EP3087229A1

EP3087229A1 - Traction and compression prevailing stress anti-sliding connector

Info

Publication number: EP3087229A1
Application number: EP14830727.5A
Authority: EP
Inventors: Davide ROMEI
Original assignee: Martina Mario; Morelli Enzo
Current assignee: Martina Mario; Morelli Enzo
Priority date: 2013-12-24
Filing date: 2014-12-23
Publication date: 2016-11-02
Also published as: ITRM20130722A1; WO2015097663A1

Abstract

The present invention relates to an anti-sliding connector and to a method of stiffening slab structures.

Description

TRACTION AND COMPRESSION PREVAILING STRESS AN Tl -SLIDING

CONNECTOR

DESCRIPTION

The present invention relates to an anti-sliding connector and to a method for stiffening slab structures.

In the current state of art the connectors are arranged orthogonally to the layers they connect to prevent the sliding of a layer one onto the other one and therefore to form a single body, such as for example a beam.

In this type of structures, the connectors, almost always, contrast with the cutting effort acting upon them by the bending of the material constituting the connector itself.

As it is known, in the building industry, the connectors are used to connect different portions, in particular different layers, to form a single body. For example, in case of several wooden boards which have to be connected in a single body to be used as a beam, the several layers (the different boards) tend to slide one onto the other one and to subject the connectors to cutting forces.

On the other side, it is known that the material thereof the connectors are made is steel and the steel, used in components with small section, is suitable to support tensile stresses, whereas it is much less suitable to support bending stresses.

In fact steel, if subjected to traction, is made to work at 2700 kg/cm², and that is at 27 kg/mm². Then an iron wire with 3-mm diameter, that is with section equal to about 7 mm², supports a traction of 7 x 27 = 189 kg.

An object of the present invention is then to overcome the above-illustrated problems and this is obtained by an anti-sliding connector as defined by claim 1.

An additional object of the present invention is a method of stiffening of a slab structure a defined in claim 7.

The present invention, by overcoming the problems of the known art, involves several and evident advantages.

First of all, the use of connectors according to the present invention allows using a lower quantity of necessary steel, as the connector, of the present invention, works with compression and tensile - instead of bending - stresses thereto the steel offers the greatest resistance. Furthermore, it requires a less working with respect to other connectors for forming bends, angles of the hole wherein the reinforcement has to be inserted, etc. All this and the higher manufacturing simplicity, consequently, involves a clear advantage even in economic terms.

Moreover, an additional advantage is due to the fact that the connector of the present invention is less invasive of the vertical connectors existing on the market. This is very important in case of wooden beams of old buildings since, as already said, it has a much thinner screw which can penetrate deeply without damages even in the old wooden beams, whereas the vertical, much bigger connectors on the market, upon penetrating these old wooden beams, can easily break them.

Still an additional advantage, at least in relation to some embodiments thereof, is due to the increase in the surface resistance to the cutting by more than 30% as the screw is arranged tilted, mostly at 45°, and the vertical cutting force involves a tilted section of the screw (not vertical to the axis thereof) which has a surface increase of more than 30%.

Still an additional advantage is linked to the less time for the assembly as the connector according to the present invention requires one single welding or to arrange only one thin screw (the small screw is used for fixing only) with respect to the connectors nowadays more widespread on the market requesting two or four big screws to be assembled with expensive screwing devices.

Still an additional advantage is that, with this type of connector, the interaction takes place directly between the two structural elements, that is between the beam and the concrete layer without involving the wooden partition which, almost always, is a wood of poor quality. In fact, the connector is filled-up with concrete. In particular, for one of the embodiments, the sliding between the two structures (wooden beam and concrete layer) is obstructed directly by the tensile effort of the screw inserted in the beam.

Additional advantages, together with the features and modes of the present invention, will result evident from the following detailed description of preferred embodiments thereof, shown by way of example and not with limitative purpose. The figures of the enclosed drawings will be referred to, wherein:

figures 1A and 1 B illustrate a known art for implementing wooden beams starting from layers of beams fastened by orthogonal connectors, of known type;

figure 2 is a view of a connector according to the present invention;

figures 3A to 3D illustrate the assembly and use of connectors according to a first embodiment of the present invention;

figures 4A and 4B illustrate a second embodiment of connectors according to the present invention.

The present invention will be described hereinafter by referring to the figures mentioned above.

In particular, figure 1A illustrates by way of example, a case wherein several wooden boards must be connected therebetween to form one single body to be used as beam.

Figure 1 B shows the deformation type (dotted portion) thereto the so- implemented beam is subjected due to the stresses and, then, the way in which the several layers (the different boards) tend to slide one onto the other one and subject the connectors - which in the known art are orthogonal to the sliding - to cutting forces.

The subsequent figure 2 is a view of a connector 1 according to a first embodiment of the present invention.

The connector 1 comprises a sheet strip 2. The strip 2 is shaped as a square triangle, with two orthogonal sides 3, 4 and an hypotenuse 5.

According to an exemplifying embodiment, such strip can be 30-mm wide and have a thickness of 3 mm. The catheti of a square triangle can be 50-mm long and the hypotenuse about 70-mm long. The sizes of the various components of the connector are indicative in the sense that they could be the most commonly used ones, but, based upon the different needs, connectors with different sizes from those shown above could be implemented.

At a medium point of the hypotenuse a hole 10 is made, thereto a second hole 1 1 , made at the contact of the catheti 3, 4, corresponds. As it will be clear from the following description, the holes 10 and 1 1 are used for the passage of a fixing member 23, preferably a screw member, of the connector to an underlying wooden beam.

Advantageously, the connector 1 can have a prolongation 6 of one of the catheti. On such prolongation a third hole 12 advantageously can be made, useful, as it will be explained hereinafter, during the assembling procedures.

A free end of the prolongation 6 advantageously can further be shaped so as to have a stiffening rib useful to improve the connection with the concrete, and then the overall stiffness of the structure, as it will be better explained hereinafter.

The subsequent figures 3A to 3D illustrate the implementation modes and then the method for consolidating a slab structure, in particular supported by wooden beams.

By making reference to figure 3A, this shows a portion of a slab structure, supported by wooden beams 20.

To such slab structure a consolidating and stiffening method according to the present invention will be applied. The anti-sliding connector 1 with tilted screw is used to connect the wooden beams of a slab directly to a concrete layer. With this technique, apart from improving the effectiveness thereof, one makes the slab infinitely stiff to the actions coplanar thereto.

A plurality of the connectors 1 , of the type described up to now, is positioned on the wooden partition 21 of the slab.

Each connector 1 , during the assembly phases and before being fastened, can be kept in position by inserting a locking screw 22 into the hole 12. Such locking screw penetrates only minimally in the underlying wood and it has no particular functions of structural sealing.

Therefore, each connector 1 is then fastened to the underlying wood by inserting a locking screw 23.

Such locking screw 23, inserted in the holes 10 and 11 of the connector, will penetrate the wood according to a tilting with respect to the slab plane.

Preferably, as illustrated in figure 3C, the connectors along the beam are assembled symmetrically. On each beam the connectors are arranged with the locking screw 23 tilted from left to right in the left half of the beam, and with the screw tilted from right to left in the right half of the beam. This arrangement is advantageous as the overlapped layers tend to slide one onto the other one from left to right in the first half of the beam and tend to slide from right to left in the other half of the beam.

The insertion of the locking screw 23 in the wooden beam is about 15-20 cm.

The distance of the connectors on the beam has to be determined by a calculation. In principle they thicken (with distance therebetween of about cm. 20) when the stresses are higher, whereas they thin out (up to 40-50 cm. therebetween) when the stresses are lower.

To the connectors, at the top thereof, longitudinal bars 24 are fastened, for example by welding, at each beam. Preferably such bars 24 have a diameter of at least 8 mm. They advantageously can be adequately prolonged within the load- bearing walls, preferably, if possible, as far as the outer peripheral load-bearing walls.

Additionally, above the longitudinal bars 24, transversal bars 25 can be provided, fastened, in turn, for example by welding, to the longitudinal bars 24. Le transversal bars can have equal diameter and equal interaxis with respect to the longitudinal ones and they, too, can be prolonged as far as the outest load-bearing walls.

Still above this system of crossed bars 24, 25 a not visible in figure electro- welded grid, with suitable diameter and mesh, and one then proceeds with a concrete cast 26, preferably for a thickness of about 5 cm.

As it can be seen in the section view of figure 3D, in the interstices between the beams 20 polystyrol sheets 27 (or other foam material) with lower thickness than the height of the connectors 1 can be arranged, with insulating function and lightened filling-up.

In this way the slab plane is made uniformly stiff in all directions, by making it more suitable to support the seismic stresses, as the existing aseismic law requires.

It is possible to increase the resistance of the whole building to the seismic stresses by even putting stiffening chains connecting all opposite faces of the building. Obviously, these chains must be inserted before the concrete cast. In this way a global intervention is made which reinforces all wooden beams, makes stiff the whole slab by connecting it, in a suitable way, as far as the outer peripheral load-bearing walls, connected therebetween even with the chains, thus obtaining the best aseismic resistance.

The subsequent figures 4A and 4B relate to a second embodiment of the present invention.

According to this embodiment, the connectors 31 must be fastened on metallic beams, for example "H"-like girders.

In such case, the fastening of the connector 31 on the girder cannot take place by means of a locking screw and therefore the connector is fastened by welding on the upper wing of this one to improve the static features thereof.

In this case, the cutting force divides into a compression acting on the hypotenuse of the connector (but there is not peak load danger as this is confined by the concrete) and a tensile force acting on the vertical cathetus.

The present invention has been sofar described by referring to preferred embodiments thereof. It is to be meant that each one of the technical solutions implemented in the preferred embodiments herein described by way of example, could advantageously be combined differently therebetween, to create other embodiments, belonging to the same inventive core and however all within the protection scope of the here-below reported claims.

Claims

1. An anti-sliding connector (1) for the stiffening of a slab structure supported by beams, comprising a sheet strip (2) shaped as a square triangle, with two orthogonal catheti (3, 4) and an hypotenuse (5), and a prolongation (6) of one of the catheti (3, 4), the connector being apt to be positioned and fixed on an underlying support beam of said slab structure,

further comprising a first hole (10) made at the medium point medium point and a second hole (1 1) made at the contact of the catheti (3, 4), said first and second holes (10, 1 1) being apt to the passage of a fixing member (23).

2. The connector according to claim 1 , comprising a third hole (12) made on said prolongation (6), said third hole being apt to the insertion of a locking screw (22).

3. The connector according to one of the preceding claims, wherein said prolongation (6) comprises a stiffening rib (7).

4. The connector according to one of the preceding claims, wherein said strip (2) has a width of about 30 mm and a thickness of about 3 mm.

5. The connector according to one of the preceding claims, wherein said catheti have a length of about 50 mm and said hypotenuse has a length of about 70 mm.

6. A method of stiffening a slab structure supported by beams, comprising the steps of:

- positioning a plurality of connectors (1 ; 31) according to one of the preceding claims on said beams (20);

- fixing said connectors (1 ; 31) to the beams (20);

- forming a metallic reinforcement (24, 25) integral with said plurality of connectors (1 ; 31);

- forming a concrete casting (26) so as to incorporate said connectors (1 ; 31) and said metallic reinforcement (24, 25).

7. The method of stiffening according to claim 6, wherein said connectors (1) are fixed to wood beams (20) by holding screws (23) inclined with respect to a plane of the slab.

8. The method of stiffening according to claim 6 o 7, wherein said metallic reinforcement (24, 25) comprises longitudinal bars (24) welded to said connectors and transversal bars (25) welded to said longitudinal bars (24).

9. The method of stiffening according to one of the claims 6 to 8, further comprising a step of inserting one or more insulating material sheets into the interstices between said beams.

10. The method of stiffening according to one of the claims 6 to 9, wherein said connectors are symmetrically positioned on each beam with respect to the centre of the beam.