Abstract:
A structural element formed from castable material, said structural element comprising: a plurality of fibre reinforced plastic, tubular members; a plurality of fibre reinforced plastic, spacer members, said spacer members extending between said plurality of tubular members; a plurality of fibre reinforced plastic, interconnecting members, said interconnecting members positioned in a different orientation to said spacing members; and castable material surrounding said members; wherein the interconnecting members and spacer members intersect with each other.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to structural elements formed from castable material. In particular, the invention relates to reinforcement of polymer concrete structural elements using fibre-reinforced plastics. However, it should be appreciated that other castable material such as standard concrete may be used to form the structural element.  
       BACKGROUND OF THE INVENTION  
       [0002]     Polymer concrete is made by polymerising a polymeric material with filler material such as aggregate (e.g. gravel, sand etc.). Polymer concrete has generally good durability and chemical resistance and is therefore used in various applications such as in pipes, tunnel supports, bridge decks and electrolytic containers. The compressive and tensile strength of polymer concrete is generally significantly higher than that of standard concrete. As a result polymer concrete structures are generally smaller and significantly lighter than equivalent structures made out of standard concrete.  
         [0003]     However, polymer concrete still requires reinforcement as with standard concrete. This normally involves the use of traditional reinforcement bars that are placed with the concrete during the forming process. In corrosive environment traditional steel reinforcement is subject to corrosion and therefore has been increasingly replaced with fibre composite reinforcement.  
         [0004]     The superior physical properties of fibre composites are well recognised. They combine high strength with low weight and have generally good durability and resistance to salts, acids and other corrosive materials, depending on the resin formulation. Based on these material characteristics, fibre composite reinforcement has a range of advantages over traditional steel reinforcement which is heavy and subject to corrosion. Fibre composite reinforcement for concrete and polymer concrete structures is available but generally has a form similar to traditional steel reinforcement. That is, different diameter, round bars and ligatures (stirrups).  
         [0005]     This type of fibre composite reinforcement does not result in any significant material or weight saving over standard steel reinforcement. Furthermore, this standard fibre composite reinforcement is expensive and rather inflexible. The straight bars are extremely difficult to shape to include cogs or hooks at the ends to improve the anchorage. The ligatures are supplied as a prefabricated item and cannot be re-shaped or adjusted for different size or shape beams.  
         [0006]     Reinforcement bars and ligatures were developed to be made of steel and used in standard concrete. As has been shown many times before, structural concepts developed for traditional materials are not necessarily the most efficient solution in fibre composites.  
       OBJECT OF THE INVENTION  
       [0007]     It is an object of the invention to overcome or alleviate one or more of the disadvantages of the above disadvantages or provide the consumer with a useful or commercial choice.  
         [0008]     It is a preferred object of this invention to enable structural elements made from concrete with continuous fibre composite reinforcement to be produced that have improved load-carrying characteristics.  
         [0009]     It is a further preferred object of the invention to allow structural elements made of concrete and continuous fibre composite reinforcement to be produced cost effectively.  
         [0010]     It is a still further preferred object of the invention to allow structural elements made of concrete and continuous fibre composites reinforcement to be produced with a significantly reduced weight.  
       SUMMARY OF THE INVENTION  
       [0011]     In one form, although not necessarily the only or broadest form, the invention resides in a structural element formed from castable material, said structural element comprising:  
         [0012]     a plurality of fibre reinforced plastic, tubular members;  
         [0013]     a plurality of fibre reinforced plastic, spacer members, said spacer members extending between said plurality of tubular members;  
         [0014]     a plurality of fibre reinforced plastic, interconnecting members, said interconnecting members positioned in a different orientation to said spacing members; and  
         [0015]     castable material surrounding said members;  
         [0016]     wherein the interconnecting members and spacer members intersect with each other.  
         [0017]     The members may be produced from any suitable glass, carbon or aramid fibre and/or plastics material dependant upon the desired properties of the structural element. A surface area of the members that contact the castable material may be abraded to increase adhesion between the castable material and the members. Alternatively, the members may be coated with sand and/or gravel interface to increase adhesion.  
         [0018]     The tubular members may be pultruded fibre reinforced plastic. Preferably, the tubular members are substantially square in transverse cross-section. The tubular members may be hollow to save maximum weight.  
         [0019]     In another form, the tubular members may be filled with standard concrete, polymer concrete or a filled resin system to increase their load carrying capacity.  
         [0020]     In yet another form, the tubular members may be filled with standard concrete, polymer concrete or a filled resin system and a metal or fibre composite reinforcing bar to further increase their load carrying capacity.  
         [0021]     The spacer members and interconnecting members are usually constructed from the same fibre reinforced plastic. Preferably, the spacer member and interconnecting members are normally stronger than the transverse strength of the tubular members.  
         [0022]     The interconnecting members may pass through the spacer members or the spacer members may pass through the interconnecting members or a combination of both.  
         [0023]     Slots may be located in either or both of the interconnecting members and/or spacer members to allow the interconnecting members and spacer members to intersect.  
         [0024]     The interconnecting members and spacer members may be locked to each other after they intersect. Notches may be provides in the interconnecting members and/or spacer members to engage with the slot on the other of the interconnecting member or spacer member to lock the interconnecting members and spacer members together.  
         [0025]     Preferably the interconnecting members are oriented so that they are substantially perpendicular to the spacer members.  
         [0026]     The castable material is usually concrete. Preferably, the concrete is polymer concrete or a filled resin system.  
         [0027]     In another form, the invention resides in a method of producing a structural element formed from castable material, said method including the steps of:  
         [0028]     producing a mould that has a portion of an outer shape of the structural element to be produced;  
         [0029]     placing fibre reinforced plastic, tubular members; fibre reinforced plastic, spacer members; and fibre reinforced plastic, interconnecting members; within the mould such that said spacer members extending between said plurality of tubular members and said interconnecting members are positioned in a different orientation to said spacing members; so the spacing members and interconnecting members intersect;  
         [0030]     locating castable material between and over said members;  
         [0031]     allowing said castable material to set to form said structural element.  
         [0032]     The members may be abraded prior to the members being introduced into the mould. Alternatively, the members may be coated with sand and/or gravel interface to increase adhesion.  
         [0033]     In one embodiment, the members may be located within the mould and castable material poured over the members.  
         [0034]     In another embodiment, the members may be located within the mould after sufficient castable material to complete the structural element has been delivered into the mould.  
         [0035]     In still another embodiment, a portion of castable material may be introduced into the mould and some of the members introduced into the mould. More castable material may then be introduced into the mould and more members may be introduced into the mould. This may be continued until the structural element has been completed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]     Embodiments of the invention, by way of example only, will be described with reference to the accompany drawings in which:  
         [0037]      FIG. 1  is a perspective view of a structural element according to an embodiment of the invention;  
         [0038]      FIG. 2  is a perspective view of a fibre reinforced plastic members according to  FIG. 1 ;  
         [0039]      FIG. 3  is a sectional side view of the structural element of  FIG. 1 .  
         [0040]      FIG. 4  is a further sectional side view of the structural element of  FIG. 3 ;  
         [0041]      FIG. 5A  is a first step in producing the structural element of  FIG. 1 ;  
         [0042]      FIG. 5B  is a second step in producing the structural element of  FIG. 1 ;  
         [0043]      FIG. 5C  is a third step in producing the structural element of  FIG. 1 ;  
         [0044]      FIG. 5D  is a final step in producing the structural element of  FIG. 1 ;  
         [0045]      FIG. 6A  is a perspective view of an interconnecting system between an interconnecting member and a spacer member;  
         [0046]      FIG. 6B  is a further perspective view of an interconnecting system between an interconnecting member and a spacer member;  
         [0047]      FIG. 6C  is a further perspective view of an interconnecting system between an interconnecting member and a spacer member;  
         [0048]      FIG. 7  is a side view of a structural element according to a second embodiment of the invention;  
         [0049]      FIG. 8  is a side view of a structural element according to a third embodiment of the invention;  
         [0050]      FIG. 9  is a side view of a structural element according to a fourth embodiment of the invention; and  
         [0051]      FIG. 10  is a perspective view of a structural member according to a fifth embodiment of the invention.  
         [0052]      FIG. 11  shows a perspective view of a structural element according to a sixth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0053]      FIG. 1  shows a structural element  100  in the form of a marine beam  101 . The marine beam  101  is produced using a polymer concrete  110  that is reinforced using fibre reinforced plastic tubular members  120 ; fibre reinforced plastic, spacer members  130 ; and fibre reinforced plastic, interconnecting members  140 .  
         [0054]     The tubular members  120  are square in transverse cross-section and are pultruded from polyester resin and glass fibre. The spacer members  130  and interconnecting members  140  are flat sheets that are produced from vinyl ester and carbon fibre.  
         [0055]     Referring also to FIGS.  2  to  4 , the arrangement of the tubular members  120 , space members  130  and interconnecting members  140  are shown in more detail. The tubular members  120  extend the length of the marine beam  101  with the spacer members  130  located between adjacent tubular members  140 . Slots are located within the spacer members  130  so that the interconnecting members  140  can be placed through the spacer members  130 .  FIG. 4  shows a cross-section of the marine beam  101  that passes through the interconnecting members  140 , whilst  FIG. 3  shows a cross-sectional side view of the marine beam  101  that passes only through the spacer members  130 .  
         [0056]     It should be appreciated that the interconnecting members  140  are spaced along predetermined lengths of the marine beam  101 . The spacing of the interconnecting members  140  along the spacer members  130  may be varied according to the structural requirements. That is, if increased lateral strength is required, the distances between adjacent interconnecting members  140  can be reduced.  
         [0057]     The advantage of a construction of the marine beam  101  is that fibre dominated behaviour is exhibited in three dimensions. That is, increased strength is provided both longitudinally, laterally and transversely. Specifically, the tubular members  120  provide both longitudinal, lateral and transverse strength to the marine beam. The spacer members  130  provide additional longitudinal and transverse strength. Further, the spacer members  130  also provide a tie for an upper and lower part of the marine beam  101  through which the tubular members  120  do not extend. This prevents the delamination of a top  102  and base  103  of the marine beam from the tubular member. The interconnecting members  140  provide additional transverse strength and also prevents lateral delamination of the tubular members  120  and spacer members  130 .  
         [0058]      FIGS. 5A  to  5 D show the process that is used to produce the marine beam  101  shown in  FIG. 1 . The first step in the process is to produce formwork of a desired shape to produce a mould  150 . In this example, the marine beam  101  is produced in an upside down manner.  
         [0059]     A level of polymer concrete  110  is then delivered into the mould shown in  FIG. 5A . The intersecting spacer members  130  and interconnecting members  140  are then lowered into the polymer concrete  110  as shown in  FIG. 5B . Individual tubular members  120  are then located in between respective spacer members  130  causing the polymer concrete  110  to surround the spacer members  130  and tubular members  120  as shown in  FIG. 5C . Interconnecting members  140  are then located through the spacer members  130  and additional polymer concrete  110  is added as shown in  FIG. 5D . The mould  150  can then be screeded or a top placed onto the mould  150 . The polymer concrete  110  is then allowed to cure and the marine beam is removed from the mould  150 .  
         [0060]     It should be appreciated that the tubular members  120 , spacer members  130  and interconnecting members  140  may be formed as shown in  
         [0061]      FIG. 2  prior to them being located within the mould. Polymer concrete  110  may be already located within the mould  150  or poured onto the members  120 ,  130  and  140  to form the marine beam  101  within the mould  150 .  
         [0062]      FIGS. 6A  to  6 C shows a variation on a rectangular slot produced in the spacer member for positioning of the interconnecting member in the marine beam  101  shown in FIGS.  1  to  4 . In this embodiment, triangular shaped slots  131  are produced within the spacer members  130 . Notches  141  are also produced within the interconnecting members  140 . The interconnecting member  140  and spacer member  130  are joined by orienting the intersecting member relative to the triangular slot  131  so that it is inserted adjacent an hypotenuse of the triangular slot  131  as shown in  FIG. 6B . The interconnecting member  140  is then rotated when the notch  141  is in alignment with the spacer member. Rotation of the interconnecting member  140  causes the interconnecting member  140  and spacer member  130  to become locked together. This is advantageous as greater tolerances are able to be obtained during the manufacture of structural elements. Further, it also allows for pre-arrangement of the members prior to insertion into a mould.  
         [0063]      FIGS. 7 and 8  show an example of different structural members  200  and  300  that can be produced using the above method.  FIGS. 7 and 8  also disclose that spacer members can be used as interconnecting members and vice versa.  
         [0064]      FIG. 9  again shows a variation of a structural element  400 . In this structural element tubular members  120  are stacked upon each other with a polymer concrete  110  that has no member located through the polymer concrete  110 . This allows for post-forming of the polymer concrete top.  
         [0065]      FIG. 10  shows a still further structural element  500  that has a base of polymer concrete  112  that is reinforced with interconnecting members  140  and spacer members  130 . The sides  501  of the structural element are formed from tubular members  120 , spacer members  130 , interconnecting members  140  and polymer concrete  110 . Along the length of the beam are intermediate sections  160  of polymer concrete that extend between the sides  501 . These are tied in to the structural member using interconnecting members that are located between respective tubular members  120 .  
         [0066]     The use of the tubular members  120  provides for a lighter structure and also reduces material costs. Another advantage is that the tubular member provides a space for electrical conduits. Still another advantage is that the size of the tubular member can be varied to produce structural elements of different densities.  
         [0067]      FIG. 11  shows a still further structural element  600  in the form of a beam  601  produced using tubular members  120 , interconnecting members  140 , and spacer members  130 , located within a polymer concrete. Tubular members  151  have been filled with concrete to increase the strength of the tubular members. Tubular members  152  have been filled with concrete and stainless steel reinforcement bars, again to increase the strength of the tubular member. Tubular members  153  have been filled with resin system and fibre reinforced bars to also increase the strength of the tubular members. It should be appreciated that the tubular members can be filled with a variety of materials to change the characteristics of the structural member.  
         [0068]     It should be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit or the scope of the invention.