DE20011987U1 - Wood-concrete composite ceiling - Google Patents

Description

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Wood-concrete composite ceiling

The present innovation concerns a wood-concrete composite ceiling with spaced-apart wooden beams and a concrete element which is connected to the wooden beams.

Wood-concrete composite elements are becoming increasingly important in the construction of residential and commercial buildings, as they offer the possibility of building with natural materials on the one hand and achieving the required strength and fire resistance values on the other.

WO 94/11589 shows a wood-concrete composite floor in which the connection between wood beams and a concrete element is made by metal plates which are attached to the side surfaces of the wood beams. A problem with this known wood-concrete composite floor is that the load-bearing capacity is limited, since only a poor force transmission between the concrete element and the wood beams is established via the metal plates used. Transverse forces occurring in the connection plane between the wood beams and the concrete element can only be inadequately introduced into the wood beams by the metal plates, since they are arranged on the side surfaces of the wood beams and extend in the longitudinal direction of the wood beams.

From DE 198 18 525 A1, a wood-concrete composite element is known in which the wood component consists of a large number of boards joined together in a board stack construction. Composite webs are formed in which shear anchors are attached, which create the connection between the wood component and the concrete component. In general, such a

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Wood-concrete composite elements can also be used in ceiling construction. However, if the required load-bearing capacity is to be achieved, constructions are required in which the board stack element is relatively thick, so that a high overall material requirement is created. In order to be able to absorb the load-bearing forces, the board stack element must be placed along a support line, as individual boards cannot absorb the resulting forces.

The problem is also known in the state of the art that the metallic connecting elements between wood and concrete elements often do not meet fire protection requirements, since in the event of a fire they are immediately exposed to high temperatures and then quickly lose their strength.

There is therefore a need for a wood-concrete composite floor that can use wooden beams on the one hand, but also achieves a high load-bearing strength. In particular, an improved connection between the concrete element and the wooden beams is sought.

These and other tasks are solved by the present innovation, whereby several shear anchors are provided in the wood-concrete composite floor according to the innovation, which run transversely to the longitudinal direction in the wood beams, whereby a section of the shear anchors protruding from the wood beam is enclosed by the concrete element.

Due to its structural design, such a wood-concrete composite ceiling has the properties of a so-called π-ceiling, so that individual ceiling elements can also be assembled into a larger ceiling by being placed next to one another

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In order to take on load-bearing functions, it is sufficient that the wooden beams are placed at suitable bearing points, which can also be advantageous from the point of view of thermal insulation, since the concrete element itself is not placed on an external wall, for example.

An advantageous embodiment is characterized by the fact that the concrete element is only directly connected to the wooden beams on their upper side. The transverse forces that occur are still introduced via the transverse force anchors provided. However, this embodiment has the particular advantage that slight movements can take place between the wooden beam and the concrete element, for example if tensile stresses occur between these elements due to different expansion coefficients.

With conventional wood-concrete composite ceilings, such shifting movements are not possible, so that greater tension can lead to hairline cracks or breaks in the concrete element. Such phenomena are safely avoided thanks to the innovation. If particular importance is attached to this property under special installation conditions, a separating and sliding layer can be installed between the wood supports and the concrete element, for which purpose foils or gelatinous separating agents can be used.

In a modified version, the concrete element also surrounds the wooden beams in the upper areas of the side surfaces. This creates a more rigid connection between the concrete element and the wooden beams, which is particularly stable against lateral displacement forces.

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Various options for designing the shear anchors have proven to be advantageous. For example, flat metal profiles can be inserted into grooves on the top of the wooden beams, with these grooves running at an angle to the cross-section of the concrete element. When shear forces occur, the flat profiles wedge themselves into the grooves of the wooden beams, so that the shear forces can be absorbed particularly well. It is also possible to use angle profiles as shear anchors, with the angle profiles being attached to the wooden beams with additional fastening elements. It is also useful to use round steel dowels as shear anchors, which are inserted in the form of a rod dowel into fitting holes in the wooden beams.

In a modified embodiment, the concrete element has a steel reinforcement or steel reinforcement to increase its strength. The shear anchors are preferably integrated directly into this reinforcement. In this way, the forces acting on the shear anchors are distributed particularly well in the concrete element, so that there are no point-like stresses or damage to the concrete element.

A further modified version of the new wood-concrete composite ceiling uses shear anchors that are integral with the concrete element instead of metal shear anchors, with areas of the concrete element extending through recesses in the wood beams. Combinations are also possible, i.e. the shear anchors consist of metal elements, for example, which can be part of the reinforcement and are surrounded by a layer of concrete.

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Depending on the application, different materials can be used to manufacture the concrete element. For example, lightweight concrete can be used to reduce the dead mass of the wood-concrete composite floor, thereby reducing the loads acting on the wooden beams.

Further advantages, details and developments emerge from the following description of a preferred embodiment of the innovation, with reference to the drawings. They show:

Fig. 1 is a perspective view of a wood-concrete composite floor;

Fig. 2 is a sectional side view of the wood-concrete composite floor according to Fig. 1;

Fig. 3 is a sectional view of the wood-concrete composite floor from the front, seen along the section line IH-III in Fig. 2;

Fig. 4 is a perspective view of a wooden beam of the wood-concrete composite floor with a milled fitting pocket;

Fig. 5 shows a modified embodiment of a shear anchor;

Fig. 6 is a sectional view of a modified embodiment of the wood-concrete composite floor, similar to that shown in Fig. 3, wherein round steel dowels are used as shear anchors.

Fig. 1 shows a simplified perspective view of a wood-concrete composite ceiling 1, which essentially consists of a concrete element 2 and several wooden beams 3. The wood

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Concrete composite ceiling 1 is designed in the form of a so-called π ceiling or ribbed ceiling. Larger ceiling areas can be put together from individual elements, such as one shown in Fig. 1. The wood-concrete composite ceiling is supported at suitable support points, with only the wooden beams 3 being placed on top, while the concrete element 2 rests on these wooden beams. In order to achieve the load-bearing properties of a π ceiling, it is necessary that there is a firm connection between the wooden beams 3 and the concrete element 2. The absorption of compressive forces acting on the concrete element 2 from above is unproblematic, since these are easily transferred to the wooden beams 3. This is already ensured by the fact that the concrete element 2 rests flat on the top of the respective wooden beam 3. When forces are introduced, however, these ceiling elements also deform slightly, so that transverse forces can occur between the concrete element 2 and the wooden beams 3. According to the innovation, these transverse forces are to be absorbed by transverse force anchors and transferred to the wooden beams.

Fig. 2 shows the wood-concrete composite ceiling 1 in a side sectional view. It can be seen that several shear anchors 5 are arranged along the longitudinal extension of the wooden beam 3. In the embodiment shown here, the shear anchors 5 are designed as flat metal profiles that are inserted into the wooden beam 3 from above at an angle to the cross section. The shear anchors 5 are therefore also located at an angle to the cross section of the concrete element 2, and extend far enough into the concrete element to absorb the shear forces that occur. The wood-concrete composite ceiling 1 is supported by the wooden beams 3 resting on bearings 6.

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In Fig. 2 it is also apparent that it is expedient to adapt the inclination of the shear anchors 5 to the direction of the displacement forces that mainly occur. In the case of the wooden beams being supported at the respective ends, the shear anchors are arranged to the left of the vertical center line of the wood-concrete composite floor with a complementary inclination compared to the shear anchors to the right of this center line.

Fig. 3 shows the wood-concrete composite ceiling 1 in a sectional view from the front. To increase the strength and to absorb and distribute (internal) tensile stresses, reinforcements 7 (e.g. mesh reinforcements) are arranged in the concrete element 2. A flat steel is used here as the shear anchor 5, which extends into both the wooden beam 3 and the concrete element 2. The shear anchors 5 can also be made from other materials and have different shapes that are suitable for introducing shear forces into the wooden beams 3. Preferably, metallic shear anchors are used. However, it is also conceivable to manufacture the shear anchors from particularly resilient plastics or from suitable material combinations (e.g. plastic with fiber reinforcement).

Fig. 4 shows a perspective view of a section of the wooden beam 3. To accommodate the shear anchors, grooves 8 or other suitable recesses are provided in the upper area of the wooden beam 3. In the example shown, these are milled fitting pockets into which the shear anchors are later inserted in a force-locking manner. Due to the inclined position of the fitting pockets 8, the shear anchors wedge themselves into the

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Wooden beams 3, so that there is no danger of the shear anchors 5 slipping out of the grooves 8. It is advisable for the shear anchors to be connected directly to the reinforcement 7 of the concrete element 2. However, if the shear anchors 5 are suitably dimensioned, the connection formed between the shear anchor and the concrete material of the concrete element 2 is sufficient to absorb the shear forces that occur. The fitting pockets also ensure that the metal shear anchors are completely enclosed by another material, namely by the concrete in the upper area and by the wood of the wooden beam in the lower area. This means that increased requirements with regard to fire protection can be met. The completely enclosed shear anchors are not

Fig. 5 shows a possible embodiment of such a shear anchor 5. The special feature is the extension of the profile in the upper area, so that the shear anchor extends laterally beyond the wooden beam and thus enables an improved force introduction into the concrete element.

In an embodiment shown in Fig. 6, the concrete element 2 surrounds the wooden beam 3 at least in the upper section, including on the side surfaces. This allows the use of shear anchors 5 that do not protrude beyond the top of the wooden beam 3. In the example shown, the shear anchors are formed by round steel dowels that are driven into through holes or fitting holes in the wooden beam. This embodiment is particularly suitable for use in the context of old building renovations.

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In other embodiments, different shapes of the shear anchors can be used. For example, it is possible to insert angle rails into grooves that run perpendicular to the cross-section of the wooden beams, whereby these angle rails are then attached to the wooden beams with additional fastening elements so that the vertical force component (tensile force) of the occurring shear forces can be absorbed and does not lead to the shear anchors being pulled out of these grooves.

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List of reference symbols

1 Wood-concrete composite ceiling 2 Concrete element 3 Wooden beams 5 Shear anchor 6 camp 7 Reinforcement 8th Grooves

Claims (12)

1. Wood-concrete composite ceiling ( 1 ) with spaced-apart wooden beams ( 3 ) and a concrete element ( 2 ) which is connected to the wooden beams, characterized in that several transverse force anchors ( 5 ) are provided which run transversely to the longitudinal direction in the wooden beams, wherein a section of the transverse force anchors ( 5 ) protruding from the wooden beam ( 3 ) is enclosed by the concrete element ( 2 ). 2. Wood-concrete composite ceiling according to claim 1, characterized in that the shear anchors ( 5 ) are completely enclosed by the wood support ( 3 ) or the concrete element ( 2 ). 3. Wood-concrete composite ceiling according to claim 1 or 2, characterized in that the concrete element ( 2 ) is in direct connection with the wooden supports ( 3 ) only at their upper side. 4. Wood-concrete composite floor according to one of claims 1 to 3, characterized in that a separating and sliding layer is arranged between the concrete element ( 2 ) and the wooden supports ( 3 ). 5. Wood-concrete composite ceiling according to claim 1 or 2, characterized in that the concrete element ( 2 ) surrounds the wooden supports ( 3 ) from above and on sections of the side surfaces. 6. Wood-concrete composite ceiling according to one of claims 1 to 5, characterized in that the shear anchors are metallic flat profiles ( 5 ) which are arranged in grooves ( 6 ) of the wooden supports ( 3 ), these grooves running obliquely to the cross section of the concrete element ( 2 ). 7. Wood-concrete composite ceiling according to one of claims 1 to 5, characterized in that the shear anchors are metallic angle profiles, one leg of which is arranged in grooves in the wood beams and which are fastened to the wood beams via fastening elements which can absorb forces acting essentially perpendicular to the concrete element. 8. Wood-concrete composite floor according to claim 5, characterized in that the shear anchors ( 5 ) are round steel dowels which are driven into fitting holes in the wooden support ( 3 ). 9. Wood-concrete composite ceiling according to one of claims 1 to 8, characterized in that the concrete element ( 2 ) has a steel reinforcement ( 7 ). 10. Wood-concrete composite ceiling according to claim 9, characterized in that the shear anchors ( 5 ) are part of the steel reinforcement ( 7 ). 11. Wood-concrete composite floor according to claim 5, characterized in that the shear anchors are formed by regions of the concrete element which extend into recesses in the wooden supports. 12. Wood-concrete composite floor according to one of claims 1 to 11, characterized in that the concrete element consists of lightweight concrete, aerated concrete or asphalt concrete.