Pre-fabricated load-bearing beam

Abstract

Pre-fabricated load-bearing beam (10) which extends between two opposing ends (10a, 10b) along a longitudinal axis (X) and comprises a bottom plate (12) and a reinforcement (11), having at least one reticular lattice (13, 14), one or more reinforcement bars (16) parallel to said longitudinal axis (X), and rest members (18) in correspondence with said opposing ends (10a, 10b).

Description

FIELD OF THE INVENTION

[0001] The present invention concerns a steel pre-fabricated load-bearing beam that can be used in the construction sector for the construction of buildings, bridges, structures or other. The beam is advantageously light and self-supporting, and has excellent fire resistance characteristics.BACKGROUND OF THE INVENTION

[0002] In the field of civil and industrial construction, fire resistance is an essential performance that characterizes multiple structural elements, including beams.

[0003] Mixed steel-concrete lattice beams of the pre-fabricated type are known, comprising one or more reticular metal lattices associated with a reinforced concrete slab or floor slab, in which the lower portion of the lattices is incorporated, or associated with a steel bottom plate.

[0004] An example of such beams is shown in KR 102 056 313. This beam has a longitudinal reinforcement element, disposed substantially on the bottom plate and protruding longitudinally with respect thereto, which is attached to the upper portion of a vertical plate to which a reticular metal lattice is also attached.

[0005] Known beams also normally comprise members used only to rest the beam on, and to close the lattice's force triangle. The rest members are formed by two so-called hammers that protrude from the beam, or by a flat that fulfils the same purpose, and by a head short beam, transverse to the beam's axis, which serves to adjust the resting surface by making it coplanar with the beam's intrados as a function of the installation height. These components are made of round or square structural carpentry rods with cross-sectional dimension or diameter from 8 to 62 mm.

[0006] In order to guarantee the required fire performance, building techniques provide the application of an external layer of flame-retardant paint (intumescent treatment) on the steel or concrete bottom plate, the use of increased thicknesses for the bottom plate exposed to fire, so as to prolong the resistance of the element during a fire, the use of beams protected by pre-fabricated concrete reinforcement covers, or the insertion of reinforcement bars, so-called "fire bars", inside the resistant section, and therefore protected from a fire thanks to a supplementary cast on site.

[0007] All these solutions have disadvantages, in particular: the application of the paint has to be done and certified on site, the increase in the components of the beam can make it uneconomical, the use of a lower concrete reinforcement cover does not allow to produce a so-called "slim floor" beam, that is, in thickness with the floor, and the insertion of reinforcement bars inside the section greatly complicates the resting of the beam, since there is a large amount of steel to be laid on site in order to guarantee the attachment of the bars.

[0008] Another problem with mixed concrete and steel lattice beams, as well as non concrete and steel mixed, which are exposed to fire is, in addition to their sudden loss of strength, the increase in centerline deformation. This increase is plausible and controllable, but can create aesthetic defects especially on the perimeter beams that normally also have side panels to contain the completing casting. These side panels, in fact, are sheets with a thickness comprised between 2 and 10 mm welded to the beam's bottom plate and with a height of between 16 and 120 cm. The beam, when inflecting, creates stress states even in the side panels, which leads them to warp, resulting in serious aesthetic and structural defects.

[0009] There is therefore the need to perfect a pre-fabricated load-bearing beam with excellent fire resistance characteristics that can overcome at least one of the disadvantages of the state of the art.

[0010] One purpose of the present invention, which corresponds to the technical problem to be solved, is to improve traditional pre-fabricated load-bearing lattice beams, made of steel or steel-concrete mix, in terms of fire resistance.

[0011] Another purpose of the present invention is to provide a steel or steel-concrete mix load-bearing beam already pre-fabricated with the reinforcement bars that will guarantee the fire resistance required by current legislation.

[0012] Another purpose of the present invention is to provide a fire-resistant load-bearing beam that has a reduced deformability of the side panels that may be present in order to contain the concrete casting.

[0013] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.SUMMARY OF THE INVENTION

[0014] The present invention is set forth and characterized in the independent claim. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0015] In accordance with the above purposes and to resolve the technical problem described above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a pre-fabricated load-bearing beam, preferably made of steel or steel-concrete mix, according to the present invention extends between two opposing ends along a longitudinal axis and comprises a bottom plate and a reinforcement, having at least one reticular lattice, one or more reinforcement bars parallel to the longitudinal axis, and rest members in correspondence with the opposing ends. The at least one reticular lattice is connected at the lower part to the bottom plate and at the upper part to at least one, preferably two or three, upper stringers. The upper stringers are essentially linear bars parallel to the longitudinal axis X with a length equal to that of the beam. In accordance with one aspect of the present invention, the reinforcement bars are attached at the head to the rest members.

[0016] Doing so achieves at least the advantage of obtaining a pre-fabricated beam with already integrated reinforcement bars, which are those that will give fire resistance characteristics to the beam, thus simplifying and speeding up on site installation.

[0017] In accordance with the present invention, each of the rest members comprises a head element external to the bottom plate and disposed transversally to the longitudinal axis, to which the reinforcement bars are attached.

[0018] In accordance with the present invention, each of the rest members can comprise at least one support element projecting cantilevered from the bottom plate parallel to the longitudinal axis, and to which the head element is attached.

[0019] According to the present invention, the reinforcement bars are disposed at a distance from the bottom plate comprised between about 20 mm and 60 mm above the support element, and have a diameter larger than that of the upper stringers.

[0020] In accordance with another aspect of the present invention, the head element comprises at least one plate, preferably made of metal, orthogonal to the bottom plate and defining a contact surface to which a head portion of the reinforcement bars is attached.

[0021] In accordance with another aspect of the present invention, the head portion is preferably welded to the contact surface.

[0022] In accordance with another aspect of the present invention, the head element can comprise an auxiliary plate disposed above the plate, parallel to the bottom plate, and connected to the at least one reticular lattice.

[0023] According to a variant of the present invention, the auxiliary plate can be disposed below the plate, parallel to the bottom plate and connected thereto.

[0024] In accordance with another aspect of the present invention, the plates can be a single component or be distinct components connected to each other, for example by welding.

[0025] In accordance with another aspect of the present invention, the beam can comprise a side panel attached to at least one longitudinal edge of the bottom plate and formed by at least two distinct side panel modules disposed side by side without a joint.

[0026] In accordance with another aspect of the present invention, two adjacent side panel modules are placed side by side with a head and tail portion thereof partly overlapping, these portions being free to slide, or to move slightly, in the event the beam flexes.

[0027] In accordance with another aspect of the present invention, the head or tail portion can be "S" shaped.

[0028] In accordance with a variant of the present invention, the beam can comprise a connection element attached to a first of two adjacent side panel modules and configured to overlap with a second of the two adjacent side panel modules.DESCRIPTION OF THE DRAWINGS

[0029] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein: fig. 1 is a lateral view of a pre-fabricated load-bearing beam according to the present invention; fig. 2 is a top plan view of fig. 1; fig. 3 is an enlarged detail of fig. 1; fig. 4 is a view along section IV-IV of fig. 1; fig. 5 is a lateral view of a pre-fabricated load-bearing beam according to the present invention comprising a side panel; fig. 6 is a top plan view of fig. 5; fig. 7 is a view along section VII-VII of fig. 5; figs. 8-10 are schematic top views showing possible coupling modes of two adjacent side panel modules; fig. 11 is a schematic lateral view of the beam of fig. 5 under normal load conditions; and fig. 12 shows the beam of fig. 11 stressed under flexion.

[0030] We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

[0031] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications.DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

[0032] With reference to figs. 1-2 and 5-6, a load-bearing beam 10 according to the present invention extends between two opposing ends 10a, 10b along a longitudinal axis X and comprises at the upper part a reinforcement 11 and at the lower part a base or bottom plate 12 which can be anchored, during use, to generic support elements, for example pillars, crossarms or similar elements, not shown in the drawings.

[0033] The reinforcement 11 and the bottom plate 12 can be made of metal, preferably steel. In some possible solutions, the bottom plate 12 can be or comprise a floor slab made of cementitious material.

[0034] The bottom plate 12 can essentially be a rectangular plate with a continuous thickness comprised between about 3mm and about 10mm, for example of about 6mm.

[0035] The reinforcement 11 comprises at least one, but preferably two reticular lattices 13, 14, each consisting of a plurality of converging diagonal rods connected to each other in a respective upper and lower portion.

[0036] The reticular lattices 13, 14 can have an essentially sinusoidal, or in any case repetitive, profile.

[0037] The reticular lattices 13, 14 are parallel to each other and extend for the entire length of the beam 10.

[0038] The reticular lattices 13, 14 are connected at the lower part to the bottom plate 12 and at the upper part to at least one, preferably two or three, upper stringers 15. The upper stringers 15 are essentially linear bars parallel to the longitudinal axis X with a length equal to that of the beam 10.

[0039] In some solutions, the beam 10 can also, or alternatively, comprise one or more lower stringers.

[0040] The beam 10 comprises one or more reinforcement bars 16 parallel to the longitudinal axis X. The reinforcement bars 16 are known to the person of skill in the art by the term "fire bars" and essentially have the function of increasing the fire resistance of the beam 10 by reducing its deformations in the event of high temperatures.

[0041] The reinforcement bars 16 are disposed close to the bottom plate 12, at a distance D from the bottom plate 12 comprised between about 20mm and about 60mm, preferably within the range of about 40mm.

[0042] The reinforcement bars 16 have a length greater than that of the bottom plate 12 and extend cantilevered beyond it. For example, the cantilever height S of the reinforcement bars 16 can be between about 2% and about 5% of the length L of the bottom plate 12, as measured along the longitudinal axis X, fig. 3.

[0043] In the example embodiment of figs. 4 and 7, the reinforcement bars 16 can have a round section with a diameter comprised between about 25 mm and about 45 mm, for example of about 32 mm.

[0044] The reinforcement bars 16 have a diameter greater than the diameter of the upper stringers 15. This is because they have an explicit structural reinforcement function, especially in the case of high temperatures caused by fire.

[0045] The reinforcement bars 16 are preferably disposed on opposing sides of the reticular lattices 13, 14, on which they can be rested, but not constrained.

[0046] The beam 10 is provided, at its ends 10a, 10b, with rest members 18, as shown in figs. 1-2 and 5-6. The rest members 18 project from the bottom plate 12 parallel to the longitudinal axis X and have at least the function of allowing the beam 10 to rest during the construction of building work. The rest members 18 constitute a kind of lengthening of the bottom plate 12.

[0047] According to the present invention, the reinforcement bars 16 are attached to the rest members 18. Therefore, the latter also function as a support for the reinforcement bars 16. In this sense, the beam 10 can already be pre-fabricated with the reinforcement bars 16 integrated, this simplifying and speeding up on site installation.

[0048] With reference to fig. 3, each rest member 18 comprises at least one support element 19, known to the person of skill in the art by the term "hammer", projecting cantilevered from the bottom plate 12 parallel to the longitudinal axis X, and a head element 20, known to the person of skill in the art by the term "short beam", attached to the end of the support element 19 transversely to the longitudinal axis X.

[0049] The head element 20 is outside the overall dimension of the bottom plate 12, in the sense that it rises relative to the plane of the bottom plate 12.

[0050] The reinforcement bars 16 are attached to the head element 20 and are disposed above the support element 19, at a certain distance therefrom. Optionally, the reinforcement bars 16 can be sustained, at certain points along their length, by containing brackets 17 in order to prevent unwanted flexural behavior before being definitively incorporated by the concrete cast on site, as shown in figs. 1-2, 4, 5-7.

[0051] With reference to fig. 3, the head element 20 comprises at least one slab or plate 21 defining a contact surface 21a for a head portion 16a of the reinforcement bars 16. The contact surface 21a is essentially orthogonal to the longitudinal axis X.

[0052] The head portion 16a of the reinforcement bars 16 can be joined to the contact surface 21a by welding.

[0053] The contact surface 21a is essentially flat and continuous. However, it is not excluded that seatings, projections or holes can be made on the contact surface 21a to allow a correct positioning of the head portion 16a of the reinforcement bars 16 before, or simultaneously with, the welding or other suitable joining technology.

[0054] In one example embodiment, the plate 21 can be a sheet with a rectangular shape and a thickness of between about 5 mm and about 40 mm.

[0055] The head element 20 can also comprise an auxiliary slab or plate 22 attached at the upper or lower part, and orthogonally, to the plate 21.

[0056] The auxiliary plate 22 can be connected, with respect to a free end thereof, to the lattices 13 and 14, if disposed above the plate 21, or to the bottom plate 12, if disposed below the plate 21.

[0057] The auxiliary plate 22 advantageously allows to reduce the stresses acting on the plate 21, as well as to close the forces triangle with the lattices 13, 14 or to connect directly to the bottom plate 12.

[0058] In one example embodiment, the auxiliary plate 22 can have a rectangular shape with a thickness of between about 5 mm and about 40 mm.

[0059] The support element 19 can comprise two distinct support bars 19a, 19b having a length M smaller than the length of the bottom plate 12, see figs. 2, 4, 6 and 7. For example, the length M of the support bars 19a, 19b can be between about 10% and about 20% the length L of the bottom plate 12, as measured along the longitudinal axis X.

[0060] According to some embodiments, figs. 5-7, the beam 10 can have a side panel 24 attached to at least one longitudinal edge 12a of the bottom plate 12 and configured to contain the completion concrete casting that is laid on site.

[0061] The side panel 24 projects vertically from the bottom plate 12, beyond the reticular lattices 13, 14 and the upper stringers 15. This is necessary for the side panel 24 to properly act as a formwork for the concrete casting.

[0062] The side panel 24 is formed by at least two distinct side panel modules 25 disposed side by side and attached to the bottom plate 12 by welding.

[0063] The side panel module 25 can essentially be a flat sheet with a rectangular shape. Optionally, the side panel module 25 can comprise an upper flap or lip 26 facing toward the inside of the beam 10. The upper lip 26 can be parallel to the bottom plate 12.

[0064] Two adjacent side panel modules 25 are placed side by side, with a head 25a and tail 25b portion thereof partly overlapping, but without a join (fig. 8). In this case, the side panel modules 25 are slightly misaligned.

[0065] The overlap between the head 25a and tail 25b portions involves a section of the order of a few centimeters, for example between about 50 mm and about 200 mm, preferably at least 80 mm.

[0066] According to a variant embodiment, the head 25a or tail 25b portion can be "S" shaped, see fig. 10.

[0067] According to another variant embodiment, fig. 9, the beam 10 can comprise a connection element 27 attached, for example by welding, to one of the side panel modules 25 and configured to overlap with the next side panel module 25.

[0068] According to some embodiments, the connection element 27 can be a metal flat or plate.

[0069] As can be seen in figs. 11-12, the side panel 24, in the event the beam 10 bends, for example due to overheating caused by temperatures, does not deform because the individual side panel modules 25 can partly overlap with each other, in this specific case thanks to the presence of the connection elements 27, maintaining the continuity of the surface without warps or deformations. The traditional aesthetic and functional disadvantages caused by monolithic side panels are therefore avoided.

[0070] It is clear that modifications and / or additions of parts may be made to the beam 10 as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

[0071] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of a pre-fabricated load-bearing beam, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0072] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

1. Pre-fabricated load-bearing beam (10) which extends between two opposing ends (10a, 10b) along a longitudinal axis (X), comprising a bottom plate (12), at least one reticular lattice (13, 14), at least one upper stringer (15), one or more reinforcement bars (16) parallel to said longitudinal axis (X), rest members (18) in correspondence with said opposing ends (10a, 10b), said rest members (18) protruding longitudinally from said bottom plate (12) and comprising a support element (19) projecting cantilevered from the bottom plate (12) and a head element (20) attached to the end of said support element (19), wherein said reinforcement bars (16) are attached at the head to the head element (20) of said rest members (18), characterized in that said reinforcement bars (16) are disposed at a distance from said bottom plate (12) comprised between about 20 mm and 60 mm above said support element (19), and have a diameter larger than that of said upper stringers (15).

2. Beam (10) as in claim 1, characterized in that said reinforcement bars (16) are disposed on opposing sides of the reticular lattices (13, 14) on which they rest, but are not constrained.

3. Beam (10) as in claim 1 or 2, characterized in that each of said rest members (18) comprises a head element (20), external to said bottom plate (12) and disposed transversally to said longitudinal axis (X), to which said reinforcement bars (16) are attached.

4. Beam (10) as in claim 3, characterized in that said head element (20) comprises at least one plate (21) orthogonal to said bottom plate (12) and defining a contact surface (21a) to which a head portion (16a) of said reinforcement bars (16) is attached.

5. Beam (10) as in claim 4, characterized in that said head portion (16a) is welded to said contact surface (21a).

6. Beam (10) as in claim 3, 4 or 5, characterized in that said head element (20) comprises an auxiliary plate (22) disposed above said plate (21) parallel to said bottom plate (12), and connected to said at least one reticular lattice (13, 14).

7. Beam (10) as in any claim hereinbefore, characterized in that it comprises a side panel (24) attached to at least one longitudinal edge (12a) of said bottom plate (12) and formed by at least two distinct side panel modules (25) disposed side by side without a joint.

8. Beam (10) as in claim 7, characterized in that two adjacent side panel modules (25) are placed side by side with a head and tail portion (25a, 25b) thereof partly overlapping, being able to slide in the event said beam (10) flexes.

9. Beam (10) as in claim 8, characterized in that said head or tail portion (25a, 25b) is "S" shaped.

10. Beam (10) as in claim 7, characterized in that it comprises a connection element (27) attached to a first of two adjacent side panel modules (25) and configured to overlap with a second of said two adjacent side panel modules (25).

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