EP1405961B1 - Steel-concrete structure for floor slabs - Google Patents

Abstract

The ceiling support is a steel girder (3) with local concrete part encased in concrete with the storey ceiling. To transfer bending movements between the girder and upright support (2) there is at least one tensile stressed reinforcement element (12) on one side anchored in the upright and guided through same into the adjoining ceiling girder, and on the other side embedded in the compound concrete part. Shear teeth are provided in the connecting seam between the upright and concrete part of the girder to transfer the transverse forces at least in the event of a fire. The reinforcement elements pass through tubular sleeves which have a setting material such as concrete inside.

Description

The invention relates to a composite steel construction for floor slabs according to the preamble of claim 1.

The trend in the construction work is increasingly going to pre-fabricate as many components as possible and only to assemble on the site. On the one hand, the production processes can be better monitored and rationalized, on the other hand, the installation times and costs on the construction site are greatly reduced.

For multi-storey buildings frame structures made of columns and horizontal bars have largely prevailed. The storey ceilings often consist of prefabricated ceiling elements made of steel or prestressed concrete, in particular so-called filigree plates with an additional in-situ concrete layer or hollow perforated plates.

In this context, the use of steel composite constructions has become more and more prevalent. Their advantage is that the pure steel beams are sufficient in the assembled state for the load of their own weight by the construction, but can be transported and mounted easier than already dimensioned for the final state precast concrete. The required load-bearing capacity and the fire resistance are achieved by the composite construction after the hardening of the in-situ concrete. In order to save the required with Filigranplatten Ortbetonschicht mounting supports when concreting on site and the associated workload, pre-stressed hollow perforated plates have become more and more prevailed. On the one hand, they achieve larger spans than these; On the other hand, the required in-situ concrete layer can be introduced to cover the transverse reinforcement without additional support.

In order to reduce the respective ceiling and construction heights, one has already begun to store the precast ceilings no longer on the upper flanges of the steel beams, but on their lower flanges. This makes it possible to run installations and cables below the floor slabs without reducing the load-bearing capacity of the steel beams through recesses in the webs.

EP 0 467 912 B1 discloses a plate carrier system whose carrier consists of welded steel plates which form a trapezoidal cavity. The prefabricated ceiling elements rest respectively on the cantilever horizontal lower flange, which is integrally formed on the webs. The lower end of the box forms a welded sheet metal, which is offset from the projecting belt plate inwards / upwards. In order to protect the under flange in case of fire, it is necessary to attach an additional fire protection panel from the outside. After installation of the prefabricated ceiling elements, the cavity of the box girder and the space between the steel girder and finished parts is filled with concrete.

A disadvantage of this construction is that due to the low height of the carrier whose rigidity is not sufficient for the load case assembly. Therefore, depending on the length of the carrier, only one or more supports have to be installed for assembly in order to limit the deformation of the carrier during the concreting process. Furthermore, it is disadvantageous that the tension of the steel beam is not protected by the construction itself in case of fire, but must also be covered with a fire protection layer.

EP 0 292 449 B1 discloses a concrete, fire-resistant steel support which interacts with concrete and consists of two mutually facing U-profiles, which are fastened on a support plate. The carrier plate serves as a support for the precast concrete elements. Also in this carrier, the cavity, which is formed by the two U-profiles, shed with concrete. For the case of fire inside the support are also provided extending straight in the longitudinal direction of the carrier reinforcing elements, which may also be biased.

Also, this carrier can not be used without support in the case of load assembly, as its pressure range in the installed state consists only of the flanges of the two U-profiles and the connecting elements and therefore does not have sufficient stability.

Another steel beam for a composite construction is also known from EP 0 328 986 A1. The steel beam disclosed therein is composed of two T-beams, which are welded parallel to each other and with their flanges in a plane along their adjacent longitudinal edges. The two plane-parallel webs carry with their free edge a thick sheet, which provided on its upper side with head bolts is and may have openings. Further openings are provided in the transition region between the webs and the thick sheet metal.

To produce a ceiling construction, the steel beam thus prepared is supported with its flanges downwards between two supports. Subsequently, prefabricated ceiling elements are placed on both sides of the carrier on the flanges. After laying the reinforcement, the cavity of the steel girder and the prefabricated ceiling elements are supplemented by an in-situ concrete layer.

Finally, from EP 0 555 232 B1, a steel beam is known, which consists of a rolled section, in particular an I-profile, which is connected on both sides via a strut framework made of sheets with a trough-shaped bottom flange, which is arranged at such a distance from the rolled section is that between the lower edge of the rolled section and the Untergurtblech a concrete layer can be introduced. The upwardly folded lower belt plate in turn serves as a support for the precast concrete slabs in the assembled state.

In multi-storey buildings in steel-concrete composite construction, the load-bearing behavior of the frame and ceiling system is sustainably influenced by the connections or connections between supports and columns. Although the frame construction allows flexible use of buildings, since neither stiffening walls nor associations disrupt the layout; However, in order to provide sufficient structural integrity, it is necessary to consider their rigidity and bearing capacity for bending moments in the design of the joints.

The usual beam-support connections differ mainly in the execution of the connection of the steel parts. Usually, these require a lot of effort in terms of design, manufacture and assembly, especially when requirements are placed on fire protection.

Basically, it must be distinguished whether the steel girders are designed to run continuously at the junctions or whether the supports pass through several floors.

In the first case, the steel girders rest fully on the lower columns. The reinforcement can be arranged continuously, regardless of whether it is a construction in which the in-situ concrete slab is provided on the upper carrier belt or on the lower belt as a slim-floor construction. For the additional supports connections must be provided in the carrier. As foot anchors of columns are very complex and the columns have to be reoriented for each floor, this is a very costly and time consuming solution.

In the second case, it is customary for mounting the steel beams during assembly on the supports brackets, catches or the like form or provide screw connections.

For steel columns, it is known to attach reinforcing elements by means of screwing to the support flanges and to embed them after installation of the carrier and Filigranplatten in the in-situ concrete slab. If fire protection requirements are imposed on such constructions, the connections must be made and columns are completely covered with concrete or other refractory materials.

Better fire protection properties have steel-concrete composite supports, which are completely surrounded by concrete. However, their production is very complex, since the interaction of the materials is ensured by suitable composite means such as welded head bolts and additional bow and longitudinal reinforcement

Therefore, prefabricated concrete columns made of reinforced concrete are increasingly used in frame structures, since the production cost and thus their production costs do not increase in fire protection requirements.

In reinforced concrete columns, it is common to form these consoles and store the steel beams during assembly on these brackets and attach it. By such a connection, however, only articulated connections can be achieved without torque bearing capability. In addition, the projecting brackets interfere with concrete precast columns made of reinforced concrete during transport and are therefore undesirable.

Against this background, the present invention seeks to provide an economical design for fire-resistant frame and floor slab constructions.

This object is achieved by the steel composite construction with the features of claim 1.

Further advantageous embodiments will become apparent from the dependent claims.

The construction according to the invention initially comprises a welded box girder with projecting lower flange, which serves as a support for the prefabricated ceiling elements. The height of the box girder is generally chosen to be greater than the thickness of the required ceiling elements and these are placed on the lower flange so that the upper flange of the box girder and the surface of the ceiling elements at least approximately form a plane. This leaves between the lower edge of the ceiling elements and the lower flange of the box girder a cavity which is filled with concrete. For the assembly of Ceiling elements are provided between the lower flange and the lower edge of the ceiling elements spacers.

By means of tension strands, tension wires or other tendons, which are guided in the interior of the box girder, this can be impressed on a biasing moment which counteracts the bending moment from external loads, and which can also cause an increase in accordance with the self-weighting deformation of the construction.

This results in a number of advantages. Due to the increased height of the carrier and the bias of the tendons in its interior, the carrier is stiffened so that the required deformation restrictions can be met in the mounting load case without installation of additional mounting brackets. The lightweight construction of sheet metal and prestressing steel simplifies transport and installation of the girders, even with large spans.

The steel-composite construction creates a fire-resistant construction. In case of fire remains after failure of the lower flange, a solid concrete section. If the cavity of the box girder and the joints between the support and ceiling elements are cast with concrete, the ceiling elements are encased in concrete round the ends. This means that the ceiling elements are better protected in case of fire, since they do not rest directly on a steel flange, which immediately loses its stiffness under the influence of heat. Furthermore, the shear resistance of the ceiling elements in particular of the hollow perforated plates is heavily dependent on the rigidity of the support. Due to the encapsulation of the support area with concrete after installation of the ceiling elements and by filling the cavities in the elements in this area, the risk of shear failure in the support area is considerably reduced.

Due to the rigid integration of the ceiling elements and the installation of an additional reinforcement perpendicular to the box girder, a controlled passage effect of the ceiling panels over an entire floor can be achieved with equal eitiger reduction of the field moments.

Another stiffening possibility for the supporting structure is, in a frame or floor slab construction in steel-concrete composite construction a create moment-loadable connection with the help of reinforcing elements. By the at least partial clamping of the ceiling beams in the supports or the achievement of a continuous action over a support, the deflection of the support for the proof of serviceability can be influenced, so that a more economical design is possible.

The proposed compound according to the invention simultaneously meets the fire protection requirements, which are also placed on the ceiling beams, columns or ceilings, so that additional measures such as fire protection paneling, paints or the like as in the classic steel construction connections, which are common in steel composite construction, are dispensable.

Fig. 1 bis 4

jeweils Querschnitte durch verschiedene Ausführungsformen einer erfindungsgemäßen Stahl-Verbund-Konstruktion im Bereich des Auflagers,

Fig. 5

einen Längsschnitt durch einen Kastenträger als Einfeldträger mit zugehöriger Spanngliedführung, die

Fig. 6

einen Vertikalschnitt durch eine erfindungsgemäße Knotenausbildung bei einem Rahmenriegel und einer durchlaufenden Randstütze aus Stahlbeton,

Fig. 7

einen gegenüber Fig. 6 um 90 Grad verschwenkten Schnitt mit Querschnitt durch den Rahmenriegel,

Fig. 8

einen Vertikalschnitt durch eine erfindungsgemäße Knotenausbildung bei einem Rahmenriegel und einer durchlaufenden Innenstütze aus Stahlbeton und

Fig. 9

einen gegenüber Fig. 8 um 90 Grad verschwenkten Schnitt mit Querschnitt durch den Rahmenriegel.

The invention is explained below with reference to the drawings. It show the

Fig. 1 to 4

each cross-sections through various embodiments of a steel composite construction according to the invention in the region of the support,

Fig. 5

a longitudinal section through a box girder as Einfeldträger with associated tendon guide, the

Fig. 6

a vertical section through a node formation according to the invention in a frame bolt and a continuous edge support made of reinforced concrete,

Fig. 7

a section with a cross section through the frame latch pivoted by 90 degrees with respect to FIG. 6,

Fig. 8

a vertical section through a knot formation according to the invention in a frame bolt and a continuous inner support made of reinforced concrete and

Fig. 9

a comparison with FIG. 8 pivoted by 90 degrees section with a cross section through the frame latch.

FIGS. 1 to 4 each show a support situation of a floor slab 1 of the steel composite structure according to the invention consisting of prefabricated ceiling elements 2 made of reinforced concrete and an associated box girder 3 made of steel in the state of assembly. The box girder 3, whose upper flange 4 with two inwardly inclined webs 5 and a lower flange 6 forms a substantially trapezoidal cross section, consists of welded steel sheets. The lower flange 6 projects on both sides beyond the trapezoidal cross section (6a). The length of the projecting parts 6a of the lower flange 6 in each case depends on the span of the ceiling elements 2.

Inside the box girder 3 tendons 7 are guided. These can, as shown in Fig. 5, consist of steel wire strands, but also of tie rods or wires. To guide the tendons 7 sheets 8 are welded with supports at the deflection points 8a in the box girder 3. Also for supporting and anchoring the tendons 7 at the ends of the box girder 3 plates 9 are provided, against which the anchoring elements 7a are supported.

In the webs 5 and 4 in the upper flange openings 10 and 11 are provided. These openings 10, 11 are required, on the one hand, to insert additional reinforcement elements 15 after assembly of the ceiling elements 2 (FIG. 1) and, on the other hand, to introduce and compact the concrete for the final state of the steel composite construction. This creates a frictional connection of box girder and concrete.

The ceiling elements 2 have at their ends at the top recesses 14 to allow the insertion of the reinforcing elements 15 and further bracket 16 and at the same time the subsequent introduction of cast-in-situ concrete. The cavities of the ceiling elements 2, in particular in hollow perforated plates are sealed by specially shaped closures 13 against ingress of in-situ concrete.

For Auflagerung the ceiling elements 2 in the assembled state 3 spacers 12 are placed on the projecting parts 6a of the lower flanges 6 of the box girder, which may consist of wood, concrete, plastic or the like. During subsequent casting of the box girder 3 and the ceiling elements 2 with in-situ concrete, the gap between the ceiling elements 2 and the lower flanges 6 is in each case laterally turned in (FIG. 1).

In Fig. 2, the projecting parts 6b of the lower flange 6 of the box girder 3 are angled upwards and thus formed trough-shaped. The ceiling elements 2 can be placed here on the angled parts 6b of the lower flange 6 in the assembled state. Due to the trough shape can be dispensed with an additional formwork during the concreting process.
In this embodiment, it is also possible to arrange a continuous longitudinal reinforcement 17 on the lower flange 6, which can also be designed according to the building supervisory requirements as a ring armor reinforcement.

3 and 4 show further embodiments of the lower flange 6. In the embodiment of Figure 3, the protruding parts 6c are bent at a planar design of the lower flange 6 at a radius upwards. in the embodiment of Fig. 4, the entire lower flange 6 including the projecting parts 6d is arcuately curved. If the customary in the floor-mounted suspended ceiling is omitted, can be achieved by the geometric shapes of the lower flanges 6 architecturally aesthetic effects.

While the box girder 3 of the steel composite construction according to the invention is shown in FIG. 5 as a single-field girder, it goes without saying that other static systems of the box girder with continuous action are also possible. The tendons 7 are then guided and fixed according to the course of the bending moments of constant load and traffic load inside the carrier 3.

In the embodiment shown in FIGS. 6 and 7, a ceiling support 21 of a floor slab 1 is connected on one side to an edge support 22. The edge support 22 is a reinforced concrete support that was prefabricated in a precast plant, transported to the construction site and mounted there. To connect the ceiling support 21 with the edge support 22, a built-in part 24 was arranged in the form of a steel plate in this.

As reinforcing elements 25, in particular for receiving bending moments, in the present case a Einspannmoments, here two steel bars are shown, which extend parallel to each other and the upper flange 4 of the box girder 3 and anchored by a steel plate 26 in the support 22. Alternatively, the reinforcing elements 25 could be executed in an angular shape and the occurring Forces are introduced via composite action in the support 22. This solution is not shown.

In order that the reinforcing elements 25, which must already be embedded in concrete during production of the support 22 and therefore protrude beyond its outer surface, do not hinder the production and during transport of the support 22, these can also be provided with a thread in the region of the installation part 24 and by a Socket joint are encountered.

For Auflagerung the box girder 3 during assembly and in use, a support bracket 27 is attached to the mounting part 24, for example, welded, screwed or plugged. After mounting the ceiling elements 2 and the installation of the carrier-side reinforcing elements 25, the cavity of the box girder 3 and the gap 28 between this and the support 22 are filled with in-situ concrete 23. In order to achieve a thrust toothing between the support 22 and the in-situ concrete 23 in this area, recesses 29 are provided in the installation part 24, into which the in-situ concrete 23 penetrates. In case of fire, the transmission of the transverse forces after removal of the support bracket 27 in the concrete cross section can thus take place. A corresponding effect can also be achieved by profiling the insert 24, for example in the form of teeth.

In contrast to the embodiment in FIGS. 6 and 7, FIGS. 8 and 9 show an inner support 30 with two ceiling supports 21 lying opposite one another. In order to achieve the desired passage action, reinforcing elements 25 are provided in the supports which pass over the support 30. In order to make this possible, cavities are provided, for example, by the insertion of cladding tubes 31 during the concreting process, through which the reinforcing elements 25 are passed after assembly of the ceiling beams 21.

To connect the ceiling support 21 to the support 30, installation parts 24 with recesses 29 are also provided here.

In order to avoid welding work on the construction site and the associated costs and inaccuracies, a cranked bracket 32 is shown in Fig. 8 for Auflagerung the ceiling support 21, which is hooked into a recess 33 provided for this purpose in the mounting part 24. For transferring the shear forces in the connecting joint are provided instead of the recesses 29 on the mounting part 24 projecting lugs 34.

Claims (16)

1. A composite steel structure for floors (1), characterised by the combination of the following features:

   - a steel box girder (3) is provided as support for installing prefabricated floor elements (2) consisting of steel or prestressed concrete, in particular hollow slabs;

   - the box girder (3) comprises an upper flange (4), two lateral webs (5) and a lower flange (6) with parts (6a, b,c,d) projecting over the closed cross-section;

   - the upper flange (4) and the webs (5) have openings (10,11) for the insertion of reinforcing elements (15) and/or for the introduction and compaction of concrete;

   - the height of the box girder (3) is greater than the thickness of the floor (1), wherein the upper side of the upper flange (4) of the box girder (3) and the surface of the floor elements (2) lie at least approximately in one plane;

   - the floor elements (2) are supported on the projecting parts (6a,b,c,d) of the lower flange (6) of the box girder (3);

   - in the installed condition, spacers (12) are provided between the lower flange (6) of the box girder (3) and the lower edge of the floor elements (2);

   - the box girder (3) is prestressed by means of tendons (7) disposed in its interior;

   - the tendons (7) are directed so that as a result of the prestressing a bending moment is created which is oppositely directed to the path of the bending moments from the external loads.
2. A composite steel structure according to Claim 1, characterised in that to guide and support the tendons (7) inside the box girder (3) plates (8,9) are provided which are preferably welded in place.
3. A composite steel structure according to Claim 1 or 2, characterised in that the spacers (12) between the lower flange (6) of the box girder (3) and the lower edge of the floor elements (2) consist of concrete.
4. A composite steel structure according to any one of Claims 1 to 3, characterised in that reinforcing elements (17) are provided in a longitudinal direction between the lower edge of the floor elements (2) and the lower flange of the box girder (3).
5. A composite steel structure according to Claim 4, characterised in that the reinforcing elements (17) are in the form of ring beams.
6. A composite steel structure according to any one of Claims 1 to 3, characterised in that the lower flange (6) of the box girder (3) with the projecting parts (6b,6c,6d) is trough-shaped.
7. A composite steel structure according to any one of Claims 1 to 6, characterised in that the box girder (3) is in the form of a simply supported beam.
8. A composite steel structure according to any one of Claims 1 to 6, characterised in that the box girder (3) is provided as a continuous girder.
9. A joint between at least one floor joist (21) and a column (22,30) in a composite steel structure according to Claim 1, characterised by the following features:

   - the floor joist (21) is in the form of a steel girder (3) with a cast-in-place component, which is cast in combination with the floor (1),

   - in order to transmit bending moments between the floor joist (21) and the column (22,30) or away therefrom into an adjoining floor joist (21), at least one reinforcing element (25) is provided which can be subjected to tension and which, on the one hand, is anchored in the column or is guided by the latter into the adjoining floor joist (21) and, on the other hand, is bonded into the cast-in-place component of the floor joist (21),

   - in order to transmit the lateral forces at least in the event of a fire a shear toothing is provided in the connecting joint between the column (22,30) and the cast-in-place component of the floor joist (21).
10. A joint between at least one floor joist (21) and a reinforced concrete column (22,30) according to Claim 9, characterised in that for passing the reinforcing elements (25) through the column (22,30) hollow spaces are formed therein, for example by introducing sheathing tubes (31).
11. A joint according to Claim 10, characterised in that the reinforcing elements (25) are pressure-grouted inside the sheathing tubes (31) with a material which sets, for example concrete.
12. A joint according to any one of Claims 9 to 11, characterised in that a built-in component (24) for supporting the floor joist (21) during installation is provided in the column (22,30).
13. A joint according to Claim 12, characterised in that a support bracket (27) is provided on the built-in component (24).
14. A joint according to Claim 13, characterised in that the support bracket (27) is suspended on the column (22,30) by means of an angled supporting limb in recesses (33) provided therefor in the built-in component (24).
15. A joint according to any one of Claims 12 to 14, characterised in that for the shear toothing between the column (22,30) and the cast-in-place component cut-outs (29) are provided in the built-in component (24).
16. A joint according to any one of Claims 12 to 15, characterised in that for the shear toothing between the column (22,30) and the built-in component (24) a profiled section is provided in the cast-in-place component.

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