A timber I-beam  701  has a top chord  702  and a bottom chord  704  forming the flanges of I-beam and a series of side by side timber blocks  706  each separated from the next by a gap  722,  together forming a uniplanar, intermittent web. Cables and pipes for a building may run transversely through the gaps  722.  A method of making the I-beam is described.

TECHNICAL FIELD 
       [0001]    This invention relates to a structural building element. More particularly, this invention relates to a comprising roof or ceiling frame supports. Still more particularly, this invention concerns beams for building construction and particularly timber beams for house construction. 
       BACKGROUND 
       [0002]    The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part. 
         [0003]    It is known to build floor joists from a top and bottom chords with an open web made of a pair of zigzag steel strips nailed to the sides of the timber chords. The chords may be spliced to each other with halving joists. Such a joist is described in US 2006/0156677 A1. 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    The steel joists leave no pathway for ducts, pipes and cables to cross the building through the joists. The earlier timber joists have great shear strength but limited torsional strength. By trading off shear strength the inventor has achieved significant advantages. 
         [0005]    The apparatus aspect of the invention provides a timber T or I-beam comprising a top plate and/or a bottom plate forming the flanges of an I-beam and a series of side by side timber blocks, each separated from the next by a gap, together forming a uniplanar intermittent web, the blocks oriented so that their grain extends transverse to the general longitudinal axis of the top plate. 
         [0006]    In this document, in discussing the terms flange, chord or plate, the word “chord” generally refers to an elongate length of timber forming part of a truss, the word “flange” refers to an elongate length of timber forming part of a beam, whereas the word “plate” is used as a generic term. In discussing the words “board” or block”, these words are generally interchangeable and generally refer to a short span of timber extending from a plate or between a pair of plates. The pitch or rake of a roof surface, or the roof frame or truss members that support and/or form part of the roof structure, describes the angle of inclination achieved on the surface. 
         [0007]    The I beam may be used as a building element of a roof truss or other roof frame. The top and bottom plates may extend parallel to one another. The blocks may be cut square. The top and bottom plates may be set at an incline with respect to one another. The top plate may be set on an incline relative to the square bottom edge of each of the blocks or may extend parallel thereto. The rake of an inclined plate may be minimal, for example around 3°. The rake may vary to achieve roof pitches between 1° and 45°. Where the T or I beam forms an A-frame, a double rake may be provided. 
         [0008]    The top and bottom plates may be made of timber of a width larger than the thickness of the boards forming the web. The term plates is used in the framing sense in that they are the horizontals which act as a contact surface for other components and connect the upright parts of the beam. 
         [0009]    The blocks may be of rectangular section, or trapezoid or other irregular shape to follow the desired inclined surface of the plate. The face of the plate which contacts the web may be prepared to include grooves or may be rough sawn. 
         [0010]    Advantageously, the rake on the plate may be 1° to 3° and still require no modifications of the rectangular sectioned blocks. Greater raking will generally require planing or cutting of one end of the block to follow the incline of the plate. 
         [0011]    The depth of the plate may be 25-110 mm, the width 30-150 mm. 
         [0012]    The web may extend along at least the intermediate part of the beam. The ends of the I or T beam may be devoid of gaps in order to provide a beam which can be docked at one or both ends. So the blocks at one or both ends are greater lengthwise than the blocks separated by gaps. 
         [0013]    The blocks are aligned so that their grain extends transversely relative to the T or I beams longitudinal axis. It is believed that significant gains in torsional strength are achieved whilst trading off on shear lineal strength, which is still more than sufficient due to the tensional strength of the plate and the blocks aligned with their grains generally transverse to the longitudinal axis of the plates. 
         [0014]    The horizontal sides of the blocks may also be planed and secured to the plates by adhesive. The sides of the blocks may project slightly into a longitudinal shallow housing in the plates. 
         [0015]    The width of the gaps may be equal along the length of the beam. The gaps width may be substantially equal to the length (the direction parallel to the longitudinal axis of the plate) of the blocks. The gap width will normally be selected to allow plumbing pipes, airconditioning ducts and extractor ducts to pass through thereon, together with smaller components such as water pipes and cables. The gap range may be preferably 90-500 mm. 
         [0016]    The beam may be made from structural pine for internal use. For external use treated pine of structural grade containing arsenic is suitable. Laminated timber plates and blocks may be used instead but at higher cost. The type of material used to form such I-beams and T-beams as described herein in accordance with the invention may be made from machine grade pine (MGP) or laminated veneer lumber (LVL), the latter being considered a generally higher grade material. Such materials may be used to achieve beams having short duration modulus elasticity (E values) of 6,100-21,500, preferably about 10,000, which correspond to MGP10. Most typically I-beams made according to the invention are required to conform to stress grade standards of F5-F27, but most typically will fall within the stress grade range of F8-F17, corresponding to E values of 9,100-14,000. For house construction, the plates may be 45-90 mm and preferably 70-90 mm in width and 35-45 mm in depth. The blocks may be 70-190 mm, preferably 90-140 mm in length (the direction parallel to the longitudinal axis of the plate), 90-190 mm, and preferably 35-45 mm in depth, noting that the height between the plates may vary depending on the application. 
         [0017]    Polyurethane adhesives suffice for indoor work. Exterior polyurethane glues are preferable for joints which support balconies and outdoor structures. 
       Advantageous Effects of Invention 
       [0000]    
       
         1. The beam is versatile in the way it incorporates into existing building construction. 
         2. Its gaps allow transverse passage of pipes, ducts and cables. 
         3. It offers a useful range of spans. 
         4. It is economical in that it allows utilisation of short pieces of block which would otherwise be scrapped. 
         5. It permits the economical production of timber I and T construction beams. 
         6. By orienting the blocks transversally, it permits the production of raked roof truss elements with minimal modification of component parts relative to beams with parallel plates. The narrower block width allows an inclined beam surface to still rest stably on its end, even if minimally raked by an incline of, say, 1°-3°. 
         7. It allows efficient production of a range of raked roof truss elements through a range of inclinations by simple cutting of the angles of the respective blocks to length and inclination. 
       
     
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0025]    Various embodiments of the invention are now described with reference to the accompanying drawings, in which: 
           [0026]      FIG. 1  is a perspective of a 6 m beam. 
           [0027]      FIG. 2  is a side view of the beam when chamfered at the end support. 
           [0028]      FIG. 3  is a side view of the beam supported at one end in an alternative manner. 
           [0029]      FIG. 4  is a side view of two beams joined at 90 degrees. 
           [0030]      FIG. 5  is an end view of the beam supported on a conventional stud wall. 
           [0031]      FIG. 6  is a side view showing the beam intersecting with a mid span/end span blocking lying in one of the gaps. 
           [0032]      FIG. 7  is a side view of part of a floor with the beam beneath projecting outside the first floor timber wall as a cantilever. 
           [0033]      FIG. 8  is the same as  FIG. 7  with alternative detail. 
           [0034]      FIGS. 9, 10 and 11  are side views of the beam connected in alternative ways to a steel I-beam. 
           [0035]      FIG. 12  is a diagram of a jig in which the beam components are arranged prior to glueing. 
           [0036]      FIG. 13  is a side view of a plano-convex beam. 
           [0037]      FIG. 14  is a side view of a biconcave beam. 
           [0038]      FIG. 15  is an end view of three I-beams braced by two bracing components. 
           [0039]      FIG. 16  is a side view of a plano convex beam of I-section. 
           [0040]      FIG. 17  is a side view of a biconcave beam of I-section. 
           [0041]      FIG. 18  is a side view of a slightly raked beam of I-section; 
           [0042]      FIG. 19  is a side view of an A-frame beam of I-section, slightly raked from a centre high point; 
           [0043]      FIG. 20  is a side view of a raked beam of I-section; 
           [0044]      FIG. 21  is an amplified view of the centre point of the embodiment shown in  FIG. 19 ; 
           [0045]      FIG. 22  is a perspective view of an I-beam in the process of being manufactured; 
           [0046]      FIG. 23  is a perspective view of the I-beam of  FIG. 22  during manufacture; 
           [0047]      FIG. 24  is an end schematic view of a timber T-beam; 
           [0048]      FIG. 25  is an end schematic view of a timber I-beam according to the invention; 
           [0049]      FIG. 26  is a side art cross sectional view of a raked I-section beam according to the invention; 
           [0050]      FIG. 27  is a side schematic part view of an I-beam with parallel chords; 
           [0051]      FIG. 28  is an end schematic view of a wall and roof truss frame combination comprising a double raked A-frame roof structure; 
           [0052]      FIG. 29  is an end view of a steeply pitched single raked building structure; 
           [0053]      FIG. 30  is a perspective view of a block; and 
           [0054]      FIG. 31  is a schematic end view of a plate. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0055]    Referring now to  FIG. 1 , the beam is made of structural pine. Top chord  2  and bottom chord  4  are made of sawn 6000×90×35-45 mm scantlings. Laser guided sawing is adequate surface finish. The web is made of nine boards, 198×240×45 mm, the sides  8  of which are glued to the faces of the chords with polyurethane. The grain of the boards lies parallel to the chords. The boards are separated from each other by a 190-320 mm rectangular gap  10  which is large enough to admit 90 mm PVC tubes or 300 mm duct. The chords  2 ,  4  create a 23 mm wide step  12  where the board meets the chord. The nine web boards  6  are separated from each other by eight equal gaps. The two outer boards  14 ,  16  are separated from the outermost boards  18 ,  20 , each a minimum 600 mm long by gaps  22 , each 198 mm wide. These can be varied in gap width to suit the construction for which they are intended. The outermost boards are made intentionally about 2.5 times the length of the web boards  6  to allow onsite docking if necessary. 
         [0056]    In  FIG. 2  outermost web board  18  and the overlying end of chord  2  are docked at incline  24  to allow the beam to rest on plate  26  within the thickness of stud wall  28 . 
         [0057]    In  FIG. 3  chords  2 ,  4  project into the walls top and bottom plates  32 , whereafter the end blocking board  34  is fixed to the members  2 ,  4 ,  34 . 
         [0058]    In  FIG. 4  beam  36  intersects beam  38  at 90□. Both chords  2 ,  4  are cut back to allow outermost board  16  to project into the space between steps  10 . A steel joist hanger  40  mutually connects the beams. The top chords of both beams are united by skew nail  42 . 
         [0059]      FIG. 5  shows an end view of a plurality of the bottom chords of beams  36  that are skew nailed to the top plate  44  and particle board flooring  46  is fixed to the top chords. 
         [0060]    In  FIG. 6 , when the beams are arranged in a parallel series across a building they are stabilised by the insertion into gap  8  of a common structural board such as a strongback  48  which is skew nailed to the chords and the upright end of web board  6 . 
         [0061]    In  FIG. 7  ground floor timber supporting wall  50  supports the beam such that it acts as a cantilever. The projecting extension portion  52  supports exterior flooring  54 . The end which is inside the building is connected by a joist hanger  40  to a twin beam  56  which abuts floor  58 . Packers  60  lie between top chord  2  and inside floor sheets  58 . 
         [0062]    In  FIG. 8  the endmost board  62  is made of treated pine and covered with exterior flooring sheets  54 . 
         [0063]    In  FIG. 9  ceiling battens  64  are fixed to bottom chord  4  to take plaster board sheets  66 . A steel I-beam  68  supports the timber beam  32 . A 35 mm timber packer  70  is secured to the web of the steel beam  68  by bolts  72  and angle bracket  74  joins outermost board  16  to the packer  70 . The chord  2  is cut back to allow the appropriate insertion. 
         [0064]    In  FIG. 10  the same arrangement is shown again with packer  70  resting on the flange  76  of the I-beam. Instead of bracket  74 , steel joist hanger  40  connects outermost board  16  to the packer. 
         [0065]    In  FIG. 11  the chords are cut back to allow the outermost board  16  to project between the steel I-beam flanges  76 . The board is fastened with bolts  78  to cleat plate  80 . 
         [0066]    In  FIG. 12  a jig for beam assembly is shown, wherein a first angle iron clamp  82  is positioned alongside a row of flat, horizontal spacer supports  84  intended to raise the web boards. An opposing angle iron clamp  86  is positioned alongside and parallel to the row of spacers  84 . Posts  88  are welded to the clamps at mid point and the posts are joined by threaded rods  90 . Nuts  92  impose the clamping force. 
         [0067]    The chord plates  2 ,  4  are laid between the spacers and the clamps and the boards  6  are aligned with the spacers. Glue  94  is applied from a gun and the clamps are tightened. In some beams the grain of the boards lie at 90□ to the axis of the plates. 
         [0068]    The clamps have pairs of holes  96  for each board so that nails can be inserted through the clamps, the plates  2 ,  4  and into the boards  6  after gluing. 
         [0069]    Referring now to  FIG. 13 , the beam has a top plate  2  and a bottom plate  4  joined by web boards  6 . The gaps  10  between boards are the same but the outermost board  20  has a cut out  82  measuring 345×120mm. The LH end of the beam is 405 mm deep and though the beam length varies, the outermost end of the beam would typically be 300 mm. The saw is programmed to modify the depth of the web boards to reduce the beam height from the inner end to the outer end. This achieves the pitch required to make a flat roof self draining. However, because the web boards  6  have substantial length the direction of the I-beam axis, they each must be individually cut, despite the shallow raked angle of 1-2°. However, it is not possible to cut them too short in their axial grain orientations. 
         [0070]    In  FIGS. 14 and 15  a pair of brace boards  84 ,  86 , the same depth as web boards  6  in  FIG. 13 , are glued and nailed to top plate  88  and bottom plate  90 . The boards lie end to end in contact and project 22 mm beyond the plates at both ends. 
         [0071]    The purpose is to lead to installation as shown in  FIG. 15 . Here the component is lowered into the gap between a pair of adjacent parallel I-beams  92 ,  94  and rotated to lie 90° to both. Alternatively, the bracing component may be installed as the I-beams are laid. The plates  88  and  90  are skew nailed to the top plates of the I-beam alongside using nails  96  and to the wall plate beneath using nails  98 . 
         [0072]    Referring now to  FIG. 16 , a top plate  2  is laminated to produce a convex shape as shown. A saw bench which docks the boards  6  is programmed to cut the boards  6  in a series to produce the shape shown. The jig is modified accordingly. Likewise in  FIG. 17 , the jig is further modified to produce the biconcave beam shown. 
         [0073]    Turning to  FIG. 18 , there is shown a raked I-beam comprising a lower chord  104  and an upper chord  102  interposed by equispaced blocks  106 . The lower chord  104  extends ( 5  flat along a tabular jig  109 , whereas the upper chord  102  declines at an angle (about 0.5-30°, preferably about 0.5-5°, and most preferably 1.5° from an end point  115  to an outer end  116 , where the I-beam  101  is cut to suit outer roofing profiles, such as guttering and outer frame structures, and for this reason the outer most block  106  comprises a board  118  that can be docked and cut to shape and size to suit the desired profile as shown in the drawing. It is noted that the description in relation to  FIG. 18  is with regard to an A-frame I-beam, but the relevant description is applicable to single raked I-beams, such as those shown in  FIG. 20 . 
         [0074]    Turning to  FIG. 19 , a shallow A-frame  201  is shown having a high centre point  215  from which the raked upper chords  202   a, b  decline either side of the centre point  215 . The lower chord  204  lies flat on the planar jig  209  and interposed between the lower and upper chords  202 ,  204  are a plurality of equispaced blocks  206  advantageously cut square to minimize costs, each block  206  beam cut the length to support the upper chords  202   a, b  in raked position through to the outer most long board  218   a, b  at either end. 
         [0075]    In  FIG. 20 , single raked I-beams are shown having a pair of upper and lower chords  302 ,  304  that are most likely spaced at a first end point  315  and converge at an angle of about 2-5° to a second end point  316 . As with the embodiment shown in  FIG. 18 , the single raked I-beam  301  comprises a plurality of blocks  306  each spaced to support and brace the upper and lower chords  302 ,  304 . Interstitial spaces  322  provide gaps to allow ducting, wiring and other building services to be passed through the I-beam  301  during the building phase, as well as once the building is erected. As shown in  FIG. 21 , the interstitial spaces  222  of A-frame I-beam  201  may be in registry with one another in situ to enable the passage of such building services. The blocks  206  may be cut square where the raking angle is shallow, such as 1-5°, or may be cut at one end to conform to the angle of incline to ensure that the upper chord  202  rests stably on each block  206 , as will be explained in more detail with reference to  FIG. 26 . 
         [0076]    With reference to  FIG. 22 , during manufacture the upper and lower chords  402 ,  404  may be placed on a planar jig table  409  and braced in place using spacer blocks  413 . Initially only one chord  404  is placed in position, glue is applied to predetermined regions on the chords internal surface  405  who correspond with the positioning of the end of face of each block  406 ,  418  that is to be placed in that glued region, the glue being a high strength semi-rigid external use polyurethane adhesive. The blocks  406 ,  418  are positioned in place and supported, spaced above the tabular jig  409  in a parallel horizontal plane by board spaces  484  positioned between the table  409  and the boards  406 ,  418 . The second upper chord  402  is then placed with its wide face against the other end of the blocks  406 ,  418 , but not before adhesive is similarly applied to corresponding regions along its inner face  407 . 
         [0077]    As shown in  FIG. 23 , the upper and lower chords  404 ,  402  are then compressed together by clamps  490  and the boards, blocks  406 ,  418  are secured in position between the upper and lower chords  402 ,  404  by the application of nails through the outer surfaces of the chords  402 ,  404  into the ends of the blocks  406 ,  418  to secure the blocks  406 ,  418  until the adhesive can form a strong bond, noting that it is the adhesive that provides the long term mechanical strength or the I-beam  401 . During manufacture, preferably a pair of nails  712  are inserted through the upper and lower chords  702 ,  704  into each block  706  at each end of the block  706  to prevent twisting. To further secure the I-beam structure  701 , screws  711  are inserted intermittently along the length of the I-beam  701  to hold or further clamp the boards or flanges  702 ,  704  in place against the adhesive  707  until the adhesive  707  sets, preferably at 500-1500 mm intervals along the length of the I-beam  701 . 
         [0078]    The I-beam  401  is then removed from the jig  409  and the process is repeated to form a new I-beam  401 . 
         [0079]    The adhesive may be a high strength, semi-rigid polyurethane glue. 
         [0080]    Turning to  FIGS. 24, 25, 30 and 31 , the I-beam may be substituted with a timber T-beam that may be defined with respect to the following dimensions:
       W=width of the chord, which may typically be 30-150 mm, preferably 44-120 mm, and most preferably 70-90 mm;   D=depth of chord  502  which may be 25-110 mm, more preferably 30-70 mm, and most preferably 35-45 mm;   H=height of block 50-400 mm, most preferably 70-290 mm, noting that H can vary depending on the pitch of the truss I-beam or T-beam, the position of the block  506  along the length of the I-beam or T-beam  501  and the mechanical properties required of the block  506  for the particular application;   t=thickness of the block  506  which may be 19-90 mm, but more preferably 35-45 mm.   Note: The web of the T-beam may or may not be continuous.       
 
         [0086]    Similarly, with respect to the I-beam  601  shown in  FIG. 25  and more clearly shown in  FIG. 30 , the block t value may be 10-90 mm and preferably 35-45 mm, the latter using F grade or machine graded pine (MGP). The value w may be 50-240mm, preferably 70-140 mm, and most preferably 70-90 mm. The raking angle may vary to accommodate different applications and may be between 0.4°-45°, with H being varied with the pitch angle. 
         [0087]    As shown in  FIG. 26 , the achievement of blocks  706  having a relatively small w value (for example 70 mm, and in some applications, as low as 45 mm), allows the block  706  to be cut square whilst still adequately supporting the inclined raking chord or flange  702 . 
         [0088]    A similarly formed I-beam  801  is shown in  FIG. 27  formed using similar principles to the I-beam  701  described with reference to  FIG. 26 . 
         [0089]    Referring to  FIG. 28 , there is shown a combined wall frame and roof truss structure using parallel I-beams  801  made according to the invention. In  FIG. 29 , there is shown a building structure with a single inclined I-beam span. It is noted that the parallel chords of the portal structure shown in  FIGS. 28 and 29  can be replaced with dual raked roof truss structures (for the example shown in  FIG. 28 ) and with a single raked I-beam structure (see the example shown in  FIG. 29 ). 
         [0090]    It is to be understood that the word “comprising” as used throughout the specification is to be interpreted in its inclusive form, ie. use of the word “comprising” does not exclude the addition of other elements. 
         [0091]    It is to be understood that various modifications of and/or additions to the invention can be made without departing from the basic nature of the invention. Materials other than timber are suitable for making into boards. Polymeric timber substitutes are suitable if they have suitable strength. These modifications and/or additions are therefore considered to fall within the scope of the invention.