US20110036031A1

US20110036031A1 - Panel for the construction of a structure resistant to bending such as a floor or the like

Info

Publication number: US20110036031A1
Application number: US12/920,899
Authority: US
Inventors: Angelo Candiracci
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-03-04
Filing date: 2009-03-02
Publication date: 2011-02-17
Also published as: EP2260158A2; ITBO20080144A1; WO2009109893A2; AR070775A1; CN101990589A; WO2009109893A3; CL2009000506A1

Abstract

A panel (10), in particular for making a structure which is resistant to bending, such as a floor (11) of a construction, in particular of a building, comprises at least a first and a second lightening block which are positioned side by side and a resistant element (12) between the lightening blocks which are positioned side by side. The resistant element (12) is a metal element for supporting the panel blocks.

Description

TECHNICAL FIELD

The present invention relates to a panel, in particular for making a structure which is resistant to bending, such as a floor of a construction, in particular of a building.

BACKGROUND ART

In the building sector, it is known that expanded polystyrene lightening blocks are used to make floors. Between said blocks there is a concrete casting designed to form a corresponding floor joist extending between the lightening blocks which are positioned side by side and also comprising reinforcing rods embedded in the concrete casting.
To make the floors in accordance with the prior art, panels, with the lightened blocks, are rested on existing opposite supports, between which the floor span is formed, with interposed crosspiece supports, which support the panels for the subsequent step of concrete casting.
Moreover, also in the prior art, in the respective panel, between the lightening blocks which are positioned side by side and preferably made of brick, there is a resistant element which supports the lightening blocks and which is made of concrete applied on a brick base. Said resistant element supports a complex steel rod lattice, designed to form the reinforcement for the subsequent floor joist portion and is interposed in the transversal space between the lightening blocks.
Said resistant elements of the prior art panels are heavy and make panel preparation complex and lengthy. A steel rod lattice has to be prepared, then positioned between the lightened blocks and on the brick base. It is also necessary to add above the base an even minimal amount of concrete in order to form the resistant structural part of said panel supporting element. Finally, before being able to use and transport the panel, it is necessary to wait until the concrete has at least partly hardened.
Moreover, such a resistant element of the reinforced concrete panel provides the panel with a resistance to bending which is limited and is not sufficient to withstand the subsequent concrete casting step, and so an excessive number of crosspiece supports have to be used.

DISCLOSURE OF THE INVENTION

It is therefore provided a panel, in particular for making a structure which is resistant to bending, such as a floor of a construction, or the like, in particular of a building, the panel comprising at least one lightening block, in particular a first and a second lightening block positioned side by side and a resistant element between the lightening blocks which are positioned side by side; said blocks, in particular, being made of insulating material, particularly plastic material, preferably expanded material, such as expanded polystyrene, the panel being characterised in that the resistant element is made of metal material and forms means for supporting the lightening blocks.
The panel obtained, in particular for making floors and the like, is easily and rapidly prepared, may have a low weight and a high resistance to bending, and is suitable for allowing particularly easy production of the corresponding construction structure.
The invention also relates to an advantageous resistant element and to an advantageous process for making a structure which is resistant to bending, such as a floor or the like.
The invention also relates to an advantageous process for making a resistant element and to an advantageous process for making a panel, both, in particular, for obtaining a structure which is resistant to bending, such as a floor of a construction, in particular of a building or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical characteristics of the panel and its various advantageous aspects are more apparent from the detailed description which follows, with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention provided merely by way of example without restricting the scope of the inventive concept, and in which:

FIG. 1 is a perspective bottom view of a preferred embodiment of the panel according to the present invention;

FIG. 2 is a perspective top view of the preferred embodiment of the panel according to the present invention;

FIG. 3A is a cross-section of the preferred embodiment of a resistant element according to the present invention;

FIG. 3B is a cross-section, showing the components, or portions, of the preferred embodiment of the resistant element according to the present invention;

FIG. 4 is a perspective top view of an intermediate step of the procedure for making the floor which can be obtained using the preferred embodiment of the panel;

FIG. 5 is a perspective top view of a final step of the procedure for making the floor which can be obtained using the preferred embodiment of the panel;

FIG. 6 is a cross-section of a portion of floor obtained using the preferred embodiment of the panel according to the present invention;

FIG. 7 is a cross-section of a detail of the lightening block illustrating in particular the grip tooth insertion zone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIGS. 1 and 2 illustrate a preferred embodiment of the panel 10 for making a floor 11, in particular illustrated in FIGS. 5 and 6, of a construction, particularly of a building.
The floor is of the type comprising lightening blocks 13 and a concrete casting 15 forming corresponding longitudinal floor joist 17 portions extending between the lightening blocks 13 which are positioned side by side.
As shown in particular in FIGS. 1 and 2, the panel 10 comprises at least a first and a second lightening block 13, 13, positioned side by side, and a resistant element 12 forming means for supporting the panel blocks 13, 13, and extending between the blocks 13, 13 which are positioned side by side.
The lightening blocks 13, 13 are, in particular, blocks of insulating material, particularly blocks of plastic material, preferably made of an expanded material such as expanded polystyrene.
In the embodiment illustrated, the panel 10 is longer than it is wide and the blocks 13, 13 extend longitudinally in particular for a length corresponding to the length of the panel 10.
Advantageously, the resistant element is a metal element 12 extending longitudinally between and supporting the first and second blocks 13, 13.
In this way, the panel is prepared easily and rapidly compared with similar panels prepared according to the prior art. It is no longer necessary to provide a corresponding concrete casting to make the resistant element to be interposed between the lightening blocks.
Moreover, the panel 10 also has a weight which is advantageously low and a high resistance to bending, allowing it to avoid, or at least reduce, the use of crosspiece supports for making the corresponding construction structure.
In particular, advantageously, the metal element 12 comprises a portion formed by or at least partly consisting of a corresponding metal plate.
Advantageously, the resistant element 12 forms transversal retaining means between the first and second blocks 13, 13 of the panels.
In particular, as it is more apparent below, the resistant element 12 forms grip means for the respective panel block 13, 13.
In particular, the resistant element 12 forms perpendicular supporting means, that is to say, with regard to loads acting perpendicularly on the respective panel block 13, 13.
In practice, the resistant element 12 is a resistant beam.
According to another advantageous aspect, the resistant element 12 is designed to form at least part of the resistant reinforcement of the floor, or the like, in which it is incorporated.
Moreover, as FIGS. 1 and 2 clearly show, the resistant element 12 extends below the respective panel block 13, 13 and the respective block 13, 13 rests on the resistant element 12.
The resistant element 12 also advantageously forms a resistant structural element for the floor being constructed.
As described in more detail below, the resistant element 12 of the panel 10 is designed to withstand the stresses to which the panel is subjected during the steps of making, or constructing, the floor 11.
Use of this resistant element 12, unlike the prior art, eliminates, or greatly reduces, the need for crosspiece supports, in particular during the steps of making the floor.
As may also be inferred with reference to FIG. 3A, advantageously, the resistant element 12 has a flange, or a core portion 14, extending transversally and a core 16 extending perpendicularly, or extending relative to said flange 14.
As illustrated, the transversal flange 14 has an upper surface 18 on which the respective block 13, 13 rests, said surface extending transversally beyond the side 13 a, 13 a of the respective block 13, 13, extending on both sides of the perpendicular core 16.
In practice, as illustrated, said transversal flange 14 consists of a first portion 14 a and a second portion 14 b each forming a continuation of the other, that is to say, being coplanar with each other, and extending in opposite directions from the core 16.
Advantageously, the resistant element 12 has means 20, 20 for insertion in the respective block 13, 13.
The means for insertion in the lightening block are tooth means 20, 20, which are inserted in a corresponding block 13, 13, in particular in a corresponding slot specially made in advance 21, 21, as shown by the detail in FIG. 7.
The respective longitudinal slot 21 extends into the body of the lightening block from the lower surface 13 c of the block and extends longitudinally relative to the corresponding block 13.
As FIG. 3A clearly shows, the respective tooth 20, 20 extends from the corresponding transversal flange 14 a, 14 b and, in particular, from the free end of the corresponding transversal flange 14 a, 14 b, with the grip tooth 20, 20 extending perpendicularly, that is to say, upwards.
Advantageously, as illustrated, the resistant element 12 extends between the first and second blocks 13, 13 which are positioned side by side.
In particular, as illustrated, the resistant element extends in contact with the corresponding lateral surface 13 a, 13 a of the respective block 13, 13.
As illustrated, each lightening block 13, 13 has a main portion 13′, below which, or to the side of which there extend corresponding extended portions 13 b forming corresponding longitudinal side surfaces 13 a, 13 a.
Advantageously, the resistant element 12 has a core 16, extending above the extended lower part 13 b, 13 b of the respective block 13, 13.
As illustrated, in particular in FIGS. 1 and 2, the resistant element 12 has a longitudinal main direction of extension which corresponds to the main direction of extension of the panel 10 and of the respective block 13, 13, which, as already indicated, are preferably longitudinally extended blocks, the length of the resistant element substantially coinciding with the length of the panel.
The resistant element 12 therefore has a perpendicular core 16, which, advantageously, forms at least part of the resistant reinforcement of the floor.
In practice, the resistant element 12 has a core 16, extending in the zone in which the resistant floor joist 17 is made, forming at least part of the structural reinforcement of the floor.
In practice, the upper wall, or part of the resistant element core 16 extends between the sides 13′a, 13′a, spaced from each other, of the upper part of the blocks 13, 13 which are positioned side by side.
In practice, as illustrated, the projecting portions 13 b, 13 b of the block 13 extend, or project, away from the respective upper lateral surface 13′a, 13′a of the block 13.
As illustrated, advantageously, the resistant element 12 has a perpendicular core portion 16, having a height “h” greater than the height “h′” of the extended portion 13 b of the block and greater than half the height “h′” of the corresponding lightening panel, although it is less than the height “h′” of the same block 13.
Moreover, the resistant element 12 has a perpendicular core 16 which forms or has means for adhering to the concrete of the floor.
Advantageously, as illustrated, the resistant element 12 has lateral or sideways widening means, extending transversally from the perpendicular core 16.
Said lateral widening means extend both from an intermediate zone of the core 16, and from an upper end zone of the core 16.
The lateral widening means, extending along the full length of the resistant element 12, therefore comprise an expanded or widened portion 22 of the perpendicular core 16, at an intermediate perpendicular zone of the core 16, in particular close to an upper zone of the core 16.
As illustrated, said extended portion 22 comprises opposite projecting portions 22 a, 22 b, forming corresponding oblique stretches 22′a, 22′b connected by a corresponding perpendicular stretch 22″, parallel with the core 16.
The oblique stretches 22′a, 22′b of the extended portion 22 extend, with opposite angles, from corresponding perpendicular portions of the core 16.
The element 22 as a whole is a substantially tubular element extending transversally on both sides of the perpendicular core 16.
The resistant element 12 also has widening means 24, 24 at a free end of the perpendicular core 16.
In practice, the widening means 24, 24 are corresponding teeth, or tabs, extending transversally and substantially parallel with the transversal flange 14, on both sides of the perpendicular core 16.
The teeth 24, 24 form resistant element grip means for the concrete casting 17.
In practice, the widening means 22, 24, 24 form means by which the resistant element 12 adheres to or retains, in a perpendicular direction, the concrete forming the resistant structure of the floor or the like.
The widening means 22, 24, 24 are also useful for forming a more reinforced resistant section for the floor joist 17.
In practice, as illustrated, the resistant element 12 has a general “T” shape, in particular the general shape of an upturned “T” and, as it can easily be inferred from FIG. 3B, it consists of a first portion and a second portion 12 a, 12 b, positioned side by side, in the form of metal plates.
Said portions 12 a, 12 b are side by side and joined to form the resistant element 12.
Advantageously, the resistant element 12 has corresponding core 16 and flange 14 portions, consisting of plates that are suitably shaped, that is to say, bent according to longitudinal bending lines.
In practice, as illustrated, the respective portion 12 a or 12 b, forming the resistant element 12, has a respective transversal flange 14 a, 14 b and a respective perpendicular core portion 16 a, 16 b, which are positioned side by side, in contact with each other, and joined to form the resistant element 12, illustrated in FIG. 3B.
Moreover, the respective portion 12 a, 12 b, forming the resistant element 12 has corresponding projecting portions 22 a, 22 b, 24, 24, respectively forming the tubular widening portion 22 and the transversal end teeth extending from the free end of the core element 16 a, 16 b.
As illustrated, the first and second portions 12 a and 12 b in the resistant element 12 have respective flange portions 14 a, 14 b, each forming a continuation of the other, that is to say, in the resistant element 12 said flange portions 14 a and 14 b are coplanar with each other.
As illustrated, the flange portions 14 a and 14 b extend relative to the core portions 16 a and 16 b, forming an angle substantially of 90° relative to them.
To join the first and second portions 12 a, 12 b of the resistant element, the portions 12 a and 12 b may be welded, as shown in the preferred embodiment in FIG. 3A.
However, according to an alternative embodiment, not illustrated in the accompanying drawings, the portions 12 a, 12 b of the resistant element could also be joined together by providing at least one of the portions 12 a and 12 b with corresponding projecting means engaging with respective recess means provided on the other portion.
For that purpose, the recess means may consist of a respective hole made in a corresponding core portion, 16 a and/or 16 b.
In particular, the recess means may consist of a plurality of holes longitudinally distributed along the corresponding core portion 16 a and/or 16 b.
The projecting means may consist of protuberances projecting from the respective core portion 16 a and/or 16 b, and, in particular, they may consist of deformed portions of the core 16 a and/or 16 b, obtained for example by means of corresponding punching of the core 16 a and/or 16 b.
In particular, there is a plurality of protuberances distributed longitudinally on the corresponding core portion 16 a and/or 16 b. Said protuberances are designed to be inserted in corresponding holes, or recesses, made in the other core portion 16 a or 16 b.
As illustrated, each portion 12 a and 12 b of the resistant element has a general “L” shape.
Advantageously, the resistant element 12 extends longitudinally over a stretch corresponding to the panel length, that is to say, substantially coinciding with the floor span and the resistant element 12 is advantageously made of steel, in particular from a sheet of galvanised steel which is suitably bent to form the separate first and second portions 12 a, 12 b.
The galvanising of the sheet metal provides advantageous coating means which give the manufactured article a good level of durability.
In particular, blocks 13 may be used which have lower surfaces shaped to rest on corresponding shaped portions of the resistant element 12.
As illustrated, the respective flange portions 14 a, 14 b of the resistant element 12 have an undulated shape with a first stretch, or part 141 which is lowered and extends from the corresponding core 16 portion, a second stretch, or part, 142 which is raised, or extending towards the core portion, and a third stretch, or end part, 143 which is lowered and is at the same height as the initial stretch 141.
As illustrated, the end stretch 143 of the respective flange portion 14 a, 14 b has a respective grip tooth 20, extending perpendicularly, that is to say, parallel with the core 16 portion.
As may be inferred from FIG. 7, the lightening block 13 has, at its lateral portions 13 b, corresponding slots 21, perpendicularly recessed from the lower surface 13 c of the corresponding block 13, and forming corresponding means for receiving the resistant element 12 grip teeth 20, 20.
As illustrated, the transversal flange 14 has a width “l” substantially equal to the width of the resistant floor joist 17.
In practice, the resistant element 12 has transversal portions 14 with a width “l” which is substantially equal to the distance “l′” between the sides 13′a, 13′a of the main upper portions 13′ of the blocks, that is to say, substantially twice the width of the projection 13 b of the respective block.
In particular with reference to FIGS. 2, 4 and 5, an advantageous process for obtaining the floor, or structure which is resistant to bending, using the panel in accordance with the present invention comprises resting the panel between longitudinally opposite supporting surfaces to form a floor span.
Then, on top of or on the back of the panel 10, a metal reinforcement is placed, in particular consisting of a metal mesh 26, as illustrated in FIG. 4.
Then, concrete is cast on the panels 10, as illustrated in FIG. 5, until the floor is complete, forming the resistant structure shown in FIG. 6.
According to an alternative embodiment of the method in accordance with the present invention, the panel 10 could also be used with a ready-fitted reinforcement mesh 26, at the top of or on the back of the panel, that is to say, having a reinforcement preferably consisting of longitudinal rods 28 and/or transversal rods 30, as illustrated, in particular, in the form of a metal wall consisting of longitudinal and transversal rods which are welded, or joined, to each other.
In this case, it is sufficient to cast, on the panels 10 laid between corresponding longitudinal end supports, the corresponding concrete to complete the floor structural element, thus eliminating the step of laying the reinforcement mesh 26 on site.
In the latter case, for example, ties or connectors may be used to connect the metal meshes 26 of panels 10 which are positioned side by side.
As illustrated, the mesh 26 consists of longitudinal rods 28 and transversal rods 30, which are suitably joined, in particular, welded to each other.
According to another aspect, in conformity with a preferred process for making a resistant element 12 for a structure which is resistant to bending, such as a floor of a construction, in particular of a building, a first portion and a second portion 12 a, 12 b of a sheet of metal with a coating consisting of a coating layer, in particular, a galvanised sheet of metal, are shaped and said first and second portions 12 a, 12 b are joined to each other, in particular at the respective core portions 16 a, 16 b and in such a way that the flange portions 14 a, 14 b are aligned with each other.
The shaping of the respective plate 12 a, 12 b means that bends are made in the undeformed plate along longitudinal bending lines 12′, as shown in FIG. 3B.
Therefore, a resistant element 12 with advantageous structural and functional properties is rapidly and easily obtained.
In this way, a resistant element 12 is provided which has a section with an advantageous moment of resistance and which is therefore able to withstand even significant bending moments.
Moreover, the resistant element 12 in accordance with the invention is not too heavy.
However, it shall be understood that the resistant element may be made with the desired dimensions according to requirements.
Obviously, although the configuration described is particularly preferred, other configurations of the resistant element are possible.
Moreover, according to an advantageous process for making a panel for obtaining a structure which is resistant to bending, such as a floor of a construction, in particular of a building, or the like, a first and a second lightening block 13, 13 are positioned side by side on the respective flange portions 14 a, 14 b of a resistant element 12, the core 16 being positioned between the sides 13 a, 13 a of the blocks 13, 13. The blocks 13, 13 are connected to the resistant element 12 by inserting the respective retaining teeth 20, 20 in the corresponding slots 21, 21 made in the lightening blocks.
The invention described above is susceptible of industrial application and may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements.

Claims

1-64. (canceled)

65. A panel (10) for making a structure which is resistant to bending of a construction, in particular of a building, the panel comprising at least a first and a second lightening block positioned side by side and a resistant element (12) between the lightening blocks (13, 13) which are positioned side by side; in which the blocks are made, in particular, of insulating material, particularly plastic material, preferably expanded material, such as expanded polystyrene, wherein the resistant element (12) is made of metal material and forms means for supporting the lightening blocks, wherein the resistant element (12) extends below the respective panel block (13, 13) and the respective block (13, 13) rests on the resistant element (12), wherein the resistant element (12) has a flange (14) extending transversally and a perpendicular core (16) portion, wherein the transversal flange (14) extends laterally relative to the perpendicular core (16), wherein the transversal flange (14) forms an upper supporting surface (18) for the respective block (13, 13), wherein the resistant element (12) has a core (16) extending between the first and second blocks (13, 13), wherein the resistant element (12) extends in contact with the corresponding lateral surface (13 a, 13 a) of the respective block (13, 13);

wherein the resistant element (12) has a core (16) extending above the extended lower part (13 b, 13 b) of the respective block (13, 13), wherein the resistant element (12) has a core (16) forming at least part of the resistant reinforcement of the floor.

66. The panel according to claim 65, wherein the resistant element (12) has a core (16) with lateral widening means forming means for adhering to the concrete of the floor.

67. The panel according to claim 66, wherein the lateral widening means extend from an intermediate zone of the core (16).

68. The panel according to claim 66, wherein the lateral widening means comprise an extended portion (22) of the core (16).

69. The panel according to claim 66, wherein the lateral widening means consist of a tubular longitudinal portion (22) of the core (16).

70. The panel according to claim 66, wherein the lateral widening means comprise a widened portion (22) close to one end of the core (16).

71. The panel according to claim 66, wherein the resistant element (12) has widening means (24, 24) at a free end of the perpendicular core (16).

72. The panel according to claim 66, wherein the resistant element (12) has widening means (24, 24) consisting of corresponding tooth means (24, 24).

73. The panel according to claim 65, wherein the transversal flange (14) comprises a first and a second portion (14 a, 14 b) extending from both sides of the core (16).

74. The panel according to claim 65, wherein the resistant element (12) extends longitudinally over a stretch corresponding to the span of the structure of the floor.

75. The panel according to claim 65, wherein it comprises reinforcement mesh (26) on the top of the panel (10).

76. The panel according to claim 65, wherein the resistant element (12) has a transversal flange having a width (l) which is substantially equal to the distance between the opposite upper lateral faces (13′a, 13′a) of the lightening blocks.

77. A panel (10) for making a structure which is resistant to bending of a construction, in particular of a building, the panel comprising at least one lightening block, in particular a first and a second lightening block positioned side by side and a resistant element (12) between the lightening blocks (13, 13) which are positioned side by side; in which the blocks are made, in particular, of insulating material, particularly plastic material, preferably expanded material, such as expanded polystyrene, wherein the resistant element (12) is made of metal material wherein the resistant element (12) extends below the respective panel block (13, 13) and the respective block (13, 13) rests on the resistant element (12), wherein the resistant element (12) has a flange (14, 14) extending transversally and a perpendicular core (16) portion, wherein the respective transversal flange (14) extends laterally relative to the perpendicular core (16), wherein the respective transversal flange (14) forms an upper supporting surface (18) for the respective block (13, 13), wherein the resistant element (12) forms transversal retaining means between the first and second blocks (13, 13) of the panel comprising means (20, 20) for insertion in the respective block (13, 13) defining grip means (20) for the respective panel block (13, 13).

78. The panel according to claim 77, wherein the insertion means are tooth means (20, 20) comprising a respective grip tooth (20, 20) extending from the corresponding transversal flange portion (14 a, 14 b).

79. The panel according to claim 78, wherein the resistant element (12) has a corresponding grip tooth (20, 20) extending from the corresponding free end of the transversal flange (14).

80. The panel according to claim 78, wherein the resistant element (12) has a corresponding grip tooth (20, 20) extending perpendicularly from the transversal flange (14).

81. The panel according to claim 78, wherein the resistant element (12) has a corresponding grip tooth extending upwards.

82. The panel according to claim 77, wherein the resistant element (12) has a transversal flange (14) extending beyond the side (13 a, 13 a) of the respective block (13, 13).

83. The panel according to claim 77, wherein the transversal flange (14) comprises a first and a second portion (14 a, 14 b) extending from both sides of the core (16).

84. The panel according to claim 77, wherein it comprises a corresponding block (13, 13) having a lower surface shaped to rest on the resistant element (12) and comprising a corresponding slot (21, 21) for receiving corresponding grip means (20, 20).

85. The panel according to claim 77, wherein the resistant element (12) extends longitudinally over a stretch corresponding to the span of the structure of the floor.

86. A panel (10) for making a structure which is resistant to bending of a construction, in particular of a building, the panel comprising at least one lightening block, in particular a first and a second lightening block positioned side by side and a resistant element (12) between the lightening blocks (13, 13) which are positioned side by side; in which the blocks are made, in particular, of insulating material, particularly plastic material, preferably expanded material, such as expanded polystyrene, wherein the resistant element (12) is made of metal material and forms means for supporting the lightening blocks, wherein the resistant element (12) has a flange (14, 14) extending transversally and a perpendicular core (16) portion, wherein the respective transversal flange (14) extends laterally relative to the perpendicular core (16), wherein the resistant element (12) is composed of a first portion and a second portion (12 a, 12 b) which are joined to each other, wherein the resistant element (12) is composed of a first portion and a second portion (12 a, 12 b) which are positioned side by side, each respective portion (12 a, 12 b) of the resistant element (12) having a transversal flange (14 a, 14 b) and a perpendicular core (16 a, 16 b), and wherein the first and second portions (12 a, 12 b) of the resistant element (12) have respective cores (16 a, 16 b) which are side by side and in contact with each other.

87. The panel according to claim 86, wherein the resistant element (12) consists of a first portion and a second portion (12 a, 12 b) which are welded to each other.

88. The panel according to claim 86, wherein the resistant element (12) consists of a first portion and a second portion (12 a, 12 b) having respective projecting means which engage with respective recess means, said recess means comprising at least one hole made in a core portion and said projecting means comprising at least one protuberance projecting from the core portion.

89. The panel according claim 86, wherein the resistant element (12) is made from respective bent sheets of metal.