ANTI-SEISMIC REINFORCEMENT METHOD

Description

This application claims priority to Italian Patent Application No. 102024000016129 filed on Jul. 11, 2024, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an anti-seismic reinforcement method for a construction element.

SUMMARY

The expression “anti-seismic reinforcement” is used to indicate a treatment capable of structurally reinforcing a construction element to confer it improved characteristics of resistance against the seismic action. The treatment of the present invention is valid to improve the resistance of the construction element against the action of any dynamic and/or vibrational stress.

The expression “construction element” is used to indicate a component which contributes to the structure and/or to the functionality of a building: it helps to keep the building stable and resistant, supporting loads, pressures and forces, and/or it contributes to the practical use of the building. The construction elements which contribute to the structure of a building may be vertical elements (for example walls, columns, and so on) and/or horizontal elements (for example slabs, foundations, lintels, and so on). The construction elements which contribute to the functionality can for example be tanks and silos used for storing materials or liquids.

Various anti-seismic reinforcement techniques which provide for the installation of metal reinforcement meshes on the construction elements are known.

The installation of such reinforcement meshes is an extremely long and complex procedure, usually accompanied by numerous treatment operations, such as the removal of existing plasters, the application of layers of mortar, and so on.

Therefore, generally, such prior art techniques are long and complex to manufacture, and, due to the numerous processing operations, they are extremely expensive. Besides this, the final result is invasive, and therefore not appealing to the end user.

DESCRIPTION

The object of the present invention is to provide an anti-seismic reinforcement method that is easy to obtain.

Another object of the method is to provide an anti-seismic reinforcement method that is more cost-effective in terms of implementation with respect to those of prior art.

A further object is to provide an anti-seismic reinforcement method that is efficient.

According to the present invention, these and other objects are attained by an anti-seismic reinforcement method.

Furthermore, these objects are attained by a construction element.

These objects are also attained by a building.

Further characteristics of the invention are outlined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the present invention will be apparent from the following detailed description of a practical embodiment thereof, shown by way of non-limiting example in the attached drawings, wherein:

FIG. 1 schematically shows a construction element, in particular a wall, reinforced through the method according to the present invention;

FIG. 2 shows a digital model of the construction element of FIG. 1;

FIG. 3 shows the digital model of FIG. 2 on which a simulation is carried out;

FIG. 4 shows an analysis of the outcome of the simulation;

FIG. 5 shows part of a building in which there is present the construction element of FIG. 1.

DETAILED DESCRIPTION

Referring to the attached figures, a construction element of a building reinforced using the anti-seismic reinforcement method of the present invention is indicated with reference numeral 1.

In the example shown, the construction element 1 is a wall. Such wall 1 is preferably made of a masonry element, for example made of solid or lightened brick, vibro-compacted concrete, stone material, lightened concrete, and so on. The wall may be a high masonry or a perimeter masonry, for example for infilling.

In other examples, not shown, the construction element 1 is a horizontal element such as the slab/or a roof, for example with barrel vaults.

In other examples, not shown, the construction element is a functional element, such as for example a tank and/or a silo.

The construction element 1 has two facades 2, 3. The latter are arranged opposite to each other along the thickness of the construction element 1. Facades 2, 3 are faced towards two different environments, which may be two rooms or the internal or external of the building.

The anti-seismic reinforcement method according to the present invention envisages providing a reinforcement material which comprises polyurea; such reinforcement material is applied on each of the facades 2, 3 of the construction element 1 by hot-spray application to obtain, on each of the facades 2, 3, a respective reinforcement layer 4. When hot-spray application the material, it is sprayed at a temperature comprised between 60° C. and 80° C., preferably 70° C.

The applicant observed that polyurea, normally used as wetproofing material, if applied on both facades 2, 3, allows the reinforcement layers 4 to carry out a function of containing the construction element 1; under seismic force effect, or generally horizontal loads, the latter does not collapse, but remains confined between the reinforcement layers 4.

In one or more versions, the reinforcement material is predominantly polyurea.

In one or more versions, the reinforcement material consists of polyurea.

In one or more versions, the reinforcement material comprises pure polyurea.

In one or more versions, the reinforcement material consists of pure polyurea.

Given that polyurea is a two-component material, that is it is obtained by mixing two separate components, the provision step envisages providing a first and a second basic component for providing the polyurea. The basic components are provided to a mixing device configured to mix them so as to obtain polyurea.

The first component is for example a mixture of isocyanates. The second component is for example a mixture of polyamines. At least one of the two components, but preferably both, contains additives, such as for example catalysis agents, stabilisers and flow agents.

During the mixing, the mixing device is configured to maintain polyurea at a temperature comprised between 60° C. and 80° C., preferably 70° C.

As mentioned above, the application step provides for a first sub-step of providing a reinforcement layer 4 on one of the facades 2, 3 and a second sub-step for providing another reinforcement layer 4 on another of the facades 2, 3. Given that polyurea catalyses quickly, depending on the size of the construction element 1, and therefore the overall application times, the reinforcement material may be prepared only once before both applications or it can be prepared before each of the applications.

In order to facilitate the application of the reinforcement layer 4 to the construction element 1, there is provided for a preparatory step in which each facade 2, 3 of the construction element 1 is treated specially. The treatment provides for the removal of friable and/or powdery parts (such as for example dust and pre-existing paint and plaster), precarious and deteriorated parts, water-proofing material and so on from the surface of the facades 2, 3. There may also be provided for carrying out a passivation of possible exposed steel reinforcements.

In some cases, the removal provides for using sanding and/or dusting, for example using compressed air jets.

The surfaces of the facades 2, 3 are then roughened by shot peening, honing and/or other prior art techniques.

In some situations, the surfaces of the facades 2, 3 are dried to reduce moisture.

Suitably, the method envisages providing a priming material. The priming material (usually also referred to as primer or adhesion promoter) is adapted to facilitate the adhesion between the reinforcement layer and the facade (as described below). Subsequently, the priming material is applied on each facade 2, 3 to obtain, on each facade 2, 3, a respective priming layer 5 on which the reinforcement layer 4 will then be applied.

The priming material is preferably applied subsequently to the treatment of the surfaces described above.

The priming material is different from the reinforcement material. Preferably, the priming material is an epoxy (two-component) primer, that is based on epoxy resins. Use of other priming material cannot be ruled out.

The reinforcement material is applied on the priming layer 5 of each facade 2, 3 by hot-spray application to obtain the respective reinforcement layer 4 on the facades 2, 3.

In particular, the reinforcement material is applied directly on the priming layer.

Therefore, the reinforcement layer 4 is applied by means of a spray apparatus. The spray apparatus is connected to the mixing device to receive the reinforcement material, and it is configured to dispense a jet of reinforcement material, for example by means of a dosing gun. The spray apparatus is configured to carry out a hot spray, that is for dispensing the reinforcement material at a temperature comprised between 60° C. and 80° C., preferably 70° C.

The spray apparatus operates at high pressure, that is it has an operating pressure comprised between 100 bar and 300 bar, preferably 180 bar or 240 bar.

In one or more versions, the reinforcement material is applied so that the reinforcement layer 4 substantially covers the entire facade on which it is applied.

In one or more versions, the reinforcement material is applied so as leave parts of the facade vacant, therefore conferring to the construction element 1 a partial permeability to vapour. In particular, the reinforcement material is applied to the strips which are spaced from each other. The reinforcement layer 4 comprises a first series of strips and a second series of strips. The strips intersect with each other. The strips of each series are substantially parallel and spaced apart from each other. The two series of strips are arranged inclined one with respect to the other, crossing each other to form a mesh structure. This allows the reinforcement layer 4 to maintain its structural containment capacity and, at the same time, to confer to the construction element 1 a partial permeability to vapour.

Preferably, the reinforcement material is applied with vertical or horizontal strips, that is the first and the second series of strips of the reinforcement layer 4 are respectively vertical or horizontal. It cannot be ruled out that the mesh structure can also be obtained with diagonal strips.

The reinforcement material is applied so that each reinforcement layer 4 has a predefined thickness. The thickness value affects the resistance of the layer to the stresses due to seismic events. The thickness of each of the reinforcement layers 4 is greater than or equal to 2 mm, preferably greater than or equal to 3 mm, even better comprised between 3 mm and 4 mm.

The choice of the thickness of the reinforcement layers 4 in various cases depends on the physical and structural characteristics of the construction element 1.

Therefore, the applicant developed a procedure which allows to determine the thickness most adapted to the characteristics of the construction element 1 to be treated. Such procedure also allows to identify, in terms of reduced stresses/movements, the advantage of the application on the construction element.

In short, such procedure provides for detecting the conformation of the construction element 1; based on the detection, there is provided a digital model 6 of the construction element 1 with reinforcement layers 4 applied thereon, whose reinforcement layers 4 have a predefined thickness; the digital model 6 is used to carry out a simulation in which there is simulated the application of one or more static and/or dynamic loads, such as for example those caused by a seismic event; the outcome of the simulation is lastly analysed to determine whether the thickness used is appropriate; if inappropriate, the thickness of the reinforcement layers 4 in the digital model 6 is removed and a new simulation is carried out.

The various steps listed above will now be described in detail.

The detection of the construction element 1 is carried out by scanning, which can be carried out for example by means of a laser scanner or manual techniques.

The scanning is supplied to an appropriate software carried out on a processor, such as for example a computer. The software comprises several instructions which, when carried out by a processor, allow to create a digital model 6 of the construction element 1.

The modelling is of the FEM type, that is that the construction element 1 is represented by means of an assembly of three-dimensional elements which, as a whole, approximate the actual geometry of the construction element 1, preferably through elements of the solid type. The Applicant observed that such type of modelling is particularly suitable for representing construction elements made of materials having non-linear behaviour, for example plastic and elastic deformations.

The construction element 1 is modelled using a static diagram. As observable hereinafter, the staticity of the construction element 1 is ensured by installing appropriate reinforcements, preferably made of metal or composite material framework. In modelling, instead, such staticity is obtained by applying respective digital constraints to the base and to the top part of the construction element 1 to prevent translation.

Besides geometric modelling, the construction element 1 is characterised with the materials: in the model there are inserted several characteristic parameters of the material, such as for example Young modulus, coefficient of Poisson, the tensile strength, stiffness reduction factor, specific weight and so on.

Also the reinforcement layers 4 applied to the construction element 1 are modelled in the digital model 6 like done for the construction element 1. They are represented by means of a set of three-dimensional elements which are finished and then characterised with the characteristics of the reinforcement material. For example, they are specific weight, viscosity, tensile strength, elongation, adhesion to other material (such as concrete and metal), hardness, resistance criterion (for example the Von Mises criterion) and so on.

The non-linear behaviour of the reinforcement layers 4, and therefore after treatment the construction element 1 it is simulated using a plasticisation start value.

Besides this, the reinforcement layers 4 are modelled by setting a predefined thickness so as to be able to verify the effectiveness thereof by evaluating the static/dynamic behaviour of the construction element 1. Preferably, the predefined thickness set in an initial step is 2 or 3 mm, better 3 mm.

To do this, the generated digital model 6 is used to analyse the structural behaviour of the treated construction element 1 in the simulated actual conditions, for example considering factors such as the distribution of loads, the stiffness of the materials, the surrounding conditions and so on.

The simulation provides for reproducing the forces caused by a seismic event on a construction element. The simulation carried out is of static type: there is provided for a gradual acceleration of the masses in direction Y substantially perpendicular to the construction element 1 (in the case of the vertical wall the direction Y is horizontal, while in the case of horizontal elements the direction Y is vertical). The acceleration is gradually increased from zero value until it reaches a maximum acceleration, defined as peak acceleration. In an example, peak acceleration is preferably 0.2 g, where “g” indicates the acceleration of gravity. However, peak acceleration may vary as a function of the inherent characteristics of the site where the building stands. Graduality is preferably of ten steps with a progressive increase of 0.02 g at each step. It cannot be ruled out that the number of steps and the progressive increase could have different values depending on the place and load to be simulated.

During the simulation, there is collected data on the behaviour of the digital model 6. Data collection provides for that, for each step, there is observed, highlight it, the relative movement between the two facades 2, 3 to verify the dilatation of the construction element 1. It is sought to verify whether 1, though dilating, it remains confined in the reinforcement layers 4. This verification is carried out by calculating that the stresses applied on the reinforcement layers 4 are lower than its tensile strength added in the modelling step (for example 20 Mpa).

If the verification is positive, and therefore there are fissures on the reinforcement layers 4, the set thickness allows the reinforcement layers 4 to reduce the support material. Therefore, this allows to apply reinforcement layers 4 to the construction element 1, as described above.

Instead, should the outcome of the verification be negative, the modelling of the reinforcement layers 4 is changed increasing the value of the predefined thickness. After which, the simulation and the analysis of the outcome are carried out again. This method is repeated until there is determined an appropriate thickness of the reinforcement layers 4.

In order to complete the analysis, it is verified whether the contact tensions between the facades 2, 3 of the construction element 1 and each reinforcement layer 4 are maintained within acceptable values to avoid possible delamination risks. To do this, there is observed the stress condition of the reinforcement layers 4 in the point of contact with the respective facade 2, 3 of the construction element 1. In particular, it should be observed that the maximum sliding tension is below a threshold value, which preferably is equal to 1.5 MPa.

Shown below is an example of determination of the thickness carried out by the Applicant.

The construction element 1 taken into account is a wall which has a height of 8 m, a width of 1 m, and a thickness of 20 cm and it is made of a masonry element with vibro-compacted concrete blocks.

The modelling of the wall 1 provides for a subdivision thereof in finite elements. The modelling also provides for the use of the model of the Strumas constitution bond which allows to homogenise the behaviour of the system. The “Strumas constitution binding” is a specific mathematical model used to describe how materials react to stresses. This helps to predict how the wall will behave under various loads making the simulation more accurate and a true picture of the reality. The material of the wall 1 is characterised by the following parameters: Young modulus 1400 N/mm2, coefficient of Poisson 0.11, tensile strength 0.165 N/mm2, and stiffness reduction factor 1e-07.

Each reinforcement layer 4 is instead modelled in finite elements measuring 1.5×50×50 mm. The material of the reinforcement layer 4 is characterised by the typical values of polyurea, that is tensile strength 18÷22 Mpa, elongation 440-470%, adhesion on concrete>1.5 Mpa.

The thickness of each reinforcement layer 4 used in the modelling is 3 mm.

FIG. 4 shows the movement difference between the nodes arranged in the centreline of the two facades 2, 3; it shows that the wall tends to dilate, but it however remains confined between the two reinforcement layers 4.

With reference to FIG. 5, described below is a further step of the method of the present invention. Such further step provides for reinforcing the construction element 1 applying at least one constraint structure 7 in the proximity of at least an end thereof. In the case of vertical construction elements, the constraint element 7 is applied at the top part (top constraint). In other words, there is applied a reinforcement which constrains the end of the construction element 1 to a further structure of the building, such as for example a beam or another masonry element.

Reinforcement examples may be a corner element, preferably glass fibre, as shown in FIG. 5. The corner element measures 250×250×1000 mm.

The corner element is constrained to the construction element 1 and to the other structure of the building by means of nails, for powder-driven nails.

There may be provided for a plurality of corner elements, for example a pair of corner elements arranged at the lateral ends of the construction element 1 and a corner element arranged at the centre.

There may be used lateral constraint structures which reinforce the constraint of the construction element with other adjacent construction elements.

Another option lies in providing for a basic constraint which comprises a constraint structure which reinforces the connection between the construction element 1 and the base of building, like the ground or floor.

In the light of the above, it has been basically observed that the disclosed invention attains the intended purposes, and in particular it should be observed that the method of the present invention allows to carry out an anti-seismic reinforcement on a construction element that is effective and inexpensive.