Abstract:
A method of producing a fibre reinforced structural element including a plurality of fittings for the fixation of the element to another structural element, includes the steps of: (i) providing a core element of fibre reinforcement material having an end part; (ii) mounting a fitting on the end part to produce a subassembly; (iii) fixating the fitting to the end part in a pultrusion process that includes covering the subassembly in fibre-reinforced resin that is then cured; (iv) machining the subassembly to provide a fitting assembly including the core element and the fitting; (v) repeating steps i-iv for producing a plurality of fitting assemblies; (vi) positioning the plurality of assemblies according to the position of the plurality of fittings; and (vii) producing the structural element including the plurality of fittings constituted by the plurality of assemblies in an extrusion, pultrusion, or fibre reinforcing production technique.

Description:
This application is a 35 USC 371 of PCT/OK03/00010, filed Dec. 09, 2003. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the technique of producing large fibre reinforced structural elements and in particular a technique of fixating bolt fixtures or bolts in the fibre reinforced structural element. 
     In the present context, the term a fibre reinforced structural element is construed as a generic term comprising any structural element made from resin or plastics based materials being fibre reinforced by means of fibres such as glass fibre, carbon fibre or kevlar fibre reinforced structural elements produced from a resin material such as polyester, vinyl ester, phenol or epoxy. Further the structural element may in itself constitute a load-carrying element or a supporting element such as an element of a building structure, a facade element, a bridge, a component of a wind mill, a component of a ship such as a deck component. 
     In the present context, the terms a bolt fixture, a bolt and a fitting are to be construed as generic terms comprising any elements such as a bolt, the shaft of the bolt, a nut, a hook, a pin with external thread, an arresting element e.g. a press fitting or snap fitting closure element etc. serving the purpose of co-operating with another fixating element e.g. a congruent or mating fixating element for the fixation of a structural element which supports the bolt fixture, bolt or fitting, or a fitting including an internal thread or a differently configurated body including a protruding outer thread part or an inner thread for receiving the thread of a bolt. 
     Within the industry the use of fibre reinforced structural elements has increased rapidly within the last decades, basically inspired by the success of the use of such elements within the wind mill industry. Apart from wind mill components such as the blades of a wind mill, fibre reinforced structural elements have also gained success within the house-building industry and ship-building industry and even within certain technical fields in which metal structures have conventionally been used. As an example within the chemical industry or the galvanising-and zinc coating industry, conventional metal structures tend to have a fairly short life time due to the excessive corrosion impact whereas fibre reinforced structural elements including containers, stairs, supporting elements, etc. may stand the exposure to the corrosive atmosphere without being to any substantial extent deteriorated or ruined. 
     Examples of structural elements and techniques of fixating various components within structural elements are described in the below patent applications and patents to which reference is made and which US patents are hereby incorporated in the present application by reference. The references comprise: EP 0 170 886, U.S. Pat. No. 4,892,462, U.S. Pat. No. 4,339,230, U.S. Pat. No. 4,278401, FR 2 758 594, FR 2 670 956, U.S. Pat. No. 5,664,820, U.S. Pat. No. 3,372,073, GB 2 119 472 and DE 196 25 426. 
     It has been realised by the applicant company that the technique of embedding and fixating bolt fixtures, bolts and/or fittings within a fibre reinforced element may impose certain problems in particular as far as the proper and accurate location of the bolt fixtures, bolts or fittings are concerned. Whereas the conventional technique has involved the simple positioning of bolt fixtures, bolts or fixtures within the fibre reinforced structural element to be machined, extruded or pulltruded in the production process, it has been realised by the applicant company that this conventional and simple technique does not allow the bolt fixtures, bolts or fittings to be positioned with the necessary accuracy needed within the industry and being a mandatory provision for the further commercial exploitation of the fibre reinforcing technique for the manufacture of structural elements. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a novel technique allowing a simple and accurate positioning of bolts, bolt fixtures or fittings within a fibre reinforced structural element at predetermined positions or locations and with an accuracy acceptable within the industry including the house-building, ship-building and wind mill industry such as an accuracy of +/−1 mm variation of the location of a specific bolt, bolt fixture or fitting or even a lower variation such as a variation of +/−0.5 mm. 
     It is a feature of the present invention that the novel technique according to the present invention provides an improved transmission of force and impact to and from the fibre reinforced structural element through the bolt fixtures, bolts or fittings thereby allowing a reduction of the size of the fibre reinforced structure i.e. providing a reduction of the weight of the fibre reinforced structure or in the alternative a reduction of the materials used for the fibre reinforce structural element. 
     It is a further feature of the present invention that the method and technique according to the present invention allows bolt fixtures, bolts or fittings to be located at specific locations and fixated within a fibre reinforced structural element in solid and high-load bearing casings. 
     It is a particular advantage of the present invention that the novel technique of positioning and fixating bolt fixtures, bolts or fittings within a fibre reinforced structural element allows the use of high-load bearing casings for the positioning of the bolt fixtures, bolts or fittings and to provide an easy positioning of the bolt fixtures, bolts or fittings in specific geometrical configuration or shape generated by particularly configurating the load-bearing casing supporting the bolt fixtures, bolts or fixtures. 
     The above object, the above features and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of the present invention are according to a first aspect of the present invention obtained by a method of producing a fibre reinforced structural element including a plurality of bolt fixtures, bolts or fittings for the fixation of the structural element to another structural element, comprising the steps of:
         i) providing an elongated core element of a material, preferably fibre reinforcement material compatible with the materials of the fibre reinforced structural element, preferably made through pulltrusion, having an end part for the mounting or fixation of one of the bolt fixtures, bolts or fittings,   ii) mounting the one bolt fixture, bolt or fitting on the end part of the core element for producing a subassembly,   iii) fixating the one bolt fixture, bolt or fitting relative to the end part of the core element in a pulltrusion process by pulling the subassembly through a pulltruder, by circumferentially covering the subassembly with reinforcing fibres and resin and by heating and curing the resin for causing the resin to provide in conjunction with the reinforcing fibres a casing circumferentially encircling the subassembly, or alternatively fixating the subassembly by adhesion to the encasing produced in a separate pulltrusion process,   iv) machining the subassembly circumferentially encircled within the casing of the reinforcing fibres and the cured resin for providing a bolt fixture, bolt assembly or fitting assembly including the core element and the one bolt fixture, bolt or fitting and the core element,   v) repeating the steps i-iv for producing a plurality of the bolt fixtures, bolt assemblies or fitting assemblies,   vi) positioning the plurality of assemblies according to the intentional position of the plurality of bolt fixtures, bolts or fittings within the final fibre reinforced structural element, and   vii) producing the fibre reinforced structural element including the plurality of bolt fixtures, bolts or fittings constituted by the pluralities of assemblies in an extrusion, a pulltrusion or a fibre reinforcing production technique.       

     According to the basic teachings of the present invention, the individual bolt fixture, bolt or fitting is pre-positioned in a casing within a bolt fixture, bolt or fitting assembly. The assembly itself is composed of a core element which is accurately positioned relative to the bolt fixture, bolt or fitting and in a separate production process step fixated relative to the bolt fixture, bolt or fitting in a puiltrusion process. It is to be emphasized that the fixation of the core element and the bolt fixture, bolt or fitting relative to one another does not necessitate a linking between the core element and the bolt fixture, bolt or fitting as the core element and the bolt fixture, bolt or fitting are mechanically fixated to the circumferentially encircling casing produced in the pulitrusion process, however the co-operation between the core element and the bolt fixture, bolt or fitting provides the necessary accuracy of positioning and fixation of the bolt fixture, bolt or fitting in the final structure. As will be described in greater details below, the use of the pulltrusion process for the production of the bolt fixture, bolt or fitting assembly allows the bolt fixture, bolt or fitting assembly to be manufactured in a specific metrical configuration promoting or ensuring the intended positioning of the individual bolt fixtures, bolts or fittings within the final fibre reinforced structural element. The production of the bolt fixture, bolt or fitting assembly also ensures the necessary load-bearing capability of the individual bolt fixture, bolt or fitting due to the pulltrusion process used for the fixation of the bolt fixture, bolt or fitting relative to the core element within the individual bolt fixture, bolt or fitting assembly. 
     The individual core element may be prefabricated e.g. through casting, machining, etc. from a material which is compatible with the materials of the fibre reinforced structural element meaning that the materials used for the core element and also for the pulltrusion process for the encasing of the subassembly comprising the bolt fixture and bolt and the core element are mechanically, structurally and chemically combinable with the materials of the fibre reinforced structural element. For most applications, the above described fibre reinforcing materials and resin materials are used and for obvious reasons, the bolt fixture, bolt or fitting assembly may be manufactured from materials compatible with the remaining materials of the fibre reinforced structural elements, however exhibiting improved strengths and load-bearing capability. Alternatively, the same materials may advantageously be used for the production of the bolt fixture, bolt or fitting assembly and for the remaining part of the fibre reinforced structural element. 
     Provided a none-pre-cast core element is used, the method according to the present invention preferably comprises the step of cutting the elongated core element from a continuous elongated core element body preferably made as already stated through pulltrusion. 
     The technique of mounting the one bolt fixture, bolt or fitting on the one end part of the core element may be easily accomplished provided the core element is configured including a recess, a bore or having a protruding part such as a fitting configured for the reception of the bolt fixture, bolt and fitting. According to a particular advantageous embodiment of the method according to the present invention, the elongated core element is provided with respective end parts for receiving a total of two bolt fixtures, bolts or fittings at opposite ends of the core element and the method according to the present invention consequently also comprises in steps ii) and iii) mounting and fixating two bolt fixtures, bolts or fittings at the respective end parts of the core element of the subassembly and comprises in step iv) machining the subassembly circumferentially encircled within the casing of the reinforcing fibres and the cured resin into two halves each constituting a bolt fixture, bolt or fitting assembly. 
     According to a still further advantageous embodiment of the method according to the present invention, the proper positioning, fixation and orientation of the bolt fixture, bolt or fitting relative to the core element is obtained by machining the end part of the core element into a specific configuration and providing the bolt fixture, bolt or fitting having an end recess part configurated in conformity with and congruent with the conical configuration of the end part of the core element, thereby providing an accurate positioning and maintenance of the bolt fixture, bolt or fitting relative to the core element before and while performing the pulltrusion process in step iii). 
     According to a further particular advantageous aspect of the method or technique according to the present invention, the casing including the core element and the bolt fixture, bolt or fitting of the assembly may be produced in a specific configuration through the pulltrusion process as the casing may be produced having a specific cross-sectional configuration such as a circular, an elliptical, a polygonal, in particular a hexagonal or square cross-sectional configuration or alternatively a combination of any of the above mentioned cross-sectional configurations. 
     Alternatively, the intentional geometrical configuration of the casing may be obtained by a separate machining step in which the casing is machined into a specific cross-section or configuration such as a circular, an elliptical, a polygonal, in particular a hexagonal or square cross-sectional configuration or alternatively a combination of any of the above mentioned cross-sectional configurations. 
     In a first embodiment of the method according to the first aspect of the present invention, the machining performed in step iv) is carried out by simply cutting vertically through the string of material provided from the pulltrusion process and the bolt fixture, bolt or fitting assembly is consequently provided having an end surface opposite to the bolt fixture, bolt or fitting fixated to the core element of the assembly extending perpendicular to the longitudinal axis of the bolt fixture, bolt or fitting assembly. According to the presently preferred embodiment of the method according to the first aspect of the present invention, the assembly is, however, provided in the machining process having a surface part defining an acute angle relative to the longitudinal axis of the bolt fixture, bolt or fitting assembly for providing a large surface of contact of the core element for fixating the assembly within the fibre reinforced structural element, and further for providing a none-rotationally symmetrical assembly which is optimally configurated for fixation within the fibre reinforced structural element. 
     The above object, the above features and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of the present invention are according to a second aspect of the present invention obtained by a method of producing a bolt fixture, bolt assembly or fitting assembly for use in a fibre reinforced structural element including a plurality of bolt fixtures, bolts or fittings for the fixation of the structural element to another structural element, comprising the steps of:
         i) providing an elongated core element of a material, preferably fibre reinforcement material compatible with the materials of the fibre reinforced structural element, preferably made through pulltrusion, having an end part for the mounting or fixation of one of the bolt fixtures, bolts or fittings,   ii) mounting the one bolt fixture, bolt or fitting on the end part of the core element for producing a subassembly,   iii) fixating the one bolt fixture, bolt or fitting relative to the end part of the core element in a pulltrusion process by pulling the subassembly through a pulltruder, by circumferentially covering the subassembly with reinforcing fibres and resin and by heating and curing the resin for causing the resin to provide in conjunction with the reinforcing fibres a casing circumferentially encircling the subassembly, or alternatively fixating the subassembly by adhesion to the encasing produced in a separate pulltrusion process, and   iv) machining the subassembly circumferentially encircled within the casing of the reinforcing fibres and the cured resin for providing a bolt fixture, bolt assembly or fitting assembly including the core element and the one bolt fixture, bolt or fitting and the core element.       

     The method according to the second aspect of the present invention may according to the teachings of the present invention advantageously comprise any of the features described and discussed above in relation to the method according to the first aspect of the present invention. 
     The above object, the above features and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of the present invention are according to a third aspect of the present invention obtained by a fibre reinforced structural element including a plurality of bolt fixtures, bolts or fittings for the fixation of the structural element to another structural element, the fibre reinforced structural element being produced in accordance with the method according to the first aspect of the present invention and including a plurality of bolt fixture, bolt or fitting assemblies produced in accordance with the method according to the second aspect of the present invention. 
     The above object, the above features and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of the present invention are according to a fourth aspect of the present invention obtained by a bolt fixture, bolt or fitting assembly for use in a fibre reinforced structural element being produced in accordance with the method according to the second aspect of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is now to be further described with reference to the drawings, in which 
         FIG. 1  is a partly sectional, perspective and schematic view of a first embodiment of an assembly from which two bolt fixture, bolt or fitting assemblies produced. 
         FIG. 2  is a schematic and perspective view illustrating a first step of a method of producing the assembly shown in  FIG. 1  including machining a pulltruded body into a plurality of core elements, 
         FIG. 3  is a schematic and perspective view illustrating a second step of the method of producing the assembly shown in  FIG. 1  including mounting bolt fixtures at opposite ends of the core element produced in the step shown in  FIG. 2 , 
         FIG. 4  is an overall perspective and schematic view illustrating a third step of the method of producing the assembly shown in  FIG. 1  constituting a process of providing in a continuous pulltrusion process a body from which the assembly shown in  FIG. 1  is cut as is illustrated in the right-hand part of  FIG. 4 , 
         FIG. 5  is a schematic view illustrating a step of cutting the assembly shown in  FIG. 1  and in the right-hand part of  FIG. 4  into two bolt fixture assemblies, 
         FIG. 6  is a vertical sectional view illustrating the assembly shown in  FIG. 1  and the bolt fixture assemblies produced from the assembly as shown in  FIG. 5 , 
         FIG. 7  is a schematic view illustrating the intentional application of the bolt fixture assembly shown in  FIGS. 5 and 6  for the production of a major fibre reinforced structure such as a wind mill element, a bridge part, a building element, the bolt fixtures being positioned along the arch of a circle, 
         FIG. 8  is a perspective and schematic view similar to the view of  FIG. 7  illustrating a slightly modified embodiment of the bolt fixture assembly used for the production of a fibre reinforced element in which the bolt fixtures are positioned along a rectilinear track, 
         FIG. 9  is a perspective and schematic view of a segment of a structural element produced from the assembly shown in  FIG. 8  illustrating the fixture of the fibre reinforced structural element to an I-beam by means of bolts and knots, 
         FIG. 10  is a perspective and schematic view illustrating the fixation of the fibre reinforced structural element produced from the assembly shown in  FIG. 7  having the bolt fixtures positioned along the arch of a circle, 
         FIGS. 11   a ,  11   b  and  11   c  are perspective, schematic and partly sectional views illustrating three alternative embodiments of improving the fixation of the bolt fixtures in the pulltrusion process, 
         FIGS. 12   a  and  12   b  are perspective and schematic views illustrating a distance element and the use of a distance element in the pulltrusion process, 
         FIG. 13  is an overall perspective and schematic view similar to the view of  FIG. 4  illustrating the method of producing a presently preferred assembly having a square cross-sectional configuration, 
         FIGS. 14   a  and  14   b  are schematic, perspective and partly sectional views illustrating differently configurated bolt fixtures fixated within the pulltrusion end casing, 
         FIG. 15  is a perspective, schematic and partly sectional view of two adjacent parts of an assembly from which end parts two assemblies having protruding bolt pins are produced, 
         FIGS. 16   a  and  16   b  are perspective, schematic and partly sectional views similar to the view of  FIG. 15  of a further embodiment of the assembly according to the present invention in which embodiment a fitting is embedded within the pulltrusion encasing for the generation of an internal thread within the pulltrusion casing, 
         FIG. 17  is a perspective, schematic and partly sectional view of a further application of the assembly according to the present invention used as a roller of a roller belt, 
         FIG. 18  is a schematic and perspective view of a differently configurated assembly produced in accordance with the method as illustrated in  FIG. 13  and shaped in an H-beam configuration, 
         FIG. 19  is a perspective and schematic view illustrating the utilisation of the technique of producing a loadbearing assembly in accordance with the teachings of the present invention for use as a load sensor, 
         FIG. 20  is a diagram illustrating the electronics of the load sensor part of the assembly illustrated in  FIG. 19 , 
         FIG. 21  is a schematic and diagrammatic view illustrating the use of the assembly shown in  FIG. 19  as a loadbearing sensor within e.g. a bridge, 
         FIG. 22  is a schematic view illustrating a different application of the loadcarrying assembly illustrated in  FIG. 19  within a bridge, and including a parallel link to a PC-based measuring station, 
         FIG. 23  is a perspective, schematic and partly sectional view of a further embodiment of the assembly according to the present invention configurated as an insulator for a high voltage cable, and 
         FIG. 24  is a perspective and schematic view illustrating the intentional application of the insulator shown in  FIG. 23 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 , an assembly  10  is shown produced in accordance with the method according to the present invention and intended to be separated into two assemblies as will be described below with reference to  FIGS. 5 and 6 . 
     According to the method of producing an assembly including a bolt fixture of bolt for use in a fibre reinforced structural element, a core element is initially produced. The core element may be produced form any relevant material including plastics based materials, wood or metal or composite materials which materials are compatible with the materials of the fibre reinforced structural element meaning that the materials of the core element like all other materials used in accordance with the technique of the present invention are combinable with the remaining materials i.e. do not react with one another in a chemical process, and a mechanically combinable or linkable meaning that the materials may be joined together in an integral structure and preferably exhibit substantial identical mechanical characteristics as far as coefficients of expansion, and mechanical strength such as tear and shear strengths are concerned. In accordance with the presently preferred embodiment of the method according to the present invention, a pulltruded core body is preferably used as is illustrated in  FIG. 2 . 
     In  FIG. 2 , a pulltruder is designated by the reference numeral  30  in its entirety and delivers from its output a puiltrusion rod  32  i.e. a rod of circular cylindrical cross-sectional configuration made from resin such as a polyester, vinyl ester or phenol or epoxy resin in which reinforcing fibres such as glass fibre, carbon fibre or Kevlar® fibres are embedded. The pulltrusion rod or body  32  is cut into individual elements one of which is designated by the reference numeral  12  by means of a cutter illustrated schematically as a saw  34 . At opposite ends of the body or rod  12 , conical end parts are produced by means of a machining device such as a cutter  36  illustrated schematically in  FIG. 2 . The cutter  36  produces the conical end parts designated by the reference numeral  20  at opposite ends of the core body  12 . 
     In a further step of the method of producing the assembly  10  shown in  FIG. 1 , bolt fixtures  22  are positioned at opposite ends of the core element  12  as is illustrated in  FIG. 3 . 
     Like the core element  12 , the bolt fixtures  22  are preferably of a circular cylindrical cross-sectional configuration having at the one end a conical recess  20 ′ configurated in conformity with the conical end part  20  of the core element  12 . Each of the bolt fixtures  22  is further provided with a through-going bore communicating with the conical recess  20 ′ and defining a narrow central cylindrical bore part  25  and a wider bore part  24  communicating with the exterior and intended to co-operate with a threaded shaft  28  as is illustrated in the lower left-hand part of  FIG. 3 . The bolt fixtures may be differently configurated as the bolt fixtures may e.g. be of an overall conical configuration tapering from the one end towards the other end e.g. from the outer end towards the inner end or from the inner end towards the outer end. Alternatively, the bolt fixtures  22  may be provided with outwardly pulltruding flanges. Further alternatively, the bolt fixtures may have a differently configurated through-going bore in which the threaded bore part communicates with the conical recess without the intermediate narrow cylindrical bore part. Further alternatively, the threaded bore may be omitted as the bolt fixture may be provided as a fixture having an outwardly pulltruding threaded shaft constituting a bolt. 
     By the provision of the co-operating conical end part and the conical recess  20 ′ of each of the bolt fixtures  22 , a self-centering and self-aligning feature is obtained as the bolt fixtures  22  due to the co-operation between the conical end part  20  and the conical recess  20 ′ tend to be maintained in the intentional aligned orientation in which the circular cylindrical bolt fixtures  22  are constituting cylindrical continuations of the central part of the core element  12 . 
     The subassembly comprising the core body and the two bolt fixtures  22  illustrated in  FIG. 3  is, as is illustrated in  FIG. 4 , introduced into a pulltrusion apparatus  40  comprising a receiving section  46  in which the subassembly described above along with a plurality of subassemblies together constituting a continuous string is introduced into the receiving section  46  of the pulltrusion apparatus  40  together with webs of fibre reinforcing materials which webs are shown in the left-hand part of  FIG. 4  and two of which are designated the reference numerals  42  and  44 . From the receiving section  46 , a string  48  including the aligned subassemblies circumferentially encircled by the fibre reinforcing materials is introduced into a resin applicator and resin heating and curing apparatus  50  communicating with a resin reservoir  52  for the supply of resin thereto. An output die of the apparatus  50  is designated the reference numeral  54  and provides a specific configurated shaping of the of a pulltrusion string  56  delivered from the die  54  apparatus  50  which string  56  is introduced into a puller apparatus  58  for pulling the pulltrusion string from the die  54  of the apparatus  50 . 
     From the puller  58 , the string  56  is delivered to a cutter  60  which separates the string  56  into distinct sections constituting the assembly  10  also shown in  FIG. 1  as the cutting of the string  56  in the sections or assemblies  10  is synchronised with the entry of the subassembly comprising the core body  12  provided with the end part covering bolt fixtures  20  to the entry end of the pulltrusion apparatus  40 . In an alternative process of producing the subassembly from which the assembly  10  shown in  FIG. 1  is produced, the bolt fixtures  20  and the core element  12  are fixated through adhesion to a cylindrical casing preferably produced through pulltrusion and constituting the casing  26  described above. It is contemplated that the fixation through adhesion to the casing  26  produced through pulltrusion and the technique of fixating the bolt fixtures  22  and the core element  12  to the casing through the pulltrusion process are constituting technical equivalencies. 
     In  FIG. 1 , the core element  12  is shown together with the bolt fixture  22  disclosing the threaded bore  24  communicating with the bore  25  and further disclosing the tapering or conical end part  20  of the core element  12 . 
     In  FIG. 1 , the outer casing produced in the pulltrusion process described above with reference to  FIG. 4  is also disclosed, which casing is designated the reference numeral  26 .  FIG. 1  further discloses the configuration of the assembly  10  which configuration defines a concave top-surface  14 , an opposite convex or circular cylindrical bottom surface  18  and opposite parallel planar surfaces  18 . The convex/concave configuration illustrated in  FIG. 1  allows, as will be described below with reference to  FIGS. 7 and 10 , the positioning of the bolt fixture assembly produced from the assembly  10  by arranging the convex outer surface  16  or one bolt fixture assembly juxtaposed and partly received within the concave surface  14  of the adjacent bolt fixture assembly. 
     From the assembly  10  shown in  FIG. 1 , two bolt fixture assemblies are produced as is illustrated in  FIG. 5  by cutting the assembly  10  into two parts along a line indicated in dotted line by the reference numeral  64 . The cutter is schematically illustrated by a saw  62 . The assembly  10  cut into two halves is illustrated in  FIG. 6  in a vertical sectional view disclosing the line of separation  64  providing opposite sloping surfaces  66  of each of the two bolt fixtures assemblies produced from the assembly  10 . Each bolt fixture assembly constituting one half of the assembly  10  includes a tapering cut part of the core element  12  and the bolt fixture  22  fixated to the core element  12  by the pulltrusion encasing  26 . By provision of the sloping surface  66  an irregularly shaped bolt fixture assembly is produced enhancing the ability of fixation of the bolt fixture assembly within the final fibre reinforce structure and further providing a major surface of contact between the central core element  12  and the final fibre reinforced structure. 
     The ability of positioning the individual bolt fixture assemblies in an orientation different from a rectilinear orientation is illustrated in  FIG. 7  as three individual bolt fixture assemblies combined into a structure in its entirety designated by the reference numeral  70  is shown and including three bolt fixture assemblies positioned having the concave surface  14  of one bolt fixture assembly receiving the convex surface  16  of the adjacent bolt fixture assembly in an overall angular orientation. The fibre reinforced structure encasing the composite structure shown in  FIG. 7  is designated the reference numeral  72 . 
     In  FIG. 8 , a slightly modified configuration of the bolt fixture assembly is illustrated as the circular concave and convex surfaces  14  and  16  are substituted by concave and convex outer surfaces having planar generators. By the planar generator configuration of the convex surface  14 ′ having a configuration corresponding to the configuration of the convex surface  16 ′ of the blot fixture assemblies, the individual bolt fixture assemblies may, as is illustrated in  FIG. 8 , be combined into a structure in which the proper rectilinear positioning of individual bolt fixture assemblies is ensured and maintained by the provision of the corresponding convex and concave surfaces of the bolt fixture assemblies. The combination of a total of four bolt fixture assemblies in  FIG. 8  is in its entirety designated the reference numeral  70 ′. From the composite structure illustrated in  FIG. 8 , a fibre reinforced structural element is produced in a further extrusion, pulltrusion or manual or automated fibre reinforcing production process by the application of reinforcing fibres and resin to the combination of the fixture assemblies and configurating the structural element according to the intentional geometrical of the final product. 
     The final product is used e.g. as illustrated in  FIG. 9  in connection with a load-bearing carrier I-beam  76  in which the bolt shafts  28  received within the bolt fixtures of the bolt fixture assemblies shown in  FIG. 8  are fixated to the I-beam  76  by means of individual bolts  74 . 
     The curved structure shown in  FIG. 7  may alternatively be used for the fixation to e.g. a planar plate element  78  as illustrated in  FIG. 10 . 
     As mentioned above, the bolt fixtures  22  described above with reference to  FIGS. 1-6  may advantageously be configurated in a conical or elliptical shape for improving the fixation of the bolt fixtures within the pulltrusion encasing  26 . In  FIGS. 11   a - 11   c , different techniques of enhancing the fixation of the bolt fixtures within the pulltrusion encasing are illustrated. Generally throughout the specification, components or elements identical to components or elements described previously are designated the same reference numerals as previously designated whereas components or elements geometrically differing from previously described components or elements, respectively, however serving the same purpose of previously described components or elements are designated the same reference integer, however added a marking for identifying the geometrical difference. 
     In  FIG. 11   a , the bolt fixture  22 ′ differs from the above described bolt fixture  22  shown in  FIG. 3  in that the outer surface of the bolt fixture  22 ′ is of a rough or rugged structure providing an uneven outer surface which improves the fixation of the bolt fixture  22 ′ to the pulltrusion casing  26 ′. In  FIG. 11  a the rough or rugged outer surface of the bolt fixture  22 ′ is for the sake of clarity somewhat exaggerated as compared to real life rough or rugged surfaces. 
     In  FIG. 11   b , a different technique of enhancing the fixation of the bolt fixture  22 ′ relative to the pulltrusion encasing  26 ″ is shown as the bolt fixture  22 ″ is provided with outer ridges defining a plurality of outer threads of left and right hand configuration serving the purpose of providing a solid embedding of the ridges within the polymer material of the outer pulltrusion encasing  26 ″. 
     In  FIG. 11   c , a further alternative technique of improving the adhesion between the bolt fixture  22 ′″ and the pulltrusion encasing  26 ′″ is shown. In  FIG. 11   c , the outer end of the bolt fixture  22 ′″ is provided with an outer shallow thread  23 ′″ in which reinforcing fibres and resin are received before the bolt fixture  22 ′″ together with the core body  12 ′″ are moved through the pulltruder such as the pulltruder further shown in  FIG. 4 . 
     In order to facilitate the cutting of the string from which the assemblies according to the present invention are cut such as the string  56  shown in  FIG. 4 , a distance body such as the body  80  shown in  FIG. 12   a  may be used. Centrally the body  80  comprises centrally a circular cylindrical disc  82  from opposite sides of which two coaxially extending pins  84  protrude. The body  80  is generally used in combination with the bolt fixtures such as two bolt fixtures  22   iv  shown in  12   b  for keeping the adjacent ends of the bolt fixtures  22   iv  spaced apart and allowing the cutter to be easily moved through the outer pulltrusion encasing, not shown in  FIG. 12   b , and through the distance body  80  which is preferably a pre-cast plastics body such as a PE, PP or similar plastics material body. 
     In  FIG. 14   a , a technique of using a carbon reinforced fitting in combination with a nut is shown. In  FIG. 14   a , a nut  22   v  is encased within the pulltrusion encasing  26   v  at the outer end of the core body  12   v . In registration with the nut  22   v  a carbon fibre reinforced cylindrical bushing or fitting  27  is enclosed within the pulltrusion encasing  26   v  for allowing the nut  22   v  to be kept spaced apart from the outer end of the assembly  10   v  and at the same time through the provision of the carbon fibre reinforced bushing  27  providing a rigid assembly. 
     In  FIG. 14   b , a different technique of centring the bolt fixture relative to the core body is illustrated as the core body  12   vi  is provided with an outer coaxially arranged pin  20   vi  on which a bolt fixture or nut  22   vi  is mounted. 
     In  FIG. 13 , a pulltrusion apparatus  40   iv  is shown, basically corresponding to the pulltrusion apparatus  40  described above with reference to  FIG. 4 , however differing from the above described apparatus in that in the receiving section  46 , the string of core bodies  12   iv  and bolt fixtures  22   iv  further includes the distance bodies  42  for the production of the string  48   iv  including the bolt fixtures  22   iv  kept in spaced apart relationship by means of distance bodies  82 . 
     From the curing apparatus  50 , a string  56   iv  is supplied having a square cross section or configuration as distinct from the above described configuration of the assembly  10 . 
     The technique of providing a distance body  80  for the maintenance of the outer ends of the bolt fixtures  22   iv  described above with reference to  FIG. 12   b  may be amended for keeping the outer ends of the bolt pins received within the bolt fixtures in spaced apart relationship. 
     In  FIG. 15 , a pre-cast plastics material body  80   vii  is provided constituting a circular cylindrical configuration having an outer diameter corresponding to the outer diameter of the bolt fixtures  22   vii  and having threaded bores for the receiving of the outer ends of the bolt pins  28   vii . After the finalising of the pulltrusion process with the pulltrusion apparatus such as the apparatus shown in  FIG. 4  or alternatively in  FIG. 13 , the pulltrusion string is cut e.g. by means of the cutter  10  as illustrated in  FIGS. 4 and 13  as the cutter is moved into the spacing between the two outer ends of the bolt pins  28   vii  received within the distance body  80   vii . 
     The integral pulltrusion technique according to the present invention also allows the usage of the fitting integrally pulltruded into the assembly according to the present invention to be used as a generator e.g. for the generation of an inner thread within the pulltrusion encasing as is illustrated in  FIGS. 16   a  and  16   b.    
     In  FIG. 16   a , an end part of an assembly  10   ix  according to the present invention is shown including a pulltrusion encasing  26   ix  in which a core body  12   ix  is encased together with a generator body  22   ix  which body is composed of a shaft  25   ix  extending from the outer end of the assembly  10   i x  and including a coarse thread  24   ix  which is embedded within the pulltrusion encasing  26   ix . The outer surface of the thread  24   ix  of the generator fitting  22   ix  is provided with a slip coating such as a PTFE coating, a powder covering or a greasy surface coating allowing the generator fitting  22   ix  to be removed from the outer end of the assembly  10   ix  as is illustrated in  FIG. 16   b  in which the generator fitting  22   ix  is disengaged from the remaining part of the assembly  10   ix , exposing the inner thread of the pulltrusion encasing  26   ix  originally generated by the external thread  24   ix  of the generator fitting  22   ix . 
     The pulltrusion encasing  26   ix  may be used for receiving e.g. a part of a roller bearing such as a roller bearing  60  illustrated in  FIG. 17  and received within the pulltrusion encasing  26   ix  of the assembly  10   ix , e.g. by means of the threads shown in  FIGS. 16   a  and  16   b  or alternatively fixated relative to the inner wall of the pulltrusion encasing  26   ix  by means of an adhesive filling out the cavities of the inner thread of the pulltrusion encasing  26   ix  as originally generated by the generator fitting  22   ix . The roller bearing  60  comprises a roller bearing part  62  fixated to the outer end of the assembly  10   ix  as already described and connected through a shaft  64  to a roller reel  66  supported on e.g. a stand or similar support. At the opposite end of the assembly  10   ix  a similar roller bearing  60  is provided. The structure shown in  FIG. 17  may e.g. be used for production plants in which a roller band is used and which roller band on the one hand may stand exposure to aggressive liquids or gasses and on the other hand may provide a light weight structure which is easily moved from one location to another. 
     The integral pulltrusion production technique described above also allows the manufacture of elaborated configurated structural elements such as a H-shaped structure element  10   x  shown in  FIG. 18  which is expelled from the curing apparatus  50  of a pulltrusion apparatus similar to the apparatus described above with reference to  FIGS. 4 and 13 . In the H-shaped assembly shown in  FIG. 18  two vertical bars are included each having integrally included bolt fixtures, bolts or fittings for allowing the H-shaped element to be fixed to another building structure. Each of the vertical bars of the assembly  10   x  is designated the reference numeral  11   x  and the horizontal web interconnecting the two vertical bars in the H configuration is designated the reference numeral  13   x . 
     The technique of providing a load carrying assembly having fittings, bolt fixtures or bolts positioned at opposite ends for allowing the element or assembly to be used as a load carrying element according to the teachings of the present invention may further be combined with the technique of measuring the load carrying capability of the element by integrating a sensor such as a strain gauge or similar impact detecting sensor into the assembly according to the present invention. In  FIG. 19 , an assembly  10   xi  is shown having two threaded pins  28   xi  extending from opposite ends of a circular cylindrical pulltrusion encasing  26   xi . Within the pulltrusion encasing  26   xi  two bushings  22   xi  are encased for receiving the threaded pins  28   xi  Centrally within the pulltrusion encasing  26   xi , a load detector sensor unit  90  is received. The load detector sensor  90  may include a strain gauge or similar impact detecting element and may be implemented as is illustrated in  FIG. 20 . The load detector sensor unit  90  is connected by two pins  92  to the bushings  22   xi  for the transmission of the load from the bushings  22   xi  to the load detector unit  90 . The load-transmitting pins  92  are each encased within a cylindrical encasing as is indicated in dotted line in  FIG. 9  and designated the reference numeral  94 . 
     The load detector sensor unit may be implemented as is illustrated in  FIG. 20  included an induction loop  100  for receiving electrical power through induction from an external energising source, which induction loop is connected to a power supply unit  102  for the supply of electrical power to electronic circuitry blocks  104  and  106 . The block  104  constitutes an input amp-stage receiving an input signal from a sensor element such as a strain gauge  108  and delivers on its output signal to a transmitter stage  106  which emits a radio wave signal to a remote receiver by means of an aerial  110 . It is to be realised that the circuitry included in the load detector sensor unit  90  described above with reference to  FIG. 20  may include any conventional signal shaping or signal conversion elements such as non-linear amplification stages, a/d converter stages etc. The technique of providing remote data locking units is well known in the art and no detailed description of the electronic circuitry of the load detector sensor element itself is being given as the implementation of the load detector sensor unit  90  itself is no part of the present invention. 
     In  FIG. 21 , two different applications of the load detector sensor unit containing assembly  10   xi  is illustrated. In  FIG. 21 , the one application of the assembly  10   xi  is as a structural element for interconnecting two sections of a bridge and the alternative application comprises the use of the assembly  10   xi  as a load-carrying element for supporting a wire of the carrying structure of the bridge. In  FIG. 21 , a receiver station for receiving data from the load detector sensor unit  90  is also illustrated comprising a receiver aerial  112  connected to a received stage  114  which deliver on its output an analogue or alternatively a digital signal to a measuring apparatus constituted by a PC designated the reference numeral  116 . 
     In  FIG. 22 , the usage of a plurality of assemblies  10   xi  is illustrated as in  FIG. 22 , a total of five assemblies  10   xi  is used for the suspension of a bridge  120  from a wire  122 . In  FIG. 22 , the data-logging is illustrated as a hard wire connection from each of the assemblies  10   xi  to the data logging PC  116  having a total of five parallel inputs, as it is contemplated that the wireless transmission technique illustrated in  FIG. 21  may readily be modified into a semi hard wire connection by the use of proximity detection technique by the use of a receiver unit positioned juxtaposed each of the assemblies  10   xi  for receiving the data or the signals output from the load detector sensor unit and at the same time energising the unit  90  by the supply of energising current to the induction loop  100  of each of the units  90  included in the assemblies  10   xi . 
     The high load bearing capability of the assembly according to the present invention also allows the technique to be used for alternative applications such as in a high voltage insulator as is illustrated in  FIG. 23  and  FIG. 24 . In  FIG. 23 , the assembly described above with reference to  FIG. 19  is modified by the omission of the load detector sensor unit  90  and by the introduction of a high voltage insulator core body  12   xii  constituted by a sealed hollow encasing in which a highly insulating gas such as SF 6  is included. The insulating core body  12   xii  serve the same purpose as the above described core body  12  discussed with reference to  FIGS. 1-6 . In  FIG. 23 , the assembly  10   xii  further comprises an outer pulltrusion encasing  26   xii  encasing the insulating core body  12   xii  and further two insulating bushings  94   xii  encircling and encasing the bushings  22   xii  in which the threaded pins  118   xii  are received and fixated. In  FIG. 23 , three bell-shaped outer insulating elements  118   xii  are further illustrated serving the purpose of preventing water or moisture from generating short-circuiting paths on the outer surface of the pulltrusion encasing  26   xii  as is well known in the art per se. 
     In  FIG. 24 , the intentionally application of the high voltage insulator assembly  10   xii  shown in  FIG. 23  is illustrated as the high voltage insulating assembly  10   xii  is suspended from a beam  127  for the support of a high voltage wire  126  which is suspended in and supported by a cross shaped fitting  128  which is fixated to the outer end of one of the threaded pins  18   xii  of the assembly  10   xii . 
     In the present specification, the terms pulltrusion and pulltruding have been used covering the technique of providing and producing the core element and the subassembly. The terms pulltrusion and pulltruding, however, are to be construed broadly covering any combined technique of producing fibre reinforced products including techniques known as pullforming, pullwinding etc. Consequently, it is to be understood that any technique covered by the above terms or equivalent techniques comprising continuous, semi-continuous or intermittent production of elements, such as the core element and the subassembly are to be construed equivalences to the pulltrusion technique described in the present specification. 
     Although the present invention has above been described with reference to specific, presently preferred embodiments, numerous modifications and amendments are obvious to a person having skill in the art and such modifications or amendments are to be considered part of the present invention without limiting the scope of the invention to the above described embodiments. Rather is the invention to be construed in the terms of the appending claims. 
     It is to be realised that the protective scope as defined in the appending claims does not cover the geometrical configuration of the assembly  10  shown in  FIGS. 1-6  itself, namely the geometrical outer shape of the ‘cedar plank’ element whereas differently configurated assemblies having specially configurated outer surfaces such as the assemblies together constituting the structure shown in  FIG. 8  are contemplated to be part of the protective scope as defined in the appending claims.