing post
(not shown but described in detail in GB-A-2391 027. The pointing posts located
within the recesses 30 on the beams 41 and engage with the dowels 31. Each dowel
31 has a groove 44 which provides an undercut shoulder which co-operates clips on
the jointing post on assembly.
If desired, wall panels 10 may be placed on top of previously assembled
walls up to three stories in height. A jointing strip 102 is utilised between panels.
By using modules of different widths the vertical joints between the panels in one
layer may be offset relative to the vertical joints in another layer.