IMPROVEMENTS IN AND RELATING TO COMPOSITE BEAMS

Abstract: The invention relates to an improvement in a steel beam in composite action with concrete, said beam (1) comprises at least one projecting, horizontal bearing plate (3) for supporting floor structures (4) and said improvement is intended to be fastened to an upper part (6) of the beam in its longitudinal extension. The improvement consists of a prefabricated ladder (2) comprising at least two longitudinal profiles (5), running parallel to and in a predetermined distance from each other, said profiles can be fixed in position to the upper part (6) of the beam (1) and between said profiles a number of transverse connecting elements (7) extend in a predetermined distance from each other for necessary transmission of shear force in reaching static composite action between the beam (1) and concrete which is performed later and said ladder (2) in increasing of the compression zone of the steel cross-section is intended to improve the load carrying capacity of the beam (1) before casting and in this way eliminate the need of propping before the concrete has hardened.

Description: Improvements in and relating to composite beams The present invention relates to an improvement in a floor beam of steel in composite action with concrete, said beam comprises at least one projecting, horizontal bearing plate for supporting floor structures and said improvement is intended to be fastened to an upper part of the beam in its longitudinal extension. For steel beams in composite action with concrete it is necessary that the transmission of shear force between the steel cross-section and concrete is guaranteed. This is often done by aid of so called studs (bolts), which are welded to the steel beam, preferably to its upper flange. Depending on actual forces which shall be transmitted, a lot of studs can be required. In the composite cross- section concrete only takes up compression forces, some- times together with a smaller part of the steel cross- section, while the tensile forces are only taken up by the steel. Before the concrete has hardened the load carrying capacity is therefore limited depending on that the con¬ crete compression zone is lacking. The load carrying ca- pacity of the steel cross-section itself often is so limited that not even the dead load of the floor can be supported, why the beam must be propped until the concrete has obtained the strength required. The propping involves an evident drawback, since it often is a bar for a rational constructing. An object of the present invention is to provide an im¬ provement in composite beams by which the steel area of the upper part of a beam in a simple way can be increased and hereby increase the compression zone of the steel cross- section before the hardening of the concrete. By this the need of propping is eliminated in the same time as the improvement in an effective way guarantee the transmission of shear force between steel and concrete in the composite cross-section. The improvement also admits that the manu¬ facturing of the same can be rationalized in that it can be prefabricated in a number of variants and sizes and be kept in stock for use to different beam sizes depending on loads and spans. The improvement also has such a design that it very easy and quickly can be fixed to the upper part of a floor structure supporting beam e.g by longutudinal, in¬ termittent welding, which also can be performed by an automatic machine. The characteristic features of the invention are set forth in the following claims. The invention will now be described in more detail below with reference to the accompanying drawing, which illu¬ strates a preferable embodiment of the improvement according to the invention in a schematic perspective view, when it is mounted to the upper part of a steel beam schematically indicated. As will be seen from the drawing it illustrates a sche¬ matically indicated, as a composite beam formed steel beam 1 in a perspective view having a preferable embodiment of • the present invention in the form of a prefabricated ladder 2, which is fastened to an upper part 6 of the beam 1 in its longitudinal extension. The beam 1 is made of steel and has a form not closer illustrated in the drawing, which admits a composite action with concrete and comprises at least one projecting, horizontal bearing plate 3 for supporting floor structures 4. The prefabricated ladder 2 comprises at least two longitudinal profiles 5 running parallel to and in a predetermined distance from each other, said profiles are positionally fixable to the upper part 6 of the beam 1. In the preferred embodiment illu¬ strated, the profiles 5 consist of rectangular steel pro¬ files. A number of transverse connecting elements 7 pro¬ vided in a predetermined distance from each other extend between the profiles 5. These bring about necessary transmission of shear force for static composite action between the beam 1 and concrete which is performed later. In the embodiment preferred according to the present in¬ vention, the connecting elements 7 consist of angle bended steel profiles, which are fixed by welding to the longi¬ tudinal profiles 5 having their apex formation 8 directed across the longitudinal extension of the profiles 5. The connecting elements 7 can be designed with any suitable form, but angle bended steel profiles are to be preferred. The connecting elements 7 are mounted in parallel to each other having a mutual distance of about 200-600 mm along the whole extension of the ladder 2.

Claims: Claims 1. An improvement in a steel beam in composite action with concrete, said beam (1) comprises at least a pro¬ jecting, horizontal bearing plate (3) for supporting floor structures (4) and said improvement is intended to be fastened to an upper part of the beam in its longitudinal extension, characterized in that a prefabricated ladder (2) comprising at least two longitudinal profiles (5) running parallel to and in a predetermined distance from each other, said profiles are positionally fixable to the upper part (6) of the beam (1) and between said profiles a number of transverse connecting elements (7) extend in a pre¬ determined distance from each other for necessary trans¬ mission of shear force in reaching static composite action between the beam (1) and concrete which is performed later and said ladder (2) in increasing of the compression zone of the steel cross-section is intended to improve the load carrying capacity of the beam (1) before casting and in this way eliminate the need of propping before the concrete has hardened. 2. An improvement according to claim 1, characterized in that the connecting elements (7) consist of angle bended steel profiles, which are fixed to the longitudinal pro¬ files (5) having their apex formation (8) directed across the longitudinal extension of the profiles (5). 3. An improvement according to claim 1, characterized in that the longitudinal profiles (5) consist of rectangular steel profiles. 4. An improvement according to claim 1 or 2, characterized in that the connecting element (7) are pro- vided in parallel to each other having a mutual distance of about 200-600 mm.

Inventors: THOR JOERGEN, THOR, JOERGEN
Applicants: THOR JOERGEN, THOR, JOERGEN
Application year: 1990
Main classification: E04B5
IPC codes: E04B5, E04C3, E04C5