EP0337120A1

EP0337120A1 - Composite structural beam

Info

Publication number: EP0337120A1
Application number: EP19890104250
Authority: EP
Inventors: Jean-Baptiste Schleich; René Pepin; Achim Rubert
Original assignee: ARBED SA
Current assignee: ARBED SA
Priority date: 1988-04-11
Filing date: 1989-03-10
Publication date: 1989-10-18
Also published as: LU87194A1

Abstract

The composite structural beam comprises a steel section (4) whose web (5) has recesses (7), a concrete slab (1) and reinforcing elements (9). The steel section (4) comprises two flanges, one (3) of which is provided with pins (2) welded onto its outer surface which, itself, is solidly in contact with the concrete slab (1) and the other (6) of which is free to the air. <IMAGE>

Description

The present invention relates to a reconstituted composite beam comprising a steel section, the core of which has recesses, reinforcing elements and concrete.
Mixed steel-concrete construction has been known for years for its exceptional static and dynamic properties. Efforts to increase the strength, lightness and economic attractiveness of these constructions date from the pre-war period. At that time, metal beams with hollow cores were already used - see in particular the patent FR 706.311. The production of such beams comprises two stages: The cutting of a laminated beam using - for example - a torch along a broken or curved line; then the assembly of the sections thus obtained by joining the projecting parts of one of the sections with the previous projecting parts of the other section. The sections of the initial beam can be made integral by the interposition of rectangular sheet metal elements. It is also possible to increase the rigidity of the new beam by adding additional profiled elements. These beams had only limited success at the time because of their high cost price. Since then, the production of these beams has been fully automated using machines cutting in a zigzag according to a given program, using a torch. Immediately after cutting and without interruption, automatic dressing and welding takes place. A larger reduction in manufacturing prices can be achieved by using a cutting press. However, these alveolar beams, which on one side have greater rigidity and which are capable of supporting more large loads have a height significantly greater than that of a solid beam. This characteristic deprives them of any interest in steel-concrete construction, since it would entail a substantial increase in the total height of a storey and therefore of the complete building.
The invention aims to provide a composite steel-concrete beam of low height, compact and light.
This object is achieved by the beam according to the invention as it is characterized in claim 1. Preferential alternative embodiments are described in the dependent claims.
The advantages which flow from the invention come mainly from its compactness and its reduced weight (reflected in the price of the material, the transport, the assembly and the weight of the construction). There is also the possibility of passing pipes, air conditioning ducts etc. through the alveoli, therefore ease of subsequent rearrangement; moreover, the false ceiling can be in direct contact with the lower wing of the beams.
The idea underlying the invention consists in compensating for the loss of rigidity due to the cells in the beam by an optimal interaction beam, concrete slab and reinforcements embedded in the concrete but integral with the beams. The beam-reinforced concrete connection can in principle be carried out by any connector means, such as stud, concrete rod, trellis etc., fixed on the beam and guaranteeing collaboration between the latter and the concrete slab. For certain applications, it will be necessary to use beams made of high quality steel, with very high yield strength, such as steel of the FeE 460 type. Similarly, the concrete must have a minimum thickness. and a high compressive strength, such as of type C 40. It should be noted that the slab is subjected to the usual longitudinal pressure to which is superposed in the present case a localized bending in the cells in the beam.
The invention will be better understood with the aid of drawings which show a possible embodiment thereof. We distinguish in

- Fig. 1 a section of a floor supported by a reconstructed composite beam and in
- Fig. 2 a section along line II - II through FIG. 1.

We distinguish in the figures, the concrete layer 1 of the floor in which are embedded the reinforcements 9 and the studs 2 welded to the upper wing 3 of the beam 4. The core 5 of the beam comprises cells 7 of trapezoidal shape separated by teeth 8; the studs 2 are located above all at the level of the teeth. The cells must not extend over the entire height of the core, but a sufficient height of material must be kept to absorb the shearing forces. This height, which is a function of the type of beam - quality of the steel, thickness of the core - is for example 20% of the total height of the core. Both the size and the shape of the cells - trapezoidal, triangular, circular, square, etc. - can vary within wide limits. Note, however, that the quantity of material removed must at most be equal to half the quantity of material from the starting core. It is possible to choose a uniform tooth width over the entire length of the beam.
Although it is in principle possible to use laminated beams with symmetrical flanges, it is often advantageous to use reconstituted beams. This technique makes it possible to choose for each wing, the optimal thicknesses and widths; the upper wing 3, providing the foundation for the concrete and for the studs, can be more dimly dimensioned than the lower wing 6 having to absorb the majority of the traction forces. To make these reconstituted beams, it is possible to take T-profiles, cut cells in the core and weld a flat iron having the required dimensions to the profile at the teeth.
A more elegant way of proceeding is to take a beam obtained by rolling, for example of the IPEA or HEAA type, to cut it along a trapezoidal line into two equivalent parts and to solder a flat iron on each set of teeth. This makes it possible to reconstruct two mixed cellular beams from a single laminated beam, which represents a definite economic advantage.
In the example shown, the beams are spaced 2.40 meters apart, for example, and have the following characteristics:
core height: 300 mm
upper wing thickness: 15 mm
upper wing width: 150 mm
lower wing thickness: 13 mm
lower wing width: 300 mm
cell height: 250 mm
large base of a cell: 500 mm
small base of a cell: 200 mm
number of studs per tooth: 4
concrete layer thickness: 120 mm
The whole, beam-concrete, as shown in FIG. 2, can be prefabricated at the factory and sold in widths and lengths up to 3 m and 10 m respectively. The dimensions of this prefabrication are obviously limited by the means of transport available.

Claims

1. Reconstituted composite beam comprising a steel profile, the core of which has recesses, reinforcing elements and concrete, characterized in that the profile (4) has two wings, the first of which (3) is in contact with less over its entire external surface with a concrete slab (1) provided with reinforcements (9) and the second (6) of which is in the open air, in that the recesses (7) in the core are extend from said first wing (3) over at most 90% of the height of the core and in that connecting means are fixed on the external face of said first wing (3) at least in places where the soul does not have a recess and extends into the reinforced concrete slab (1).

2. Mixed beam according to claim 1, characterized in that the recesses (7) have a trapezoidal, square, circular or oval shape.

3. Mixed beam according to claim 1, characterized in that the concrete slab has at least a thickness of 10 centimeters.

4. Mixed beam according to claim 1, characterized in that the connector means are studs (2) welded to the external face of said first wing.

5. Mixed beam according to claim 4, characterized in that the studs (2) are arranged in groups of four.

6. Mixed beam according to claim 1, characterized in that a recess (7) extends at most over 80% of the height of the core.

7. Mixed beam according to claim 1, characterized in that said first wing (3) of the profile has a width less than said second wing (6).

8. Mixed beam according to claim 1, characterized in that said first wing (3) of the profile has a thickness less than said second wing (6).

9. Combined beam according to claims 1, 7 or 8, characterized in that said first wing (3) of the profile has a lower quality steel than that of said second wing (6).

10. Mixed beam according to claims 1 or 9, characterized in that the steel of the second wing (6) is at least of the FeE460 type.