PREFABRICATED SURFACE ELEMENT OF COMPOSITE TYPE

Abstract: A prefabricated surface element of composite type (1) for use in the building industry, as load-bearing frame, framing of joists, roof-trusses, roofs, balconies, light bridge constructions, etc., or for walls as facade elements for dwellings, industrial and agricultural buildings and as support elements in pool and silo buildings. The surface element comprises a slab (2) of reinforced cast concrete forming the upper surface (3) of the element, thin sheet-metal sections (4) running longitudinally and partially embedded in the lower part of the slab, reinforced cast concrete beams (5, 6) arranged transversely at the short ends of the slab, and one or more reinforced cast concrete beams (7, 8) arranged between the two short-end beams (5, 6). The concrete is preferably of light-ballast type.

Description: Prefabricated surface element of composite type The present invention relates to a prefabricated surface element of composite type for use in the building industry, for instance as framing of joists, in walls, ceilings and rooves. Prefabricated building elements are being used to an ever increasing extent in the building sector and a number of different types are available. The joist framing elements used are of light concrete or are made up of thin concrete layers combined with lengths of wood. One of the draw¬ backs of these knownelements, however, is that they have limited free-bearing capacity and are themselves relati- vely heavy. Other drawbacks of known elements of this type are that they complicate the installation of electricity and plumbing facilities, and to a certain extent limit the choice of -material for the load-bearing construction above a joist framing of this type. Prefabricated joist-framing elements made entirely of wood are also available. However, these are used almost exclusively by the manufacturers of prefabricated timber houses. The object of the present invention is to provide an element with as much flexibility as possible, βombined with low weight. This is achieved by the surface element according to the present invention, which is characterized by a slab of reinforced cast concrete forming the load-distributing O and protective surface of the element, thin sheet- metal sections running longitudinally and partially embedded in the rear of the slab, reinforced cast concrete beams arranged transversely at the short ends of the slab, and one or more reinforced cast concrete beam(s) arranged between the two short-end beams. According to a preferred embodiment of the invention the slab and the cast beams are made of light-ballast concrete. The thin sheetsmetal sections constitute the primary units for absorbing bending stress, the cast short-end beams cons itue the primary supports and the cast intermediate beams constitute the primary connecting units of the surface element. The intermediate beams also provide the internal re- inforcement necessary and can even act as intermediate supports if the surface elements are placed on more than two supports. The thickness of the slab should be preferably between 20 and 100 mm and the ballast may consist of Leca v^ (aerated clay balls) , for instance. The slab and the cast beams may be reinforced. -If more than two supports are used, reinforcement again -?-st bending r may be provided as well as reinforcing netting, which is usually sufficient. According to another preferred embodiment of the invention the reinforcement of the transverse beams extends un- broken from one long side to the other and thus runs throug apertures punched in the thin sheet-metal sections. "BUREAU _0MPI This design thus makes the intermediate transverse beams free-bearing over relatively long spans, with the result that the elements are more rigid, i.e. less prone to bending and that when the surface element is used as framing placed on more than two supports, the intermediate supports may consist of pillars. The distance between pillars may then be up to about 4 meters. Examples of constructions for which the surface elements can be used are load-bearing frames, framing of joists, roof-trusses, rooves, balconies, light bridge construc¬ tions, etc., or for walls as facade elements for dwellings, industrial and agricultural buildings and as support elements in pool and silo buildings. The surface element according to the present invention has several advantages. Its load-bearing capacity is considerable and its free-bearing span is extensive in relation to its weight. With a dead weight of ca 0.7 - 0.9 kN/m 2 and a useful load of 1.5 kN/m2, spans of up to at least 8.4 m are possible, i.e. the width of a normal private house. The surface elements according to the invention are extremely flexible and one and the same element which can manage large free spans can also be placed as a continuous beam on several supports or act as a canti¬ lever for a balcony or bridge, for instance. Ά The same element which can take up vertical lo^ds in a joist framing, for instance, can be used as 'facade element in an industrial hall, for instance, thus enabling the elements to reach to considerable heights. The main limitations here are dictated by transportation of the elements, but heights of 12-15 m are possible. If the surface elements are used as joist framing on more than two supports, i.e. as a continuous beam, the central supports may consist of pillars spaced about 4 m apart, since the intermediate transverse beams of the surface element can be made free-bearing over relatively large spans. When using the surface element according to the inven¬ tion as joist framing in private houses, for instance, the following advantages are obtained: The shape and design of the element permit wind-tight connection to outside wall and present no limitations in the choice of material for structural walls outside the joist framing. Thanks to the design of the sheet-metal sections, considerable freedom is possible with respect to electri¬ cal and plumbing installations. Furthermore, there is little curve in relation to the free span and the element is also practical to handle since it can be cut, sawn, nailed or screwed. Additional features of the invention are revealed in the following claims. The invention will be described in more detail with reference to the accompanying drawings showing one embodiment of the invention, in which Figure 1 shows a perspective view of a surface element according to the invention, and '. Figure 2 shows a cross section taken along 'the line II-II in Figure 1. In Figure 1 the surface element according to the invention is designated 1. A cast slab 2 forms the upper surface 3 of the element. Longitudinal thin shee metal sections 4 0MP1 extend along the entire length of the surface element and are cast at the ends into transverse cast beams 5,6 of concrete. Between the transverse beams at the short ends of the surface element are additional transverse beams 7,8, also of concrete. Figure 2 shows a cross section of the surface element according to the invention, taken along the line II-II in Figure 1. It can be seen here that the slab 2 is reinforced, preferably with reinforcing netting 9. The transverse beams 5-8 are also reinforced. To achieve maximum strength in the cast transverse beams, the re¬ inforcing is preferably unbroken from one long side of the element to the other and thus runs through apertures punched in the thin sheet-metal sections. The longitudinal sections consist of thin sheet-metal sections 4a, 4d. In the embodiment shown they are provided with a waist 10 having a lattice-like construc- tion. The free edge of the section is provided with a U-shaped edge-stiffener 11 and its embedded edge is bent over having apertures to enable cooperation between concrete and sheet-metal. The metal in the struts forming the lattice in the sections is folded out 12a-d, providing • additional rigidity. As mentioned in the introduction, according to a preferred embodiment of the invention, both slab and cross-beams are cast in light-ballast concrete. The slab aήd beams are reinforced, as is also mentioned above, suitably with 4 mm reinforcing netting. The density of the light-ballast concrete is about 2 800-1100 kg/m , corresponding to twice the density of wood but less than half the density of ordinary concrete. This means that the surface element according to the invention has a dead weight as low as ca 0.70 - 2 0.90 kN/m and the free-bearing length can be as long 2 as 8.4 m with a useful load of 1.5 kN/m , i.e. that required according to building standards for joist framing in private houses. This must be compared with a similar element made of conventional concrete, which would have a dead weight exceeding the useful load. The slab 2 thus forms the upper surface 3 of the element distributing the useful load and taking up stresses from the bending torque. The longitudinal thin sheet-metal sections take up bending and shearing stresses while the transverse beams between the short- end beams contribute by providing internal rigidity in individual elements as well as enabling several elements to be joined in a manner enabling these intermediate beams to take up a certain amount of torque. The transverse intermediate beams are also of great help in handling the element, for instance when turning and lifting it. The beams cast at the short ends of the element have several different functions of significance to the invention. These beams hold the construction together and rest on supports which, as mentioned, may ^consist of the parallel, longitudinal walls of a dwelling. Since the sheet-metal sections have been cast ,into these transverse beams at the short ends, they can brace the sheet-metal sections at the same time as sealing against the support and edge covering. They also form the supports for the structural walls in the floor about the joist framing where the surface element is being used as framing for joists. All the advantages described above are achieved with a slab thickness of 30-60 mm, at the same time offering an element having minimum weight. When manufacturing surface elements according to the invention, the concrete slab and the two short-end beams and transverse beams of concrete are cast together with the thin sheet-metal sections in a manner ensuring full cooperating between the concrete and the thin sheet- metal sections. If the surface element is to be used as a joist framing element, the thin sheet-metal sections can be pre-stressed according to one embodiment of the invention so that they exert a constant bending stress on the finished element. To position and space the thin sheet-metal sections in the casting mould in which the element is manufactured with the upper side facing down, the longitudinal edge of the sections which is to be embedded is provided with attachment elements, at least one at each end. These elements can then also be used to lift the finished surface elements. The intermediate transverse concrete beams are provided at both ends with embedded attachment elements^ ' which are used for joining adjacent elements when assembling the finished surface elements according to the invention. The cast concrete slab may also be provided at the manufacturing stage with a system for absorbing and emitting thermal energy. The finished surface element OMPI may also be provided with thermal and/or sound insulation in the space between the sheet-metal sections. The invention is of course not limited to the embodiments described above and the various design details can be modified in many ways. One embodiment of the thin sheet-metal sections is shown in the drawings by way of example. It should, however, be noted that the pattern is punched out for the purpose of achieving the lowest possible dead weight and material consumption, and also to offer the greatest freedom in installation. However, in some cases it may be expedient to use a section with solid waist or with some other pattern. In the embodiment shown the free edge of the sections is provided with a U-shaped edge-stiffener 11. However, this is not absolutely necessary and the edge may be stiffened by means of a simple fold. The embedded longitudinal edge may also have a U-shaped edge-stiffener, but in the embodiment shown it consists of a simple fold with notches punched out to give the best cooperation between sheet-metal and concrete. The cross-section of the thin sheet-metal sections may also be varied. In this case a Z-section is preferred, but a U-section functions satisfactorily. OMPI

Claims: C l a i m s 1. Prefabricated surface element of composite type for use in the building industry, characterized by a slab (2) of reinforced cast concrete forming the load- distributing and protective surface (3) of the element, thin sheet-metal sections (4) running longitudinally and partially embedded in the rear of the slab, reinforced cast concrete beams (5,6) arranged transversely at the short ends of the slab, and one or more reinforced cast concrete beams (7,8) arranged between the two short- end beams (5,6). 2. Surface element according to claim 1, characterized in that the slab (2) and beams (5,6,7,8) are cast out of light-ballast concrete. 3. Surface element according to claim 1, characterized in that the cast concrete slab (2) is reinforced with reinforcing netting (9) . 4. Surface element according to claim 3, characterized in that besides the netting (9) to reinforce the slab against cracking, the slab is also provided with reinforce¬ ment against bending to enable it to withstand support torque at an intermediate support, if any. 5. Surface element according to claim 1, characterized in that a pattern is punched out in the waist lO) of the thin sheet-metal sections (4) and that the-free edge of each section has a U-shaped edge-stiffener .(11) . 6. Surface element according to claim 1, characterized in that the embedded edge of the section (4) is bent over and provided with a punched-out pattern to cooperate with the concrete. 7. Surface element according to claim 1, characterized in that the concrete slab (2) , the two short-end beams (5,6) and the transverse beams (7,8) of concrete are cast together with the thin sheet-metal sections (4) in a manner ensuring full cooperation between the concrete and the thin sheet-metal sections. 8. Surface element according to claim 1, characterized in that the longitudinal casting edge of the sections (4) to position and space the sections in the mould and to lift the finished elements is provided, before being placed in the mould, with at least one attachment element at each end. 9. Surface element according to claim 1, characterized in that the intermediate transverse beams (7,8) of concrete are provided at both ends"with embedded attachment elements to be used during assembly of the finished elements, to connect adjacent surface elements. 10. Surface element according to claim 1, characterized in that the reinforcement of the transverse beams (5,6, 7,8) is unbroken from one long side to the other long side of the element and runs through apertures punched in the thin sheet-metal sections (4) . 11. Surface element according to claim 1, characterized in that the cast concrete slab is provided with systems for absorbing and emitting thermal energy. 12. Surface element according to claim 1, characterized in that it is provided with thermal and sound insulation in the space between the thin sheet-metal sections.

Inventors: JOHANSSON JOHNNY, JOHANSSON, JOHNNY
Applicants: JOHANSSON JOHNNY, JOHANSSON, JOHNNY
Application year: 1983
Main classification: E04B5
IPC codes: E04B5