Hollow-core slab bearer

Abstract

Presented is a hollow-core slab bearer for bearing an end of a hollow-core slab, which end borders on an opening or similar structural discontinuity. The hollow-core slab bearer comprises a profile (1) with an open L-shaped cross-section comprising a base plate (9) and a web plate (10), the profile (1) having a first end (2) and a second end (3), a first end plate (4) at the first end (2) of the profile (1), and a second end plate (5) at the second end (3) of the profile (1), and a reinforcement (8) between the first end plate (4) and the second end plate (5), which reinforcement (8) binds the first end plate (4) and the second end plate (5) together.

Description

Field

[0001] The invention relates to a hollow-core slab bearer as defined in the preamble of independent claim 1.

[0002] Publication EP1180187 presents a hollow-core slab bearer.Objective

[0003] The object is to provide a hollow-core slab bearer with a high fire resistance class.Short description

[0004] The hollow-core slab bearer is characterized by the definitions of independent claim 1.

[0005] Preferred embodiments of the hollow-core slab bearer are defined in the dependent claims.List of figures

[0006] In the following the invention will described in more detail by referring to the figures, of which Figure 1 shows a first embodiment of the hollow-core slab bearer, Figure 2 shows the first embodiment of the hollow-core slab bearer shown in figure 1 as seen from one side, Figure 3 shows a second embodiment of the hollow-core slab bearer, Figure 4 shows a third embodiment of the hollow-core slab bearer, Figure 5 shows a fourth embodiment of the hollow-core slab bearer, Figure 6 shows a fifth embodiment of the hollow-core slab bearer, Figure 7 shows a sixth embodiment of the hollow-core slab bearer, Figure 8 shows a seventh embodiment of the hollow-core slab bearer, Figure 9 shows an eight embodiment of the hollow-core slab bearer, Figure 10 shows a ninth embodiment of the hollow-core slab bearer, Figure 11 shows a tenth embodiment of the hollow-core slab bearer, Figure 12 shows an eleventh embodiment of the hollow-core slab bearer, Figure 13 shows the eleventh embodiment of the hollow-core slab bearer illustrated in figure 12 as seen from another angle, Figure 14 shows a twelfth embodiment of the hollow-core slab bearer, Figure 15 shows the twelfth embodiment of the hollow-core slab bearer illustrated in figure 14 as seen from another angle, Figure 16 shows a thirteenth embodiment of the hollow-core slab bearer, Figure 17 shows the thirteenth embodiment of the hollow-core slab bearer illustrated in figure 16 as seen from another angle, Figure 18 shows a fourteenth embodiment of the hollow-core slab bearer, Figure 19 shows the fourteenth embodiment of the hollow-core slab bearer illustrated in figure 18 as seen from another angle, and Figure 20 shows in cross-section view an embodiment of the hollow-core slab bearer that is provided with an additional reinforcement bar between the first fastening area and the second fastening area and a load transfer structure in the profile with an open L-shaped cross-section. Detailed description of the invention

[0007] Next the hollow-core slab bearer for bearing an end of a hollow-core slab (not illustrated in the figures), which end borders on an opening or similar structural discontinuity, and some embodiments and variants of the hollow-core slab bearer will be presented in greater detail.

[0008] The hollow-core slab bearer is preferably, but not necessarily, made of metal such as of steel.

[0009] The hollow-core slab bearer comprises a profile 1 with an open L-shaped cross-section.

[0010] The profile 1 comprises a base plate 9 and a web plate 10.

[0011] The base plate 9 is preferably, but not necessarily, planar.

[0012] The web plate 10 is preferably, but not necessarily, planar.

[0013] The profile having a first end 2 and a second end 3, the hollow-core slab end which borders on the opening or similar structural discontinuity being placeable into the profile 1 with an open L-shaped cross-section.

[0014] The hollow-core slab bearer comprises a first end plate 4 at the first end 2 of the profile 1 with an open L-shaped cross-section, and a second end plate 5 at the second end 3 of the profile 1 with an open L-shaped cross-section.

[0015] The first end plate 4 is preferably, but not necessarily, planar.

[0016] The second end plate is preferably, but not necessarily, planar.

[0017] The hollow-core slab bearer comprises a first support member 6 which allows the hollow-core slab bearer to be mounted onto a first hollow-core slab or structure adjacent to the hollow-core slab, which borders on the opening or similar structural discontinuity.

[0018] The hollow-core slab bearer comprises a reinforcement 8 between the first end plate 4 and the second end plate 5. The reinforcement 8 binds the first end plate 4 and the second end plate 5 together.

[0019] The profile 1, the first end plate 4, the second end plate 5 and the reinforcement 8 are preferably, but not necessarily, made of metal such as of steel.

[0020] When the hollow-core slab bearer is in use and is installed in a building, the end of a hollow-core slab will be supported at the base plate 9 and the reinforcement 8 will be situated in a space (not illustrated) between the end of the hollow-core slab and the web plate 10 of the profile 1 with an open L-shaped cross-section. Because concrete (not illustrated) will be cast into said space, the reinforcement 8 will be embedded in concrete. Said concrete will provide for fire protection for the reinforcement 8.

[0021] The reinforcement 8 being fastened to the first end plate 4 at a first fastening area 11 so that more than 50 %, preferably more than 70 %, more preferably more than 90 % of the volume of the reinforcement 8 is located vertically between a first level h1 of the first fastening area 11 and the base plate 9 of the profile 1 with an open L-shaped cross-section The first level h1 of the first fastening area 11 is located at such distance from the base plate 9 of the profile 1 with an open L-shaped cross-section, which distance corresponds to the distance between the base plate 9 of the profile 1 with an open L-shaped cross-section and the first fastening area 11 as measured along the first end plate 4 and wherein the first level h1 of the first fastening area 11 extends in the same direction or in parallel with the base plate 9 of the profile 1 with an open L-shaped cross-section.

[0022] The reinforcement 8 being fastened to the second end plate 5 at a second fastening area 12 so that more than 50 %, preferably more than 70 %, more preferably more than 90 % of the volume of the reinforcement 8 is located vertically between a second level h2 of the second fastening area 12 and the base plate 9 of the profile 1 with an open L-shaped cross-section. The second level h2 of the second fastening area 12 is located at such distance from the base plate 9 of the profile 1 with an open L-shaped cross-section, which distance corresponds to the distance between the base plate 9 of the profile 1 with an open L-shaped cross-section and the second fastening area 12 as measured along the second end plate 5 and wherein the second level h2 of the second fastening area 12 extends in the same direction or in parallel with the base plate 9 of the profile 1 with an open L-shaped cross-section.

[0023] Such fastening of the reinforcement to the first end plate 4 and to the second end plate 5 protects the reinforcement 8 against the heat caused by the heat of the fire the base plate 9 may be subjected to and extends in this way the time that the reinforcement 8 does not lose its strength due to heat, and raises therefore the fire class of the hollow-core slab bearer, because the reinforcement 8 will be attached to the first end plate 4 and to the second end plate 5 at such distances from the lower ends of the first end plate 4 and the second end plate 5, which distances are greater than the corresponding distances for example in the hollow-core slab bearer known from publication EP1180187. Such fastening of the reinforcement to the first end plate 4 and to the second end plate 5 allows however allows to arrange the reinforcement 8 close to the base plate 9 of the profile 1 with an open L-shaped cross-section and the advantage of this is that this prevents bending of the construction at the hollow-core slab bearer. In other words, heat caused by fire heats up the base plate 9 and thermal energy is conducted from the base plate 9 to the first end plate 4 and from the first end plate 4 to the reinforcement 8 via the first fastening area 11 and thermal energy is correspondingly conducted from the base plate 9 to the second end plate 5 and from the second end plate 5 to the reinforcement 8 via the second fastening area 12. When thermal energy is conducted from the base plate 9 to the first end plate 4 and from the first end plate 4 to the reinforcement 8 via the first fastening area 11, and when thermal energy is correspondingly conducted from the base plate 9 to the second end plate 5 and from the second end plate 5 to the reinforcement 8 via the second fastening area 12, concrete in contact with the first end plate 4 and with the second end plate 5 will also consume thermal energy as some of the thermal energy is conduced into concrete (not illustrated) that has been cast into the hollow-core slab bearer. Some thermal energy will also be conducted by the concrete surrounding the reinforcement 8 from the base plate 9 to the reinforcement 8, but this amount is very small because thermal energy is absorbed by the concrete, i.e. thermal energy heats up the concrete, and because the volume of the concrete is normally much larger than the volume of the material of the hollo- core slab bearer. The greater the distance between the first fastening area 11 and the base plate 9 is and the greater the distance between the second fastening area 12 and the base plate 9 is, the better, because metal has a much better thermal conductivity than concrete.

[0024] The reinforcement 8 comprises preferably, but not necessarily, a reinforcement bar 13.

[0025] If the reinforcement 8 comprises a reinforcement bar 13, the reinforcement bar 13 can be directly fastened to the first end plate 4 by welding and the reinforcement bar 13 can be directly fastened to the second end plate 5 by welding. In such embodiments, the reinforcement bar 13 can have a head 18 at the first fastening area 11 and / or at the second fastening area 12, as in the ninth embodiment of the hollow-core slab bearer illustrated in figure 10. In such embodiments of the hollow-core slab bearer, the reinforcement bar 13 has at least one at least partly curved and / or angled section 14 between the first end plate 4 and the second end plate 5. In such embodiments of the hollow-core slab bearer, the reinforcement bar 13 can for example consist of a curved section which means that the reinforcement bar 13 is curved from the first end plate 4 to the second end plate 5 or vice versa. In such embodiments of the hollow-core slab bearer, the reinforcement bar 13 can for example comprise a straight section 15 extending in the direction of the base plate 9 and one curved and / or angled section 14 between the straight section 15 and the first end plate 4 and another curved and / or angled section 14 between the straight section 15 and the second end plate 5.

[0026] If the reinforcement 8 comprises a reinforcement bar 13, the reinforcement bar 13 can be fastened to the first end plate 4 by means of a first reinforcement part 16 of the reinforcement 8 so that the reinforcement bar 13 being fastened to the first reinforcement part 16 by welding and so that the first reinforcement part 16 is fastened to the first end plate 4 by welding, and the reinforcement bar 13 can be fastened to the second end plate 5 by means of a second reinforcement part 17 of the reinforcement 8 so that the reinforcement bar 13 being fastened to the second reinforcement part 17 by welding and so that the second reinforcement part 17 is fastened to the second end plate 5 by welding.

[0027] The first reinforcement part 16 is preferably, but not necessarily, a first plate part (not marked with a reference numeral), and the second reinforcement part 17 is preferably, but not necessarily, second plate part (not marked with a reference numeral).

[0028] The first plate part can extend transversally to or in the direction of the reinforcement bar 13.

[0029] The second plate part can extend transversally to or in the direction of the reinforcement bar 13.

[0030] If the reinforcement 8 comprises a such first reinforcement part 16 and a such second reinforcement part 17, the reinforcement bar 13 is preferably, but not necessarily, spaced apart from the first end plate 4, and the reinforcement bar 13 is preferably, but not necessarily, spaced apart from the second end plate 5 as in the tenth embodiment illustrated in figure 11.

[0031] If the reinforcement 8 comprises a reinforcement bar 13, the reinforcement bar 13 has preferably, but not necessarily, as illustrated for example in figures 5, 7 and 10 a straight section 15 extending in the direction of the base plate 9,.

[0032] If the reinforcement 8 comprises a reinforcement bar 13 having a straight section 15, the straight section 15 of the reinforcement bar 13 extends preferably, but not necessarily, in the direction of the base plate 9 for over 50%, preferably for over 75%, more preferably for over 90% of the distance between the first end plate 4 and the second end plate 5.

[0033] If the reinforcement 8 comprises a reinforcement bar 13 having a straight section 15, the straight section 15 of the reinforcement bar 13 extending for over 50%, preferably for over 75%, more preferably for over 90% of length of the reinforcement bar 13.

[0034] It is also possible that the reinforcement 8 comprises a reinforcement bar 13 that is curved all the way between the first end plate 4 and the second end plate 5 as in the fourth embodiment of the hollow-core slab bearer illustrated in figure 5 and in the seventh embodiment of the hollow-core slab bearer illustrated in figure 8.

[0035] As in the eleventh embodiment of the hollow-core slab bearer illustrated in figures 12 and 13, in the twelfth embodiment of the hollow-core slab bearer illustrated in figures 14 and 15, in the thirteenth embodiment of the hollow-core slab bearer illustrated in figures 16 and 17, and in the fourteenth embodiment of the hollow-core slab bearer illustrated in figures 18 and 19, the reinforcement 8 can comprise an additional reinforcement bar 23 between the first fastening area 11 and the second fastening area 12, and a load transfer structure 24 can be provided in the profile 1 with an open L-shaped cross-section, which load transfer structure 24 connects the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8. One purpose of the additional reinforcement bar 23 is to improve compression resistance of the top section of the hollow-core slab bearer and thereby improve the bending resistance of the hollow-core slab bearer. One purpose of the load transfer structure 24 is to improve buckling resistance of the additional reinforcement bar 23 by connecting together the additional reinforcement bar 23 of the reinforcement 8 and the reinforcement bar 13 of the reinforcement 8.

[0036] If the reinforcement 8 comprises an additional reinforcement bar 23 between the first fastening area 11 and the second fastening area 12 and a load transfer structure 24 in the profile 1 with an open L-shaped cross-section, which load transfer structure 24 connects the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8, the additional reinforcement bar 23 has preferably, but not necessarily, the form of a substantially straight bar, as illustrated in figures 12 to 17.

[0037] If the reinforcement 8 comprises an additional reinforcement bar 23 between the first fastening area 11 and the second fastening area 12 and a load transfer structure 24 in the profile 1 with an open L-shaped cross-section, which load transfer structure 24 connects the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8, the first distance d1 between the web plate 10 of the profile 1 with an open L-shaped cross-section and the reinforcement bar 13 of the reinforcement 8 is preferably, but not necessarily, essentially the same as the second distance d2 between the web plate 10 of the profile 1 with an open L-shaped cross-section and the additional reinforcement bar 23 of the reinforcement 8 additional reinforcement bar 23, as illustrated in figure 20.

[0038] If the reinforcement 8 comprises an additional reinforcement bar 23 between the first fastening area 11 and the second fastening area 12 and a load transfer structure 24 in the profile 1 with an open L-shaped cross-section, which load transfer structure 24 connects the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8, the load transfer structure 24 can comprise a truss construction 25 comprising bars 26 fastened between the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8, as illustrated in figures 12 to 15. In such case, at least some of the bars 26 of the truss construction 25 are preferably, but not necessarily, as illustrated in figures 12 to 15, in the form of substantially straight bars extending inclined with respect to the additional reinforcement bar 23.

[0039] If the reinforcement 8 comprises an additional reinforcement bar 23 between the first fastening area 11 and the second fastening area 12 and a load transfer structure 24 in the profile 1 with an open L-shaped cross-section, which load transfer structure 24 connects the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8, the load transfer structure 24 can, as illustrated in figures 16 to 18, comprise a plate construction 27 fastened between the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8. Such plate construction 27 comprises preferably, but not necessarily, apertures 28 as illustrated in figures 16 to 18.

[0040] In the thirteenth embodiment of the hollow-core slab bearer illustrated in figures 16 and 17, the plate construction 27 is only attached to the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8 and the plate construction 27 is not attached to the first end plate 4 or to the second end plate 5.

[0041] In the fourteenth embodiment of the hollow-core slab bearer illustrated in figures 18 and 19, the plate construction 27 is attached to the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8 and to the first end plate 4 and to the second end plate 5. This means that in the fourteenth embodiment of the hollow-core slab bearer illustrated in figures 18 and 19, the plate construction 27 attached to the first end plate 4 and to the second end plate 5 connects the first end plate 4 and the second end plate 5 together.

[0042] If the reinforcement 8 comprises an additional reinforcement bar 23 between the first fastening area 11 and the second fastening area 12 and a load transfer structure 24 in the profile 1 with an open L-shaped cross-section, which load transfer structure 24 connects the reinforcement bar 13 of the reinforcement 8 and the additional reinforcement bar 23 of the reinforcement 8, the reinforcement bar 13 of the reinforcement 8 can be being fastened to the first end plate 4 at the first fastening area 11 by means of the load transfer structure 24, and the reinforcement bar 13 of the reinforcement 8 can be fastened to the second end plate 5 at the second fastening area 12 by means of the load transfer structure 24.

[0043] It is also possible to form the reinforcement 8 of an elongated plate member 19 that extends between the first end plate 4 and the second end plate 5 and that binds the first end plate 4 and the second end plate 5 together as in the eight embodiment of the hollow-core slab bearer illustrated in figure 9. Such elongated plate member 19 can be provided with holes 20 configured to be filed with concrete when the hollow-core slab bearer so at to anchor the elongated plate member 19 in concrete.

[0044] The first end plate 4 and the first support member 6 can be formed of a second profile with an L-shaped cross-section, where the first end plate 4 extend perpendicularly or transversely with respect to the first support member 6.

[0045] The hollow-core slab bearer can comprise a second support member 7 which allows the hollow-core slab bearer to be mounted onto a second hollow-core slab or structure adjacent to the hollow-core slab which borders on the opening or similar structural discontinuity, the second hollow-core slab or structure being on the other side of the hollow-core slab which borders on the opening or similar structural discontinuity, when seen from the first hollow-core slab. The second end plate 5 and the second support member 7 can be formed of a third profile with an L-shaped cross-section, where the second end plate 5 extend perpendicularly or transversely with respect to the second support member 7.

[0046] The first end plate 4 can have a first aperture 21 at the first fastening area 11 so that the reinforcement 8 projects through the first end plate 4 in the first aperture 21, as in the first embodiment of the hollow-core slab bearer illustrated in figures 1 and 2, in the fourth embodiment of the hollow-core slab bearer illustrated in figure 5, and in the sixth embodiment of the hollow-core slab bearer illustrated in figure 7.

[0047] The second end plate 5 can have a second aperture 22 at the second fastening area 12 so that the reinforcement 8 projects through the second end plate 5 in the second aperture 22, as in the first embodiment of the hollow-core slab bearer illustrated in figures 1 and 2, in the fourth embodiment of the hollow-core slab bearer illustrated in figure 5, and in the sixth embodiment of the hollow-core slab bearer illustrated in figure 7.

[0048] It is apparent to a person skilled in the art that as technology advanced, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

Claims

1. A hollow-core slab bearer for bearing an end of a hollow-core slab, which end borders on an opening or similar structural discontinuity, the hollow-core slab bearer comprising a profile (1) with an open L-shaped cross-section, the profile (1) comprising a base plate (9) and a web plate (10), the profile having a first end (2) and a second end (3), the hollow-core slab end which borders on the opening or similar structural discontinuity being placeable into the profile (1) with an open L-shaped cross-section; a first end plate (4) at the first end (2) of the profile (1) with an open L-shaped cross-section, and a second end plate (5) at the second end (3) of the profile (1) with an open L-shaped cross-section; a first support member (6) which allows the hollow-core slab bearer to be mounted onto a first hollow-core slab or structure adjacent to the hollow-core slab which borders on the opening or similar structural discontinuity; and a reinforcement (8) between the first end plate (4) and the second end plate (5), which reinforcement (8) binds the first end plate (4) and the second end plate (5) together, characterized by the reinforcement (8) being fastened to the first end plate (4) at a first fastening area (11) so that more than 50 % of the volume of the reinforcement (8) is located vertically between a first level h1 of the first fastening area (11) and the base plate (9) of the profile (1) with an open L-shaped cross-section, and by the reinforcement (8) being fastened to the second end plate (5) at a second fastening area (12) so that more than 50 % of the volume of the reinforcement (8) is located vertically between a second level h2 of the second fastening area (12) and the base plate (9) of the profile (1) with an open L-shaped cross-section.

2. The hollow-core slab bearer according to claim 1, characterized by the reinforcement (8) comprising a reinforcement bar (13).

3. The hollow-core slab bearer according to claim 2, characterized by the reinforcement bar (13) being directly fastened to the first end plate (4) by welding, by the reinforcement bar (13) being directly fastened to the second end plate (5) by welding, and by the reinforcement bar (13) having at least one at least partly curved and / or angled section (14) between the first end plate (4) and the second end plate (5).

4. The hollow-core slab bearer according to claim 2 or 3, characterized by the reinforcement bar (13) being fastened to the first end plate (4) by means of a first reinforcement part (16) of the reinforcement (8) so that the reinforcement bar (13) being fastened to the first reinforcement part (16) by welding and so that the first reinforcement part (16) is fastened to the first end plate (4) by welding, and by the reinforcement bar (13) being fastened to the second end plate (5) by means of a second reinforcement part (17) of the reinforcement (8) so that the reinforcement bar (13) being fastened to the second reinforcement part (17) by welding and so that the second reinforcement part (17) is fastened to the second end plate (5) by welding.

5. The hollow-core slab bearer according to claim 4, characterized by the first reinforcement part (16) being a first plate part, and by the second reinforcement part (17) being second plate part.

6. The hollow-core slab bearer according to claim 4 or 5, characterized by the reinforcement bar (13) being spaced apart from the first end plate (4), and by the reinforcement bar (13) being spaced apart from the second end plate (5).

7. The hollow-core slab bearer according to any of the claims 2 to 6, characterized by the reinforcement bar (13) having a straight section (15) extending in the direction of the base plate (9).

8. The hollow-core slab bearer according to claim 7, characterized by the straight section (15) of the reinforcement bar (13) extending in the direction of the base plate (9) for over 50%, preferably for over 75%, more preferably for over 90% of the distance between the first end plate (4) and the second end plate (5).

9. The hollow-core slab bearer according to any of the claims 2 to 8, characterized by the reinforcement (8) comprising an additional reinforcement bar (23) between the first fastening area (11) and the second fastening area (12), and by a load transfer structure (24) in the profile (1) with an open L-shaped cross-section, which load transfer structure (24) connects the reinforcement bar (13) of the reinforcement (8) and the additional reinforcement bar (23) of the reinforcement (8).

10. The hollow-core slab bearer according to claim 9, characterized by the additional reinforcement bar (23) having the form of a substantially straight bar.

11. The hollow-core slab bearer according to claim 9 or 10, characterized by the load transfer structure (24) comprising a truss construction (25) comprising bars (26) fastened between the reinforcement bar (13) of the reinforcement (8) and the additional reinforcement bar (23) of the reinforcement (8).

12. The hollow-core slab bearer according to claim 10 and 11, characterized by at least some of the bars (26) of the truss construction (25) being in the form of substantially straight bars extending inclined with respect to the additional reinforcement bar (23).

13. The hollow-core slab bearer according to any of the claims 9 to 12, characterized by the load transfer structure (24) comprising a plate construction (27) fastened between the reinforcement bar (13) of the reinforcement (8) and the additional reinforcement bar (23) of the reinforcement (8).

14. The hollow-core slab bearer according to any of the claims 9 to 13, characterized by the reinforcement bar (13) of the reinforcement (8) being fastened to the first end plate (4) at the first fastening area (11) by means of the load transfer structure (24), and by the reinforcement bar (13) of the reinforcement (8) being fastened to the second end plate (5) at the second fastening area (12) by means of the load transfer structure (24).

15. The hollow-core slab bearer according to any of the claims 1 to 14, characterized by the first end plate (4) and the first support member (6) being formed of a second profile with an L-shaped cross-section, where the first end plate (4) extend transversely with respect to the first support member (6).

16. The hollow-core slab bearer according to any of the claims 1 to 15, characterized by a second support member (7) which allows the hollow-core slab bearer to be mounted onto a second hollow-core slab or structure adjacent to the hollow-core slab which borders on the opening or similar structural discontinuity, the second hollow-core slab or structure being on the other side of the hollow-core slab which borders on the opening or similar structural discontinuity, when seen from the first hollow-core slab, and17. The hollow-core slab bearer according to claim 15, characterized by the second end plate (5) and the second support member (7) being formed of a third profile with an L-shaped cross-section, where the second end plate (5) extend transversely with respect to the second support member (7).

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