IMPROVED STRUCTURAL BEAM OF THE MIXED TYPE CONCRETE-METAL STRUCTURE

Abstract: The so-called mixed structure type beams for buildings are comprised of concrete having embedded therein a metal girder formed with a base plate (1), along the median line of which a so-called lattice structure is applied by welding, being made of a web (2) which is welded to the base plate (1) and supports an upper stringer comprising one or more sec­ tion irons (4, 4′) welded to the web (2). According to the inven­ tion this metal girder is improved so as to reduce up to the 40% the weight of iron required for its preparation, what is obtained by welding the firder web (2) to the base plate (1) parallel to the median line (X) of the latter and at a distance therefrom at least sufficient for the lattice structure to be comprised in one of the two longitudinal half portions of the base plate (1).

Description: "IMPROVED STRUCTURAL BEAM OF THE MIXED TYPE CONCRETE-METAL STRUCTURE" The present invention relates to an improvement to the building beams of the so-called mixed structure type, i.e. those comprised of concrete embedding a selfsupporting metal girder. The self-supporting metal girders presently used for manufacturing mixed-structure beams are generally comprised of a base plate, along the median line of which a lattice structure is welded, being made of at least one web welded to the base plate and supporting an upper stringer which is also welded to the web. The upper stringer is usually formed of one or more section irons and the web is formed of zigzag bent rounds bars, diagonal rods or, in its simplest configuration, a perforated plate of adequate thickness when considering that the iron required for obtaining said web must be in a quantity enough to render it suitable to withstand the stresses caused by the relative motion between the upper and the lower stringers. These beams are commonly manufactured in specialized factories and then transported to the building yards where they are installed and anchored each other by means of reinforced-concrete rods (U-bolts) being stretched or compressed. For manufacturing these U-bolts quantities of iron are required which add to the quantity necessary to manufacturing the metal girders, Wi tii consequent increase of the final costs. It is the object of the present invention to improve the metal girders hitherto known, so as to substantially reduce the quantity of iron required for their manufacture and installation. This object is achieved through a modification of the structure of the metal girder to the effect that its web is welded to the base plate in a direction parallel to the median line thereof and at a suitable distance therefrom, rather than being welded directly onto the median line itself. The metal girders of the present invention thanks to their novel, offset construction, are capable to be laid with juxtaposed ends for a given length at the pillar regions, so that said ends, coupled by the subsequent concrete casting, co-operate each other in the load distribution. Such a co-operation allows for a lightening of the girder web structure, thus saving some iron required for the manufacture of the web. Advantageously an appreciable saving of iron is achieved already in the girder construction. A further advantage is in the fact that an additional saving of iron can be obtained in the building yard when the beam is laid, as the iron required to make the U-bolts for anchoring the beams to the pillars is totally saved, these U-bolts being no longer necessary. In fact the ends of two beams placed side by side in the zone of a pillar are mutually joined and anchored to the pillar by a concrete casting, thus rendering superfluous the adoption of said U-bolts. These and additional advantages of the beam according to the invention will clearly result to those skilled in the art from the following detailed description of an embodiment thereof with reference to the annexed drawing wherein: FIGURE 1 shows a side elevation view of a metal girder according to the invention; FIGURE 2 shows a cross-section view of the same girder along the line A-A' of Fig. 1; FIGURE 3 shows a side elevation view of two girders of the invention laid with their ends placed side by side in correspondence with a pillar; FIGURE 4 shows a top plan view of the girders shown in Fig. 3; and FIGURE 5 shows a cross-section view along the line B-B' of Fig. 3. With reference to Figs. 1, 2 it is seen that the embodiment of beam chosen for the metal girder of the present invention is of the type known under the trademark "REPP" and being the object of prior patents in the name of the same applicant. The girder comprises a base plate 1, of metal sheet, having a web 2 welded thereon which supports an upper stringer 3. This stringer 3, in the embodiment shown, is formed of a pair of round bars 4, 4' between which the ends of a multiplicity of diagonal rods 5 are welded, having the other ends clamped between another pair of round bars 6, 6' or onto a lower plate. The whole of the diagonal rods 5 together with the pair of round bars 6, 6' forms the web 2 of this embodiment of metal girder. With reference to Fig. 2 it is seen how the web 2, by means of the pair of round bars 6, 6' being a part thereof, is welded to the base plate 1 at some distance from the median line X of said plate, so that the web 2 is positioned within one of the two half portions of the base plate 1. It is clear that the distance of the welding zone from the median line X of the base plate 1 may be chosen as desired,. but it should however be appreciated that such a distance cannot be less than a lower limit given by the thickness of web 2, since otherwise this would partially extend beyond the line X into the other half portion. As shown in Fig. 1, the girder of the invention has the feature that the web 2 and the upper stringer 3 have a length greater than the base plate 1, thus extending at each end beyond said plate 1 along a given length L. Such a length L is predetermined through the calcula tions by which the beam is proportioned at the moment of its manufacture. Referring to Fig. 3 it is seen how two beams according to the invention are installed on the pillars 7, 8, 9 with special reference to the pillar 7 where the two beams are laid side by side. Such a positioning is made possible by the fact that the web 2 and the upper stringer 3 of each girder project into the half portion cleared by the web 2 and the upper stringer 3 of the other girder. The length of the base plate 1 corresponds to the distance between pillar 7 and 8 or pillars 7 and 9. It is preferred that the length of the base plate is slightly greater than this distance so as to render the beam installation operations easier. The portion of girder laid between pillars 7 and 8, protruding beyond the pillar 7 overlaps the plate 1 of the girder laid between pillars 7 and 9; similarly the portion of the latter girder, protruding beyond the pillar 7 overlaps the plate 1 of the girder laid between pillars 7 and 8. No iron is required to mutually join the two girders in the pillar area, as the junction is subsequently provided by the concrete casting. In this way the use of the so-called U-bolts is completely abolished, so far necessary for the beams of the prior art. At the outer ends of the beams, corresponding to the external pillars (designated 8 and 9 in the drawings) the girders are anchored to the pillars in a traditional way, such as by stubs. Figs. 4 and 5 clearly show how two stringers are mutually arranged in proximity of a pillar 7 without using auxiliary means to join the ends of the stringers, positioned side by side.

Claims: CLAIMS 1. An improved beam for building purposes with a metal girder comprising a base plate (1) along which a lattice structure is welded being formed of at least a web (2) for supporting an upper stringer (3), characterized in that said lattice structure is welded parallel to the median line of the base plate(2) and at a distance therefrom at least sufficient for the lattice structure to be comprised in one of the two half portions of the base plate (2). 2. An improved beam according to claim 1, characterized in that said lattice structure has a length greater than the base plate (2). 3. A n improved beam according to claim 2, characterized in that said lattice structure projects beyond the base plate (2) at both the girder ends.

Inventors: LEONE, SALVATORE
Applicants: EDIS S.P.A.
Application year: 1985
Main classification: E04C3
IPC codes: E04C3