EP4183953A1

EP4183953A1 - Device for diatonic connection of two faces of a hollow box wall

Info

Publication number: EP4183953A1
Application number: EP22208011.1A
Authority: EP
Inventors: Alberto CAPITANUCCI
Original assignee: CoGeMar Engineering Srl; Co Ge Mar Engineering SRL
Current assignee: CoGeMar Engineering Srl; Co Ge Mar Engineering SRL
Priority date: 2021-11-19
Filing date: 2022-11-17
Publication date: 2023-05-24
Anticipated expiration: 2042-11-17
Also published as: ES2975492T3; PT4183953T; IT202100029360A1; EP4183953B1

Abstract

Device (100) for the diatonic connection of the two faces (201, 202) of a hollow box wall (200); said device (100) comprising a shank (1) having a first end (10) and a second end (11), a flange (2) suitable for projecting radially outwardly from the first end (10) of the shank and a bottom (3) disposed in the second end (11) of the shank; wherein the shank (1) is suitable for passing through a hole (205) of the first face (201) of the wall, in such a way that the bottom (3) is attached to an inner surface (202a) of the second face of the wall by means of an adhesive cushion (4) and the flange (2) is attached to an outer surface (201b) of the first face by means of an adhesive.

Description

The present invention relates to the building industry and specifically to a device for the diatonic connection of the two faces of a hollow box wall.
Hollow box walls, also known as cavity walls or double-wall masonry, are formed of two layers (faces) that are more or less spaced apart, a gap being created between said faces for the insertion of a layer of insulating material.
Hollow box walls are commonly used for the cladding of buildings with reinforced concrete structure and are available in different constructive solutions depending on the date of construction of the building and/or on the geographical area wherein the building is located.
Depending on the materials used for the masonry, one can have:

hollow box walls made of bricks and perforated brick elements, which are the most commonly used;
hollow box walls made of perforated brick elements on both faces, in sheet or in flat configuration;
hollow box walls with an outer face made of bricks or highly perforated brick blocks and an inner face made of cellular concrete elements.

Most Italian residential buildings (approximately 77%) were built before 1981, when only about 25% of the territory was classified as seismic. In addition to historic masonry buildings, the buildings that are not seismically protected are concrete structures built in the postwar years that represent a significant share of the Italian buildings. As shown by the seismic events of the last thirty years, such buildings are frequently characterized by a high vulnerability of the structural and non-structural elements that require a general plan of interventions for the mitigation of the seismic risk, also in view of the significant levels of exposure.
As it is known, in a building with reinforced concrete structure, the perimeter cladding walls are composed of single-layer or multi-layer masonry panels, which are defined and confined by the pillars vertically and by the beams horizontally.
Under the action of an earthquake, the walls are also subject to "out of the plane" actions, that is to say actions in orthogonal direction to the walls.
The behavior of a wall in case of "out of the plane" actions is mainly governed by the level of connection of the wall with the elements of the load-bearing structure. In particular, two different collapse mechanisms can occur:

1. because of overturning of the wall;
2. because of lateral instability or breaking of the wall due to bending.

The first mechanism is triggered in the presence of a weak or ineffective adhesion of the upper and lateral sections of the wall with the load-bearing structure. When subjected to the inertia forces activated by the seismic acceleration, the wall undergoes an overturning with rigid body motion that involves the wall, either entirely or partially. The activation of such a mechanism is strongly favored by the possible damage of the wall due to actions in the plane of the wall that may cause the detachment of the wall from the load-bearing structure and the consequent degradation of the constraint conditions between the wall and the load-bearing structure. Also an interplane displacement in orthogonal direction relative to the plane of the wall will favor the loss of stability and the ejection of the wall out of its original plane.
In the presence of an effective constraint along the perimeter of the wall, the wall responds with a plate-like behavior to the actions that are directed out of its plane. In the post-cracking phase, for each one of the main directions, an "arc" resistant mechanism is activated inside the thickness of the wall, with the formation of three hinges with linear development disposed at the ends of the wall and at about half of its height. The direction along which the formation of such a mechanism can be expected is a function of the relationship between the thickness and the dimensions of the wall. In particular, the axes of the hinges will be disposed along the largest dimension, and, therefore, in a wall with length L and height H, the axes of the hinges will have a horizontal development if L>H and, conversely, a vertical development if L<H.
In several instances, the collapse of the wall is favored by the fact that the wall is made in "through" continuity with respect to the pillars: in such a case, the constraint is represented by the slabs projecting from the beams - with dimensions equal to the thickness of the panels - and, therefore, the cladding panel is confined only at the top and at the base.
As a general rule, the cladding panels must always be confined in the vertical and horizontal elements of the load-bearing structure and must be in contact with them for the entire thickness of the panels. In addition, in the case of very high and very thin walls, it is almost always necessary to insert secondary elements inside the thickness of the wall in order to limit the possibility of overturning due to out-of-plane actions.
Multi-layer hollow box walls consist of two faces (an inner face and an outer face) and of a cavity provided between the faces. Therefore, the confinement along the perimeter of the panel must be guaranteed for both faces to ensure the safety of the panel against collapsing kinematics.
A significant increase in the safety of the hollow box wall can also be achieved through an effective transverse connection between the faces by means of diatons that are appropriately distributed on the wall surface. By way of example, diatons can be realized by applying compression-resistant elements (e.g. solid bricks) inside cavities obtained in each one of the faces and constraining the two faces by means of traction using tie rods made of polymer fiber. Typically, said technique provides for the coupling with a reinforcement system made of bands of fiber-reinforced material. Therefore, it is evident that such a solution can be conveniently used only in cases where it is possible to intervene on both the inner face and the outer face.
In summary, the vulnerability of hollow box walls to out-of-plane actions can be reduced in two ways:

1) by ensuring the efficacy of the perimeter constraint of the multi-layer cladding panel, and by intervening on the elimination of the overturning kinematics around the cylindrical base hinge, through the provision of bands made of composite material (FRP) between the cladding panel and the structural grid, on both faces (inner face and outer face);
2) by ensuring a congruence constraint of the displacements between the two faces of the wall through the formation of a diatonic system that reduces the possibility of establishing both a cylindrical median hinge and a cylindrical base hinge.

However, the diatons according to the conventional technique as illustrated above have the drawback of requiring interventions on both the inner face and the outer face. Obviously, if one of the two faces were a valuable face, the invasiveness of the traditional technique would irreparably compromise its aesthetic appearance. Moreover, it would be impossible to guarantee the efficacy of the intervention by operating only on one side of the wall.
In any case, the installation of the conventional diatons in the wall is an invasive, time-consuming and complex operation.
The purpose of the present invention is to eliminate the drawbacks of the prior art by providing a device for the diatonic connection of the two faces of a hollow box wall in a way that allows one of the two faces to be safeguarded.
Another purpose is to provide such a device that is simple to make and install, as well as efficient and reliable in connecting the two faces of the hollow box wall.
These purposes are achieved in accordance with the invention with the features of the appended independent claims.
Advantageous achievements of the invention appear from the dependent claims.
Further features of the invention will appear clearer from the following detailed description, which refers to a merely illustrative and therefore nonlimiting embodiment, illustrated in the appended drawings, wherein:

Fig. 1 is an exploded perspective view of the device for the diatonic connection of the two faces of a hollow box wall according to the invention;
Fig. 2 is a perspective view of the device of Fig. 1 assembled in a final condition, without the reset plate;
Fig. 3 is a perspective view illustrating a sheet for the realization of a flange of the device of Fig. 2;
Fig. 4 is a perspective view illustrating the device of Fig. 1 assembled in an initial condition, without the reset plate;
Fig. 5 is a perspective view illustrating the device of Fig. 4 after cutting the sheet for making the flange;
Fig. 6 is a side view of the assembled device in the initial condition of Fig. 4;
Fig. 7 is a side view of the assembled device in the final condition of Fig. 2;
Figs. 8, 9 and 10 are cross-sectional views taken along the section planes VIII-VIII, IX-IX and X-X of Fig. 7, respectively;
Fig. 11 is a perspective cross-sectional view of a hollow box wall;
Fig. 12 is a perspective view illustrating a first preparation step of the hollow box wall for the assembly of the device according to the invention;
Fig. 13 is a perspective view illustrating the device according to the invention mounted in the hollow box wall;
Fig. 14 is a perspective view illustrating a final assembly step, wherein the device according to the invention has been installed and the reset plate is applied to a face of the hollow box wall.

With the aid of the Figures, the device for the diatonic connection of the two faces of a hollow box wall according to the invention, which is comprehensively indicated by reference numeral 100, is described.
Fig. 11 illustrates a hollow box wall that is comprehensively indicated with reference numeral 200. The wall (200) comprises a first face (201), a second face (202) and a cavity (203) disposed between the two faces. The first face (201) has a thickness (D1), the second face (202) has a thickness (D2) and the cavity (203) has a width (D3).
The first face (201) has an inner surface (201a) facing the cavity (203) and an outer surface (201b) facing the outside. Similarly, the second face (202) has an inner surface (202a) facing the cavity (203) and an outer surface (202b) facing the outside. Plaster (204) is placed on the outer surfaces (201b, 202b) of the first face and of the second face.
With reference to Figs. 1 and 2, the device (100) comprises:

a shank (1) having a first end (10) and a second end (11),
a flange (2) suitable for protruding radially outward from the first end (10) of the shank, and
a bottom (3) arranged in the second end (11) of the shank.

The shank (1) is suitable for passing through a hole (205) of the first face (201) of the wall, so that the bottom (3) is attached to the inner surface (202a) of the second face of the wall by means of an adhesive cushion (4) and the flange (2) is attached to the outer surface (201b) of the first face by means of an adhesive.
The device (100) may optionally comprise a reset plate (5) suitable for being applied to the flange (2) and glued to the flange (2) and to the first face in order to reset the outer surface of the first face.
The shank (1) has a length (L) equal to the width (D3) of the cavity (203) of the wall increased by the thickness of the only face that can be perforated. In the example of Figs. 11- 14, only the first face (201) is perforated, so the length (L) of the shank is equal to the width (D3) of the cavity increased by the thickness (D1) of the first face. Obviously, only the second face (202) may be perforated, and in such a case the length (L) of the shank would be equal to the width (D3) of the cavity increased by the thickness (D2) of the second face.
The shank (1) can have a cylindrical hollow tubular shape. The shank can be made with cylindrical sheet metal, such as galvanized steel.
The thickness and the diameter of the shank (1) depend on the type of intervention to be carried out. For illustrative purposes, the shank can be obtained from a cylindrical S235JR steel plate having a diameter of 88.9 mm and a thickness of 3.0 mm.
Referring to Fig. 3, the flange (2) is obtained from a sheet (6) having a rectangular shape, with a first longitudinal edge (60) and a second longitudinal edge (61). Going from the first longitudinal edge (60) to the second longitudinal edge (61), the sheet has a coupling portion (62) suitable for being coupled with a collar (12) of the shank and a useful portion (63) suitable for projecting from the shank in order to form the flange (2).
The sheet (6) is bent in such a way to form a cylinder (65) (see Figs. 1, 4 and 6). The coupling portion (62) of the cylinder is fitted onto the collar (12) of the shank (1), around and near the first end (10) of the shank.
Fixing means (64) are interposed between the collar (12) of the shank and the coupling portion (64) of the cylinder (65) to securely fasten the cylinder (65) to the shank. The fixing means (64) may be adhesive means, such as an epoxy resin or polyurethane resin, or other equivalent fixing systems, such as welding, interlocking, press fitting, threaded fitting, and the like.
In a transverse direction, the sheet (6) has a length (W), the coupling portion (62) has a length (W1), and the useful portion (63) has a length (W2). The length (W2) of the useful portion (63) of the cylinder (65) is equal to the radial extension of the flange (2).
As shown in Fig. 5, in order to obtain the flange (2), longitudinal notches (66) are made on the useful portion (63) of the cylinder (65), e.g. four longitudinal notches (66) angularly spaced apart by 90°. In such a way, fins (67) are obtained, which are bent outward at the first end (10) of the shank in such a way to obtain the flange (2) that protrudes radially from the shank (1) (shown in Figs. 2, 7 and 10.)
Advantageously, the sheet (6) used for the cylinder (65) can be an FRP (Fiber Reinforced Polymers) fabric comprising carbon, glass and basalt fibers. Advantageously, the arrangement of the fibers is a one-way arrangement, i.e. with axial direction with respect to the axis of the cylinder (65).
The cylinder (65) can also be made of sheet metal, such as galvanized steel sheet, just like the shank.
In addition, the flange (2) can be made in one piece with the shank (1).
Advantageously, before use, the device (100) has a cylindrical shape so that it can be easily transported and packaged. In such a case the device comprises the cylindrical useful portion (63) suitable for being cut with longitudinal notches (66) to obtain fins (67) that are bent so as to obtain the flange (2). In such a case, evidently, the thickness of the useful portion (63) must be such as to allow the operator to cut longitudinal notches (66) with ordinary manual cutting devices and to manually bend the fins (67). In such a case, the useful portion (63) can be obtained from a sheet of FRP fabric or from a sheet metal with thickness lower than 3 mm.
With reference to Figs. 1 and 8, the bottom (3) is made of perforated sheet metal with holes (30) of about 2-3 mm suitable for the penetration of the pasty adhesive of the adhesive cushion (4).
In such a case, the bottom (3) is attached to the second end (11) of the shank by means of welding, such as spot welding.
The adhesive cushion (4) is made of resin, such as epoxy resin in pasty state. The adhesive cushion (4) is applied to the bottom (3) in contact with the inner surface (201a) of the second face.
The reset plate (5) is rectangular in shape and preferably made of an FRP (Fiber Reinforced Polymers) fabric comprising carbon, glass and basalt fibers oriented in a two-axial or a multi-axial way.
Now with reference to Figs. 11-14, an installation process of the device (100) is described.
Fig. 11 illustrates the hollow box wall (200) before the process is performed. Only the first face (201), and not the second face (202), is perforated.
With reference to Fig. 12, a hole (205) with a circular shape is drilled in the first face (201) by means of a circular cutter (7). The diameter of the hole (205) is slightly larger than the diameter of the shank (1), so that the shank (1) can be inserted into the hole (205).
The plaster (204) around the hole (205) on the outer surface (201b) of the first face is removed to form an adhesion seat (206) suitable for accommodating the flange (2) and the reset plate (5). Such an adhesion seat (206) is appropriately treated and cleaned to allow the adhesive to set effectively.
An adhesion surface (207) is prepared and cleaned on the inner surface (202a) of the second face whereon the bottom (3) of the device is to be glued by means of the adhesive cushion (4).
Referring to Fig. 13, the adhesive cushion (4) is applied to the bottom (3). The shank (1) of the device is inserted into the hole (205) of the first face until the adhesive cushion (4) goes in contact with the adhesion surface (207) of the second face, thus fixing the device (100) to the second face (202).
At this point, the longitudinal notches (66) are cut on the useful part (63) of the cylinder (65) so as to obtain the fins (67) that are bent outward in order to obtain the flange (2) that abuts the outer surface (201b) of the first face, inside the adhesion seat (206). An adhesive, such as epoxy resin, is disposed in the adhesion seat (206) to glue the flange (2) to the first face (201). In such a way, the device (100) is also fixed to the first face (201).
As shown in Fig. 7, the reset plate (5) is disposed in the adhesion seat (206), abutting above the flange (2), and adhesive is applied to glue the reset plate (5) to the flange (2) and to the first face (201). Then the plaster is applied onto the adhesion seat (206) in such a way to cover the reset plate (5).
With the exception of radical renovation and consolidation works, in which generally the heavy consolidation of the walls is comparable to their replacement, the reduced invasiveness of the device (100) may be a discriminating factor when choosing how to proceed. The device (100) is particularly useful in cases where the intervention also affects the inner face (in many cases the inner face consists of brick elements with 6cm thickness) and, consequently the interior of the building is involved.
A similar condition occurs when the outer face consists of valuable elements (visible brick face, face covered with stone, marble and the like) which would be damaged by any type of intervention.
In all situations where a low invasiveness level is the pre-requisite for proceeding with an intervention to reduce the vulnerability of the hollow box wall, the device (100) is the only solution capable of achieving a good result, operating only from one side of the wall.
The operating principle of device (100) is that of mutual constraint of the two faces (201, 202) of the wall. The device (100) comprises the tubular shank (1) closed with the bottom (3) on the second end (11) and provided with either a rigid or a moldable flange (2) on the first end (110).
The connection between the faces (101, 102) is established between the outer surface (201b) of the first face (201) and the inner surface (202a) of the second face (202), by gluing the bottom (3) to the inner surface (202a) of the second face (202) and the flange (2) to the outer surface (201b) of the first face.
The adhesion surface (207) of the second face and the adhesion seat (206) of the first face are freed from possible mortar accumulation and are prepared by removing the unstable finishing layers.
The adhesive cushion (4), which consists of a layer of adhesive, such as epoxy resin and/or any other type of adhesive material with pasty consistency, is applied onto the bottom (3). The device (100) is inserted into the hole (205) of the first face and adhered to the second face (202). The size and the length of the hole (205) of the first face are such that the device (100) is kept in a correct position for a proper adhesion of the bottom (3) to the second face.
The adhesion of the first face to the outer surface (201b) is achieved by attaching the flange (2). The flange (2) has a circular crown development with an area greater than or equal to that of the bottom (3).
If the flange (2) is made of FRP fabric, the gluing to the first face (201) is the ordinary gluing used for all FRP fabrics. Once the flange (2) has adhered to the first face (201), the outer face of the first face (201) is reset by applying the reset plate (5) and the surface flatness is restored by means of plastering and finishing.
The arrangement and the number of the devices (100) depend on the specific construction and on the geometry of the wall. Generally speaking, the recommended arrangement is the "quincunx" arrangement.
The device (100) can be made of any material of proven mechanical properties and durability, in welded or mechanical composition. If the device is made of steel, it can be obtained by press-forming. If the device is made of plastic material, it can be obtained by thermo-welding. The device can be entirely made of resin-stabilized FRP fabrics.
Preferably, the shank (1) and the bottom (3) are made of steel, although they can be made of any other material. Preferably, the bottom (3) is made from a perforated sheet plate with circular holes that is spot-welded to the edge of the shank. The assembled component (shank and bottom) is subjected to a (hot or electrolytic) galvanization process.
The flange (2) is preferably made from a fabric with one-way fibers with high mechanical properties (carbon, glass, basalt), although it can be made from any other material. The fabric is glued to the collar (12) of the shank by means of epoxy resin and/or any other type of adhesive material. However, the flange (2) can also be made of sheet steel.
Equivalent variations and modifications may be made to the present embodiments of the invention, within the scope of a person skilled in the art, but still within the scope of the invention as expressed by the appended claims.

Claims

Device (100) for the diatonic connection of the two faces (201, 202) of a hollow box wall (200); said device (100) comprising:
- a shank (1) having a first end (10) and a second end (11),

- a flange (2) suitable for projecting radially outwardly from the first end (10) of the shank, and

- a bottom (3) disposed in the second end (11) of the shank;

wherein the shank (1) is suitable for passing through a hole (205) of the first face (201) of the wall, in such a way that the bottom (3) is attached to an inner surface (202a) of the second face of the wall by means of an adhesive cushion (4) and the flange (2) is attached to an outer surface (201b) of the first face by means of an adhesive; and

said shank (1) is internally hollow

characterized in that

the bottom (3) is made of perforated sheet metal provided with holes (30) suitable for allowing for the penetration of the adhesive of the adhesive cushion (4).
The device (100) according to claim 1, wherein said shank (1) has a cylindrical shape.
The device (100) according to any one of the preceding claims, wherein said shank (1) is made of sheet steel.
The device (100) according to any one of the preceding claims, wherein said flange (2) comprises an FRP (Fiber Reinforced Polymers) fabric.
The device (100) according to claim 4, wherein said FRP fabric of the flange (2) comprises carbon, glass and basalt fibers.
The device (100) according to claim 4 or 5, wherein said fibers of the FRP fabric of the flange (2) have a one-way arrangement.
The device (100) according to any one of the preceding claims, wherein said flange (2) is obtained from a cylinder (65) having a useful portion (63) that protrudes from said shank (1); wherein the useful portion (63) of the cylinder is cut in such a way to obtain longitudinal notches (66) and fins (67) that are bent outwardly so as to obtain said flange (2).
The device (100) according to any one of the preceding claims, further comprising a reset plate (5) suitable for being applied to the flange (2) and glued to the flange (2) and to the first face (201) of the wall.
An installation process of a device (100) according to any one of the preceding claims, for the diatonic connection of the two faces (201, 202) of a hollow box wall (200), said process comprising the following steps:
- drilling a first face (201) of the wall so as to obtain a hole (205) having a diameter calibrated to the diameter of the shank (1),

- insertion of the shank (1) of the device in the hole (205) of the first face,

- gluing of the bottom (3) to the inner surface (202a) of the second face by means of the adhesive cushion (4), and

- gluing of the flange (2) to the outer surface (201b) of the first face by means of an adhesive.