The present invention relates to a multi-chamber closed structural element and a method of manufacturing the multi-chamber closed structural element, said element used especially as vertical, columnar supporting structures or as profiles in frame structures. The subject-matter of the present invention can be used in construction, mining or power engineering for the making of vertical supporting structures.

One of the most important structural elements used in a wide range of technical fields are pillars being vertical, free-standing structural supports. As poles and columns, they are used to carry and bear the load of the structure of a building, bridge, viaduct, etc. Supporting structural elements are also used in mining as roof supports in corridors, or as structures used in small architecture, for example in the construction of pergolas.

On the other hand, in the frame structures used, for example, for the construction of vehicle bodies, profiles are used that, when properly connected to each other, form a frame of a desired shape and desired strength properties. An important factor in frame structures is their strength, which is dictated by, inter alia, the strength of the components, i.e. profiles, and their empty weight, also related to the weight of the components.

PL224768B1 describes a mining bearer pole comprising: longitudinal layers, each comprising a pair of outer beams substantially parallel to each other which define two longitudinal walls of the pole, and transverse layers, each comprising a pair of outer beams substantially parallel to each other which define two transverse walls of the pole, with the transverse layers arranged alternately with the longitudinal layers such that the outer beams of the transverse layers intersect with the adjacent outer beams of the longitudinal layers at four intersection points and that the former and the latter are joined through notches made in the upper and lower surfaces of the longitudinal beams and transverse beams. Such structures are used in deep sea mining as protection elements, supporting the roof or stretching the floor from the roof in mining headings. Increasing the bearing capacity of the pole is achieved by filling its interior with a self-curing mixture, for example, a mineralcement mixture, and forming a composite structure.

PL67807Y1 relates to a structural element, in particular a sheet metal section, intended for use in sheet metal structures. The structural element has inner walls with longitudinal edges that are bent inwardly, preferably in the centre of the base. The inner walls are folded and tilted with the edge walls away from each other, preferably perpendicular to the side walls. Preferably the edges are close to the surface of the side walls. The inner walls on the arc of the transition from the base plane are additionally connected with spot welds.

Polish patent application P.432278 describes a method of manufacturing a multichamber structural element, where to form a multi-chamber structural element, with chamber profiles extending radially from a centre defined by the connection of the chamber profiles, the method includes the following steps: at least three chamber profile preforms are provided, each chamber profile preform comprising two walls made of a sheet of metal material and arranged in substantially parallel planes with respect to one another with a gap between them, wherein edges of the individual walls converge, wherein a vent is arranged on at least one wall; the unconnected edges of the walls of each chamber profile preform are sealed by means of a seal to form a closed hermetic hollow internal space of the chamber profile preform; a pressurised fluid is introduced through a vent into the internal space of the chamber profile preform to form a deformed chamber profile, at least three chamber profile preforms or chamber profiles are connected with each other in the area of corresponding inner edges of the chamber profile preform or chamber profile, said edges proximal to the connection axis, along at least a portion of the inner edges. A multi-chamber structural element is also disclosed in the description of the invention.

The present invention is intended to solve the technical problem behind it by providing such a method of manufacturing a multi-chamber closed structural element that will make it possible to make a multi-chamber closed structural element with desired properties, especially in terms of strength and load capacity to weight ratio, while maintaining the required dimensional accuracy. It is desirable that the method of manufacturing a multi-chamber closed structural element should be characterised by a limited number of technological steps and should be implemented without the use of specialised and complex apparatus, which will directly translate into economic benefits of a simplified, less timeconsuming and thus cheaper process of manufacturing a multi-chamber closed structural element. Moreover, it is desirable that the method of manufacturing a multi-chamber closed structural element should be characterised by low material consumption and should make it possible to manufacture a multi-chamber closed structural element with a wide range of geometric parameters, especially with different heights, spatial shape, with both symmetrical and asymmetrical characteristics. It is also important to provide a method of manufacturing a multichamber closed structural element that will make it possible to easily modify the shape of the multi-chamber closed structural element within a wide range of geometric parameters, without the need to rearrange the apparatus used for manufacturing. Importantly, it is also desirable to provide a multi-chamber closed structural element that will be easy to transport and assemble at the destination. The present invention is intended to solve the technical problem behind it also by providing a multi-chamber closed structural element with the above-mentioned features and with the desired performance parameters. In one aspect the present invention provides a method of manufacturing a multichamber closed structural element, characterised in that it comprises the steps of: a) at least one chamber profile preform is provided, comprising an inner wall and an outer wall made of a sheet of metal material and arranged in substantially parallel planes with respect to one another with a gap between them, wherein the edges of the individual walls converge, wherein a vent is arranged on at least one wall, b) the unconnected edges of the walls of the chamber profile preform are sealed by means of a seal to form a closed hermetic hollow internal space of the chamber profile preform, said space comprising the end edges of the chamber profile preform, c) the end edges of at least one chamber profile preform are connected to each other to form a preform of the multi-chamber closed structural element, the preform comprising a central chamber surrounded by an innerwall of the chamber profile preform, d) a pressurised fluid is introduced through a vent into the internal space of at least one chamber profile preform to form a deformed chamber profile.

Preferably, after step a), the chamber profile preform is bent inwardly along the bending line and an inner seal is formed along the bending line to form at least two chamber profile preforms, the inner seal being formed with fluid communication between the internal spaces of the resulting at least two chamber profile preforms.

Preferably, in step a), the chamber profile preforms are provided in a number corresponding to the number of chamber profiles in the multi-chamber closed structural element.

Preferably, the chamber profile preforms in the preform of a multi-chamber closed structural element have varying widths. Preferably, the central chamber is filled with filler, preferably with concrete, plastic or loose material. For example, sand, gravel or aggregate can be indicated as preferred loose material.

Preferably, the chamber profile preform has areas of the inner wall and/or outer wall with increased metal sheet thickness.

Preferably, the chamber profile preform has areas of the inner wall and/or outer wall made of different materials.

Preferably, the chamber profile preform has at least one opening formed in the area of the inner wall and the outer wall and sealed by means of a seal to form a closed hermetic hollow internal space of the chamber profile preform.

Preferably, step c) is carried out simultaneously for all chamber profile preforms corresponding to the chamber profiles in the multi-chamber closed structural element.

Preferably, the seal and/or the inner seal is produced by welding, pressure welding, gluing or squeezing.

Preferably, the fluid is air, water, oil, fluid concrete or fluid plastic.

In another aspect, the present invention provides a multi-chamber closed structural element, characterised in that it comprises at least three chamber profiles deformed with pressurised fluid introduced into their hermetic hollow space, wherein the chamber profiles are connected to each other by corresponding seals, along at least a portion of the seal, to form the multi-chamber closed structural element which forms, in cross-section, an annular structure comprising a central chamber surrounded by inner walls of the chamber profiles.

Preferably, at least one chamber profile has a greater or lesser width than the other chamber profiles. Preferably, the central chamber is filled with filler, preferably with concrete, plastic or loose material. Sand, gravel or aggregate can be indicated as preferred loose material.

Preferably, the chamber profile has areas of the inner wall and/or outer wall with increased metal sheet thickness.

Preferably, the chamber profile has areas of the inner wall and/or outer wall made of different materials.

Preferably, the chamber profile has at least one opening formed in the area of the inner wall and the outer wall, sealed by means of a seal.

Preferably, the seal and/or the inner seal is a weld, a pressure weld, a glue layer or an overlap joint.

Preferably, the fluid is air, water, oil, fluid concrete or fluid plastic.

In the present description, a multi-chamber closed structural element is understood as a structural element formed from chamber profiles, which, when connected to each other, form an annular structure in cross-section, with a closed internal space, referred to as a central chamber, surrounded by inner walls of the chamber profiles.

The method of manufacturing a multi-chamber closed structural element according to the present invention makes it possible to make a structural element with desired properties, especially in terms of the stiffness and strength coefficient of the structural element and the load capacity to weight ratio. In particular, by using for the manufacture of a multi-chamber closed structural element mostly a relatively thin metal sheet, the multi-chamber closed structural element manufactured by the method of the invention makes it possible to significantly increase the load capacity to weight ratio compared to the classic solutions known in the art. Moreover, the method of manufacturing a multi-chamber closed structural element according to the present invention is implemented by using uncomplicated machinery, which translates into economic benefits and a significant simplification of the manufacturing process of a multi-chamber closed structural element. A small number of seals affects the speed and leads to reduced labour consumption of the manufacturing process of a multi-chamber closed structural element. In addition, the manufacturing of a single chamber profile, being the basic structural element of a multi-chamber closed structural element, said manufacturing based on the introduction of pressurised fluid into a hermetically sealed internal space of the chamber profile preform, makes it possible to modify to a wide extent the parameters of the manufactured chamber profile and thus the target multi-chamber closed structural element, especially in terms of its final geometry. Importantly, the multi-chamber closed structural element, through the use of relatively thin chamber profile preforms made of a sheet of metal material, and through the use of uncomplicated machinery, makes it possible to easily introduce components into places that are difficult to access, e.g. into mine corridors, where it is possible to make and erect it using simple operations, thus creating a supporting element for roof structures. Moreover, the use of material sheets with areas of different thickness and/or made of different materials to build a chamber profile preform makes it possible to additionally shape the geometry of the target multi-chamber closed structural element by influencing the degree of deformation of a given area under the influence of pressurised fluid introduced into the interior of the chamber profile preform. Moreover, filling the central chamber, formed inside the multi-chamber closed structural element, with filler being, for example, concrete, plastic or loose material (such as sand, aggregate or gravel) makes it possible to improve the strength characteristics of the resulting multi-chamber closed structural element, leading to increased stiffness or load capacity of the structural element.

The solution according to the invention is illustrated in the following embodiment and is illustrated in the drawing, in which: Fig. 1 shows an embodiment of the multi-chamber closed structural element of the present invention in a cross-sectional axonometric view,

Fig. 2A-C show various embodiments of the preform of the multi-chamber closed structural element of the present invention in a cross-sectional view,

Fig. 3A-D show various embodiments of the multi-chamber closed structural element of the present invention in a front view,

Fig. 4 shows another embodiment of the multi-chamber closed structural element of the present invention in a front view,

Fig. 5 shows a further embodiment of the multi-chamber closed structural element of the present invention in a front view,

Fig. 6 shows another embodiment of the multi-chamber closed structural element of the present invention in a cross-sectional axonometric view,

Fig. 7A, B show further embodiments of the multi-chamber closed structural element of the present invention in an axonometric view.

Example 1

The first embodiment of the multi-chamber closed structural element of the present invention is schematically shown in a cross-sectional axonometric view in Fig. 1.

The illustrated example of the multi-chamber closed structural element is manufactured by the method of the present invention, which comprises the step wherein at least one chamber profile preform 2 is provided, comprising two walls 3, 4 made of metal sheet, i.e. an inner wall 3 and an outer wall 4, arranged in substantially parallel planes with respectto one anotherwith a gap between them, wherein the edges of the individual walls 3, 4 converge. A vent 6 is arranged on at least one of the walls 3, 4. The vent 6 is a pneumatic or hydraulic attachment element and makes it possible to tightly affix the supply line 7 from an external source of pressurised fluid. In some embodiments of the invention, the vent 6 can be a valve, especially a non-return valve. The location of the vent 6 does not limit the scope of the present invention and so the vent 6 can be located in any area on the metal sheet, provided that a connection to the internal space of the chamber profile preform 2 is ensured.

In the embodiment shown in Fig. 2C, four chamber profile preforms 2 are provided to form a multi-chamber closed structural element comprising four chamber profiles 1. The number of chamber profiles 1, and thus the number of chamber profile preforms 2, used in the method of manufacturing a multi-chamber closed structural element does not limit the scope of the present invention, and in alternative embodiments, the multi-chamber closed structural element can comprise a smaller or larger number of chamber profiles 1, but said number must be greater than three to form, in cross-section, a closed annular structure comprising a central chamber 8 surrounded by chamber profiles 1 (their inner walls 3). Various non-limiting embodiments of a multi-chamber closed structural element, comprising a different number of chamber profiles 1, are shown in front views in Fig. 3A-D, where Fig. 3A shows a multi-chamber closed structural element comprising three chamber profiles 1, Fig. 3B shows a multi-chamber closed structural element comprising four chamber profiles 1, Fig. 3C shows a multichamber closed structural element comprising five chamber profiles 1, while Fig. 3D shows a multi-chamber closed structural element comprising eight chamber profiles 1.

In the present embodiment, the chamber profile preform 2 is formed from two walls 3, 4, each wall 3, 4 being a separate metal sheet. In alternative embodiments, it is possible to provide a single sheet of metal material which, in known cold bending operations, is bent along one edge to form two walls 3, 4 arranged in substantially parallel planes with respect to one another. This embodiment of the invention has the advantage that already in the step of providing the sheet of metal plate, one edge of the manufactured chamber profile preform 2 is sealed (at the place the sheet of metal plate is bent), which reduces the number of subsequent sealing operations.

In the next step of the method of manufacturing a multi-chamber closed structural element, each chamber profile preform 2 is sealed to form a sealed hermetic internal space. The sealing is carried out on the edges of the metal sheet forming the walls 3, 4 of the chamber profile preform 2 after they have been juxtaposed. In the present embodiment, all peripheral edges of the juxtaposed walls 3, 4 of each chamber profile preform 2 are thus sealed, wherein Fig. 2C shows front longitudinal seals 5, which are also referred to as end edges of the chamber profile preform 2. In the present embodiment, the sealing was carried out by welding corresponding edges together to form, inter alia, longitudinal welds. The edges of the juxtaposed walls 3, 4 located on the front and rear sides of the chamber profile preform 2 are also sealed. The sealing of all said edges results in a sealed hermetic internal space in the chamber profile preform 2, as shown in the cross-section in Fig. 2C. The type of seal 5 in this case does not limit the scope of the present invention, and in alternative embodiments, it is possible to use any type of seal 5, provided that a sealed internal space in the chamber profile preform 2 is formed, such as by welding, soldering, gluing, bending or pressing.

In a further step of the method of manufacturing the multi-chamber closed structural element of the present invention, the end edges of the four chamber profile preforms 2 are connected to each other in series, with the last end edge of the fourth chamber profile preform 2 being connected to the first end edge of the first chamber profile preform 2, thereby forming an annular structure in cross section. Thus, a preform 9 of the multi-chamber closed structural element is formed, the preform comprising a central chamber 8 surrounded by inner walls 3 of the four chamber profile preforms 2, as shown in Fig. 2C. The connecting of the end edges of the chamber profile preforms 2 is implemented by any technical means ensuring a durable connection of metal sheets, including by welding, pressure welding, soldering, gluing, etc. The connecting may be implemented along the entire length of the end edge of the chamber profile preform 2, including partial connecting or spot connecting. It is important in this case that the connection of the chamber profile preforms 2 will withstand the next step of introducing the pressurised fluid into the internal space of the chamber profile preforms 2 and the associated deformation of the metal sheets. In alternative embodiments of the present invention, the step of connecting the end edges of the chamber profile preforms 2 may be implemented simultaneously with the step of sealing the chamber profile preform 2, as described above. In such an implementation, an advantage is gained of a reduced number of operations leading to the manufacturing of the target multi-chamber closed structural element.

In a further step, an external source of pressurised fluid is connected to the vent 6 via the supply line 7. In the present embodiment, the fluid is air, the source of pressurised fluid is a compressor, while the supply line 7 and the vent 6 form a pneumatic attachment. The type of the external source of pressurised fluid and of the attachment equipment does not limit the scope of the invention, and in alternative embodiments, it is possible to use fluid in the form of water, fluid cement, machine oil, fluid plastic such as one, two or three-component foam (e.g. flex 140 type), etc., together with appropriate attachment equipment for these fluids and a source of pressurised fluid. The less compressible the fluid, the more controlled the conditions for the deformation of the chamber profile preform 2.

In a further step of the method of manufacturing the multi-chamber closed structural element of the present invention, fluid is provided at a specified pressure to the sealed internal space of the chamber profile preform 2. The technology of introducing a pressurised fluid into the closed sealed chamber elements made of a sheet of metal to deform it and give it its final form is known, inter alia, from patent application EP2110189A1. As a result of providing pressurised fluid to the internal space of the chamber profile preform 2, the walls 3, 4 of the chamber profile preform 2 deform, with the greatest degree of deformation localised in the centre of the chamber profile 1, as best illustrated in fig. 3B, where a cross-section of a multi-chamber closed structural element is shown, revealing the chamber profiles 1 formed from the chamber profile preforms 2. As can be observed, there was a significant deformation of the walls 3, 4 of each chamber profile preform 2.

In the present embodiment, the step of introducing fluid at a specified pressure into the sealed internal space of the chamber profile preforms 2 was carried out simultaneously for all chamber profile preforms 2 in the preform 9 of the multichamber closed structural element. This resulted in a more homogeneous distribution of deformations of the individual chamber profiles 1 comprising the target multi-chamber closed structural element. In alternative embodiments, this step may be carried out in series, for each chamber profile preform 2 one by one or in groups of several chamber profile preforms 2.

It is worth mentioning that the introduction of pressurised fluid into the internal space of the chamber profile preform 2 is implemented in cold technology (i.e. at room temperature), but this does not limit the scope of the present invention, and in alternative embodiments this process may be carried out at elevated or high temperatures.

In one embodiment of the present invention, the step of introducing the pressurised fluid was carried out with the following process parameters:

- process temperature: 20°C,

- working pressure: 5 bar,

- deformation time: 1 min to equalize the pressure in the chamber profile preform 2, - pressure maintenance time: 30 seconds,

- total deformation time: 1.5 min.

Example 2

A further embodiment of the method of manufacturing the multi-chamber closed structural element according to the present invention uses the preform 9 of the multi-chamber closed structural element schematically shown in Fig. 2A. The illustrated embodiment of the method of manufacturing a multi-chamber closed structural element is substantially identical to the method of manufacturing a multi-chamber closed structural element illustrated in Example 1, which is why identical steps will not be discussed in detail for the sake of clarity of this disclosure.

In the present example of a method of manufacturing a multi-chamber closed structural element, in a first step, one chamber profile preform 2 is provided, which is subjected to successive processing steps prior to the step of sealing the edge of the chamber profile preform 2. Said processing steps involve bending the chamber profile preform 2 inwardly along three bending lines 10. In the embodiment shown in Fig. 2A, the bends are formed at right angles and involve both walls 3, 4 of the chamber profile preform 2. Making three right-angled bends along the bending line 10 creates a structure which is essentially rectangular in cross-section. In the next step, an inner seal 11 is formed also along the bending line 10 to form four chamber profile preforms 2, wherein the inner seal 11 is formed with fluid communication between the internal spaces of the resulting four chamber profile preforms 2. The inner seals 11 are made by known techniques which make it possible for a seal to be formed by two metal sheets arranged at a short distance from each other. A non-limiting example of such a technique is laser welding. Fluid communication between the resulting chamber profile preforms 2 can be provided by making a discontinuous inner seal 11. Maintaining fluid communication between the chamber profile preforms 2 thus formed is essential to provide pressurised fluid to each chamber profile preform 2 from only one vent 6. Alternatively, in the chamber profile preform 2, before the bending step, more vents 6 may be provided, in a number corresponding to the number of target chamber profiles 1 in the multi-chamber closed structural element, in areas corresponding to individual chamber profiles 1, wherein in such an implementation it is not necessary to provide fluid communication in the step of creating the inner seal 11.

In alternative embodiments, to form a multi-chamber closed structural element comprising four chamber profiles 1, it is also possible to provide two chamber profile preforms 2 and to perform a right-angle bending operation on each of them, as described above, followed by the operation to make the inner seal 11. Each of the two chamber profile preforms 2 is then divided into another two chamber profile preforms 2, as shown in Fig. 2B.

In a further alternative embodiment, to form a multi-chamber closed structural element comprising four chamber profiles 1, it is also possible to provide two chamber profile preforms 2 and to perform two right-angle bending operations on one of them along the bending line 10, as described above, followed by two operations to make the inner seal 11, respectively. The chamber profile preform 2, bent twice, forming a U-shaped structure in its cross section, is then divided into three further chamber profile preforms 2, wherein the preform 9 of the multichamber closed structural element is supplemented with the remaining chamber profile preform 2. This example is not illustrated in the figures.

It should be emphasised that the bending angle, the number of bends and the number of inner seals 11 made depend on the geometry of the target multichamber closed structural element, especially on the number of chamber profiles 1 that compose it.

Example 3 Further non-limiting embodiments of the multi-chamber closed structural element are shown in various views in Figs. 4-7.

The example of a multi-chamber closed structural element shown in a front view in Fig. 4 differs from the previous embodiments in that the central chamber 8 is filled with filler 12. The filler 12 is introduced into the central chamber 8 after the multi-chamber closed structural element is made, i.e. after the introduction of pressurised fluid into the hermetic internal space of each of the chamber profiles 1. The filler 12 has a fluid form when introduced into the central chamber 8 and may solidify after some time. Non-limiting examples of fillers 12 are fluid concrete or fluid plastics. The introduction of the filler 12 into the central chamber 8 gives additional properties to the resulting multi-chamber closed structural element, said properties associated with the type of filler 12 used, such as increased strength and stiffness, and in certain situations also dampening the vibration of the resulting structure (e.g. the use of suitably selected plastic foam makes it possible to absorb vibrations and prevents adverse induction of resonant vibrations in the multi-chamber closed structural element).

The example of a multi-chamber closed structural element shown in cross-section in Fig. 5 differs from the previous embodiments in that different materials are used to form the individual chamber profile preforms 2. In the illustrated example, the inner wall 3 is formed of a material other than the one of the outer wall 4. The materials for the individual walls 3, 4 differ in the coefficient of susceptibility to deformation under the influence of the pressurised fluid. In particular, the inner wall 3 is made of a material such as non-alloy steel S235JR which is more susceptible to deformation (is more plastic) with respect to the material such as non-alloy steel S355JR of which the outer wall 4 of each chamber profile preform 2 is made. As a result, after introducing the pressurised fluid into the hermetic internal space of each chamber profile preform 2, a different degree of deformation is obtained for the inner wall 3 and the outer wall 4. As can be observed in Fig. 5, the outer wall 4, made of a material with lower susceptibility to deformation, has deformed less than the inner wall 3, made of a material with higher susceptibility to deformation. The presented example does not limit the invention, and in alternative embodiments, different materials can be used in each of the chamber profile preforms 2 to obtain the desired target shape of the multichamber closed structural element. An exemplary non-limiting list of structural materials for inner walls 3 and outer walls 4 of the preform of the multi-chamber closed structural element includes low carbon steels, steels from group S235JR to S355JR, DC01-05 steel, steels from group DP500 to DP600, stainless steels such as 1.4301, 1.4404, HSS high-speed steel, aluminium from group 1000 and 5000 (e.g. 1050, 5754). Similar functionality can be achieved by using the same material for the inner wall 3 and the outer wall 4 of a given chamber profile preform 2, but of different thickness of the metal sheet. In this non-limiting embodiment, the inner wall 3 is made of 1 mm thick HSS steel, while the outer wall 4 is made of the same material, but its thickness is 1.5 mm. Thus, by using a thicker metal sheet for the outer wall 4, it is possible to influence the degree of deformation in a manner analogous to the above. Again, use of different thicknesses of metal sheets in the multi-chamber closed structural element does not limit the scope of the present invention.

The example of a multi-chamber closed structural element shown in cross- sectional axonometric view in Fig. 6 differs from the previous embodiments in that one of the chamber profiles 1 has a different width from the other chamber profiles 1. The width dimension of the chamber profile 1 is understood herein as the smallest distance between the end (longitudinal) edges of the chamber profile 1. The result is a multi-chamber closed structural element that resembles a trapezoid in cross-section. In alternative embodiments, it is possible to form a multi-chamber closed structural element from chamber profiles 1, wherein some or even all are of different widths, thereby adjusting the external dimensions of the multi-chamber closed structural element to the construction requirements at the place of use.

The example of the multi-chamber closed structural element shown in axonometric view in Fig. 7A differs from the previous embodiments in that each chamber profile 1 making the multi-chamber closed structural element comprises openings 13 formed in the area of the inner wall 3 and the outer wall 4 (through), sealed by means of a seal 5. The openings 13 are arranged along the length of the individual chamber profile 1. Fig. 7A shows the openings 13 in the shape of a circle, but the shape of the openings 13, their number as well as their arrangement in the area of a single chamber profile 1 or all chamber profiles 1 is not limiting, and in alternative embodiments, it is possible to make a smaller or larger number of openings, in a shape other than circular (for example, a triangle (Fig. 7B), a rectangle, a polygon, especially a regular polygon, an irregular shape) and on one or more chamber profiles 1. The formation of openings 13 in the multi-chamber closed structural element makes it possible to reduce the empty weight of the multi-chamber closed structural element, without significant loss of strength properties. Furthermore, unlike the previous embodiments, in the multi-chamber closed structural elements shown in Fig. 7A and 7B, the vents are located on the inner walls 3 of the individual chamber profiles 1 (not visible in the figures).

It should be emphasised that the number of chamber profiles 1 making the multichamber closed structural element, as well as the geometry of the chamber profile 1 making the multi-chamber closed structural element, are not limited to the scope presented in the present embodiments, which are only exemplary and possible implementations of the invention. In alternative embodiments, the multichamber closed structural element can comprise more than three chamber profiles 1, wherein the chamber profiles 1 can take a shape different from those shown, including a combination of the shapes disclosed herein. Example 4

Comparative tests (based on numerical calculations) were performed on the multichamber closed structural element manufactured by the method of the present invention, said tests comparing the element with a standard structural element commonly used in the art. The results of the comparative tests are summarised in the following Table 1. The tested multi-chamber closed structural element manufactured by the method of the present invention is designated in Table 1 as FIDU1 and FIDU2. The comparative structural element, designated as STANDARD, is a standardised one with geometric dimensions of 100 mm x 100 mm x 1000 mm and a wall thickness of 2 mm. The numerical models used in the comparative simulations are shown in cross-section and in an axonometric view in Fig. 8A-C, where Fig. 8A shows the STANDARD element, Fig. 8B shows the FIDU1 element, while Fig. 8C shows the FIDU2 element.

In the simulations for the profile, the material used was DC01 steel. The multichamber closed structural element according to the present invention, designated FIDU1, was formed from four chamber profiles 1 shown in Fig. 8B. The FIDU1 multi-chamber closed structural element formed from chamber profiles 1 presents a square structure defined by the outer walls 4 of chamber profiles 1 with external dimensions similar to the external dimensions of the STANDARD element. Each component chamber profile 1 was formed of a 1 mm thick material (inner walls 3 and outer walls 4) using process parameters shown in Example 1. The FIDU2 multi-chamber closed structural element formed from chamber profiles 1 also presents a square structure defined by the outer walls 4 of chamber profiles 1 with external dimensions similar to the external dimensions of the STANDARD element. Each constituent chamber profile 1 has an inner wall 3 having a thickness of 0.8 mm and an outer wall 4 having a thickness of 1.2 mm and has been formed using the process parameters shown in Example 1. Table 1 - performance parameters of structural elements

As can be seen in Table 1, all the numerically tested elements had the same empty weight of 6.15 kg. Various performance parameters of the structural elements were analysed, such as resistance to compression, compression with a rigid plate, twisting and bending.

Stiffnesses were determined in linear analyses geometrically and materially for 3 load states. Critical forces/breakdown torques were determined in linear buckling analyses. These analyses are used to quickly estimate the load capacity of an object. The determined breakdown loads cause a loss of stability. The strength of the profiles was defined as the highest load during the test, under given loading conditions. Virtual quasi-static analyses were carried out using the explicit method.

In this case, both elements manufactured by the method of the invention, i.e. FIDU1 and FIDU2, exhibited greater stiffness and strength relative to the STANDARD element. Of note is the critical force, which for compression was more than twice the critical force with the STANDARD element. In the case of the rigid plate compression test, greater strength of FIDU1 and FIDU2 elements in relation to the STANDARD element was obtained. On the other hand, the breakdown torque for the twisting test for the FIDU1 and FIDU2 elements assumed a greater value than the STANDARD element. In the case of bending, the FIDU1 element is characterised by almost three times the critical force, while the FIDU2 element is more than three and a half times the critical force in relation to the STANDARD element.

List of reference signs:

1 - chamber profile

2 - chamber profile preform

3 - inner wall

4 - outer wall

5 - seal

6 - vent

7 - opening

8 - central chamber

9 - preform of the multi-chamber closed structural element

10 - bending line

11 - inner seal

12 - filler

13 - opening