EP1131511A1

EP1131511A1 - Lightweight i-beam and lightweight building unit

Info

Publication number: EP1131511A1
Application number: EP98957278A
Authority: EP
Inventors: Roger Ericsson; Ture Marklund; Gustav NÄSLUND
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-11-20
Filing date: 1998-11-20
Publication date: 2001-09-12

Abstract

I-beam of thin sheet plate folded so that the flanges (102) of the beam (101) consist of two layers of plate laid on one another and that the mid-section (103) of the beam consists of a single layer of plate. It is distinguished in that the two layers of plate that are laid on one another in the flange are firmly attached to one another by means of holes (104) or rivets punched through both plates.

Description

Lightweight I-beam and lightweight building unit

The present invention relates to a lightweight beam in the form of an I-beam made of thin sheet plate and a lightweight building unit composed of the said beams and concrete. Today, the most commonly used lightweight beams usually have a C or Z- shaped profile. Lightweight beams are used in floor structures and in intermediate partitioning walls and outer walls as well as in rafters. In general, lightweight profiles are a part of lightweight building technology for forming lightweight units or are a part of sound insulation beams. Lightweight profiles can also be part of loading pallets. Lightweight C and Z-shaped sheet plate profiles have experienced an ever increasing interest as components in different types of building construction. The profiles are screwed or glued together in different ways at slabs and in this way form, for example, a composite, rigid wall unit. However, a large number of screws are needed to take advantage of the static characteristics of the unit. Gluing is problematic with regard to the requirements for fire prevention. Because of the asymmetric shape of the profiles, the slabs that are to be attached next to one another with the intermediate lightweight beam cannot be locked mechanically to the steel profile. Instead, only one of the flanges of the profile will be able to interact in a profile of one of the slabs, while the other flange of the profile will extend outside of the surface of the side of the slab. In addition, these C and Z-shaped thin plate profiles are pliant and unstable in the flange that extends upwards above the plane of the slab. At the same time, they are sharp and have sharp-edged burrs. The flanges are rarely bent at an angle of 90° from the rib, which is why it is difficult to mount the flanges in the grooves of the slabs, which are made wider than needed to facilitate assembly, which results in loose play around the flange in the groove. The wall units that are built up with the aid of these beams must also be projected and planned very carefully, because the asymmetry of the beams requires a special design at the transition to windows, doors, joints and corners. According to US, A, 1457303 and 2065378 and the Swedish application 9701931-9 there is, however, an alternative design that has an I- shaped symmetric profile where several of the weaknesses of the C and Z-shaped profiles are eliminated. The reason why this type of I-shaped profile has not been used more widely is most likely mainly due to the cold rolling pinch pass technique that makes the production of the C and Z-shaped profiles so efficient was not sufficiently well developed to apply to I-profiling. The I-beam is difficult to manufacture and transport and there is even the static disadvantage that, unlike the C and Z-shaped profiles, it cannot naturally overlap in joints, which is something that plays a key role for the normal, static- demanding properties, loading ability and deflection. This disadvantage more than adequately counter-balances the possible improved properties of the I-beam due to its symmetry. When used as an individual component, the I-beam is thus not sufficiently interesting. One way to motivate an I-beam made of thin plate is that its use provides such added value that these disadvantages are overcome.

To take advantage of the increased amount of material in the flanges, all known I-profiles require that the double folded plates in the flanges are firmly joined with one another. The methods pointed out in the known technology are, however, marred by significant disadvantages. The said US, A, 2065378 and the Swedish application 9701931- 9 indicate solutions such as riveting or soldering/welding. The methods mean extra costs and are furthermore unsuitable for beams that are primarily manufactured of surface- treated thin plate as the surface treatment is ruined. The locking of the flange plates described in US, A, 1457303 does not work in practice and is primarily only a theoretical solution.

The floor structures commonly used today are often manufactured on site and are cast as homogeneous, reinforced concrete constructions that function in an acceptable manner from a sound-proofing and fire prevention point of view. The material required is readily available in most of the markets and the way of working is traditional. There are several variations that increase the degree of prefabrication. These are generally focused on completing the false ceiling in concrete including reinforcement and, with the aid of mould supports, casting the upper interacting layer of concrete. The reasons for not wholly completing the floor structures during prefabrication are the heavy transport, problems of tolerance and the fact that on-site casting shall often take place anyway. Despite these attempts, the use of prefabrication is still not very common. The main reason is still the weight and that the economic gains are of no significance. The decision process is mainly based on access to personnel having time for the task. Fully prefabricated concrete floor structures are not especially attractive for the same reasons. As disturbance from noise is a growing problem in residential areas, there is no acceptably good and sufficiently cheap solution with homogeneous floor structures as the solution of using almost homogeneous joints means more concrete.

A solution of double layers, i.e. a separate upper floor and a suspended false ceiling has revealed the possibility of reducing the amount of concrete and increasing the degree of prefabrication in floor structures. One such alternative is to utilise reinforced concrete beams or extruded steel beams of the types IPE or HEA profiles, either as carriers of different types of slab units or in direct interaction with a reinforced concrete slab cast on site or in a factory. This does not, however, lead to any significant reduction in the total amount of material used since the construction is still over dimensioned to be able to support its own weight and the respective material cannot be optimised with regard to the demands for loading and rigidity. Take, for example the case where a steel beam that because of its method of manufacture cannot be scaled down to the "correct" dimension, has such a good load-bearing ability and rigidity that its optimal c/c- measurement makes optimisation of the associated and interacting upper concrete slab impossible. One always comes to the conclusion that the amount of concrete or steel becomes substantially over-dimensioned. The same limitations apply to the essential hanging or suspended false ceiling that must be suspended or held separately on the beams with a relatively large c/c distance to suit the slab materials that form the false ceiling and that must also support themselves and deflections, which means that they cannot be too heavy so that they cannot be handled and therefore require relatively short c/c distances between the cross beams relative to the primary beams. This solution becomes too expensive as soon as one tries to apply it in housing and it occurs, therefore, mainly where there is a need for channelling in the false ceiling, often in offices, hotels, etc.

Thin sheet plate, with its superior capacity for shaping and its ability to be adapted to different sizes, is used on a small but increasing scale in combination with poured concrete. It is then used as the so-called interacting plate to create the casting mould and simplify reinforcement, and it can be moulded together with the concrete. This is, however, not a prefabricated solution but is suitably carried out on site. Even in this case, a separate bolting and assembly of the false ceiling is needed and the reduction of concrete is limited by sheet profile occupying space for the concrete. It should be noted that the concrete is only used to advantage in the area of a floor structure under pressure and it is therefore an expensive and unnecessarily heavy material for stiffening the steel in the tension zone.

Lightweight beams in thin plate, C or Z profiles, are not suitable due to the large forces that are to be accommodated and the known weakness of these beams with the risk that they will buckle and deform. It is mainly the asymmetric shape of the beams that thus limits their use, among other things because of buckling, and that the bearing forces are so great that significant and complex problems arise to prevent deformation in the bearing. The current invention solves these problems and, in association with EPO- 95923633.2, also achieves a fixing point and interaction according to the invention that further strengthens the possibilities of the product.

With the aid of the invention, the problem of the previous known lightweight beams of I-shaped thin plate profiles and a light prefabricated floor structure in concrete with beams in thin plate have been solved in a way that is evident from the characteristics sections of the claims. The invention will be described in greater detail in the form of examples with reference to the drawings, where Figs. 1 and 2 show schematically known techniques with the use of a Z and C profile respectively joined with a heat insulating slab, for example, Fig. 3 shows schematically the principle of a known I-beam in perspective, Figs. 4 and 5 show schematically a detail of the invention from the side and longitudinal cross-section respectively, Fig. 6 shows schematically a corner joint for lightweight beams according to the invention, Fig. 7 shows schematically a corner joint in a spread out state, Figs. 8 and 9 show schematically an end connection for a lightweight beam according to the invention in section and perspective respectively, Fig. 10 shows schematically an angled connection between two lightweight beams according to the invention, Fig. 11 shows a section through part of the angled connection shown in Fig. 10, Fig. 12 shows another form of a corner joint between two lightweight beams according to the invention, Fig. 13 shows a section through a T-joint of lightweight beams according to the invention, Fig. 14 shows schematically a rafter built with the aid of the lightweight beans included in the invention, Fig. 15 shows a further example of the use of the invention, Fig. 16 shows schematically another form of the lightweight beams according to the invention in perspective, Figs. 17 and 18 show schematically a detail of this I-beam from the side and in longitudinal cross- section respectively, Fig. 19 shows an alternative form of invention, Figs. 20 to 23 show alternative forms of the profile as well as this applied for casting columns in accordance with EPO 95923633.2, Fig. 24 shows schematically a floor frame structure according to the invention, Figs. 25 and 26 show schematically applications of the invention from the short and long sides, Figs. 27 and 28 show variations of the beam form and their use in the floor frame structure, Figs. 29 to 31 show alternative forms of the floor frame structure with loops in the floor and insulation against heat and/or sound, Fig. 32 shows a variation for stiffening the beam with insulation, Figs. 33 and 34 show the floor frame structure arranged respectively before and after pouring fixed in a wall beam in accordance with EPO 95923633.2, Fig. 35 shows an example of an assembly and suspension arrangement for a false ceiling in perspective, Figs. 36 and 37 show the false ceiling suspended from the floor frame structure across and along the beams, Figs. 38 to 41 show schematically alternative concrete slab structures for the upper floor or false ceiling in cross-section and Fig. 42 shows the use of these.

In brief, the current use of the known technique used today as treated in the introduction and shown in Figs. 1 and 2 will be described. Use of the lightweight beams, which are made of thin plate profiles of Z (Fig. 1) or C (Fig. 2) shapes respectively, leads to limitations due to their asymmetric shapes. Due to this, these beams 1, 2 can easily buckle and deform under loading. For example, when beams 1 , 2 are assembled with heat insulating slabs 3 as shown in Figs. 1 and 2, the groove in one of the slabs 3 that accommodates the flange must be made wider than necessary to facilitate assembly due to the asymmetry and weakness of the profiles and their imprecise shape. This leads to the risk of free play between the flange and the groove. In addition, the slabs 3 must be formed with a recess and a tongue because the slabs are not mechanically joined to one another with the aid of the plate profiles 1 and 2. The element that is built up must also be projected and planned very carefully since the asymmetry means that a special design is needed at transitions to windows, doors, joins and corners.

As is shown schematically in Fig. 3, a known steel profile is made of thin plate, which is folded from a thin plate strip so that both flanges 5 ^' are formed of double plates while the mid-section 6 ' consists of a single plate. This folding is clearly evident from Fig. 3. The profile is generally designated 4 '. To improve their static properties, the flanges 5 ' formed from double plates are firmly joined to one another, for example by riveting, (indicated by 7 ') or by means of soldering, welding, etc. This joining is, however, not always necessary.

According to the invention, the mid-section 6 of such a profile 4 is provided with stiffening local indentations 8 that are shown more clearly in Figs. 4 and 5. The indentations 8 have essentially elongated parallelogram shapes with their longitudinal direction transverse to the longitudinal direction of the beam and, as is evident from Fig. 4, are arranged to alternate in different directions. The stiffening effect of the indentations 8 can be further improved by arranging the indentations 8 so that they are made to a predetermined depth, after which they are pressed back out again to a final shallower depth of indentation. Refer to that documented in Swedish claim 469 968, patent no. 9200854-9 regarding the indentations. It should be understood that the indentations can deviate from the parallelogram shape, e.g. be triangular and can naturally also be made from only one direction.

Fig. 6 shows how two profiles can be assembled next to each another, in this case at a 90° angle relative to one another. The assembly takes place with the aid of a corner plate 9 that is folded so that the respective I-beams 4 can slide in on four lips, 10 respective 11 , that fit between the double plates of the flanges , which for this purpose are separated somewhat from one another. Fig. 7 shows the corner section 9 in a spread out state. Assuming that the plate section designated 12 shall form the "roof" of the folded corner plate 9 according to Fig. 6 and that plate section 13 forms the "forward facing" side of the folded corner plate 9 according to Fig. 6, a person skilled in the art should be able to see how the final folded corner plate 9 is achieved. To facilitate the introduction of the lips 10 respective 11 between the plates of the flanges, the lips are suitably somewhat bevelled, which is indicated by 14. Figs 8 and 9 show an end fitting 15 for an I-beam according to the invention.

This fitting is folded from thin plate to a cross-sectional "T-shape" with lips 16 extending on the sides. The length of the lips 16 is essentially equal to the height of the mid-section 17 of the "T". End fitting 15 is mounted on the end of an I-beam according to the invention so that the plate lips 18 that form the mid-section 17 are placed on each side of the mid-section 6 of the I-beam while the lips 16 are inserted in between both plates of the beam flanges 5 in the same way as that mentioned in connection with corner plate 9 according to Figs. 6 and 7. To lock the end fitting 15 to the I-beam, the example shown uses a screw that is screwed through both mid-section plates 18 and the mid-section 6 of beam 4. (Fig. 8). A screw joint of the type shown in connection with Fig. 11 where it is designated 22 can naturally also be used.

Fig. 10 shows how a beam 4 is attached to another beam 4 ^' " at a specified angle where 6 also lies in the same plane. Attachment of the beams to one another takes place with the aid of two angled plates 18 that are mirror images of one another (only one is seen in Fig. 10). The respective angled plates consist of two flat plate sections 19 with a width equivalent to the mid-section of beam 4 ' ' and with an angle to one another that matches the intended angle of mounting for the I beams. The two plate sections 19 are jointed to one another via an upwardly extending bridging plate 20 that bridges and grips one flange of the intact beam 4 " , as is clearly evident from Fig. 10. The connecting I- beam 4 is cut to the intended angle. The flat plate sections 19 of the angled plate 18 are also provided with upwardly extending deflections 21 that abut the insides of the respective flanges 5 of the I-beam 4. As is evident from Fig. 10, the flat plate section 19 located in profile 4 ' As provided with only one deflection 21 because the connecting plate bridge 20 is used for the same purpose, to guide the angle plate 18 in beam 4 " . Screw fitting 22 locks the respective angled plate 18 to the respective beam 4, 4 " . The respective screw fitting 22 consists of a screw with a nut 23 and two washers 24. To better distribute the loading shearing stress appearing in the beams, which would affect the screws, the mid section 6, the flat plate sections 19 of the angled plates 18 as well as the washers 24 are, as is shown in Fig. 11, all provided with a uniform relief of indentation (elevation) with a circular form in relation to the axis of the screw, whereby the shearing forces are distributed over a larger area.

Fig. 12 shows a corner connection between two beams according to the invention with the mid-section 6 in the same plane. The beams 4 are bevelled as wanted, depending on the intended angle between the beams. An angled plate fitting 25 is put in position on either side of the mid-section 6 of the beams. The angled plate fitting 25 is angle-shaped with its edges 26 folded upwards, in principle with the same function as the angled plates 18 according to Figs. 10 and 11. The angled shape of the angled plate fitting 25 is the angle intended between beams 4. In the same way as the design according to Figs. 10 and 11, the angled plate fittings 25 positioned on either side of the beam mid- section 6 are held together with the aid of a screw fitting 22, which is designed in the same way as shown in Fig. 11.

That presented so far has described an I-beam of thin plate with a symmetric form. Those skilled in the art will naturally realise that the flanges need not necessarily run at right angles to the mid-section of the beam, and that all flanges need not necessarily have the same width.

Fig. 13 shows a T-connection between two lightweight beams according to the invention. One lightweight beam is standing with its short end above the other lightweight beam. The beams are joined to one another by means of an angled fitting 26 of thin plate. Respective angled fittings 26 consist of two folded sections at 90° to one another, each of which has a flat plate section 27 and two side sections or deflections 28 angled outwards from this, whereby the flat plate sections 27 are so wide that the deflections connect with the inside of the flanges of I-beam 4. Two such angled fittings 26 are arranged with two of their flat plate sections 27 on either side of the mid-section 6 of the meeting I-beam 4. The other plate sections 27 of the angled fittings 26 abut the mid- section 6 of the intact I-beam. As indicated in the figure, the angled fitting 26 has been pressed and the deflections 28 have not been provided with any cut-outs, which thus causes the deflections 28 to fold, as indicated on the drawing by 29. In a way similar to that shown in Fig. 11, angled fitting 26 is attached to the I-beams 4 with the aid of a bolted joint and washers 23 and 24.

Figure 14 illustrates just one example of the use of the I-beam according to the invention to construct a rafter. The use of the different fittings is evident with sufficient clarity. As is indicated by the dashed lines in Fig. 13, a second I-beam 4 can naturally meet at the other side and be attached with an angled fitting 26 in the same way as described.

Fig. 15 shows a further example of the use of the I-beam according to the invention, here to solve the problem that was described in connection with Figs. 1 and 2. Even if the groove 32 in slabs 30, 31, for example insulating cellular plastic slabs, can be made with a narrow tolerance due to the design of the I-beam and the flanges 5 of the profile lock into grove 32, it can in some cases still be suitable to use glue for locking the flanges. The I-beam according to the invention thus has uses constructing building walls such as described in Swedish patent 9200889-5, to which reference is made. Through the invention, a lightweight beam has been achieved in the from of an I-shaped steel profile whose folded flanges are smooth and lack sharp cutting edges. The beam according to the invention is about 18% lighter than an equivalent C or Z- shaped beam but can carry more than 15% greater loading than the known beams. The deflection of the beam according to the invention is less rhan that of known beams and its sideways deformation is insignificant, whereas the deformation of C or Z-shaped beams is of necessity large due to their asymmetric profiles.

A beam according to the invention eliminates the problems that are associated with known solutions. As the flanges of the beam according to the invention consist of double plates and are thus effectively stiffened, the load bearing ability of the beam becomes very much dependent on the height of the mid-section. During assembly of the I- beam according to the invention equivalent to that discussed in Figs. 1 and 2, however, stiffening of the beam is automatically obtained in that a large part of this is bedded between the slabs. At the same time, a mechanical strengthening of both slabs is obtained at the sceel profile, whose flanges are thick (double plate thickness), and lack sharp cutting dgos and have good relative tolerances, which allows a better fit to the width of the groove in the slabs.

The invention, which is also shown schematically as another embodiment in Fig. 16, consists of a steel profile of thin plate generally designated 101 that is folded from a strip of thin plate so that both flanges 102 are formed from double plates while mid- section 103 consists of a single plate. This folding is clearly evident from Fig. 16. To improve their static properties, the flanges formed from the double plates are firmly joined to one another by punched holes 104 extending through both plates. The mid-section 103 of the profile 101 is provided with stiffening openings 105 that are shown more closely in Figs. 17 and 18. Stiffening openings 105 can be executed in different shapes with the aim of creating the maximum openings but with no or minimum reduction in the static properties of the beam. Fig. 18 shows how the openings 105 are formed with stiffening folded-out section suitably arranged alternately in different directions in relation to the plane of the mid-section to maintain symmetry in the beam, since the symmetry is of great significance for the load bearing ability of the beam, but above all for its stiffness and safety with regard to buckling- With regard to the installation of floor structures, for example, it is a significant advantage and sometimes quite essential that the mid-section of the beam is open. Fig. 19 shows that the interaction and bracing of the two plates in the flange 102 can also take place by a fold-down 106 of one of the flange plates against the mid-section and by executing hole punches 104 through this fold-down 106 and the mid- section 103. This stiffens the flanges and counteracts unwanted movement, which is of great significance for the special design and use of the beam as a casting profile at the ends of the wall elements used according to patent EPO 93908216.0 and EPO 95923633.2. Fig. 20 shows a special design of the casting profile with the increased resistance to bending against forces F provided by the double plates and the locking by means of hole punches 104 in mid-section 103 and folds 106. Fig. 21 shows hole punches 108 in the flanges that allow the profile to be used in connection with the concrete poured later 109 (Fig. 23) in the moulds used to form the columns that consist of profiles 101 that have been brought together according to Fig. 22 in accordance with the EPO patent referred to above. Fig. 23 shows moulds used to form columns that, depending on the requirement and form of the column, consist of several I-beams with poured concrete 109, as well as a prefabricated reinforcement cage 110' , depending on need. The beams included in the column can have angled flanges as indicated in the figure. The floor frame structure according to the invention that is shown schematically in Fig. 24 consists of I-profiles 101 in thin plate whose upper flanges 102 are joined together with the concrete to form a stiff slab 109 that is reinforced with a steel net 110. To improve the static properties, the upper flanges 102 can be permanently attached with the steel net 110, for example by welding 111.

Fig. 25 shows the invention across beams 101 and reinforcement 110 plus the concrete slab 109 formed following pouring. The pouring can take place with the concrete slab uppermost as in Fig. 24 in a suitable form or reversed with the concrete slab below. The whole floor frame structure is then turned prior to assembly. It is also possible to use other reinforcement such as fibres, and that the interaction is created by the design of the flanges, punched or barbed flanges and/or concrete with high adhesion.

Fig. 26 shows the floor frame structure according to Fig. 25 from the side with punched holes 105 that strengthen the mid-section at the same time as they fulfil a static function in that being corbelled out, they create an open floor structure that facilitates subsequent installation and ventilation. Fig. 27 shows a variation of the profile where the upper flange 112 is reduced (or eliminated). To avoid welding beams and the steel net together, one can simply design the upper flange 112 with interacting barbs or recesses where the concrete and steel are locked together by interacting with one another. Fig. 28 shows this profile in the floor structure where the concrete 109 and the reinforcement take up the pressure forces and, due to interaction with the I-beam, the flange of the I-beam can therefore be significantly reduced. Openings 105 and the fold against mid-section 103 that stabilise the construction with increased moment can also be seen clearly from the drawings. The risk of collapse and buckling that exists just because of the weight and movement of the concrete, and that is obviously even greater during loading, would be great if it were not for these folds affecting and increasing the stabilising moment. The effect is achieved due to the symmetry being maintained.

Fig. 29 shows where the heating and cooling loops 113 have been laid to function in the concrete layer, while insulation 114 works to prevent the loss of energy in a downwards direction. As the concrete slab is wanted to be as thin as possible, there is a risk that the tendency to oscillate increases.

Fig. 30 shows a well known way to compensate for this by using a sound- absorbing soft mineral of glass-fibre wool or similar insulation 115 that has here been fitted to the lower flanges 2. A new way to arrange a simple composite floor structure where the sound insulation 116 simultaneously constitutes the false ceiling is shown in Fig. 31. The insulation comprises rigid boards with good sound absorption, e.g. concrete bound wood chip boards. Note that the broad recesses in the slabs mean that they can hang free and flexibly on the flanges, possibly lying on an elastic underlay such as soft silicone or similar and thereby separated from the oscillations of the beam. As the said boards are relatively open, they generally need to be sealed from below. This can take place by putting in place a lower board or alternatively boards finished in plaster or concrete, or with a cast or sprayed surface. An additional solution is accomplished with reference to the method described below according to Figs. 38-41. Fig. 32 similarly shows a rigid insulating slab 114 that like before is easily fitted to the beams where it eliminates thermal bridges and stiffens the beams. With the slab cast in concrete 109, one can thus create the prerequisites for a clearly effective outer roof or foundation plate. The roof has a proper air space, which means that it can be classed as a so-called cold roof that to a person skilled in the art is increasingly evident as the safest solution for keeping the roof construction dry and functional from an insulation point of view. Naturally, a false ceiling board in plaster, concrete or similar can also be considered necessary, just as the insulation board can comprise different sufficiently rigid board materials to fulfil the functions required.

It should be realised that the examples shown in Figs. 29-32 can also be applied to walls.

Fig. 33 shows the floor structure pre-mounted on an outer wall according to EPO 95923633.2. The end of the I-beam 1 to be held up rests in a delineated, beam- forming cavity 117, formed between the raised slab 118 of the outer wall and the end of the from 119 in the floor structure. When the concrete beam 120 is pored according to Fig. 34, a fully cast join over the resting end of the I-beams is achieved and the normal load-restricting and tilt-sensitive I-beam is lightened and thus stiffened. An advantage of using I-profiles of thin plate is that the c/c distance is limited so that the fitting and suspension of the false ceiling board can be accomplished without separate bolting. Fig. 35 shows a fitting 121 for attaching false ceiling boards in the loading I-profiles of the prefabricated floor structure. The respective fittings are designed so that when the fitting is attached in the prefabricated false ceiling, the flanges 122 can snap in and attach to the floor structure. The size of the flanges is such that the false ceiling is hung in a suspended manner. Figs. 36 and 37 show a complete prefabricated floor structure in cross-section and longitudinally respectively in an alternative embodiment with an false ceiling 123 of double plasterboards glued together to achieve great stiffness and reduced deflection downwards, where the suspending fittings 121 are attached in the lower flanges of the beams 1 to give a flexible suspension of the boards.

The person skilled in the art knows that a major problem when prefabricating concrete elements is that the concrete shrinks when it sets. Large forces arise, which makes production that places demands on narrow tolerances difficult. High quality industrial construction requires small, preferably marked joins and a simple system of assembly without disrupting deviations in tolerances. One aspect of the present invention is to eliminate this problem. It is known that by means of a thin cement mixture, polymer material or similar, it is possible to "glue" together different types of ballast material such as fired clay pellets, stones or wood chip by coating these with the mixture and letting it harden in a mould to thus form a block or slab with pockets of air. This technique has the advantage that the block does not shrink as the cement or polymer is thin and on located the surface and the ballast particles that abut one another eliminate shrinkage. Ballast material 124 in Fig. 38 is merely glued together to a light and airy "skeleton" with an outer layer of cement 125 or similar, Fig. 39. The cement/water mixture can be pigmented. When excess material is used, either for gluing the skeleton or after this has been accomplished, the mixture that naturally covers the ballast can run down into the bottom 125 ' of the mould (Fig. 39) so that it forms a durable, water-tight, resistant, coloured and smoothable upper surface when the floor structure is finally taken from the mould and turned upside down. In many cases, this surface can be accepted as the final coating. When cement is used, a modified cement mixture that both glues effectively and that has good buoyancy characteristics is needed. The strength of the bound together ballast will be limited, but one does accomplish a homogeneous body or skeleton. In some cases, this skeleton can be used directly, the cemented wood-chip board, for example, but it is also possible to carry out an additional casting that then takes place wholly without shrinkage. When the skeleton has been cast and set, it can be filled with a suitable composite and buoyant cement mixture 126 or similar. When this hardens, there is no shrinkage. Instead, the filled "skeleton" acts to distribute the natural shrinkage of the mixture over the whole volume and in all the small cavities contributed by the skeleton, while the block as a whole retains its size. The construction of the floor frame structure according to the invention is evident from Fig. 42.

Note that the castings according to this method can be used to create a suitable upper floor structure or false ceiling, and similarly that the casting can take place in moulds that face up or down or that are at right angles. The amount of filling in both the first and the second casting can vary. When the slab is used as a upper floor structure 109, the ballast material 124 suitably comprises a sorted and clean fraction of crushed stone, while the ballast in the false ceiling suitably comprises fired clay pellets, wood chips or similar that can contribute to good insulation and fire prevention characteristics. Even other mixmres 126, for example, such as foam concrete, fine sand or other material can be used. Filling out with foam concrete in the said skeleton is utilised primarily when the loading is not so great and when resistance to fire is more important than the resistance to pressure, for example when one wants to manufacture a layer that is to constitute a false ceiling. Fig. 41 shows a variation with several different layers of filling in the skeleton, for example, concrete mixture 126, plus 127 and a new concrete layer 126, i.e. a special type of sandwich with good capabilities to dampen vibration. If one wants an outer layer other than that created by excess cement mix 126 and at the same time avoid having to cast against a mould, the final outer coating in both the false ceiling and the upper floor can constitute a mould bottom 128 that forms part of the finished construction. The above method of casting can be utilised to achieve a very narrow level of tolerance in a floor structure according to the invention with a false ceiling and a high "ready-to-use" level, see Fig. 42 in which a floor structure with a false ceiling 130 and an upper floor 109 cast according to the method above with a "finished" floor layer and good resistance to pressure and with a "free" suspended false ceiling of suitable rigidity, weight and fire resistance. The false ceiling can also consist of the solution described in Fig. 31, suitably filled with a mix 126 of cement or foam concrete, Finally the floor structure can be executed with regard taken to guiding all factors of importance for the function of the floor structure, meaning that static, sound and fire prevention demands are solved with a minimum use of materials, and with optimised and integrated thermodynamic functions for warming and cooling, a maximum level of prefabrication "ready-to-use" and with an economically advantageous result. The said mixture 126 can comprise different compositions of cement/water, foam concrete, etc. This means of casting prefabricated concrete slabs can be used in many different connections with the advantage that the slabs can be made thin and free of shrinkage.

As is evident from Fig. 25, one can vary the thickness of the slab 109 and the distance between the beams 101 to reduce the oscillations of the beam and interfere with the factors that transport sound. The transport of sound and absorption can be improved by the skeleton in slabs 109 and 130 (Fig. 42) not being completely filled out but being left open with cavities in the skeleton that can absorb sound waves. Loops 113 are positioned in the upper slab 109 to direct heat emission upwards whereas loops 113 ^' for cooling are suitably positioned in the lower slab where they can act in a downwards direction. Foam concrete is the most suitable filing 126 of the skeleton in slab 130 as it insulates between the planes at the same time as it provides slab 130 with a very good fire protection. That described above can provide optimised warming and cooling by having heating loops in the upper floor structure and cooling loops in the lower floor structure in a prefabricated, flexible suspended ceiling. Heating works best from below and cooling best from above. The suspended ceiling can (like the floor above it) only be partially filled to create the ability to absorb sound waves in both layers and thereby eliminate the need for further material for absorption. Normal insulation that also serves as insulation of heat transport between different planes can also be used. The ballast of the lower ceiling can be insulating (fired clay pellets) and/or the filling (26) can be insulating and at the same time have a very high degree of fire protection (foam concrete).

Claims

1. I-beam of thin sheet plate folded so that the flanges (102) of the beam (101) consist of two layers of plate laid on one another and that the mid-section (103) of the beam consists of a single layer of plate characterised in that the two layers of plate that are laid on one another in the flange are firmly attached to one another by means of holes (104) punched through both plates.

2. I-beam of thin sheet plate folded so that the flanges (102) of the beam (101) consist of two layers of plate laid on one another and that the mid-section (103) of the beam consists of a single layer of plate characterised in that the inner plate layer that faces the mid-section is folded so that one part (106) abuts the mid-section and that the said parts (106) of the flanges (102) are firmly attached to one another by means of holes (104) punched through both plates.

3. I-beam characterised in that the mid-section (103) is provided with a number of indentations (105) in alternating directions in which openings are arranged along the mid-section.

4. I-beam according to any of claims 1-3 characterised in that it is provided with an end unit (9, 15) that is provided with two lips (10, 11, 16) inserted between the two plate sheets of the flanges (5).

5. I-beam according to claim 4characterised in that the end unit (9) is provided with two pairs of lips (10, 11) arranged at an angle in relation to one another.

6. I-beam according to any of claims 1-3 characterised in that the end unit (15) includes two lips (16) as well as two plates (18) extending between them, where the lips (16) and plates (18) are joined to an end plate that forms an I-beam and that the plates (18) are arranged on either side of the mid-section (6) of the beam.

7. I-beam according to any of claims 1-3 characterised in that it is provided with a joint fitting in the form of two plates (18, 25) joined with one another at an angle for joining to another beam and where these plates are arranged on either side of the beam and abut with their mid-sections and have a width that is equivalent to the width of the mid-section (6) of the beam and with edges (21,26) that are folded-up against the flanges of the beam.

8. I-beam according to claim 7characterised in that the attachment between the plates (18) consists of a plate section (20) that bridges over the half flange (5) of one of the beams (4 ').

9. I-beam according to any of claims 7or8characterised in that the joining fittings are joined to the I-beams and one another with the aid of a screw fitting

(22).

10. Use of an I-beam (4) of thin plate whose flanges (5) consist of two layers of plate laid on one another and where the mid-section (6) of the beam consists of a single layer in a construction section comprising at least two slabs (30, 31) edge to edge, whereby one or both flange sections of the I-beam (4) are inserted into a longitudinal groove (32) in the edges that meet one another.

11. Use of an I-beam according to claim 10 characterised in that the said first flange section is glued in the longitudinal groove in the edge of the slab.

12. Use of an I-beam of thin plate for manufacturing a concrete column characterised in that at least two beams are pressed together each with two flange edges meeting one another and that the space enclosed by the beams is filled with concrete (Figs.22, 23).

13. Use of an I-beam of thin plate for manufacturing a floor frame structure characterised in that concrete is poured around one pair of flanges of the beams, and that as so reinforced, they form the slab (109) of the floor frame structure (Figs.24- ^• 26).

14. Use according to claim 5characterised in that the reinforcement is firmly attached (111) to the upper flanges (Fig.24).

15. Use according to claims 5or6characterised in that heating and/or cooling loops (113) are incorporated into the concrete slab and that insulation is arranged under the concrete slab (114).

16. Use of an I-beam of thin plate characterised in that the slab (109) of the floor structure is formed from bodies of ballast material (124) that have been joined to one another in a mould by means of a thermosetting adhesive (125) and allowed to set.

17. Use of an I-beam of thin plate characterised in that parts that partition the I-beams that are included in the floor structure have their ends extending outwards from the concrete slab and resting in a cavity (117) in an outer wall or equivalent (118), which is completely filled with poured concrete.

18. Use of an I-beam of thin plate according to claim 16 characterised in that the set ballast material is wholly or partly filled out with thermosetting adhesive.

19. Use of an I-beam of thin plate characterised in that the slab (109) of the floor structure is formed from bodies of ballast material (124) that have been joined to one another in a mould by means of a thermosetting adhesive (125), whereby excess adhesive is allowed to run down and cover the bottom of the mould for forming the outer layer of the slab.

20. Use of an I-beam of thin plate characterised in that the lower flanges of the beam form the means of supporting suspendable false ceiling slabs (123) by means of fittings (121).