EP1669505B1 - Steel-concrete composite joist with fire-resistant support for ceiling elements - Google Patents

Abstract

An improved support structure for floors in construction has steel profiles (2) filled with concrete and fitted between upright supports (1). The profiles have outer trough shaped flanges (5) to carry flooring panels (3) and are strengthened by steel rods (20). The support flanges are rolled over extensions of the steel profile and the trough profiles are filled with a fire retarding material, e.g. concrete, mineral wool etc. Steel support plates (14) are fitted over the support flanges and are secured by profiled ends located into slots and cut outs in the steel profile.

Description

The invention relates to a composite steel beam for forming a ceiling structure according to the preamble of claim 1 protection.

In the construction of buildings, a trend towards the use of prefabricated components can be determined as a result of increasing cost and time pressure. These allow a rational production while maintaining high quality standards and as far as possible decoupling the production of prefabricated components from the construction progress of the construction site. The construction work on site is thus reduced to the composition of the prefabricated components, which a considerable time savings is possible.

A known manner of construction in this context is to assemble precast columns and precast beams into a frame construction and insert prefabricated ceiling elements between the precast beams. If necessary, an in situ concrete layer can be added subsequently.

In this context, in addition to precast beams made of reinforced and prestressed concrete, steel composite beams have also been used as cross members. Steel composite beams have a steel profile, for example, a hollow box cross-section, the bearing behavior is sufficient to accommodate transport and assembly-related load conditions. For load transfer in use, the steel girder is supplemented with concrete. This can be done, for example, by introducing concrete into the box cross-section, optionally after prior laying of the reinforcement. The cross-section of the steel composite beam thus consists of areas with steel and areas with concrete, which interact during the load transfer.

Of great importance in the manufacture of structures is compliance with the relevant requirements for fire protection. The relevant provisions make it necessary that a building remains functional even in case of fire for a predetermined period of time to provide sufficient time for rescue operations. This concerns above all supporting components and here again in particular the cross member and the Auflagerung the ceiling elements on the cross members.

From the EP 0 467 912 A1 a plate carrier system is known, whose carrier consists of welded steel sheets, 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 inwardly offset. The resulting offset makes it possible to attach an additional fire protection panel for the fire from the outside. After installation of the prefabricated ceiling elements of the cavity of the box girder and the space between steel beams and precast parts is filled with concrete.

In addition to disadvantages in static terms, which go back to the low height of the wearer, another disadvantage of this construction is that in case of fire, the tension of the steel beam is not protected by the construction itself, but must also be clad with a fire protection layer. The fire protection layer does not extend to the projecting horizontal lower flanges, so that they are directly exposed to the heat in case of fire and therefore no longer carry any support function. To ensure the structural behavior of the structure in the event of fire, the ceiling elements are connected to the girder via an elaborate connection reinforcement, which is subsequently embedded in concrete on site.

The EP 1 405 961 A1 discloses a composite steel deck construction in which the steel composite beam known in the market under the name "HODY beam" has in the lower region two longitudinal side flanges which serve as lineal supports for the ceiling elements. In this case, a distance is maintained between the bottom of the ceiling panels and the top of the side flanges, which is filled with concrete.

The advantage of this construction method is, inter alia, that the casting in case of fire unfolds protective effect for the overhead ceiling elements. However, the steel flange of the composite support of the fire heat is directly exposed, so that it can not assume a supporting function in case of fire and a failure of the line support would be expected. For this reason, a connection reinforcements is provided in the connection area of the ceiling elements to steel composite support, which is subsequently cast with concrete.

In addition, from the EP 0 555 232 A1 a steel beam known, which consists of a rolled section, in particular an I-profile, which is connected on both sides via a strut framework or connecting straps made of sheet metal with a trough-shaped lower belt plate. The attachment of the Untergurtblechs done in such a way that the roll profile is maintained a vertical distance, which is cast during the completion of the ceiling construction with concrete. The upwardly folded and filled with concrete Untergurtblech serves in this case as a support for the ceiling elements.

It is described as advantageous that the concrete layer between the lower edge of the steel girder and lower girder plate serves as fire protection for the steel girder. But since the Untergurtblech is directly exposed to the fire heat in the event of fire, with the Untergurtblech also fails the support for the ceiling elements. That's why one is here too appropriate connection reinforcement may be provided which connects the ceiling elements with the steel composite support.

To improve the construction of the connection between the cross member and ceiling elements of a floor slab construction is according to the WO 90/01596 already proposed a T-shaped composite steel beam, which is prefabricated in reverse position of use. The function of the steel profile is essentially limited to the formation of the formwork for the concrete to be introduced. The load transfer takes place via prestressed reinforcement elements, which are arranged in the concrete cross-section. In the assembled state, the upright T-shaped steel composite carrier forms lateral longitudinal flanges on which the ceiling elements rest. About the fire protection, however, no statements are made.

In the EP 1 371 794 A1 there is described a steel composite beam having an open cross-section formed by upper and lower longitudinal reinforcement joined by an upright transverse reinforcement. The lower portion of the Trägerguerschnitts is formed by two lateral longitudinal flanges, which serve to support the ceiling elements. Angle pieces are arranged in the area of the bearing surface of the ceiling elements, two of which are connected in each case by means of a transverse bar to two angle pieces that lie in a cross-sectional plane. In the state of use of the steel composite beam, the transverse rods are completely embedded in the concrete of the main cross-section of the beam.

A composite steel beam according to the preamble of claim 1 is disclosed in US Pat. No. 6,332,301 B1 described.

Against this background, the invention has for its object to provide an improved steel composite support for a ceiling structure, the support area for the ceiling elements meets the requirements of fire protection and thereby structurally simple and economical to implement and beyond the aesthetic requirements of a building is justified ,

This object is achieved by a composite steel carrier with the features of the protection claim 1.

Advantageous embodiments will be apparent from the dependent claims.

The essence of the invention lies in the provision of a fire-protected support in steel composite beams for the ceiling elements to be attached. The invention is based on the assumption that reduced loads of the static calculation are to be used for the case of fire compared with the state of use. While for the condition of use in addition to the dead weight also traffic loads are to be brought into approach, which are removed via the side flanges, reduce the static load to be considered for the load case fire significantly. This uses the invention and provides in case of fire before a load transfer only on the bearing elements. By integrating the bearing elements through the lateral longitudinal webs into the concrete of the main cross-section of the composite steel beam, the load from the ceiling elements is entered via the bearing elements in the steel composite beam. The bearing elements are stressed essentially bending. The longitudinal flanges, which are directly exposed to fire heat in the event of fire, take over load case fire no supporting function more, but essentially serve only the protection of the bearing elements from the fire heat.

An advantage of the invention is therefore that the heat of the fire due to the shielding by the longitudinal flanges does not directly reach the support area for the ceiling elements. It is therefore achieved without further measures, such as the attachment of a refractory lining or painting sufficient fire protection. The inventive design of the fire protection is not visible and therefore extremely advantageous in terms of aesthetic concerns.

In terms of design and execution, the solution according to the invention is very simple, so that no appreciable additional material or work effort is created when it is realized. This provides the invention with economic advantages over prior art solutions. Due to the additional supporting effect of the bearing elements arranged under the bearing elements longitudinal flanges no longer need to be dimensioned to the load case fire and can therefore be designed more economical. In addition, the buoyancy of the bearing elements allows a reduced dimensioning of the longitudinal flanges for the use state, which in turn allows a more economical construction of the composite steel beam.

In an advantageous embodiment of the invention, the area between the bearing elements and the longitudinal flanges is filled with a fire insulation. The fire insulation can consist of fiber mats or intumescent materials that ensure effective thermal insulation with low weight and ease of workability.

However, preferred is a casting of hardening material, such as concrete, which primarily increases the fire protection for the bearing elements. In addition, the casting in the event of fire forms a load transfer system in which the bearing element according to the invention interacts as a tensile zone and casting as a pressure zone. The result is a higher bearing capacity of the support in the support area.

It is possible to arrange the bearing elements according to the invention continuously over the entire length of the composite steel beam on the longitudinal flanges. In contrast, a preferred embodiment of the invention in the arrangement of only individual selectively provided bearing elements. It suffice already two points of support for a ceiling element at each ceiling edge.

Although it is conceivable to store the ceiling elements directly on the bearing elements; However, it is preferred to provide elastomeric bearings between the bearing elements and the ceiling elements. As a result, voltage spikes are largely avoided, which could otherwise lead to damage.

To improve the bond between the bearing elements and the concrete, the bearing elements may for example have profilings or bends. This leads to an improved load transfer behavior in the support area.

To form the longitudinal flanges, the underside of the composite steel support advantageously consists of a metal sheet, whose side edges projecting beyond the main cross section are bent upwards. On the one hand, this increases the stability of the sheet. At the same time created in this way a trough-shaped bottom, which simplifies the introduction of the fire insulation and in particular the potting.

The bent longitudinal edge of the sheet further simplifies the production of the ceiling construction by providing support surfaces for the bearing elements, to which the bearing elements merely need to be laid. Optionally, the bearing elements may be non-positively connected to the longitudinal edge of the sheet. This can be done by welding, for example. Preferably, however, is a positive connection, for example, with formation of a toothing between the bearing element and the longitudinal edge of the sheet. As a result, a position assurance of the bearing element relative to the composite steel beam is achieved in the first place. In the case of a non-positive connection such as welding, the load transfer capacity of the storage area is additionally increased.

An inventive steel composite support is not bound to a particular cross section, so that both hollow box sections and open cross sections are suitable, provided that the cross section has at least two longitudinal webs with openings through which the bearing elements extend into the region of Hauptguerschnitts. Cross-sections , such as π-cross-sections, are preferred by the invention . The advantage of hollow box sections is, in addition to their higher torsional stiffness, especially in the provision of a formwork for the concrete, so that additional formwork omitted. The arrangement of slots of the hollow box at the same time forms a bearing surface for the bearing elements, which facilitates the laying of the bearing elements.

In order to increase the bearing behavior of the bearing elements in case of fire is provided according to an advantageous embodiment of the invention to attach the bearing elements to the steel profile of the steel composite beam. This is preferably done by welding the bearing element on the web plate.

The bearing elements according to the invention are advantageously formed plate-shaped. This makes them easy and inexpensive to manufacture, easy to lay and form a flat support surface for the ceiling elements.

By arranging several legs in the covering area with the concrete, the bond between the concrete and the bearing element is increased, so that the bearing element can absorb higher forces. In a further development of this idea, the load transferability can be additionally increased by the bearing elements are connected directly or indirectly non-positively to the longitudinal reinforcement of the steel composite beam.

An arrangement of the longitudinal flanges of the steel composite support below the top allows finally the realization of lower floors and in the case of a flush arrangement with the underside of the steel composite support an advantageous installation of installation cables.

The invention will be discussed below with reference to an embodiment shown in the drawings.

Show it

Fig. 1

an oblique view through a section of a ceiling construction according to the invention,

Fig. 2

a side view of a portion of a composite steel beam according to the invention,

Fig. 3

a top view of the in Fig. 2 illustrated composite steel beams including the ceiling elements,

Fig. 4

a cross section through the in Fig. 3 illustrated composite steel beam along the line IV - IV,

Fig. 5

a side view of a section of the in Fig. 4 illustrated composite steel beam,

Fig. 6

a section through the in Fig. 4 illustrated composite steel beams along the line VI - VI,

Fig. 7

a plan view of a bearing element according to the invention,

Fig. 8

a cross-sections of another embodiment of the invention and

Fig. 9a -

d the stepwise production of a ceiling construction according to the invention on the basis of several cross sections.

Fig. 1 to 3 give an overview of a ceiling construction according to the invention. FIG. 1 shows a node where support 1, support (or steel composite support) 2 and ceiling element 3 meet. The support 1 has on the carrier 2 associated with the inner side of a console 4 for supporting a carrier 2. Between two such opposing supports 1 (from the in Fig. 1 only one is shown), a carrier 2 is inserted in each case. This creates a support frame, which forms the backbone of the ceiling construction together with a plurality of parallel support frame. The space between the individual support frames is covered by the ceiling elements 3, which rest on the supports 2 at the edge ( Fig. 3 ). In addition to a flaccid reinforcement, a carrier 2 which is suitable for this purpose usually also has tensioning members for applying a pretensioning in the longitudinal direction, the course of which advantageously follows the bending moment characteristic. Of the Carrier 2 has lateral longitudinal flanges 5, on which the ceiling elements 3 rest with their edge. By adding an in situ concrete layer (Figure 11d), the ceiling construction is completed.

In case of fire, the underside of the carrier 2 and the ceiling elements 3 of the fire heat is directly exposed. In order to prevent a static failure of Auflagerbagerbereichs for the ceiling elements 3 on the beams 2, therefore, additional measures are required, as described in more detail below according to the invention.

Based on FIGS. 4 to 7 the inventive design of the carrier 2 can be described in detail. There you can see a carrier 2 in the form of a steel composite carrier. The longitudinally supporting main cross section of the carrier 2 is composed of a steel section 6 with box section and concrete 7, which fills the box cross-section. In the area of the concrete 7, a longitudinal reinforcement 20 may be provided in order to increase the carrying capacity of the carrier 2.

The box cross-section is formed by two mirror-symmetrically arranged oblique web plates (or longitudinal webs) 8, whose upper longitudinal edges are connected by a further, a top flange 10 forming sheet steel. The lower longitudinal edges of the web plates 8 are connected in a similar manner via a steel plate forming a lower flange 11, the longitudinal edges 12 of the lower flange 11 projecting laterally beyond the main cross section of the steel composite carrier 2 to form longitudinal flanges 5. By a bending of the longitudinal edges 12 upwards creates a trough-shaped design of the lower belt eleventh

The longitudinal edges 12 each form together with the web plates 8 bearing areas for bearing elements 14, their exact training Fig. 7 evident. There you can see in plan a bearing element 14, which consists of a steel plate with a thickness, for example in the range of 0.5 to 2 cm. In plan view, the bearing element 14 has a rectangular Shape on, a narrower side has a short approach 15. Opposite a rectangular recess 16 is provided centrally on the other narrow side, which leads to the formation of two legs 17.

For receiving the bearing elements 14, the longitudinal edges 12 of the lower belt 11 at predetermined intervals recesses 18, which correspond in shape and size to the approach 15. In the web plates 8, these recesses 18 at the same height opposite, in each case two spaced apart slots (or openings) 19 are inserted. These serve to receive the legs 17 of the bearing element 14, which comes to lie in the inserted state with the projection 15 in the recess 18 of the longitudinal edges 12. This positive connection between the bearing element 14 and the carrier 2 serves primarily to secure the position of the bearing element 14. In the penetration area of the two parts, the bearing elements 14 can be welded to the web plates 8 to improve the structural behavior.

The tub-shaped bottom chord 11 is filled over its entire length to the upper edge of the longitudinal edges 12 with a hardening potting material 21, advantageously mortar or concrete. The hardening potting material 21 is preferably introduced only after placing the ceiling elements 3 on the bearing elements 14, so that it wets both the bottom of the bearing elements 14 and the underside of the ceiling elements 3 in the support area. Alternatively, other fire insulation may be provided instead of the hardening material, such as fire protection mats made of fiberglass or mineral wool.

An exemplary distribution of the bearing elements 14 over the length of the composite steel support 2 is mainly from Fig. 3 seen. One sees an arrangement of the bearing elements 14 at regular intervals, wherein a ceiling part 3 rests centrally on a bearing element 14 and on each edge on a half bearing element 14.

FIG. 8 shows an alternative embodiment of a steel composite beam 33, the steel profile of two parallel, upright web plates (or longitudinal webs) 34 and a lower longitudinal edges of the web plates 34 connecting lower flange 35 is formed. The lower flange 35 in turn projects laterally beyond the web plates 34 and forms with the bent-up longitudinal edges 36, as already under the FIGS. 4 to 7 described, trough-shaped side flanges (or longitudinal flanges) 37. The bearing elements 14 are also stored in this embodiment of the invention on the one hand on the longitudinal edges 36 of the side flanges 37 and on the other hand in longitudinal slots in the web plates 34. After placing the ceiling elements on the bearing elements 14, optionally with the interposition of elastomeric bearings 32, concrete 38 is ejngebracht between the web plates 34 of ungekehrten π - shaped steel profile and the trough-shaped side flanges 37 provided with a hardening potting material 39.

The production of a ceiling construction according to the invention is described below with reference to Figures 9 a - d described. First, how will Fig. 9 a visible, at this time only as a steel profile 6 existing carrier, which is already equipped with a longitudinal reinforcement 20 and the necessary internals in this context, provided with the bearing elements 14. This is done by the bearing elements 14 are inserted with their legs 17 in the slots in the web plates 8 and then placed with their approach 15 in the recess in the longitudinal edges 12 of the lower belt 11. To increase the fire protection may optionally Bearing elements 14 are welded in the penetration area with the web plates 8. In addition, the bearing elements 14 are provided on their upper side with elastomeric bearings 32. A carrier prepared in this way can subsequently be deposited on the brackets 4 of two mutually opposite supports 1.

After a field to be covered is spanned in a corresponding manner with a plurality of parallel carriers, the ceiling elements 3 can be inserted between the carriers. This condition is in Fig. 9b shown. It can be seen two ceiling elements 3, which rest with its bottom edge on the longitudinal flanges 5 and there exactly on the elastomeric bearings 32 on the bearing elements 14. The load from the ceiling elements 3 is entered via the bearing elements 14 in the longitudinal flanges 5 and further in the carrier.

Then it will look like Fig. 9c can be seen in the area of the carrier concrete 7 introduced. The concrete 7 can fill both the hollow box profile of the carrier, as well as the area between the lower flange 11 and the bearing elements 14 and the underside of the ceiling elements 3, as well as the area between the web plates 8 and the end faces of the ceiling elements 3. After hardening of the concrete 7 the bearing elements 14 with their located within the main cross-section legs 17 firmly anchored in the manner of a clamping. In the region of the longitudinal flanges 5, after hardening of the concrete 7, a line bearing extending over the entire length of the carrier 2 is created for the ceiling elements 3, which is intended to introduce additional loads such as traffic loads in use directly into the longitudinal flanges 5.

In a last step will be like under Fig. 9d illustrated an in-situ concrete layer 31 extends, which extends over the entire ceiling construction.

From this type of construction it follows that, in use, the loads, including the traffic loads, are completely registered via the side flanges 5 in the main cross-section of the carrier 2 carrying in the longitudinal direction. The bearing elements 14 serve essentially only for the transfer of the load portion of its own weight in the side flanges 5. This load transfer system basically changes when the fire occurs.

In case of fire, the fire heat in the area of the steel composite beam 2 directly on the lower flange 11. This loses a large part of its load capacity, so that the load transfer is taken over in the other with reduced load assumptions of the bearing elements 14. The bearing elements 14 are firmly anchored in the supporting part of the carrier 2 with their part extending into the main cross-section. As a result of their flexural rigidity, the bearing elements 14 are able to hold the ceiling elements 3. The potting material 21 between lower flange 11 and bearing element 14 forms a protection against the fire heat.

In the presence of a bond between the potting material 21 and the bearing element 14 is supportive added that the potting material 21 forms the pressure range of a parallel-acting load transfer system, in which the bearing elements 14 absorb the tensile forces. In this way it is ensured that the ceiling elements 3 are supported by the steel composite beams 2 without further measures even in case of fire.

Claims (21)

1. A steel composite beam (2,33) for forming a fire-proofed floor structure in combination with floor elements (3), with a main cross-section, which is assembled for load removal in a longitudinal direction, consisting of steel section (6) and concrete (7,26,38), wherein in the operative condition the main cross-section has an upper side, an underside and laterally two longitudinal sides, and with a longitudinal flange (5,37) which is arranged on one or both longitudinal sides of the steel composite beam (2,22,32) and which serves for mounting the floor elements (3), wherein to form fire-proofed mounting zones for the floor elements (3) rigid mounting elements (14) are disposed above the longitudinal flange (5,27,37) and extend with a part of their length transversely to the longitudinal extension direction of the steel composite beam (2,33) and at a distance from the underside of the longitudinal flange (5,37) in the main cross-section of the steel composite beam (2,33) filled with concrete (7,38), wherein the steel composite beam (2,33) has two longitudinal webs (8,34) for the lateral boundary of the main cross-section, characterised in that the mounting elements (14) extend through openings (19) in the longitudinal webs (8,34) in the vicinity of the main cross-section.
2. A steel composite beam (2,33) according to Claim 1, characterised in that fire insulation is provided between the longitudinal flange (5,37) and the mounting element (14).
3. A steel composite beam (2,33) according to Claim 2, characterised in that the fire insulation consists of a casting material (21,39) which sets, in particular concrete.
4. A steel composite beam (2,33) according to Claim 2, characterised in that the fire insulation consists of a fire mat, in particular a fibre mat.
5. A steel composite beam (2,33) according to Claim 2 or 4, characterised in that the fire insulation consists of an intumescent material.
6. A steel composite beam (2,33) according to any one of Claims 1 to 5, characterised in that elastomeric layers (32) are arranged on the mounting elements (14).
7. A steel composite beam (2,33) according to any one of Claims 1 to 6, characterised in that a plurality of individual mounting elements (14) are spaced apart at predetermined distances over the length of the steel composite beam (2,33) and form spot-type mounting zones for the floor elements (3).
8. A steel composite beam (2,33) according to any one of Claims 1 to 6, characterised in that a mounting element is arranged on each longitudinal flange (5,37) over the entire length of the steel composite beam (2,33), which forms a linear mounting for the floor elements (3).
9. A steel composite beam (2,33) according to any one of Claims 1 to 8, characterised in that the mounting elements (14) have profiled sections or bent-up portions in the contact zone with the concrete (7,38).
10. A steel composite beam (2,33) according to any one of Claims 1 to 9, characterised in that in order to form the longitudinal flanges (5,37) the underside of the steel composite beam (2,33) consists of a metal sheet which projects beyond the longitudinal sides of the main cross-section and the longitudinal edges (12,36) of which are bent up towards the mounting elements (14).
11. A steel composite beam (2,33) according to Claim 10, characterised in that the mounting elements (14) bear on the longitudinal edge (12,36) of the metal sheet.
12. A steel composite beam (2,33) according to Claim 11, characterised in that the mounting elements (14) are connected in a force-locking manner to the longitudinal edge (12,36) of the metal sheet, in particular welded thereto.
13. A steel composite beam (2,33) according to Claim 11 or 12, characterised in that the mounting elements (14) and the longitudinal edge (12,36) of the metal sheet are connected by form-locking, preferably by the formation of a toothing in the contact zone, most preferably in the form of a projection (15) on the mounting element (14) and a recess (18) in the longitudinal edge (12,36).
14. A steel composite beam (2,33) according to any one of Claims 1 to 13, characterised in that in a penetration zone with the longitudinal webs (8,34) the mounting elements (14) have a force-locking connection to the longitudinal webs (8,34), preferably are welded thereto.
15. A steel composite beam (2,33) according to any one of Claims 1 to 14, characterised in that the steel section (6) of the steel composite beam (2,33) is in the form of a box section.
16. A steel composite beam (2,33) according to any one of Claims 1 to 14, characterised in that the steel section (6) of the steel composite beam (2,33) is in the form of a T-beam.
17. A steel composite beam (2,33) according to any one of Claims 1 to 16, characterised in that the mounting element or elements (14) is/are formed substantially panel-shaped.
18. A steel composite beam (2,33) according to any one of Claims 1 to 17, characterised in that the mounting element or elements (14) has/have a plurality of arms (17) in a connection zone with the concrete (7,38) of the main cross-section.
19. A steel composite beam (2,33) according to any one of Claims 1 to 18, characterised in that the steel composite beam (2,33) has a longitudinal reinforcement (20) in the main cross-section and the mounting element or elements (14) is/are attached to the longitudinal reinforcement (20).
20. A steel composite beam (2,33) according to any one of Claims 1 to 19, characterised in that in the installed condition the mounting element or elements (14) is/are arranged on spacers (29) on the longitudinal flanges (5,37).
21. A steel composite beam (2,33) according to any one of Claims 1 to 20, characterised in that the longitudinal flanges (5,37) are arranged under the upper side of the steel composite beam (2,33), preferably in a plane with the underside of the steel composite beam (2,33).

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