Shear and punching reinforcing elements for reinforced concrete slabs

Abstract

 A puncturing-cutting reinforcement element for slabs comprising a series of omega-shaped elements (12) spaced between each other and connected by means of a pair of electrowelded longitudinal wires (13) which can be associated with a structural network of flexible reinforcing bars (19, 20, 21, 22) of the slabs.
The structure can be composed of a series of omega-shaped elements (12) flanked and joined to each other in correspondence with their lower straight end sections (16).

Description

[0001] The present invention relates to puncturing reinforcement elements for slabs.

[0002] It should be pointed out that the term slabs refers hereunder to foundations, concrete slabs, etc. made of reinforced concrete filled, lightened and post-stretched.

[0003] In the building industry there are currently operations before the laying of the concrete which have various problems: one of these operations effected on the worksite is envisaging puncturing-cutting reinforcements.

[0004] In this respect, the problem of the puncturing-cutting of slabs is at present mainly solved using two known methods.

[0005] A first method consists in preparing a series of shaped reinforcements.

[0006] The anti-puncturing elements are produced by the shaping of B 450 C steel bars. In this case, there is no single consolidated form but various types, which is left to the imagination and inventiveness of the designer. Reinforcements having the form of "grecques", pins and hooks can be found, to classical rods and folded elements.

[0007] This way of forming puncturing reinforcements is especially widespread in Italy.

[0008] This solution creates considerable assembly difficulties, even more so than the solution with nails described further on.

[0009] The difficulty is mainly due to the presence of reinforcing bars in the two orthogonal directions in both the lower and upper grid. It is in fact extremely difficult to insert flexible reinforcements inside shaped elements, with the direct consequence that the assembly of the reinforcements is not adequately effected.

[0010] Furthermore, the laying times are extremely lengthy with high labour costs and a complex control of the assembly on the part of the work supervisor.

[0011] It often happens that due to the difficulty of assembly, the shaped reinforcements do not fit all four reinforcement directions, with the result that the solution is not statically correct.

[0012] For the same reason and due to the fact that the bent bars create a concentration of stress in the concrete, the standard UNI EN 1992-1-1:2005 recommends their use only below certain load rates of the floors.

[0013] Another problem is that, in order to limit the number of shaped bars and consequently simplify their assembly, they are concentrated near the pillar and are not extended sufficiently for covering the whole area involved by the puncturing phenomenon.

[0014] A second method envisages anti-puncturing nails.

[0015] As is known, anti-puncturing nails are elements consisting of steel bars, smooth or with an improved adherence, at whose ends two circular-shaped heads are produced by means of pressure casting processes, with a diameter equal to about 2-3 times that of the leg.

[0016] This type of technology is widespread throughout the world and above all in Northern Europe.

[0017] This second method also has various disadvantages and critical aspects and requires a search for alternative ameliorative solutions.

[0018] There is in fact a high production cost of the nails whose price can be even ten times higher than that of the reinforcing concrete steel.

[0019] A critical aspect also lies in a non-perfect positioning as, in this case, the nails do not fit the 4 reinforcing directions.

[0020] There is also a certain positioning difficulty due to the size of the heads if the reinforcement of the concrete slab is particularly dense.

[0021] From a static point of view, the anti-puncturing nails produce a concentration of stress in the concrete, due to the fact that the anchoring of these elements is normally achieved by means of their heads.

[0022] A general objective of the present invention is to solve the drawbacks of the known art described above in an extremely simple, economical and particularly functional way.

[0023] A further objective is to find a solution which avoids the difficulty of effecting a correct positioning under uncomfortable worksite conditions, allowing the puncturing and cutting reinforcement to be optimized, by increasing the laying rate.

[0024] Another objective is to produce puncturing reinforcement elements for slabs which respect all the provisions of the regulations in force such as DM 14-01-2008 and UNI EN 1992-1-1:2005 and, above all, to obtain a static behaviour which corresponds perfectly to the state of stress of the element.

[0025] In view of the above objectives, according to the present invention, puncturing reinforcement elements have been conceived for slabs having the characteristics specified in the enclosed claims.

[0026] The structural and functional characteristics of the present invention and its advantages with respect to the known art will appear more evident from the following description, referring to the enclosed drawings, which, among other things, also show an embodiment of puncturing reinforcement elements for slabs produced according to the present invention.

[0027] In the drawings:

• figure 1 is a schematic perspective view of a puncturing reinforcement element for slabs produced according to the present invention;
• figure 2 is a schematic perspective which shows the arrangement of a series of reinforcement elements as shown in figure 1;
• figure 3 is a raised sectional view of the complete structure of a concrete slab incorporating the puncturing reinforcement elements of figure 1;
• figure 4 is a raised sectional view of the complete structure rotated at 90° with respect to that shown in figure 3, of a concrete slab incorporating the puncturing reinforcement elements of figure 1;
• figure 5 is a schematic perspective view which illustrates what is shown in figures 3 and 4, in greater detail.

[0028] With reference to figure 1, this illustrates a schematic perspective view of a puncturing reinforcement element for slabs produced according to the present invention, indicated with 11.

[0029] Each element 11 comprises a series of omega-shaped elements 12 spaced between each other and connected by means of a pair of electrowelded longitudinal wires 13, to a straight end section 16.

[0030] The omega bending of each element 12 divides it into a flat straight upper central portion 14 from which two vertical portions 15 extend, arranged at 90° with respect to the upper portion 14 and two straight lower end portions 16, also arranged at 90° with respect to the two vertical portions 7.5. The electrowelded longitudinal wires 13 are positioned on the two lower portions 16 above and below with respect to this.

[0031] The omega-shaped elements 12 are produced with rounded sections having a diameter ranging from 5 mm to 24 mm. It should be pointed out that the height of the omega varies in relation to the thickness of the concrete slab, the concrete covers and diameters of the flexible reinforcements which are positioned therein. The length of the upper section 14 of the omega element 12 depends on the pitch of the puncturing reinforcements which, in turn, depend on the useful height of the concrete slab. The length of the lower sections 16 of the omega element 12 is determined by the anchoring requirements.

[0032] Figure 1 shows how the elements 12 are preassembled in the factory "in strips" 11 by means of an electrowelded longitudinal wire 13. The pitch is determined on the basis of the structural calculation and normally ranges from 10 cm to 30 cm.

[0033] A further assembly step enables the various strips 11 to be joined thus obtaining the multiple element shown in figure 2 to be positioned on a cylinder caisson, schematized in 17. The assembly is effected by means of omega-shaped elements 12 flanked and joined to each other in correspondence with their lower straight end sections 16 for example by means of electrowelding.

[0034] It should be pointed out that each omega-shaped element 12 is superimposed in correspondence with a lower end section 16 with the subsequent one, so as to form a continuous development.

[0035] In this way, a rectangular or square netted grid is obtained of the vertical elements which are shear-proof and with an anti-puncturing function around a pillar structure, schematized in 18.

[0036] The grid is studied so as to be perfectly coupled with the structural network of lower flexible reinforcing bars in both perpendicular directions 19 and 20 and upper bars in both perpendicular directions 21 and 22. This is also the case when the bars are pre-packaged in the form of monodirectional or bidirectional network panels.

[0037] Additional reinforcements 26, 23, 27 and 24 which reinforce the structure, can be envisaged both below and above.

[0038] In particular, the additional reinforcements of the fourth order (reinforcements 24) should be positioned below the upper section 14, so as to close the strut tie knot between upper reinforcements and the compressed strut.

[0039] Furthermore, distancing elements 25 are envisaged between the lower and upper networks which are made-to-measure for each concrete slab. In this way, the required height and perfect positioning of the bars 24 inside the omega-shaped element are guaranteed for the upper reinforcements.

[0040] The whole structure is positioned on the cylinder caisson 17 after arranging lower distancing elements 26 made of plastic or fibre-cement.

[0041] According to the embodiment shown in the figures, the construction arrangement for the assembly of the reinforcements in the slabs is described hereunder.

[0042] First of all, the lower distancing elements 26 made of plastic or fibro-cement are positioned, followed by the immediate positioning of the self-supporting puncturing reinforcement elements 11 one by one as shown in figure 1 or directly arranged in array as shown in figure 2.

[0043] At this point, bars 19 are positioned in a first lower base reinforcement direction X with possible additional bars 26 and bars 20 are then positioned in a second lower base reinforcement direction Y with possible additional bars 23.

[0044] Distancing elements 25 are then arranged between the lower and upper networks.

[0045] Finally, the upper set-up is completed by first positioning the first upper direction of reinforcement bars 21 in the base direction X with a relative additional reinforcement 27 followed by the positioning of the second upper direction of reinforcement bars 22 in the base direction Y with a relative additional reinforcement 24 inside the omegas.

[0046] The insertion of the additional bars of the fourth direction inside the omega-shaped element, is fundamental for the static functioning of the element.

[0047] This provides an extremely stable, simple and safe structure thanks to the presence of the self-supporting puncturing reinforcement elements 11 of the present invention.

[0048] The simplicity and rapidity of the implementation can also be seen.

[0049] The advantages due to the use of the puncturing reinforcement element for slabs produced according to the present invention are therefore evident.

[0050] As this element is supplied on-site assembled "in strips" or also "in multiple strips", as it is self-supporting and allows a simple assembly of the upper and lower flexible reinforcement bars, it represents an unexpected and important innovation with respect to the systems currently in use.

[0051] Compared with the traditional reinforcements described in the preamble, this element, in fact, considerably improves the performances from the point of view of various aspects.

[0052] In particular, with respect to the embodiment with shaped reinforcements:

• it significantly increases the assembly velocity of the element itself and that of the reinforcement bars of the concrete slab;
• it envisages a predefined assembly scheme and, as it is pre-packaged in the factory, it avoids the possibility of errors;
• it respects all the provisions of the regulations in force DM 2008 and EC2;
• the omega-shaped element allows the whole group of reinforcements to be covered by closing the upper strut tie knot between the upper reinforcements and the compressed strut.

[0053] There are also various advantages with respect to the alternative system with nail reinforcements as:

• it increases the laying velocity, in particular when the reinforcement network is dense;
• the omega-shaped element allows the whole group of reinforcements to be covered by closing the upper strut tie knot between the upper reinforcements and the compressed strut;
• the stress is not concentrated in the concrete as occurs for the anchoring, as the nail heads are shaped with a much wider development and are much more numerous with respect to the nails.

[0054] The objective mentioned in the preamble of the description is therefore achieved.

[0055] The forms of the structure for the production of puncturing reinforcement elements for slabs, object of the invention, as also the materials and assembly modes, can obviously differ from those shown for purely illustrative and non-limiting purposes in the drawings.

[0056] The protection scope of the invention is therefore delimited by the enclosed claims.

Claims

1. A puncturing-cutting reinforcement element for concrete slabs characterized in that it comprises a series of omega-shaped elements (12) spaced between each other and connected by means of a pair of electrowelded longitudinal wires (13) which can be associated with a structural network of flexible reinforcing bars (19, 20, 21, 22) of the slab.

2. The reinforcement element according to claim 1, characterized in that each of said omega-shaped elements (12) comprises a flat straight upper central portion (14) from which two vertical portions (15) extend, arranged at 90° with respect to the upper portion (14) and two straight lower end portions (16), also arranged at 90° with respect to the two vertical portions (15).

3. The reinforcement element according to claim 2, characterized in that said electrowelded longitudinal wires (13) are positioned along the two lower sections (16).

4. The reinforcement element according to one or more of the previous claims, characterized in that said structural network of flexible reinforcing bars of the concrete slab comprises lower flexible reinforcing bars (19, 20) and upper flexible reinforcing bars in both perpendicular directions (21, 22) constrained to said omega-shaped elements (12).

5. The reinforcement element according to one or more of the previous claims, characterized in that it comprises a series of said omega-shaped elements (12) flanked and joined to each other in correspondence with their lower straight end sections (16).

6. The reinforcement element according to one or more of the previous claims, characterized in that it comprises the positioning in a second upper direction of reinforcing bars (22) in the base direction Y with a relative additional reinforcement (24) situated inside the omega-shaped element (12).

Drawing