Steel plate beam and manufacturing method of such

The invention relates to a steel plate beam, which comprises an upper flange having a smaller upper width and a lower flange having a larger lower width, which flanges are at a distance of the height from each other, and two webs at a variable width distance from each other, which both are formed of the same web plate and extend from the upper flange to the lower flange, and welds that connect said web plate to at least the upper flange. The invention also relates to a method for manufacturing a steel plate beam consisting of an upper flange and lower flange at a distance of the height from each other, and two webs at a variable width distance from each other, which both are formed of the same web plate and extend from the upper flange to the lower flange, and welds that connect said web plate to at least the upper flange.

WO-90/12173 describes a fire-resistant prefabricated steel beam, which has been adapted to function together with concrete as a load-bearing composite structure in various slab constructions and which comprises two web parts and horizontal cantilever flange parts extending to the outside thereof. At least both web parts and the horizontal cantilever flange part connected to the web part and extending to the outside thereof have been formed of a continuous strip of material in a way that the web part and the cantilever flange part connected to it constitute a seamless whole and so that the web part is in an inclined position in relation to the flange part, that the web parts have been arranged side by side so that they are in an inclined position towards each other and connected to each other at the edges that are closer to each other by means of a horizontal upper part, and at the edges that are further from each other and connected to the cantilever flange parts by a plate welded to the web parts and that apertures have been made in the vicinity of the upper edges of the web parts and/or in the horizontal upper part for filling the space delimited by the upper part of the web parts and the plate with concrete in a manner known as such. WO-03/100186 describes a method and means for manufacturing a steel beam, which steel beam functions together with concrete as a load-bearing composite structure in various slab constructions, in which method the base plate of the beam, the web parts and the upper plate are cut from plate material, the parts are assembled in such a manner that a space is formed between the parts for concrete to be fed through the apertures in the web part, and the parts are welded into a unity. The web plates are cut to a curved shape according to a preliminary raise. Side braces that determine the position of the web plates and centre braces that determine the position of the upper plate are fastened to the base plate at predetermined distances in the longitudinal direction of the beam. The base place is subjected to a force, which forces the base plate to a curvedness determined by

the web plates, whereupon the side braces determine the position of the web plates and the centre braces the curvedness of the upper plate to be fitted on place. The means comprises a part, of which the first end has been adapted to determine the position of the lower edge of the web plate, and the second end has been adapted to determine the position of the upper edge of the web plate.

EP-1 416 101 describes a composite beam element, which is used particularly as a load-bearing horizontal structure of the prefabricated framework of a building, bearing the slab structures of the horizontal planes of the building, which composite beam is connected and fastened to the prefabricated column by a load transferring connection part, and which composite beam element includes an essentially closed casing of steel enclosing a space to be filled with concrete, which casing consists of a planar lower flange of steel, side walls and an upper flange, which lower flange extends over the side walls of the casing with protruding parts, and which beam element is provided with longitudinal, deformed bars. On the upper surface of the casing there are essentially rectangular apertures having their edges bent downwards and with necks between the apertures, and two or more deformed bars have been fastened to the necks on the upper surface of the casing of the beam element in the longitudinal direction of the beam element.

However, the manufacture of composite beams of this type is relatively laborious, because, in the first place, the beams require complicated jigs during manufacture in order to make proper welds in them. This means numerous steps of work, which are time-consuming. In the beams described above, it is also difficult to achieve an optimal strength of the steel material and other optimal dimensions at each point of the construction. The beam becomes easily underdesigned at some point and overdesigned at some other point. If then, in that publication, an attempt has been made to solve this problem by welding additional parts to the beam, the result is at least an increase in the number of steps of work. It must also be taken into account that some steel qualities should undergo a thermal treatment after welding, which means that the selection of steel qualities is limited if thermal treatment is not desired, or then the thermal treatment brings again an additional, slow step of work, if it is desired that all possible steel qualities should be utilized.

The problems described above can be solved and the objectives defined above can be achieved by a steel plate beam according to the invention, which is characterized in what is set forth in the characterizing part of Claim 1 , and by a method according to the invention, which is characterized in what is set forth in the characterizing part of Claim 17.

In the following, the invention will be described in more detail with reference to the following drawings, in which

Figs. 1A -> 1C depict the three manufacturing steps of the preferred first embodiment of a steel plate beam according to the invention as a cross-section against the length of the beam in the perpendicular direction.

Figs. 2A -» 2B depict the two manufacturing steps of the second embodiment of a steel plate beam according to the invention as an axonometric cross-section.

Figs. 3A → 3C show the three manufacturing steps of the second embodiment of a steel plate beam according to the invention as a cross-section against the length of the beam in the perpendicular direction.

Figs. 4 and 5 show in detail the connection of the web plate to the lower surface of the upper flange and correspondingly to the edge surfaces in the steel plate beam according to Fig. 3C, in the area I of Fig. 3C and in a larger scale.

In general, this is a steel plate beam 1 with an upper flange 2 having a smaller upper width W2 and a lower flange 3 having a larger lower width W3, i.e. the width of the upper flange W2 < the width of the lower flange W3. These flanges 2 and 3 are at a distance of the height H1 from each other. The steel plate beam 1 also has two webs 4a, 4b at a variable or constant width distance W from each other, which are both formed of the same web plate 14 and extend from the upper flange to the lower flange. In addition, the steel plate beam 1 has at least welds 7, which connect the two adjacent webs 4a and 4b formed by the one web plate 14 to at least the upper flange 2 and in some cases also to the lower flange 3. It is thus a steel plate beam 1 made from rolled steel plate or rolled steel plates by cutting, bending and welding.

At first the most preferred first embodiment of the invention will be described with reference to figures 1C and 2B, in which it is shown as complete. According to the invention, the upper flange 2, which is originally a separate part, has edge surfaces 5c, 5d and a lower surface 5a facing the lower flange, and the lower flange 3 has an upper surface 6y facing the upper flange. In this case, the lower flange 3 is originally a separate part, to which the uniform web plate 14 forming both webs 4a, 4b has been welded fixed. The web plate 14 has been fastened by the upper welds 7 to the above mentioned lower surface 5a of the upper flange and/or possibly to the edge surfaces 5c, 5d - in a corresponding manner, for example, as in the second embodiment, which will be described below - and fastened to the above mentioned upper surface 6y by the first lower welds 8a. It is particularly emphasized that the two adjacent webs 4a, 4b are in contact with the lower surface 5a of the upper flange by means of the upper surface 9y of the web plate 14 forming the webs, i.e. merely with the surface and not welded to the edges of the upper flange, the distance between which constitutes the upper width W2. Hence the upper surface 9y of the web plate is in contact with the lower surface 5a of the upper flange, and the upper welds 7 are located in the contact area and between

these surfaces. The upper welds 7 are welds without filler metal, running in the longitudinal direction L of the steel plate beam, and preferably the upper welds 7 are laser welds. There are at least two of the upper welds, at a distance Wh in the direction of the upper width W2 of the upper flange from each other. The distance Wh is typically slightly, by a clearance G, shorter than the upper width W2 for causing the laser weld going through the web plate 14 to meet a solid, even bond surface, i.e. the lower surface 5a, to which the upper surface 9y of the web plate can effectively adhere. A small clearance G between the folding lines L _A , L _B and the outermost upper welds also has an importance in that the bending to be explained later does not take place exactly at the upper welds but at the above mentioned lines, but yet the distance Wh between the upper welds 7, i.e. the transverse support distance, can be made as long as possible, i.e. nearly as long as the minimum distance W4. In practice, the magnitude of the clearance G is a few millimeters at most. In this embodiment, the upper welds 7 are between the web plate and the lower surface 5a of the upper flange in the upper portion 24 of the web plate 14.

In the case that the webs 4a, 4b have a variable width distance W ¹ , it has a minimum distance W4 in the area of the upper flange 2 and a maximum distance W5 in the area of the lower flange 3, which minimum distance W4 is smaller than or equal to the upper width W2 of the upper flange, and the maximum distance W5 is smaller than the lower width W3 of the lower flange. Then the webs 4a, 4b together with their upper portion 24 connecting them and with their lower edge, which is placed against the lower flange - i.e. the longitudinal edges 4' or the maximum distance W5 of the inner edges of the lower edge folds 11 - form the opposite, non-parallel sides of a trapezium, as can be seen in figures 1C and 2B. However, in the case that the webs 4a, 4b have a constant width distance W", there prevails a minimum distance W4 on the whole vertical dimension H1 , which minimum distance is smaller than or equal to the upper width W2 of the upper flange and the lower width W3 of the lower flange, and extends as such from the upper flange 2 to the lower flange 3. Then the webs 4a, 4b together with their upper portion that combines them and their lower edge, which is placed against the lower flange, form the opposite, parallel sides of the trapezium, as can be understood although this embodiment is not shown in the figures. Also in this embodiment it is possible to apply a minimum distance W4, which is larger than the upper width W2, like in Fig. 5.

In the most advantageous case, the webs 4a, 4b additionally comprise at the opposite longitudinal edges 4 ¹ of the web plate lower edge folds 11 , which are directed away from each other and are mutually parallel, as can be seen from figures 1 B and 1C. The distance W1 between the outer edges of the lower edge folds 11 is normally smaller than the lower width W3, but they can also be equal. In this embodiment, the first lower welds 8a, by which the web plate 14 has been

welded at its longitudinal edges 4 ¹ , or more accurately at its lower edge folds 11 , together with the wide lower flange 3, can be either welds with filler metal or welds without filler metal. In the case of the lower edge folds 11 , the first lower welds 8a are preferably laser welds, and they are in the area of the lower edge folds 11 of the web plate 14. Another alternative is to use a web plate 14 which does not have lower edge folds of the type mentioned, in which case the first lower welds 8a, by which the webs 4a, 4b have been welded at their bent longitudinal edges 4' together with the wide lower flange 3, are typically welds with filler metal, but they can also be laser welds. According to the first embodiment of the invention described above, the thicknesses S2, S3 of the upper flange 2 and the lower flange 3 are larger than the thickness S4 of the webs 4a, 4b. With regard to typical dimensioning, it can be said that the upper width W2 of the upper flange 2 is generally in the range of 150 mm to 340 mm, and the thickness S2 is 8-50 mm, preferably 15-30 mm. The lower width W3 of the lower flange 3 is generally in the range of 190 mm to 500 mm, and the thickness S3 is 8-50 mm, preferably 12-25 mm. The thickness of the web plate 14 is generally in the range of 4 mm to 8 mm, and the height H1 between the upper flange 2 and the lower flange 3 is typically in the range of 150 mm to 500 mm.

According to the invention, the above described preferred steel plate beam 1 according to the first embodiment is manufactured in a way described below.

An upper flange 2 having a length L' and a transverse upper width W2 against it and a lower surface 5a is cut by a suitable cutting method from a first rolled steel plate having the desired thickness S2 for the upper flange. In a corresponding manner, a planar web plate 14 having a length L" and longitudinal edges 4', an initial width Wβ transverse against said length and an upper surface 9y is cut by a suitable cutting method from a second rolled steel plate having the desired thickness S4 for the web plate. In the next step, this upper flange 2 and the web plate 14 are placed in contact with each other so that the lower surface 5a of the upper flange and the upper surface 9y of the web plate are against each other, as shown in Fig. 1A. Then the web plate is welded by longitudinal L upper welds 7 without filler metal together with the upper flange. Two or more parallel welding heads 32 can then be used, and these are schematically shown in Fig. 1A, in which case all the longitudinal L, L", L" upper welds 7 can be made simultaneously. Naturally, fewer welding heads can be used and more times of welding can be carried out in order to achieve the specified number of welding beads. According to the invention, especially these upper welds 7 are advantageously carried out by laser welding. After this, the web plate 14 and the upper flange 2 are welded to each other by at least two upper welds 7, of which the distance between the outermost is W4-2χG. In the next step, the web plate 14 is bent along two longitudinal L central area lines LA, LB having a mutual minimum distance of W4,

for the amount of the first angle α away from the level of the upper flange 2, which is schematically shown in Fig. 1A. The first angles α are at least 30° and at the most 90°, when the angle α , or the bending or turning angle is measured between the web and the planar web plate, outside the web. The lower edge folds, if such are made, are also made in this step, but if not, the process continues from the next step. A lower flange 3 having a length L ¹ " and a transverse lower width W3 against it and an upper surface 6y is cut by a suitable cutting method from the first or third rolled steel plate having the desired thickness S3 for the lower flange. In this connection it must be noted that if the lower flange has been designed to be of the same steel type and of the same thickness as the upper flange, it can naturally be cut from the same billet plate as the upper flange, but if not, from some other billet plate. Then the bent web plate 14, which is fixed with the upper flange, is welded in the area of the longitudinal edges 4 ¹ with the first longitudinal L lower welds 8a together with said lower flange 3, or to its upper surface 6y to be more accurate. The first lower welds 8a can be of any weld type suitable for the purpose. The length of the upper flange L ¹ , the length of the web and the web plate L" and the length of the lower flange L ¹ " are normally equal and naturally parallel with the length/length direction L of the steel plate beam.

When the web plate 14 is bent along the central area lines L _A , L _B connected to the upper flange, for achieving an advantageous beam form, the longitudinal edges 4 ¹ of the web plate can also be bent along two longitudinal L edge area lines Lc, LD for the amount of the second angle β in the direction of the upper flange 2, i.e. in the opposite direction with regard to the angle α, as can be understood from Fig. 1A. The edge area lines Lc, LD are at a distance of the bending width W7 from the longitudinal edges of the web plate, and the result is the lower edge folds 11 , which are in the steel plate beam 1 parallel with the upper portion of the webs 4a, 4b. This parallelness is the result of the fact that the first angles α are as large as the second angles β, but turned or directed to different directions. Especially in the case that the webs 4a, 4b of the steel plate beam 1 include these lower edge folds 11 , the first lower welds 8a are made through each lower edge fold to the lower flange by laser welding or some other welding method without filler metal using welding heads 32. In principle, the first lower welds 8a can also be made by some welding method with filler metal, especially when there are no lower edge folds in the webs, like shown in Fig. 2B. The bending order is relatively free; the bends can first be made along the central area lines L _A , LB and then possible bends along the edge area lines L ₀ , L ₀ , or first bend along the edge area lines Lc, L ₀ and then bend along the central area lines L _A , LB.

The second embodiment of the invention has the following features. In this case, too, the upper flange 2, which is originally a separate part, has opposite edge surfaces 5c, 5d at a distance of the smaller upper width W2 from each other, and between them an upper surface 5y and a lower surface 5a facing the lower flange.

The lower flange 3 also has an upper surface 6y facing the upper flange and a larger lower width W3, although the lower flange 3 is in this embodiment made in a different manner than in the first embodiment. Similarly, the web plate 14 is by the upper welds 7 bound on the lower surface 5a of the upper flange and/or on the edge surfaces 5c, 5d of the upper flange. In this embodiment, the web plate 14 is of one piece with the lower flange 3, i.e. the lower flange and the webs have been made from one metal plate by bending and welded at least by the upper welds 7 to the upper flange. Then the lower flange 3 comprises a lower portion 20 and mutually parallel flange folds 10 pointed towards each other from its outer edges. Such a lower flange can be without welds, but it is also possible to connect the flange folds 10 to the lower portion 20 with other lower welds 8d, which alternative may be more advantageous than the alternative without welds. The second lower welds 8b are welds without filler metal and preferably laser welds. The lower flange, i.e. the combination of the lower portion and the flange folds is thus formed of the web plate 14. As an extension of the flange folds 10, said one web plate 14 further comprises webs 4a, 4b directed towards the upper flange 2. These webs 4a, 4b are of the same type in both embodiments in principle. Furthermore, as an extension of the webs 4a, 4b there are upper edge folds 17 on the opposite longitudinal edges 4" of the web plate. The upper edge folds 17 can be simple folds, in which case the web plate 14 is placed against the lower surface 5a of the upper flange 2, as shown in Figs. 3C and 4, or the upper edge folds 17 can be N-shaped folds like in Fig. 5, V-shaped folds etc., in which case the web plate 14 is placed at least against the side surfaces of the upper flange 2. In this embodiment, the thickness S2 of the upper flange and the side thickness S5 of the lower flange 3 at the flange folds are larger than the width S4 of the webs 4a, 4b. The centre thickness S6 of the lower flange 3 between said webs, or the thickness of the lower portion 20, is equal to the thickness of the webs S4.

In the case that the webs 4a, 4b have a variable width distance W, they have a minimum distance W4 in the area of the upper flange 2 and a maximum distance W5 in the area of the lower flange 3, which minimum distance W4 is smaller than or equal to the upper width W2 of the upper flange, and the maximum distance W5 is smaller than the lower width W3 of the lower flange. Then the webs 4a, 4b together with their combining upper portion 24 and their lower edge, which is placed against the lower flange - i.e. the maximum distance W5 of the longitudinal edges 4' or the flange folds 10 - form the opposite non-parallel sides of a trapezium, as can be seen in Fig. 3C. However, in the case that the webs 4a, 4b have a constant width distance W, there prevails a minimum distance W4 on the whole vertical dimension H1 , which minimum distance is smaller than or equal to the upper width W2 of the upper flange and the lower width W3 of the lower flange, and extends as such from the upper flange 2 to the lower flange 3. Then the webs 4a, 4b together with their combining upper portion and their lower edge, which is placed against the lower flange, form the opposite parallel sides of a parallelogram.

The minimum distance W4 can be smaller than the upper width W2, like in Figs. 3C and 4, or larger than the upper width W2, like in Fig. 5.

According to the invention, the above described steel plate beam 1 according to the second embodiment is manufactured in a way described below. An upper flange 2 having a length L ¹ and a transverse upper width W2 against it between opposite edge surfaces 5c, 5d and a lower surface 5a is taken from the first rolled steel plate having the desired thickness S2 for the upper flange. In a corresponding manner, a planar web plate 14 having a length L" and longitudinal edges 4", an initial width W6 transverse against said length and an upper surface 9y is taken by a suitable cutting method from a second rolled steel plate having the desired thickness S4 for the web plate. Then the web plate 14 is bent as a second bending along at least two longitudinal L lines Lj, L« to form an upper edge fold 17, the lines Lj, LK of which are at such a distance from each other that in the final steel plate beam the webs 4a, 4b have a minimum distance W4. Said distance is W6-2XWRT, in which WRT is the width required by the edge folds. The next step is to bend, as a third bend, the web plate 14 along two longitudinal L lines LE, LF, which are at a distance of the lower width W3 from each other, to an angle of 180° into the flange bends 10 and the lower portion 20 between them, and along two other longitudinal L lines LG, LH , the distance between which is such that it causes a maximum distance W5 for the webs 4a, 4b, for the amount of the third angle χ away from the level of the web plate 14 on said lower width. In practice, the bend along the lines LQ, LH is made first, the distance between the lines being W6-(2XWRT+2XW7+2XWL), in which WL is the width of the webs, and only after that along the lines LE, L _F . After these bends, the upper edge folds 17 of the web plate 14 and said upper flange 2 are brought into contact with each other so that the lower surface 5a and/or the edge surfaces 5c, 5d of the upper flange and the surface of the web plate are against each other - in this case it has to be taken into account that depending on the shape of the upper edge fold, the surface connected to the web plate can be the upper surface or the lower surface of the original straight board - and the web plate is welded with longitudinal L upper welds 7 without filler metal together with the lower surface 5a of said upper flange and/or the edge surfaces 5c, 5d. When required, the flange folds 10 are welded with second lower welds 8b also without filler metal together with the lower portion 20 of the web plate. The second lower welds 8b are typically made by laser welding. The result is that the lower portion 20 of the web plate 14 and the two flange folds 10 form the lower flange 3 of the steel plate beam having a length L ¹ " and a transverse lower width W3 against it.

In both embodiments of the invention, both webs 4a, 4b are thus formed of the same web plate; in the first embodiment the web plate 14 extends - as the upper portion 24 - across the upper flange 2 while the longitudinal edges 4' are in the area of the lower flange 3, and in the second embodiment the web plate extends -

as the lower portion 20 - across the lower flange 3 while the longitudinal edges 4" are in the area of the upper flange 2. The steel plate beam 1 according to the invention is typically used in the manner shown by Fig. 2B. There the reinforced concrete slabs 30 of the base floor, intermediate floor or roof, for example, are placed on the side portions of the lower flange 3 of the steel plate beam, the width of the side portions being approximately (W3-W5)/2, on which the concrete slabs stay firmly. The gaps between the steel plate beam 1 and the reinforced concrete slabs 30 and perhaps the upper surface of the slabs, too, are filled with filler concrete 31. For achieving a bond to the filler concrete 31 , the upper flange 2 may comprise at its longitudinal edges concrete bonds 13 for achieving a composite effect between the steel plate beam 1 and the concrete B surrounding it. The concrete bonds 13 can be holes and/or indentations, like in Fig. 2B, and/or incisions, the edges of which are bent suitably, or pins 23 welded to the upper surface 5y of the upper flange 2, like in Fig. 2A, or longitudinal edge areas of the upper flange, which are bent as wavelike, or corrugated, like the corrugations 25 shown by dashed lines in Fig. 1C, or edges bent lengthwise. If one or more of the above mentioned bends are made only upwards, they can be made in any manufacturing step, advantageously before the upper flange and the web plate are placed in contact with each other, i.e. in connection with cutting the upper flange from the steel plate, but the bends downwards can be made only after the web plate 14 has been bent along two longitudinal lines LA, LB. The upward pins 23 can also be made in any step.

Further according to the invention, when fire safety is required, the webs 4a, 4b comprise fire protection steel sections 16 in the longitudinal direction L, L', L", L" ¹ of the steel plate beam, which have been fastened by welds 15 to the webs 4a, 4b and can be outside the web plate in both webs 4a, 4b, like in the web on the left in Fig. 2B ₁ or inside the web plate, like in the web on the right in Fig. 2B, or one outside the web plate and one inside the web plate, like in Fig. 2B. Because the steel plate beam according to the invention can be made such that it has sufficient bearing strength without concrete inside the beam, when desired, the webs 4a, 4b, the upper flange 2 and the lower flange 3 in the portion between the webs, i.e. approximately on the minimum distance W4 and the maximum distance W5 can be without holes, like seen in Figs. 2A and 2B, which further increases the strength and rigidity of the beam. The cavity 12 delimited by the webs 4a, 4b between them can be empty, i.e. contain only air, or it can be filled with some solid, fire-resistant material, such as foam or cellular concrete, or expanded clay aggregate concrete - for which the general name lightweight concrete is used - or mineral wool or other corresponding material. In these cases, the weight by volume of the content of the cavity 12 delimited by the webs 4a, 4b is at the most 500 kg/m ³ . In the case that some fire-resistant material that can be casted has been arranged in the cavity 12, such as lightweight concrete of the type mentioned above or some other type of

concrete, i.e. stronger and heavier conventional, or normal concrete, it is also possible to place reinforcement steel in it in some known or novel manner. in order to improve the fire resistance of the steel plate beam 1 , longitudinal L fire protection steel sections 16 can be welded together with the upper surface 9y and/or to the lower surface 9a of the web plate 14 before the upper flange and the web plate are put into contact with each other. The fire protection steel sections 16 can thus be outside the webs and/or in the cavity formed by the webs, and there can be a plurality of them. The cavity 12 delimited by the webs 4a, 4b of the steel plate beam 1 between them can be let to contain only air, i.e. it can be left empty and not filled with solid material, like shown in Fig. 2B. As an alternative, the cavity 12 delimited by the webs 4a, 4b between them can be filled with porous, fire- resistant material having a weight by volume preferably no more than 500 kg/m ³ . The fire-resistant material can be foam concrete or lightweight aggregate concrete - generally lightweight concrete - or mineral wool, as shown in Fig. 1C, or the like. Especially if mineral wool is used as the fire-resistant material, it can be placed in the cavity 12, or the cavity is filled with fire-resistant material before welding the web plate 14 according to the embodiment either with the first lower welds 8a together with the lower flange 3 or with the upper welds 7 to the upper flange 2. This order is suitable for the relatively light fire-resistant materials according to the invention. On the other hand, nothing prevents filling the cavity 12 with fire-resistant material only after the web plate 14 has been welded, according to the embodiment, either with the first lower welds 8a together with the lower flange 3 or with the upper welds 7 to the upper flange 2. In the case that the fire-resistant material is foam concrete or lightweight aggregate concrete and that the cavity 12 contains' concrete reinforcement when it is filled with foam concrete or lightweight aggregate concrete, or lightweight concrete, or possibly with normal concrete.