Support joist and formwork system

Abstract

The present invention concerns, in a first aspect, a support joist (1) for lightweight roof formwork systems, defined by a longitudinal body provided with a smooth upper surface, its length being equal to the length of the panels of the formwork systems, and its height at the longitudinal ends and in the central area (11) equal to the height of said panels. The support joist comprises at least one reinforcement portion (12) defined on the lower surface and configured to reinforce the longitudinal body between the central area (11) and at least one of the longitudinal ends of the longitudinal body, said at least one reinforcement portion (12) comprising a lower coupling (13) configured to couple with the end of a prop. A second aspect of the invention concerns a formwork system comprising said support joist (1).

Description

[0001] DESCRIPTION

[0002] Shoring beam and formwork system.

[0003] OBJECT OF THE INVENTION

[0004] The present invention relates, in a first aspect, to a support beam suitable for lightweight roof formwork systems using props with high load-bearing capacity. A second aspect of the invention relates to a formwork system comprising said support beam.

[0005] BACKGROUND OF THE INVENTION

[0006] Lightweight slabs are a well-known construction technique that allows for significant concrete savings. In addition to their economic advantages, they reduce the environmental impact of construction, so their market presence is expected to remain stable or even increase. The lightweight elements used can be hollow blocks or made of lightweight materials such as expanded polymers, thus losing their structural function and therefore not designed to transmit loads.

[0007] Also common in construction are roof formwork systems that allow for the reuse of part of the formwork before the concrete reaches its design compressive strength (Fck). This involves removing the beams and supporting panels and leaving a number of props under the slabs, at least until they bear the loads of the floors being built above them. In many cases, this allows the dismantled material to be reused on subsequent floors, starting as early as the third day, resulting in significant savings.

[0008] For the dismantling of part of the formwork in an early stage of concrete curing, the slab must be left shored with spans between supports that do not exceed 2.5 meters at any time. Depending on the morphology of each system, it may or may not be necessary to change the position of the props (re-shoring) during the early recovery process. Systems that do not use re-shoring rely on alignments of secondary beams or purlins that incorporate removable intermediate elements on which the slabs rest and which can be removed to allow the dismantling of the slabs without moving the beams. An example of this type of formwork is shown in patent ES2264296A1. In this case, the removable intermediate support elements must be mounted on the purlins that house them and then removed, resulting in greater complexity and increased costs in materials and labor.Furthermore, in this type of system, purlins are left aligned on the props that support the slab after the early removal of the formwork. This means that, with the current pace of construction work, it is necessary to provide, in addition to the material needed to form the desired area, a significant additional quantity of purlins that will be temporarily immobilized on the two or three floors requiring shoring.

[0009] To reduce the cost of this material, shoring beams in the form of profiles were introduced to the market. These beams are inserted parallel to each other between the slabs approximately every 2 meters. In these systems, before the early removal of the formwork, the purlins are moved to these additional elements located between the slabs. These elements have protrusions to center the struts on their underside and, in some cases, if the width of the profile is less than that of the strut's top plate, they incorporate spacers so that the strut plate does not immobilize the adjacent slabs. Once the struts are re-anchored, alignments of these elements remain in all the supported slabs. Systems with this configuration can be seen in patent ES2007490 and utility model ES1015178U.These systems require straps with shoulders or protrusions on the sides for the support of boards, but it is not necessary for these protrusions to be removable since, once the shoring beams are propped up, all the straps supporting the boards are removed, leaving them free of support to proceed with their recovery.

[0010] The height of these support beams is the same as the thickness of the formwork panels (usually 27 mm), so they can be installed between them without protruding above (which would mark the concrete) or below (which would interfere with the stringers supporting the panels). This severely limits their ability to distribute the thrust of the prop over a wide area of ​​the slab. This limitation is not a problem in solid slabs, but in lightweight slabs with hollow elements, it can be very dangerous, as the support beam might not be able to withstand the force distribution if the corresponding prop is located under a hollow section of the slab.

[0011] On the other hand, successive updates to formwork and shoring systems aim for ergonomic and productivity improvements, reducing the number of props used by increasing their load-bearing capacity. With the existing high-load-bearing props, it would be possible to halve the number of shoring props. However, the distance between rows of shoring beams cannot exceed two and a half meters, as the slab they support has not yet gained sufficient strength (currently, the usual spacing is between 1.5 and 2.5 meters).

[0012] Therefore, there is still a need for a solution that allows the recovery of all the straps in a formwork system and the use of high load capacity props, in order to take advantage of the benefits that this provides.

[0013] DESCRIPTION OF THE INVENTION

[0014] The present invention relates, in its first aspect, to a support beam, also known as a crossbeam or joist in the aforementioned references, intended for use in formwork systems for lightweight roofs. The support beam is defined by a longitudinal body with a smooth upper surface intended to be in contact with the concrete in its intended use. Its longitudinal ends and central section are intended to be supported by the same purlins and stringers that support the longitudinal ends and central sections of the formwork panels. Therefore, the length of the support beam is equal to the length of the formwork panels, and its height at the longitudinal ends and in its central section is equal to the height of said panels (height being understood as the vertical dimension in its intended use).

[0015] Unlike known shoring beams, this shoring beam is characterized in that it comprises at least one reinforcing portion defined on its lower surface and configured to reinforce part of the longitudinal body located between the central zone and a longitudinal end of the longitudinal body. This at least one reinforcing portion includes a lower coupling configured to engage with the end of a strut. Thanks to this configuration, it is possible to place high-load-bearing struts under a reinforcing portion of the shoring beams without risk of punching holes in the lightweight concrete slab elements due to flexural failure of the beams, as this reinforcing portion distributes the stress along its contact with the aforementioned longitudinal body located between the central zone and said longitudinal end of the longitudinal body.This support beam is positioned between a prop and the ceiling to transmit the prop's thrust directly to the slab ribs (solid sections of the slab located between two lightweight sections). In this way, regardless of whether the prop is located under a solid or lightweight section, the load can be transferred to the ribs without the possibility of failure due to rupture of the lightweight section.

[0016] In one possible embodiment, at least one reinforcing portion extends longitudinally towards the central area of ​​the support beam to a position such that, when the support beam is supported in its central area by a formwork member, said at least one reinforcing portion is as close as possible to said member. For example, if the support beam has two reinforcing portions symmetrical to each other with respect to the beam's center, the central area of ​​the support beam preferably has a length equal to the width of the formwork members. This reinforces the support beam in the area closest to its center and better distributes the load it receives. Preferably, at least the longitudinal end of the at least one reinforcing portion adjacent to the central area is defined at an angle.In this way, the stringers of the formwork system can include support shoulders and the reinforcement portion can be very close to these stringers.

[0017] In a preferred embodiment, the distance between at least one lower coupling for a strut and the corresponding longitudinal end of the longitudinal body is equal to or greater than the length of the slab's lightweight areas, equivalent to the distance configured to span between two consecutive slab ribs between which the coffers or structural elements that form the slab's lightweight areas are located. Conventionally, this length ranges from 600 to 700 mm, depending on the type of coffer or structural element used to lighten a ceiling. For calculation purposes, the non-lightweight concrete beams are dimensioned with a center-to-center distance of 800 mm. If the beams are between 100 and 200 mm wide, the resulting lightweight spaces are between 600 and 700 mm.To avoid unnecessary material from at least one reinforcement portion, the longitudinal ends of said at least one reinforcement portion are positioned symmetrically with respect to the lower coupling for a strut of the reinforcement portion itself. With this configuration, the installation of this shoring beam, due to the length of its reinforcement zone and the arrangement of the lower coupling, allows for the effective distribution of transmitted forces.

[0018] In one possible embodiment, the shoring beam comprises a metal profile that defines both the length of the longitudinal body and the height of its ends and central section, with at least one reinforcing portion being an addition welded to the lower surface of the metal profile. This attachment of the reinforcing portion to the lower part of the metal profile improves the stability of the shoring beam by distributing the support force exerted by the strut across the metal profile, thus preventing or minimizing its deflection at the point of contact with the strut.

[0019] In a preferred implementation, this metal profile has a trapezoidal cross-section, with its upper surface being the larger base of the trapezoidal section. This facilitates the removal of adjacent panels.

[0020] In another possible preferred implementation, said at least one reinforcement portion comprises a sheet, preferably of steel, folded in a shape similar to a U or a V, and whose ends are welded to said metal profile.

[0021] This latest implementation may include a stiffening element welded inside at least one portion of the reinforcement, configured to provide rigidity to the area of ​​the reinforcement portion intended to rest on a strut, preventing deformation under the applied load. This securing of the reinforcement portion within the metal profile improves its stability when transmitting the support force exerted by the strut, thus preventing or minimizing the possibility of collapse.This connection is preferably made by welding the stiffening element onto the side walls of the reinforcement portion so that the stresses are transmitted through these walls of the reinforcement portion more homogeneously along this reinforcement portion towards the metal profile that forms the support beam, minimizing, as mentioned, the possibility of the side walls of the reinforcement portion collapsing.

[0022] Preferably, the corresponding lower coupling for a strut is welded to the stiffening element. This ensures that, in the event of an impact on the projection of the lower coupling, deformation of the lower surface of the corresponding reinforcement area is prevented. This placement of the lower coupling on the stiffening element itself guarantees that the force from the strut is transmitted more homogeneously through the stiffening element and this coupling to the reinforcement structure, specifically to the metal profile of the support beam. This minimizes the possibility of bending at any point and thus prevents potential punching shear in the lightweight areas.

[0023] In one possible embodiment, the shoring beam comprises two reinforcing portions symmetrical to each other with respect to the midplane of the longitudinal body. This relieves the operator of the responsibility of placing the shoring beams in the same line with the same orientation.

[0024] Regarding the width of the support beam, this is determined by weight, load distribution, and the required strength. Since the height is defined by the thickness of the boards, the wall thickness must be at least 2 mm to be impact-resistant. The width at the top of the support beam is preferably between 50 mm and 90 mm, and even more preferably closer to 70 mm, so that the weight of the support beam remains reasonable without being so narrow as to leave a mark on the floor slab.

[0025] The aim is to ensure that the load transmission is done directly through the walls of both the strut tube and the support beam, so the lower face of the support beam reinforcement section preferably has a width substantially similar to that of a strut tube.

[0026] A second aspect of the present invention concerns a formwork system for lightweight roofs comprising: formwork panels for supporting the hardening material of a lightweight roof, purlins configured to support hardening material of the lightweight roof on their upper surface and provided with shoulders configured to support the longitudinal ends of the formwork panels, stringers intended to longitudinally support the central region of the formwork panels, purlin holders comprising housings on their upper face for housing and supporting perpendicularly the purlins and stringers, and high load-bearing struts, preferably telescopic.

[0027] Unlike known formwork systems in the prior art, the present system is characterized by the inclusion of support beams, as described above, which are placed in rows between every four or five panels. This ensures that, after early formwork removal, the slab is supported by the support beams every two to two and a half meters. Thanks to this system, it is possible to use high-load-bearing props in conjunction with support beams without risk of punching holes in either the beams or the lightweight concrete slab elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1.- It is a perspective and semi-transparent representation of an example of the construction of the support beam, where the stiffening element can be seen inside the reinforcement portion.

[0029] Figure 2.- It is an elevation representation of the example of the construction of the support beam shown in figure 1.

[0030] Figure 3.- It is a perspective representation of section AA indicated in figure 2.

[0031] Figure 4.- It is a perspective representation of an example of the implementation of the formwork system for lightweight roofs.

[0032] Figure 5.- It is a perspective representation of the concreting phase of the formwork system shown in figure 4.

[0033] Figure 6.- It is a perspective representation of a first phase of early recovery of the formwork system shown in figure 4.

[0034] Figure 7.- It is a perspective representation of a second phase of early recovery of the formwork system shown in figure 4.

[0035] Figure 8.- It is a perspective representation of the final phase of the early recovery of the formwork system shown in Figure 4.

[0036] DESCRIPTION OF PREFERRED REALIZATIONS

[0037] Figures 1 to 3 show an example of the implementation of the shoring beam (1) for lightweight roof formwork systems of the present invention.

[0038] As can be seen in Figures 1 and 2, this embodiment of the shoring beam (1) is defined by a longitudinal body provided with a reinforcing portion (12) defined on its lower surface and configured to reinforce the longitudinal body between its central zone (11) and one of its longitudinal ends. In turn, the reinforcing portion (12) comprises a lower coupling (13) configured to couple with the end of a strut.

[0039] In this embodiment, the support beam (1) comprises a metal profile (10) that defines both the length of the longitudinal body and the height of its ends and central section (11), dimensions that are equal to those of the panels of a formwork system. The reinforcement portion (12) is defined by a folded plate in the shape of an I, the ends of which are welded to said metal profile (10). Inside this plate, a stiffening element (14) is welded to the side walls of the reinforcement portion (12). In this embodiment, the lower coupling (13) passes through the plate of the reinforcement portion (12) to the stiffening element (14), to which it is welded. In this embodiment, this stiffening element (14) is configured as a closed trapezoidal profile, thus facilitating and simplifying its placement and subsequent welding to the reinforcement portion (12).Alternatively, with respect to the stiffening element, it is also possible, in terms of rigidity, to place two horizontal plates parallel to each other and to the plane formed by the metal profile.

[0040] The central section (11) of the support beam (1), half of which is indicated in Figure 2 with a dashed line, is intended to be supported by the same stringers that support the central sections of the formwork panels. Therefore, it measures a distance (d) equal to the width of the stringers. In other words, the reinforcing portion (12) extends longitudinally into the central section (11) of the support beam (1) to a position such that, when the support beam is supported in its central section (11) by a stringer of the formwork system, the reinforcing portion (12) is as close as possible to that stringer. In the opposite direction, the reinforcing portion (12) extends the same distance from the lower coupling (13), making it symmetrical with respect to the coupling.In order for the formwork system stringers to include support shoulders and for the reinforcement portion to be equally close to said stringers, the longitudinal ends of the reinforcement portion are defined at an angle.

[0041] In this embodiment, the distance (D) between the lower coupling (13) and the corresponding longitudinal end of the support beam (1) is 700 mm, which is the maximum length that the lightweight areas of the floor slabs can have.

[0042] As can be seen in Figure 3, the side walls of the metal profile (10) and the reinforcing portion (12) are slightly inclined inwards, in a trapezoidal shape, with the intention of transmitting the supported load to the strut tube and not to the perimeter of its plate, to prevent it from bending. Figures 4 to 8 show the different stages of formwork removal for an example of the formwork system for lightweight roofs of the present invention.

[0043] Figure 4 shows the assembled formwork system of this embodiment, whose components are: rows of four formwork panels (2) each, arranged to support the fresh concrete of the lightweight roof (7) to be slab, purlins (3) arranged perpendicularly between the formwork panels (2), being provided with shoulders configured to support the longitudinal ends of the formwork panels (2), support beams according to the example embodiment described above, positioned parallel to every four formwork panels (2), stringers (4) positioned perpendicular to the formwork panels (2) and the support beams (1), and supporting the central region of both the formwork panels (2) and the support beams (1), purlin carriers (5) that support the purlins (3) and the stringers (4) perpendicularly to each other, and telescopic struts (6) that support the strap holders (5).

[0044] Figure 5 shows the formwork system after the concreting phase of the lightweight roof (7). As can be inferred from Figures 4 and 5, prior to the recovery of the formwork, the stringers (4) support both the formwork panels (2) and the shoring beams (1).

[0045] Once the formwork recovery begins, the first components to be removed are the purlin holders (5), as shown in Figure 6. Next, the shoring beams (1) are braced and the stringers (4) are removed, as shown in Figure 7. Finally, the purlins (3) and the formwork panels (2) are removed, as shown in Figure 8.

Claims

CLAIMS 1. Shoring beam (1) for lightweight roof formwork systems, defined by a longitudinal body provided with a smooth upper surface, its length being equal to the length of the panels of the formwork system of which it forms part, and the height of the longitudinal body at its longitudinal ends and in its central zone (11) being equal to the height of said panels, characterized in that it comprises at least one reinforcing portion (12) defined on the lower surface and configured to reinforce part of the longitudinal body located between the central zone (11) and at least one of the longitudinal ends, said at least one reinforcing portion (12) comprising a lower coupling (13) configured to couple with the end of a strut.

2. Support beam (1) according to claim 1, characterized in that said at least one reinforcing portion (12) extends longitudinally towards the central area (11) of the support beam (1) to a position such that, when the support beam (1) is supported in its central area (11) by a stringer of the formwork system, said at least one reinforcing portion (12) is as close as possible to said stringer.

3. Support beam (1) according to claim 1 or 2, characterized in that at least the longitudinal end of the at least one reinforcing portion (12) that is located adjacent to the central zone (11) is defined at an angle.

4. Support beam (1) according to any of the preceding claims, characterized in that the distance between said at least one lower coupling (13) for a strut and the corresponding longitudinal end of the support beam (1) is at least the length of the lightened areas of the lightweight roof to be formworked.

5. Support beam (1) according to any of the preceding claims, characterized in that the longitudinal ends of said at least one reinforcement portion (12) are located symmetrically with respect to the lower coupling (13) of the reinforcement portion (12) itself.

6. Shoring beam (1) according to any of the preceding claims, characterized in that the shoring beam (1) comprises a metal profile (10) that defines the length of the longitudinal body and the height of its longitudinal ends and its central zone (11), said at least one reinforcing portion (12) being an addition welded to the lower surface of the metal profile (10).

7. Shoring beam (1) according to claim 6, characterized in that said metal profile (10) has a trapezoidal section, the upper surface being the larger base of the trapezoidal section.

8. Shoring beam (1) according to claim 6 or 7, characterized in that said at least one reinforcing portion (12) comprises a folded plate in the shape of II, the ends of which are welded to said metal profile (10).

9. Shoring beam (1) according to claim 8, characterized in that said at least one reinforcing portion (12) comprises a stiffening element (14) welded inside and configured to provide stiffness to the area of ​​the reinforcing portion (12) intended to rest on a strut.

10. Shoring beam (1) according to claim 9, characterized in that the corresponding lower coupling (13) is welded to the stiffening element (14).

11. Shoring beam according to any of the preceding claims, characterized in that it comprises two reinforcing portions symmetrical to each other with respect to the mid-plane of the longitudinal body.

12. Formwork system for lightweight roofs comprising: formwork boards (2) for supporting the settling material of a lightweight roof (7), purlins (3) configured so that settling material of the lightweight roof rests on their upper surface and provided with shoulders configured to support the longitudinal ends of the formwork boards (2), stringers (4) intended to be placed perpendicularly under the formwork boards (2) and to support the central region thereof, purlin holders (5) comprising housings on their upper face for housing and supporting perpendicularly upon themselves the purlins (3) and the stringers (4), and struts (6), characterized in that it comprises support beams (1) according to any of the preceding claims.

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