A BEAM INTENDED FOR COOPERATION WITH BETON

Abstract: The invention relates to a beam intended to cooperate with cast concrete and provided with devices (1) for improving the connection between the beam (3) and the concrete (11) which is cast against the beam (3). The invention is characterized in that the beam (3) is provided with at least one elongated anchoring device (1) which is welded along the beam and which extends into the concrete (11) such as to be grouted thereby, and in that the anchoring device is configured in a manner to impart large crush areas to the concrete (11) upon the occurrence of shear in different directions.

Description: A beam intended for cooperation with beton. The present invention relates to a beam having provided thereon devices which function to improve the connection between the beam and a concrete mass cast or moulded against said beam, and therewith to enhance the mutual coaction between beam and concrete. More specifically, the invention relates to the problem of binding steel profiles to concrete in a manner which will prevent sliding between the two materials and thus ensure that occurrent shear forces are transmitted therebetween, this transmission of shear forces being necessary if effective coaction between the materials is to be obtained. The most common field of application lies in beam profiles which support a concrete slab or plate on the lower flange of said beam, said slab being capable of enhancing the stiffness and load-bearing capacity of the beam, provided that the transfer of shear forces can be ensured. Another field of application lies in column or pillar structures which incorporate an internal steel- profile core and a concrete mass cast around said core, for different reasons; if an effective shear bond is achieved, the concrete can be used for force trans¬ mission purposes and for increasing the rigidity of the column (inertia radius). The desired coaction between steel and concrete is achieved conventionally, by welding to the beam so- called studs, often with the aid of special apparatus - or other intermittent devices, such as blocks, ties etc. These traditional methods are encumbered with drawbacks, however: For instance, when flash-welding studs onto the beams, the welding zones are subjected momentarily to large quantities of energy, which has a deleterious effect on the beam profile material; Furthermore, the studs must also be relatively long, so that the shear-capacity of the studs is not restricted excessively by crush zones in the concrete. This con¬ stitutes problems when the outer surface of the concrete grout lies close to the steel profile. Furthermore, the studs are easily bent when subjected to load, which contributes towards fracturing of the concrete in the vicinity of the studs. Those methods in which blocks and ties are used also require the application of manual welding operations; Finally, the costs involved with known methods are high when seen in relation to the shear-transfer capacity of each separate device. The object of the present invention is to provide an alternative anchorage device which can be welded quickly to the beam and which will result in coaction between the beam and the concrete which is at least equally as effective as the coaction achieved with methods known hitherto. This object is achieved in accordance with the present invention by providing the beam with at least one elon¬ gated anchoring device which is welded firmly to the beam along the length thereof and which extends into the concrete cast therearound, and which device is con¬ figured such as to form large crush areas in the con- crete upon the occurrence of shear in different direc- tions. The anchoring device may be produced in the same lengths as the beams, and may comprise a flat bar which has been pressed or rolled to a configuration such as to obtain the aforesaid large crush areas. By this is meant that the anchoring device is given a configuration such that when embedded or grouted in the concrete, it is impossible for the device to twist or bend in any direc¬ tion, but will result in crushing of the concrete over a large area thereof. The anchoring device may also con- sist of angle iron, although in this case the crush area will be small in the longitudinal direction of the device when shear takes place, unless the legs of the angle iron are appropriately deformed prior to the concrete being cast. According to one preferred embodiment of the invention, the anchoring device is configured with a straight foot part, which is welded to the beam and which merges with a curved part intended for embedment in the concrete and which extends in wave-form in the longitudinal direction of the anchoring device, alternately on both sides of the foot part, with the greatest amplitude at its free edge. Such an anchoring device can be produced and welded to the beam very easily, and will give rise to large crush areas. Thus, an elongated anchoring device configured in accor¬ dance with the invention can be manufactured from simple starting material in an automated process and can be welded to the beam in a conventional automatic welding line. For example, the anchoring device can be welded to the beam at the same time as the beam components are welded together. Furthermore, in the case of the present invention, the application of heat is more gentle than in the case of resistance welding. Other advantages reside in the fact that the transmission of load to the concrete is continuous, in the absence of pronounced cleavage forces which characterize traditional methods, while because of its geometry, the anchoring device requires only a small amount of space, i.e. the outer defining surfaces of the concrete can be allowed to lie close to the steel beam. The invention can be applied with particular advantages in the construction of beam floor structures, in which steel load-carrying beams are placed on the same level as flooring slabs, irrespective of whether these slabs are moulded on-site or prefabricated with concrete cast on site on the upper side of the slabs and jointed onto the steel beams. In the case of floor structures of this configuration - which is rapidly winning ground in its prefabricated variant - it is particularly important to ensure that the aforesaid coaction will be achieved, since the low cross-sections of the beams used result in problematic downward flexing of the beams, which problem can be counteracted by using concrete to enhance the bending resistance of the beam zones, such concrete being necessary under all circumstances. This can have particular importance in the event of fire. Furthermore, the requirements of building standards relating to progressive collapse can be satisfied at lower costs, by attaching the necessary connecting iron between concrete slab and beam to the beam via the anchoring device. The dimensions and quality of the starting material can be varied, so as to be adequate for different fields of use. For instance, different dimensions are required for bridge deck structures than for the floor structures of conventional domestic dwellings. The invention will now be described in more detail with reference to an exemplifying embodiment thereof illu- strated in the accompanying drawing, in which Figure l is a plan view of the anchoring device; and Figure 2 is a cross-sectional view of a beam provided with the anchoring device and shows one end of a con- crete flooring slab placed adjacent the beam and grouted in concrete. Figure 1 illustrates a preferred embodiment of an anchoring device 1, seen from the right in Figure 2. The foot part 2 of the anchoring device is welded to the web 4 of the beam 3 and the main part 5 of the anchoring device, i.e. the part thereof which is embedded or grouted in the concrete, extends in a wave form, sym¬ metrically and alternately on both sides of the foot part 2. The free edge 6 of the main part 5 has the greatest amplitude. As will be seen from Figure 2, the beam has a bottom and a top flange 7 and 8 respectively, between which one end part 9 of a concrete flooring slab 10 is fitted. A space located between the beam 3 and the end part 9 of the slab 10 is filled with jointing or grouting concrete 11, which surrounds the anchoring device 1 and merges with a layer 12 of top concrete, which spreads along the concrete slabs 10 and the upper flange 8 of the beam 3, to increase the bending resistance of the structure with regard to downward bending. It will be understood that the invention is not restric- ted to the described and illustrated embodiment, and that modifications can be made within the scope of the invention defined in the following claims. In the case of H-beams, an anchoring device can be welded solely to one side of the web with good results, even when con- crete slabs are placed on both sides of the web. The anchoring device may also have the form of a flat strip having formed therein two longitudinally extending, parallel slots with short interruptions, these slots enabling tongues to be bent out from the anchoring device, alternately in opposite directions, optionally while twisting the tongues.

Claims: -AMENDED CLAIMS [received by the International Bureau on 1 November 1989 (01.11.89) original claims 1 and 2 replaced by amended claim 1 (1 page) ] A beam comprising a web (* ) and two flanges (7,8) extending along the edges of the web and directed in the same direction, which beam is inτende for coaction with cast concrete and is provided with devices (1) for improving the connection between the beam (3) and the concrete (11) which is cast against the beam (3), c h a r a c t e --- -- c in that the beam (3) is provided with at least one elonga¬ ted anchoring device (1) which has a plane foot part (2) which is welded to the web (4*) of the beam, and merges with a curved grouting part (5) configured to exte d in a wave form in the longitudinal direction cf the anchoring device, alternately on both sides of the foot part (2) with the largest amplitude at the free edge (6) of the grouting part (5) , which anchoring device extends into the concrete (11) and is grouted therein.

Inventors: HOLM THURE, HOLM, THURE
Applicants: CREATOR CONSULT AB
Application year: 1989
Main classification: E04C3
IPC codes: E04B5, E04C3