FI20185575A1

FI20185575A1 - Construction element

Info

Publication number: FI20185575A1
Application number: FI20185575A
Authority: FI
Inventors: Tommi Purtilo
Original assignee: Stalatube Oy
Priority date: 2018-06-27
Filing date: 2018-06-27
Publication date: 2019-12-28
Also published as: EP3587689A1

Abstract

The construction element for load-carrying structures of buildings or similar constructions comprises an inner tube (1) made of stainless steel and configured to carry axial loads, an outer layer (3) made of stainless steel and arranged around the outer perimeter of the inner tube (1) and insulating material (2) at least partly filling the space between the inner tube (1) and the outer layer (3).

Description

Construction element Technical field of the invention

The present invention relates to a construction element for load-carrying structures of buildings or similar constructions in accordance with claim 1.

Background of the invention

An important aspect that needs to be taken into account in the design and construction of buildings is the fire resistance of structural elements. The use of steel in load-carrying structures of buildings or similar constructions provides many 10 benefits, such as good adaptability and light and slender structures. However, a problem related to the properties of steel is that steel loses its load-carrying capacity relatively quickly at high temperatures. In case of fire, the temperature of a steel structure can rise in half an hour to several hundred degrees centigrade or even close to 1000 Ό. At those temperatures, th e strength and stiffness of 15 steel are only a fraction of the original strength and stiffness.

To meet the requirements set for the fire safety, steel structures often need to be protected against fire. Known methods of fire protection include for instance covering of the structure by a fire-resistant material or painting the structures with a fire-resistant paint. Both methods increase the construction time and costs 20 and may also need maintenance several times during the lifecycle of the building, which increases the lifecycle costs of the building.

20185575 prh 27-06- 2018

Summary of the invention

The object of the present invention is to provide an improved construction ele25 ment for load-carrying structures of buildings or similar constructions. The characterizing features of the construction element according to the invention are given in claim 1.

The construction element according to the invention comprises an inner tube made of stainless steel and configured to carry axial loads, an outer layer made 30 of stainless steel and arranged around the outer perimeter of the inner tube, and

20185575 prh 27-06- 2018 insulating material at least partly filling the space between the inner tube and the outer layer.

The combination of two stainless steel layers and the insulating material between the layers provides as a combined effect a good fire resistance, which 5 allows the construction element to be used in load-carrying structures of buildings without a need for separate fire protection measures during construction work. The construction element provides many benefits: It is ready for assembly without surface treatment, the surface of the construction element is not prone to damages during assembly and provides a good resistance to stains and van10 dalism in public places, and the surface is easy to clean using such cleaning methods that allow use of the construction element also in places having high standards for hygiene. The construction element does not usually require maintenance and the construction element is easy to recycle at the end of its lifecycle.

According to an embodiment of the invention, the outer surface of the outer layer is brushed or polished stainless steel. A brushed or polished surface has a lower emissivity than a steel surface without a mechanical surface treatment. Emissivity describes the effectiveness of a surface to emit energy as thermal radiation. The fire resistance of the construction element is thus improved.

According to an embodiment of the invention, the wall thickness of the outer layer is at most 65 % of the wall thickness of the inner tube. The inner tube thus forms a principal load-carrying part of the construction element. The inner tube is protected from fire by the outer layer and the insulating material, and in case of fire, the load-carrying capacity of the construction element can be maintained 25 at a high level for a longer period of time.

According to an embodiment of the invention, the insulating material has a thermal conductivity of at most 0.1 W/(nrK). This helps keeping the outer dimensions of the construction element small.

According to an embodiment of the invention, the insulating material is mineral 30 wool.

According to an embodiment of the invention, the insulating material is aerogel. The use of aerogel as an insulating material allows good thermal insulation even

20185575 prh 27-06- 2018 with a very small thickness of the insulating material. The aerogel can be silica aerogel.

According to an embodiment of the invention, the insulating material is polyurethane.

According to an embodiment of the invention, the inner tube has a rectangular profile. The inner tube can have a square-profile.

According to an embodiment of the invention, the outer layer has a square-profile, and the inner tube is fixed inside the outer layer into a rotational position, where each corner of the inner tube is in contact with a longitudinal center line 10 of an inner side of the outer layer. The inner tube can thus be rotated by 45 degrees relative to the outer layer and attached to the outer layer for example by welds. This increases the toughness of the construction element and also its ability to absorb energy, for instance in case of an earthquake.

According to an embodiment of the invention, on each side of the inner tube a 15 first row of slots is arranged next to each corner of the inner tube in the longitudinal direction of the inner tube, and a second row of slots is arranged next to the first row of slots, and the slots of the second row are shifted in the longitudinal direction of the inner tube so that the heat conduction path from the areas between the slots of the first row to the other side of the slots of the second row is 20 lengthened. When the inner tube is in contact with the outer layer, heat conduction from the outer layer to the inner tube is increased. This effect can be compensated by the slots on both sides of each corner.

According to an embodiment of the invention, the insulating material forms an insulating material layer surrounding the outer perimeter of the inner tube. When 25 the insulating material layer completely surrounds the outer perimeter of the inner tube, heat conduction and radiation to the inner tube is minimized.

According to an embodiment of the invention, the outer layer is made of a sheet material.

According to an embodiment of the invention, the construction element is a pillar.

According to an embodiment of the invention, each end of the construction element is provided with a flange or an end plate. By means of the flanges or end plates, the construction element can be connected to other structures of a building.

20185575 prh 27-06- 2018

Brief description of the drawings

Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which

Fig. 1 shows a side view of a construction element according to an embodiment of the invention,

Fig. 2 shows a perspective view of the construction element of figure 1,

Fig. 3 shows an end view of the construction element of figure 1,

Fig. 4 shows a cross-sectional view of the construction element of figure 1 taken along line A-A,

Fig. 5 shows a side view of a construction element according to another embodiment of the invention,

Fig. 6 shows a perspective view of the construction element of figure 5,

Fig. 7 shows a cross-sectional view of the construction element of figure 5 taken along line B-B,

Fig. 8 shows a side view of a construction element according to still another embodiment of the invention,

Fig. 9 shows a cross-sectional view of the construction element of figure 8 taken along line C-C,

Fig. 10 shows a cross-sectional view of the construction element of figure 8 taken along line D-D, and

Fig. 11 shows a cross-sectional view of the construction element of figure 10 25 taken along line E-E.

20185575 prh 27-06- 2018

Description of embodiments of the invention

The figures show different views of construction elements according to different embodiments of the invention. The construction element according to the invention can be used in load-carrying structures of buildings. The construction ele5 ment can be used for example as a pillar or as a diagonal beam. The construction element can be used for example in residential buildings, office buildings, storage buildings or industrial buildings. It could also be used in other similar constructions, such as different constructions of machines or infrastructure.

The construction element is an elongated part having a first end and a second 10 end. The direction from the first end towards the second end is the axial or longitudinal direction of the construction element. The construction element according to the invention comprises an inner tube 1, an outer layer 3 and insulating material 2 between the inner tube 1 and the outer layer 3. The inner tube 1 and the outer layer 3 are dimensioned so that the outer surface of the inner tube 1 is 15 at least partly apart from the inner surface of the outer layer 3. A space is thus formed between the inner tube 1 and the outer layer 3. The insulating material 2 at least partly fills the space between the inner tube 1 and the outer layer 3.

The insulating material 2 surrounds substantially the whole outer perimeter of the inner tube 1, but not necessarily completely.

The inner tube 1 is a load-carrying part that is configured to carry axial loads. The inner tube 1 is hollow. The inner tube 1 is empty, i.e. it is not filled with insulating material. The inner tube 1 forms the principal load-carrying part of the construction element. Also the outer layer 3 can be configured to carry axial loads, but that is not necessary. In some applications, also the insulating mate25 rial 2 could have some load-carrying capacity, but that is not necessary, and in most applications the insulating material 2 should be optimized in respect of thermal insulation capacity.

In the embodiments of figures 1-7, the insulating material forms an insulating layer 2 that is arranged around the outer perimeter of the inner tube 1. The in30 sulating layer 2 extends over the whole outer perimeter of the inner tube 1. The outer layer 3 is arranged around the outer perimeter of the insulating layer 2.

The main purpose of the insulating material 2 and the outer layer 3 is to protect the inner tube 1 in case of fire. The insulating material 2 extends in the longitudinal direction of the inner tube 1 essentially over the whole length of the inner

20185575 prh 27-06- 2018 tube 1. In the embodiments of figures 1-7, the insulating layer 2 also extends over the whole perimeter of the inner tube 1. The outer layer 3 extends in the longitudinal direction of the insulating material 2 over the whole length of the insulating material 2. In the embodiments of figures 1-7, The outer layer 3 also 5 extends over the whole outer perimeter of the insulating layer 2. The insulating layer 2 lies directly against the outer surface of the inner tube 1. The outer layer 3 lies directly against the insulating layer 2. The insulating layer 2 thus fills completely the space between the inner tube 1 and the outer layer 3.

Both the inner tube 1 and the outer layer 3 are made of stainless steel. By using 10 stainless steel, the fire resistance and other properties of the construction element are significantly better than the properties would be with structural steels. Stainless steel maintains its strength and stiffness at elevated temperatures better than structural steels. In the inner tube 1, the use of stainless steel thus improves the strength of the structural element in case of fire. In the outer layer 3, 15 the use of stainless steel provides many benefits. Stainless steel has a lower emissivity than structural steels. Emissivity describes the effectiveness of a surface to emit energy as thermal radiation. The emissivity of stainless steel is typically around 0.4, whereas the emissivity of carbon steel is typically around 0.7.

Lower emissivity of the outer layer 3 improves the fire resistance of the construc20 tion element, as it slows down the heating of the inner tube 1. Additional benefits of the stainless steel in the outer layer 3 are that the surface of the construction element is not prone to damages during assembly and provides a good resistance to stains and vandalism in public places. The surface is easy to clean using such cleaning methods that allow use of the construction element also in 25 places having high standards for hygiene, such as in hospitals or in buildings used in food industry.

The properties of the outer layer 3 can be even further improved by brushing or polishing the outer surface of the outer layer 3. A brushed or polished surface has a lower emissivity than a surface in an as-welded state.

In the embodiments of the figures, the inner tube 1 has a square profile. However, in the embodiments of figures 1-7, the inner tube 1 could also have some other cross-sectional profile. The profile could be rectangular or for example circular. The thickness of the insulating layer 2 is preferably uniform. Therefore, the cross-sectional profile of the outer layer 3 is preferably the same as the pro35 file of the inner tube 1.

20185575 prh 27-06- 2018

The wall thickness of the inner tube 1 depends on the load-carrying capacity required from the construction element. Also the other dimensions of the inner tube 1 may depend on the required load-carrying capacity, but may also be affected by other factors. Depending on the application, the wall thickness can be, 5 for instance, in the range of 2-20 mm. The width of a side of a rectangular tube or the diameter of a round tube can be, for instance, in the range of 20-500 mm.

The insulating layer 2 is made of a material having a lower thermal conductivity than stainless steel. The purpose of the insulating layer 2 is to slow down heating of the inner tube 1 in case of fire. The insulating layer 2 could be made of con10 Crete. However, it is preferable that the thermal conductivity of the insulating layer 2 is at most 0.1 W/(nrK). The thickness of the insulating layer 2 depends on the thermal conductivity of the insulating material and the required fire resistance of the construction element. The insulating material can be, for instance, mineral wool or polyurethane. The thickness of the insulating layer 2 can 15 be, for instance, in the range of 20 to 200 mm, in case polyurethane, mineral wool or similar insulating material is used. However, if a material with very good thermal insulation properties is used, the thickness of the insulating layer 2 can also be smaller, for instance in the range of 5 to 20 mm. An example of a material group with excellent thermal insulation properties is aerogels. Aerogels are solid, 20 rigid and porous materials. Aerogel is microporous solid having gas as a dispersed phase. Different types of aerogels exist. For example silica-based aerogels can be used as the material of the insulating layer 2. Thermal conductivity of silica aerogel can be 0.020 W/(nrK) or even lower.

The dimensions of the outer layer 3 naturally depend on the dimensions of the 25 inner tube 1 and the thickness of the insulating layer 2. The thickness of the outer layer 3 is chosen based on the desired properties of the construction element. The outer layer 3 can be used as part of the load-carrying structure of the construction element. However, in order to provide good fire resistance together with low material costs, it is more efficient to use the inner tube 1 as a sole or 30 principal load-carrying part. The outer layer 3 can thus have a thickness that is at most 65 percent of the thickness of the inner tube 1. The outer layer 3 can function mainly as a protective element without carrying a significant part of the total load carried by the construction element.

In the embodiment of figures 1 -4, both the inner tube 1 and the outer layer 3 are 35 RHS tubes. The insulating layer 2 is made of mineral wool. The wall thickness

20185575 prh 27-06- 2018 of the inner tube is 5 mm. The wall thickness of the outer layer is 3 mm. The outer dimensions of the inner tube 1 are 150x150 mm and the outer dimensions of the outer layer 3 are 200x200 mm. The thickness of the insulating layer 2 is thus 22 mm.

In the embodiments of figures 1-7, the first end of the construction element is provided with a first end plate 4 and the second end of the construction element is provided with a second end plate 5. The first end plate 4 closes the first end of the construction element and the second end plate 5 closes the second end of the construction element. The end plates 4, 5 are made of stainless steel. The 10 cross-sectional area of the end plate 4, 5 seen in the longitudinal direction of the construction element is larger than the cross-sectional area within the outer perimeter of the outer layer 3. The end plates 4, 5 thus form flanges at the ends of the construction element. The end plates 4, 5 are provided with holes 6, 7. In the embodiments of the figures, each end plate 4, 5 is provided with four holes 15 6,7, but there could be more holes 6, 7 in each end plate 4, 5. By means of the end plates 4, 5 and the holes 6, 7, two construction elements according to the invention can be connected to each other or the construction elements can be attached to other structures. The end plates 4, 5 can be attached to the inner tube 1 by welding. In the embodiment of figures 1-4, the end plates 4, 5 are 20 attached to the inner tube 1 by plug welds. The end plates 4, 5 are provided with slots 8, which are filled with weld metal. The slots 8 allow the end plates 4, 5 to be welded after the insulating layer 2 has been arranged around the inner tube 1 and the outer layer 3 has been arranged around the insulating layer 2. The end plates 4, 5 could also be attached to the outer layer 3. However, since the 25 inner tube 1 is the principal load-carrying part, it may not be necessary to have a rigid connection between the outer layer 3 and an end plate 4, 5. Instead of the end plates 4, 5, also flanges could be arranged at the ends of the construction element.

In the embodiment of figures 5-7, the insulating layer 2 is made of silica aerogel. 30 Because of the good thermal insulation properties, the thickness of the insulating layer 2 is only 10 mm. The outer layer 3 is not made of an RHS tube, but of a sheet material. This allows the end plates 4, 5 to be welded to the inner tube 1 before arranging the insulating layer 2 around the inner tube 1. Fillet welds can be used for welding the inner tube 1 and the end plates 4, 5 together. The outer 35 layer 3 is arranged around the insulating layer 2 after installing the insulating layer 3. Figure 6 shows a longitudinal seam 9 of the outer layer 3. The outer

20185575 prh 27-06- 2018 layer 3 can be welded to form a closed profile. Sheet material could be used as the material of the outer layer 3 even in case the insulating material is not aerogel.

Figures 8-11 show a slightly different embodiment of the invention. Also in this embodiment, the construction element comprises an inner tube 1, an outer layer 3 and insulation material 2 between the inner tube 1 and the outer layer 3. The insulation material 2 extends in the longitudinal direction of the construction element substantially over the whole length of the inner tube 1 and surrounds substantially the whole outer perimeter of the inner tube 1. The insulation mate10 rial 2 thus completely fills the space or actually the plurality of spaces between the inner tube 1 and the outer layer 3. However, the insulation material 2 does not form a continuous layer extending completely around the inner tube 1. Both the inner tube 1 and the outer layer 3 have a square-profile. The inner tube 1 and the outer layer 3 are coaxial. However, the sides of the inner tube 1 and the outer layer 3 are not parallel, but the inner tube 1 and the outer layer 3 are rotated by 45 degrees in respect of each other about the longitudinal axis of the inner tube 1 and the outer layer 3. The inner tube 1 and the outer layer 3 are dimensioned so that each corner of the inner tube 1 can be attached to one side of the outer layer 3. Each corner can be welded to the outer layer 3. In the em20 bodiment of figures 8-11, the insulating material can be, for instance, mineral wool or foam-type insulating material, such as polyurethane. End plates are not shown in figures 8-11, but also in this embodiment the construction element can be provided with similar end plates or flanges as the construction elements of figures 1-7.

The construction element of figures 8-11 has a good toughness and ability to absorb energy. It could thus be used for example in areas with a high earthquake risk. Because the inner tube 1 is attached to the outer layer 3 by welds and the insulating material 2 does not completely surround the inner tube 1, heat conduction rate to the inner tube 1 can be higher than in the embodiments of figures

1-7. In order to reduce heat conduction, the inner tube 1 can be provided with slots 10, 11. On each side of the inner tube 1, a first row of slots 10 is arranged close to each weld seam between the inner tube 1 and the outer layer 3. The slots 10 are arranged at short intervals in a row that extends substantially over the whole length of the inner tube 1. A second row of slots 11 is arranged in a similar way at a distance from the first row of slots 10. The slots 11 of the second row are shifted in the longitudinal direction of the construction element relative to the slots 10 of the first row. In a direction that is perpendicular to the longitudinal direction of the construction element, the heat conduction path from the weld seam to the other side of the second row of slots 11 is thus not straight. This makes the heat conduction path from the weld seam to the middle area of 5 each side of the inner tube 1 longer and reduces heat conduction.

In all the embodiments, the outer layer 3 of the construction element can be made, for instance, of austenitic steel. The inner tube 1 can be made, for instance, of ferritic steel.

The construction element according to the invention can be prefabricated, which 10 minimizes the assembly time at a construction site. Furthermore, fittings of the parts can be made precise, seams can be made tight and variations in quality can be minimized. Because of the use of stainless steel, the corrosion resistance of the construction element is good.

It will be appreciated by a person skilled in the art that the invention is not limited 15 to the embodiments described above, but may vary within the scope of the appended claims.

Claims

Claims

I. A construction element for load-carrying structures of buildings or similar constructions, the construction element comprising

- an inner tube (1) made of stainless steel and configured to carry axial

5 loads,

- an outer layer (3) made of stainless steel and arranged around the outer perimeter of the inner tube (1), and

- insulating material (
2) at least partly filling the space between the inner tube (1) and the outer layer (3).

10 2. A construction element according to claim 1, wherein the outer surface of the outer layer (3) is brushed or polished stainless steel.
3. A construction element according to claim 1 or 2, wherein the wall thickness of the outer layer (3) is at most 65 % of the wall thickness of the inner tube (1)·

15
4. A construction element according to any of claims 1-3, wherein the insulating material (2) has a thermal conductivity of at most 0.1 W/(nrK).
5. A construction element according to any of the preceding claims, wherein the insulating material (2) is mineral wool.
6. A construction element according to any of claims 1-4, wherein the insu20 lating material (2) is aerogel.
7. A construction element according to claim 6, wherein the aerogel is silica aerogel.
8. A construction element according to any of claims 1-4, wherein the insulating material (2) is polyurethane.

25
9. A construction element according to any of the preceding claims, wherein the inner tube (2) has a rectangular profile.
10. A construction element according to any of the preceding claims, wherein the inner tube (2) has a square-profile.

II. A construction element according to claim 10, wherein the outer layer (3) 30 has a square-profile, and the inner tube (1) is fixed inside the outer layer (3) into a rotational position, where each corner of the inner tube (1) is in contact with a longitudinal center line of an inner side of the outer layer (3).
12. A construction element according to claim 11, wherein on each side of the inner tube (1) a first row of slots (10) is arranged next to each corner of the inner 5 tube (1) in the longitudinal direction of the inner tube (1), and a second row of slots (11) is arranged next to the first row of slots (10), and the slots (11) of the second row are shifted in the longitudinal direction of the inner tube (1) so that the heat conduction path from the areas between the slots (10) of the first row to the other side of the slots (11) of the second row is lengthened.

10
13. A construction element according to any of claims 1-10, wherein the insulating material forms an insulating material layer (2) surrounding the outer perimeter of the inner tube (1).
14. A construction element according to any of the preceding claims, wherein the outer layer (3) is made of a sheet material.
15 15. A construction element according to any of the preceding claims, wherein each end of the construction element is provided with a flange or an end plate (4, 5).