[0002] Steel beams of the above type, so-called steel composite beams, have long been known in the construction industry. During installation, these steel composite beams act as a steel beam for installation-time loads.

After the concreting, which takes place following the installation of the slabs, the beam acts as a composite structure together with the concrete. In said concreting, the beam is cast full of concrete in connection with the joint grout- ing of the slabs and a possible topping.

[0003] Several different solutions for steel composite beams have been developed over the years. Examples of previously known solutions in- clude the solutions disclosed in the Finnish patent publications 85745 and 92089.

[0004] Steel composite beams are either single-span or plural-span beams. This means that the beam is supported either at its ends, i. e. in the area of the supporting points in the area of its ends or, alternatively, it com- prises intermediate supports such that the beam also includes supporting points between the supporting points in the area of its ends. This is why it is not practical to make the beam similar over its entire length, but additional steel parts are fastened to the basic cross-section according to stresses.

[0005] Typically, the beam is subjected to a high shearing stress in the vicinity of the support arranged in the supporting point. In previous solu- tions, this high shearing stress has been received by welding a chamfered plate inside the beam in the vicinity of the supporting point.

[0006] The drawback in the above structure is that the plate in- creases the weight of the beam and thereby its price. The plate is also difficult to fasten on a production line because the welding position is unfavourable since, in practice, the labourer has to bend and at the same time reach up- wards. Typically, the shearing force decreases linearly from the end of the beam towards the middle. However, the plate is of uniform section, its thick- ness being determined according to the highest value of the shearing force.

Thus, part of the capacity of the plate is unnecessary and remains unutilized.

[0007] The object of the invention is to provide a steel beam allow- ing the drawbacks of prior art to be eliminated. This is achieved with a steel beam of the invention. The steel beam of the invention is characterized in that at least one peg member whose one end is fastened to the lower surface of the upper part and whose other end is provided with an anchoring expansion or widening section is arranged inside the space defined by the web parts and the horizontal upper part, in the area of the supporting points.

[0008] An advantage of the invention over prior art is that the peg members are light and their number can be changed very easily over the length of the beam. Accordingly, superfluous capacity and weight are not cre- ated in the beam. An additional advantage of the invention is that the peg members are much easier to fasten to the beam than the previously used plate. The peg members can be fastened to the plate constituted by the upper part of the beam from the top, i. e. the welding can be carried out from above for instance by placing the peg member into a hole provided in the plate. This eliminates the inconvenient working position caused by the welding of the pre- viously used plate.

[0009] In the following, the invention will be described in detail by means of an exemplary embodiment described in the accompanying drawing, wherein Figure 1 shows a steel beam according to the invention seen in the longitudinal direction of the beam, and Figure 2 is a perspective view of a beam according to the invention.

[0010] Figures 1 and 2 show an embodiment of the steel beam ac- cording to the invention. The steel beam comprises two web parts 1 and hori- zontal cantilever parts 2 extending outside thereof. The web parts 1 are ar- ranged adjacent at a distance from each other and interconnected at one edge of each web part 1 by means of a horizontal upper part 3. The web parts 1 and the horizontal upper part 3 are arranged to constitute a space 4 that can be filled with concrete.

[0011] In the example of the figures, the lower edges of the web parts 1 are interconnected by means of a horizontal lower part 5. The web parts 1 are provided with openings 6 enabling the feed of concrete into the space 4.

[0012] The above facts are evident to a person skilled in the art, and they are therefore not described in any detail herein. As for the above facts, reference is made to the previously mentioned Finnish patent publication 85745.

[0013] In accordance with the essential idea of the steel beam of the invention, peg members whose ends comprise an expansion or widening section acting as an anchoring are used in the vicinity of a supporting point. As the figures show, at least one peg member 7 is arranged inside the space 4 defined by the web parts 1 and the horizontal upper part 3, in the area of the supporting points. One end of the peg member 7 is fastened to the lower sur- face of the upper part, as shown particularly clearly in Figure 1. The other end of the peg member 7 is provided with an expansion or widening section 8 that helps the anchoring.

100141 The number of peg members 7 over the length of the beam may change, avoiding unnecessary capacity. Accordingly, there may be either one or more peg members 7 according to the need, and the number may also change e. g. in the longitudinal direction of the beam. The peg members 7 may be placed in either one or more lines. Figure 1 shows a solution wherein the peg members are in two lines. The peg members 7 are placed in the area of the supporting points, i. e. at the ends of the beam and, if need be, also in the area of the supporting points between the ends of the beam.

[0015] The peg members can be made either from a smooth bar or from a ribbed bar. The shape of the expansion or widening section 8 acting as the anchoring end is optional as long as it constitutes an anchoring member.

The shape of the anchoring end can be e. g. round, oval, etc.

[0016] The expansion or widening section acting as the anchoring end can be implemented by using any suitable technique. However, an imple- mentation wherein the peg members 7 are made from jolt pegs has been found to be particularly advantageous.

[0017] The embodiment of the invention described above is in no way intended to restrict the invention, but the invention can be modified freely within the scope of the claims. It is therefore evident that the steel beam of the invention or its details no not necessarily have to be exactly as shown in the figures, but also other solutions are feasible.