The present invention relates to a method for manufacturing a plastic support profile, plastic support profile and construction provided with such a support profile.

For the purpose of manufacturing constructions, such as for bridges or buildings, use is generally made of metal support profiles such as I-profiles. Such support profiles do however have the drawback that they are heavy and require regular maintenance. It is known to obviate these drawbacks by using plastic, particularly fibre-reinforced plastic.

The manufacture of these plastic support profiles is however an expensive process, irrespective of whether the plastic is moulded, extruded or pultruded, since a specific mould has to be made for each dimensioning of the support profile. The cost of such a mould makes the production of small numbers of support profiles in a specific dimensioning unattractive. In addition, the extrusion and pultrusion techniques limit the design freedom of the support profiles to support profiles with a constant section over their cross-section. It is therefore an object of the present invention to at least partially obviate the above stated prior art drawbacks, or to provide a usable alternative.

The invention proposes for this purpose a method for manufacturing a plastic support profile, comprising of providing a first flange formed by a substantially flat glass fibre- reinforced plastic sheet, a second flange formed by a substantially flat glass fibre- reinforced plastic sheet, and connecting the first and the second flange to each other by means of at least a web plate formed by a substantially flat glass fibre-reinforced plastic sheet such that, at least in a cross-section of the thus created support profile, the first and second flange run substantially parallel in a cross-section and that in width direction the web plate extends substantially perpendicularly of the first and second flange between the first and second flange.

In this manner a plurality of support profiles can be manufactured on the basis of standardized parts and, making use of extrusion or pultrusion technique, flanges having in principle unlimited length can even be manufactured in this way with a determined mould. Different support profiles can particularly be manufactured using one determined type of flange by selecting the width of the web plate in accordance with the intended height and/or loadability or load-bearing capacity (strength and/or stiffness) of the support profile to be manufactured. In addition to a single web plate, use can be made of a plurality of web plates placed at a mutual distance, preferably placed parallel to each other, or such that the cross-section of the thus resulting support profile is substantially trapezoidal.

The web plate can be welded onto the flanges or be fused thereto, the web plate and the flanges can be connected to each other by means of screws or bolts, or these parts can be connected to the first and the second flange by means of glueing. This latter method has produced particularly good results using structural adhesives commercially available under the brand names Araldite 2011 , Araldite 2015 or Plexus MA425.

In order to obtain a good glueing surface and further increase the strength of the thereby resulting connection, the method according to the present invention also comprises of providing on the first and the second flange at least one, and preferably at least a pair of protrusions placed at a mutual distance the thickness of the web plate (plus in fact twice the glue thickness) from each other for fixing the web plate respectively thereagainst and therebetween. Such protrusions also contribute toward a correct positioning and form retention of the support profiles obtained on the basis of the flanges.

A further advantage of the present invention is obtained in that the flanges are flexible in a longitudinal direction as long as they are not connected to a web plate, whereby they can be placed against web plates with curved edges and can then be connected thereto. It is hereby possible to manufacture support profiles with shapes which would not be possible according to prior art methods without developing a specific mould for this purpose.

Although the shaping possibilities are in principle unlimited, an arcuate shape, a curved part, a half-moon shape, a trapezium shape and a wedge shape are specifically mentioned here as suitable shapes. In these shapes the upper side and the underside as well as combinations of upper sides and undersides can be curved. Recesses can also be made in the web plates for the purpose of weight-saving, mounting of parts connected to the support profile or for other needs such as aesthetic requirements.

For further weight-saving or in order to provide multiple possibilities for the use of the same mould to make the flange, the method according to the present claim can comprise of providing at least a cavity in at least the first or second flange. Further material can be subsequently arranged in this cavity if necessary for strengthening, reinforcing and/or stiffening purposes. The flange preferably comprises a glass fibre-reinforced core or a carbon fibre- reinforced core, such as an ultra-high modulus carbon fibre core. The manufacture of at least the first or second flange by means of pultrusion is recommended since these techniques do not require moulds of a predetermined length.

The invention will now be elucidated with reference to the following figures, in which:

- Figures la and lb show a cross-section of a support profile manufactured by means of the method according to the present invention;

- Figure lc shows a detail cross-section of a flange for manufacturing the profile of figures 1 and 2;

- Figures 2a and 2b show a perspective view of a support profile according to the present invention;

- Figures 3 a and 3b show a perspective view of a construction manufactured with a support profile according to the present invention; and

- Figure 4a shows a table with widths of the web plate and thereby heights of the profile for given span lengths, and figures 4b and 4c show these data in graph form.

Figure la shows a cross-section of a support profile 1 manufactured by means of the method according to the present invention. The support profile consists of a first flange 2 formed by a substantially flat glass fibre-reinforced plastic sheet; and a second flange 3 formed by a substantially flat glass fibre-reinforced plastic sheet, as well as a web plate 4 formed by a substantially flat glass fibre-reinforced plastic sheet. It can be seen that the first and second flange 2, 3 are mutually connected such that the first and second flange 2, 3 run substantially parallel in a cross-section and that in width direction 5 web plate 4 extends substantially perpendicularly of the first and second flange 2, 3. The width 5 of web plate 4 can be varied in order to obtain a support profile 1 with a varying load-bearing capacity. The first and second flange 2, 3 each have a pair of protrusions 6, 7 placed at a mutual distance the thickness of the web plate from each other for fixing web plate 4 respectively thereagainst and therebetween. Both first flange 2 and second flange 3 are each provided with cavities 8, 9, which in the shown embodiment are empty.

Figure lb shows a cross-section of a support profile which is similar to support profile 1 of figure 1 but wherein a filling is arranged in cavities 8, 9 of flanges 2, 3 for further strengthening of flanges 2, 3, and thus of profile 1.

Figure lc shows flange 2 of figures la and lb in further detail, wherein non-limitative exemplary dimensions are included in the figure. Figure 2a shows a perspective view of a support profile 1 ' according to present invention, wherein a first flange 2' and a second flange 3' are connected to an arcuate web plate 4', thus forming an arcuate support profile.

Figure 2b shows a perspective view of a support profile 1" according to the present invention, wherein a first flange 2" and a second flange 3" are connected to a web plate 4" curved for a specific purpose, thus forming a specific support profile 1". Web plate 4" is provided with recesses 10 in order to save weight.

Figures 3a and 3b show perspective views of constructions 11 and 12, both bridges, manufactured with support profiles according to the present invention.

Figure 4 shows a table with heights of support profiles substantially corresponding with the width 5 of the web plate used, with the thus obtained cross-sectional areas, the weight per length, the stiffness and the bending strength. Three types of flange are mentioned in the table, wherein Flange type A designates a flange with hollow spaces 8, 9, Flange type B a flange in which the cavity comprises a glass fibre-reinforced filling and Flange type C a flange with for instance an ultra-high modulus carbon fibre core. Figures 4a and 4b likewise show the stiffness and bending strength in graph form. In addition to the stated examples and embodiments many variations of the present invention are possible, all of which are deemed to fall within the scope of protection as laid down in the following claims.