WO2000020702A1

WO2000020702A1 - A building element and a method for making same

Info

Publication number: WO2000020702A1
Application number: PCT/NO1999/000291
Authority: WO
Inventors: Eivind Hjellum
Original assignee: Norwegian Marine As
Priority date: 1998-09-22
Filing date: 1999-09-17
Publication date: 2000-04-13
Also published as: NO984421D0; NO307977B1; NO984421L; AU6011299A

Abstract

Building element of trusswork structure, comprising at least two beams (2) being kept at a distance from each other by means of at least two more or less transversal braces (3) lying in between. An element (1) is moulded as a single integral piece wherein the transitions between beams (2) and braces (3) continue unbrokenly; as the material (10) (the materials (1; 4, 5, 6)) being included in beams (2) and braces (3) is (are) continous in all transitions. The invention also relates to several methods for manufacturing of elements, among other by moulding and vacuum-injection into a mould (11).

Description

A BUILDING ELEMENT AND A METHOD FOR MAKING SAME

The present invention relates to a building element of trusswork structure, a module for constructing such elements, and a method for manufacturing such modules and/or elements.

Truss beams are usually made of steel profiles being welded together to a continuous trusswork. Today, trusswork structures are also made of plastics, particularly fibre reinforced thermoset plastics. In principle, these are manufactured in the same manner as a steel trusswork in that premanufactured profiles are cut and assembled into a trusswork. Profiles of glass fibre reinforced plastics (GFRP) are currently manufacured mechanically through a so- called pultrusion process. Joining of such profiles is done by means of bolt connections, in principle in thesame manner as a prior steel trusswork. Pultruded, glass fibre reinforced profiles are difficult to laminate or glue together to give adequate and provable strength. Thus, usually bolting is utilised for such joining. Trusswork structures made of GFRP have the following advantages above steel trussworkε : They are of far lighter weight, they are corrosion resistant and require minimal maintenance. Particularly, for structures being exposed to humidity, or where low weight is of importance, GFRP trussworks are preferable.

However, the process of building trussworks of pultruded profiles is demanding, and joining by means of bolts has the weakness that the bolts, usually made of steel, are exposed to corrosion and must be maintained and even be replaced at regular intervals. Bolts may work loose, and heavily loaded bolt connections give rise to local stress concentrations in the trusswork elements.

GB 8.708.500 of 09.04.87 is referred to as an example of a prior truss beam. Here a beam is shown being composed of several different elements which at first are assembled step by step, and thereafter fused together. The process is time-consuming, lots of semi-products would have to be stocked, the manufacturing require much preparatory work and only leads to one specific type of beam being difficult to connect to other or similar elements.

The present invention relates to a structure and a manufacturing method in which reinforced or unreinforced composite material may be manufactured in one moulding, wherein the entire trusswork is a single integral structure without joints requiring joining of several separate parts. However, a major trusswork may be assembled of several modules, each one in its turn being manufactured according to the present invention. The material being utilised is then a mouldable synthetic material as plastics, and, if required, this material, below denoted as matrix material, may be reinforced by using fibre reinforcements of GFRP or FRP (fibre reinforced plastics) when moulding. A preferred truss beam may in principle be manufactured as two inverted halves being joined back to back by means of glueing, laminating, fusing or another manner. The two halves are then manufactured in a U-shaped mould wherein an elevation is arranged in a pattern corresponding to the desired shape, location and dimension of the braces in the trusswork. In the mould the trusswork is fused to the amount of reinforcement being locally desired for the individual parts of the trusswork. The amount of reinforcement material may thus be varied from location to location in the mould, the parts of the beam under most stress being provided with more reinforcement than the parts under less stress. When the two halves are assembled to a single integral beam, additional reinforced laminate, e.g., on the upper and/or lower flange as descriged more closely in the examples given below. However, if the matrix material itself is strong enough, using only the matrix material is possible. In this case, the thickness of the matrix material may of course be varied in embodiments as required. The thickness of the matrix material may, of course, be varied for embodiments wherein the amount of the reinforcement material is also varied so as to combine both solutions .

The entire beam surface, may either be moulded as a single integral moulding without apertures between the elements of the trusswork, or may be moulded in the form of strips of material of suitable width along all braces or reinforcement elements required, the beam having apertures between the reinforcement parts in the same manner as a trusswork of conventional structure. The advantage of making the entire trusswork as a single, continuous moulding, is that the moulding process is simplified, while at the same time the plate area of the braces or reinforcement parts contributes to reinforce the entire structure, and may also act as support for other elements in a structure. The moulding process itself may be done by manually applying the matrix material in a mould and by inserting prepared FRP elements in the matrix material in the desired thickness .

The moulding may also be done in a per se known vaccuum forming or vacuum moulding.

The object of the present invention is to provide a new trusswork element or a new, complete trusswork being lightweight, robust and inexpensive. This is achieved using elements and methods according to the claims as stated below. To provide a clearer understanding of the invention, the detailed description given below of the accompanying drawings , where :

Fig. 1 shows a cross section of a mould including at least one embedded "elevation" for the inclined braces in the trusswork, fig. 2 shows a cross section of half a trusswork beam removed from the mould, where the section A-A is given in fig. 3, fig. 3 indicates how two elevations in the mould give a cross section which alone, or together with a corresponding element, constitute an inclined brace in the trusswork, fig. 4 shows a cross section of a fully assembled beam, wherein two halves (1) are joined together back to back, and wherein a reinforcement (2) thereafter is applied to each of the flanges or the beam parts, fig. 5 in principle shows a longitudinal view of a complete truss beam wherein the inclined stays appears in the form of an elevated and possibly reinforced pattern in the moulding, but with a whole plate between the braces, fig.6 shows a corresponding beam as in fig. 5, but here shown with recesses between the braces, fig. 7 shows a trusswork structure for a ridge roof, fig. 8 shows a trusswork structure with curved or arched upper flange, fig. 9 shows that upper and lower flange may be manufactured as plane or open flanges with place for reinforcing elements, fig. 10 shows a solution with another shape of the upper flange fig. 11 shows a section of a specially shaped inclined braces having reinforcing embedments, fig. 12 shows a section of an inclined brace of a different structure, fig. 13 shows a truss beam with integrally moulded brackets for supporting additional structural elements, fig. 14 shows an example of how a major trusswork may be assembled using modules made according to the present invention, fig. 15 shows an example of a mould which also may be utilised for vaccuum injection, fig. 16 shows the mould according to fig. 15, wherein a core part comprising applied reinforcement layer, and fig. 17 shows the final step; a moulding process compris- ing vaccuum injection and the use of a core part.

This description and the drawings show examples of embodiments. The embodiments may, however, be modified in several ways according to the scope of the present invention. It should be mentioned that the drawings are principle drawings in which some technical details may be omitted for avoiding overloading of the drawings. Moreover, the drawings are not necessarily to scale, neither mutually among the figures nor in different directions within one and the same drawing. So far, using the same reference numerals to corresponding components in all drawings is found to be expedient .

Fig. 1 shows a cross section across a mould 11 provided with at least one elevation 12 in the bottom. The braces 3 may be formed on these elevations. The mould 11 may be manufactured of any suitable material and may be of arbitrary length across the plane of the sheet and be of arbitrary width along the plane of the sheet . The number of inclined braces and the distance between these, and also their angle, are determined from ordinary calculations of strength. When manufacturing a truss beam 1, the matrix or plastics material 10 is injected or brushed to the internal side of the mould 11 so that this is covered. Thus, this applied plastics material 10 constitutes the matrix material in the truss beam 1. Thereafter, the material in the beam 1 is laminated by repeated application of layers, as armouring or fibre reinforcements 4,5,6 also may be embedded at the most exposed areas . The number of layers with such reinforcement may vary within the beam, so that the most loaded areas is provided with most reinforcement with fibres. For applications entailing less loading, the reinforcement may be omitted entirely. When being utilised, reinforcement should be thoroughly wetted by the matrix material before hardening of the matrix material. When the matrix or plastics material is hardened, the truss beam can be removed from the mould 11, and the cross section of the manufactured truss beam or module, is shown in fig. 2. The beam shown here is a U-shaped beam, but with supporting and reinforcing braces 3 extending between the two sidewalls 2. Usually, the braces 3 extend inclined and are then denoted inclined braces .

Fig. 3 shows an enlarged section of the beam 1 shown as intersections in the plane A-A in fig. 2, and shows an intersection of two inclined braces 3, and beam sections 9 lying in between, here shown plane.

Fig. 4 shows how two U-shaped beams 1 of the type shown in fig. 2, may be assembled back to back to form a symmetric truss beam 15. The two symmetric halves 1 may be joined to each other by means of matrix material being hardened, upper flange 13 and lower flange 14 may be additionally reinforced by joining to additional reinforcement elements 16,17 and the shown braces 3 are assumed to be equally positioned and shaped inclined braces, which is shown more closely in fig. 5 and 6.

In fig. 5, a section of a truss beam 1 (asymmetric 1 or symmetric 15) is shown according to fig. 2 or 4 , and here the extension of the inclined braces is shown with dot-and- dash lines. The manner is indicated in which the inclined braces 3 may be reinforced using embedded fibre elements 4,5,6 under production. The fibre elements 4,5,6 are then preferably arranged overlapping each other and may also continue to upper and lower flange 13,14. If the two halves 1 of the truss beam 15 has completely concurring inclined braces 3, reinforcement elements may be inserted in the cavity arising between the two halves, that is, within the braces 3. Such reinforcements may also be attached to the beam, possibly by means of the the matrix material or another adhesive means, and may itself be made of the matrix material, fibre material, wood, steel or other construction materials or combinations of such.

The fibre elements 4,5,6 may be mats or weaves of fibre materials wich are cut or otherwise formed to the desired shape and may be inserted in dry condition into the mould or may be compressed into already applied matrix material. The fibre elements may also be mono- or multifilamεnts which are arranged in the desired manner within the mould.

Fig. 6 indicates how recesses 18 may be arranged between the inclined braces 3, thereby forming cavities. However, the preferred embodiment is as shown in fig. 5, having a whole wall between the inclined braces 3. The reason for this is a simpler manufacturing process and greater strength. Moreover, no significant weight reduction is obtained when removing or omit buliding up the areas between the braces 3, because the matrix material is relatively light-weighted compared to other construction materials .

For the present, relatively plain truss beams 1,15 are shown as examples of an embodiment of the invention. However, the invention may be utilised on manufacturing large, complete trusswork constructions, e.g., support structures 29 for ridge roofs for buildings of all kinds, and also beam span 28 having curved upper flange 13 or lower flange 14, as shown in fig. 8. Such elements may of course be utilised in other structures such as bridges, supporting walls and similar.

As shown in fig. 9, upper flange 13 and/or lower flange 14 may be made as concave or hollow flanges 19,20, wherein reinforcing material may be included or embedded in the form of support elements 21,22 or beams made of any structural material.

Further, as indicated in fig. 10, upper flange and/or lower flange may be made having another, closed or plane shape allowing for embedment or connection to stabilizing elements 17,23. Thus, in fig. 10 an upper flange is shown in the form of a hollow cylinder, wherein such stabilizing elements 23 in the form of pipes or bars may be located. In a similar manner, a section is in fig. 11 shown a section through one of the braces 3, which also may be made as a hollow cylinder, and thus may receive, e.g., tube elements 24 for reinforcement. Similar solutions is also indicated above in connection with fig. 5 and 6, but the idea is here not to include reinforcements. Fig. 12 indicates that the inclined braces 3 may be constructed about a shaped core material 25 being located on an existing plane beam 9. The core material 25 may comprise fibre material (FRP and GFRP) or another structural material as, e.g., steel, and may be covered by strips 40 comprised by plastics material or, if required, using fibre material being impregnated with matrix material 10.

Fig. 13 shows a truss beam 15 similar to the one shown in fig. 4,5,6,7,8,9 or 10, but here having additional equipment in the form of integrally moulded brackets or consoles 26 for supporting additional transverse beams or covers 27.

Fig. 14 shows that the present invention may be utilised to produce similar or, if any, dissimilar, relatively small and simple modules 30 being transversely or longitudi- nally joined in the desired pattern, thereby obtaining a larger and more complex trusswork structure as, e.g., ridge roof span 29 or beams 28.

Automated production could offer great advantages to produce such beams or modules by an in itself known vakuum- injection. Then, a closed mould could be utilised, wherein reinforcement, if any, may be inserted before the matrix material is sucked into the mould. As a further explanation of vacuum-injection, (also known as RTM, resin transfer moulding) , reference is made to the explanation given below and to figs. 15, 16 and 17.

Fig. 15 shows a mould 11, like the one shown in fig. 1, but being closable at the top by means of a foil or a tight- fitting cap, as explained below. The reinforcement material 4,5,6 in the form of glass fibres or other suitable material, is inserted into the mould 11 at the correct amount, after which the reinforcement material 4,5,6 is covered of an air-tight foil of suitable material enclosing the entire finished element and being sealed air-tight against the underlying mould 11, or of a tight-fitting, mould part or "top mould" 31 which is made having a geometry corresponding to the desired surface of the finished building element 1. Between the bottom-mould 11 and top mould 31 a cavity corresponding to the volume and geometric shape of the finished element 1. Air is then sucked out of the cavity between the two mould parts, or between mould and said foil, e.g., through a duct system 33, after which the matrix material 10 is allowed to flow into the cavity and thus wetting the reinforcement material 4,5,6. The matrix material enters the cavity within the mould through a system of ducts or conduits being adapted for the product and the process such that the reinforcement material 4,5,6 is wetted by means of the matrix material 10. Thereafter, the matrix material is allowed to harden, or to harden in part, before top mould or foil 31 is removed and the finished element 1 can be removed from the mould 11.

Instead of using vaccuum for sucking matrix material into the reinforcement material, the matrix material may be pumped by means of a certain gauge pressure. In this case, a good result dependends on a solid mould which entirely encloses the finished product. Foil, as mentioned above, cannot be utilised. Dividing of this mould should be possible in order to remove the finished product. This method is probably best suitable for small components . The mould 11 can also be made comprising a concave pattern for inclined braces and upper/lower flange for manufacturing a whole beam in one moulding, that is, without assembling two parts back to back. The manufacturing method may then be as in fig. 17. The mould is made corresponding to the external geometry of the finished element . The reinforcement material 4,5,6 is inserted in a dry condition. For upper/lower flanges and for inclined braces, at least one core 34 of suitable material may be arranged. The required amount of reinforcement material 35 is packed around the core(s) 34. Subsequently, the entire assembly is covered with a foil, or possibly a "top mould" 31 as mentioned above . The air is then sucked out by means of a vaccuum pump connected to a duct system 33, and the matrix material 10 enters through a planned system of conduits or ducts 32 in the mould 11. In this manner, a symmetric trusswork may be manufactured as one moulding instead of two halves as described above .

The core(s) 34 may in that case be made of a support material as the abovementioned elements 21-25. If a core 34 is utilised when moulding a "half" , asymmetric beam or module, such as shown at 1 in fig. 2, the core may be removed after finishing the moulding process, and a second reinforcement element may possibly be inserted when assemb- ling.

The present invention may be modified in different manners within the scope of the attached claims, and as examples of the variation possibilities, the following may in particular be mentioned. The beam may be made of unreinforced material, e.g, using only the matrix material 10; without any fibre reinforcement 4,5,6, and including more or less reinforced material .

The beam parts 1 may be utilised separately, that is, without joining two inverted halves back to back.

Instead of profiling the mould itself, a suitable strip of core material 25 may be arranged in the trusswork pattern and construct the composite material around said strip, thus creating closed inclined braces. This is also indicated in connection with fig. 12.

An entire trusswork may be laid up in a mould, and, if required, be given a curved shape, making it suitable for supporting a dome-shaped roof or vaulted ceiling. Each indi- vidual trusswork element may be plane or extend spaciously. And even if the individual element is plane, the entire structure may have a strictly 3 -dimensional structure, this being determined from the assembling of the various elements. Said brackets 26 indicated in fig. 13 may be die moulded or laminated after the beam itself is premanufactured, or produced together with the beam.

When the manufactured truss beams are utilised as modules 30 for major trusswork structures, they may be assembled adjacent each other, opposite each other or displaced in relation to each other, also with the possibility of repeated overlapping from module to module, for assembly of the desired complete structures. Joining of the modules into one continuous structure may then be done by applying matrix material which is allowed to harden.

When saying that transitions in the materials are continuous, this includes that both the transitions of the reinforcement elements continue unbrokenly in a manner such that the filaments in the reinforcement continue unbrokenly, and also that the reinforcement elements consists of semimanufactured articles such as textiles or weaves of fibre material being made and arranged with overlapping of adjacent elements being combined through the matrix material. Thus, as long as the reinforcement as formed is continuous, the filament in the reinforcement are not required to be continous.

The materials may be chosen among all suitable construction materials having the required properties. Thus, the matrix material may be any plastics or composition of plastics, even if carbon fibres, and kevlar fibres may be mentioned as interesting, both alone or together with glass fibres .

Finally, when expedient, one or more of the above- mentioned embodiments may be combined.

Claims

C l a i m s

1. Building element of trusswork structure, comprising at least two beams (2) being kept at a distance from each other by means of at least two, more or less transversal, braces

(3) lying in between, c h a r a c t e r i z e d i n that an element (1) is moulded as a single integral piece wherein the transitions between beams (2) and braces (3) continue unbrokenly; as the material (10) (the materials (1; 4,5,6)) being included in beams (3) and braces (3) is (are) continuous in all transitions .

2. Building element (l) of trusswork structure according to claim (1) , c h a r a c t e r i z e d i n that the element (1) consists of an external. covering matrix material (10) , and a reinforcement material (4,5,6) being incorporated therein, together forming a uniform element wherein the transitions of all trusswork elements (2,3) continue unbrokenly, both regarding the matrix material (10) and the reinforcement material (4,5,6) .

3. Building element according to claim 1 or 2 , c h a r a c t e r i z e d i n that the element is shaped such that both beams and brace (s) (3) essentially lie in the same plane .

4. Building element according to claim 3 , c h a r a c t e r i z e d i n that the beams (2) and/or the brace (s) (3) have a curved or angled profile, increasing the bending resistance of the beams (2) and the brace (s) (3).

5. Building element according to claim 3 or 4, c h a r a c t e r i z e d i n that the beams (2) and/or the tie bars (3) , or at least some of these, are shaped with an inner cavity which may be reinforced or stabilized by means of embedded, rigid structure parts

(21,22,23,24,25), preferably being firmly connected to each other and/or to the surrounding material .

6. Building element according to claim 1-5, c h a r a c t e r i z e d i n that two by two mirror symmetric elements (7,8) of equal size are assembled to into a combined, symmetric building element (1) .

7. Building element according to one of the claims 1-6, c h a r a c t e r i z e d i n that the matrix material is plastics and the reinforcement material is fibre, e.g., kevlar, carbon, glass or a combination of such fibres.

8. Method for manufacturing a building element of trusswork structure, comprising at least two beams (2) being kept at a distance from each other by means of at least two braces (3) , c h a r a c t e r i z e d i n that a hollow, concave mould (11) is utilised with a given shape complementary to the desired element (1) , that a matrix material (1) of plastics is injected, applied or vaccuum-injected to the interior of the mould (11) , and that reinforcement material (4,5,6), if any, is arranged in at least one layer on predetermined locations in the mould (11) before, during or after the matrix material is added, such that the reinforcement material (4,5,6) is wetted by the added matrix material (10), whereupon the element is allowed to harden and to be removed from the mould (11) .

9. Method according to claim 8, c h a r a c t e r i z e d i n that the mould (11) is formed such that on predetermined locations, recesses or cavities (19,20) in the formed element (1) are formed, and that reinforcements (21,22,23,24,25) are located in these recesses (19,20) and preferably are attached to these before utilising the element (1) .

10. Method according to claim 8 or 9, c h a r a c t e r i z e d i n that two or more part elements (1) of symmetric or identical form are located adjacent each other in a entirely or partly overlapping manner and are attached to each other by means of an adhesive as, e.g., additional parts of matrix material (10) being added to the contact surfaces and allowed to harden.