CONSTRUCTION PROCESS OF EARTHQUAKE-PROOF MASONRY WALLS

Here disclosed is a construction process for earthquake-proof walls, comprising the steps of building lines and columns of masonry elements (1) bricks or other construction material blocks and connecting one to the other with a binder (2). According to the invention, said binding step of the blocks is carried out with a binder in the presence of an elastic material. Said elastic material is interposed between the masonry elements (1) and transforms the masonry having a fragile behaviour into an element having a ductile behaviour suitable to withstand the forces of an earthquake. The present invention can be applied to all kinds of masonry elements.

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Description

The present invention relates to a construction process of masonry walls (brickwork), in particular to walls built with bricks or similar blocks, provided with earthquake-proof properties.

Construction and related industry have existed since humans became residents. As soon as agriculture began, humans started building houses, more comfortable than caves, available also in plain areas, with the possibility to live there with their own family, thus also enjoying a certain domestic intimacy.

In the beginning, houses and buildings were generally huts, built with widely available materials, such as, for example, straw and mud, materials that today are still in use for construction in some hot areas, mainly in the Third World. Straw represents a structural element, while mud acts as a binder, keeping the straw together and, once dried, making the obtained structure stiffer, so as to obtain a stable form and a certain robustness against the main bad weather. Nevertheless, wind and rain can represent a danger for this type of building, and they are essentially defenseless against the effects of outer temperatures.

Another construction material still in use and having a very ancient origin is wood, with the use of logs and parts thereof, dovetailed and/or bound with each other, or boards, nailed with each other. Structures obtained in this way are very solid and, as demonstrated for example in northern Europe, where they are still widely used, they are resistant to temperature changes and can be easily heated, with heat losses being modest, after all. The main drawback of these buildings is the high risk of fires, since wood is easily flammable: in 1906 the city of San Francisco, for example, was destroyed by a fire that developed following a violent earthquake, killing more people than the earthquake itself.

Later, bricks were discovered. They are blocks of a solid inert material—normally glazed clay—that are stacked and bound with each other by a binder, to form walls. Similar to bricks are blocks of cement material, expanded concrete and other similar materials, also composite. As binders, in time, mainly lime, concrete, and gypsum have been used.

Concrete, a slurry consisting of water, cement and inert materials, is also used in the presence of metal rebars, to create the so-called reinforced concrete, which can also be used for buildings, even though the insulating effect of reinforced concrete is extremely poor, which entails high air-conditioning costs and/or the need to coat the walls made with it with one layer of insulating material, such as, for example, foamed polystyrene (the so-called insulating coatings), to be plastered and painted at the end of construction.

A well-done building must be stable and solid, protect from rain, wind, and hot and cold climate, and must be fire resistant, in order to prevent the risks of fire, and must withstand the loads to which it is subjected.

Another hidden danger that has always and heavily undermined the stability of buildings is the instability of the ground on which they are built. In particular, landslides, bradyseisms and earthquakes still represent important causes of damage or even collapse of buildings. While it is relatively simple to become aware of a bradyseism and, given the slow process, react to neutralise its negative effects (in the worst case demolishing the building and building it again in a more suitable area), this is not possible for landslides and earthquakes. In particular, earthquakes are sudden phenomena, almost never predictable, given the huge number of causes that can cause them, extended on very wide surfaces and therefore generally affecting a remarkable number of buildings, often creating real emergencies.

The energy produced in an earthquake is very variable, as well as the localisation of the so-called earthquake epicentre. Two main scales were elaborated to determine the energy produced by an earthquake: the Richter scale and the Mercalli scale. The Richter scale is directly linked to the amount of energy actually released, while the Mercalli scale is linked to the macroscopic effects of the earthquake. The latter is divided into twelve degrees, from degree 1, which refers to an earthquake that is detected only by instruments and nobody can sense it, to degree 12 where destruction of every object, presence of few survivors, destruction of the ground, destructive tsunamis and displacement of earth's crust occur.

While the Richter scale rating depends solely on the earthquake and cannot be affected in any way by men, the Mercalli scale rating can strongly depend on human action, so that two earthquakes for which the same score on the Richter scale is recorded can result in very different scores on the Mercalli scale. For example, an earthquake scoring a degree of 8 on the Mercalli scale in a place where no prevention measures were provided, might score a degree of 5 in an area where precautions were taken to make earthquake-proof buildings, even having the same score on the Richter scale. In some particularly seismic areas of the world, such as Japan, earthquake-proof construction is well established, with a remarkable reduction in the number of victims and less damage to the building stock. Italy, following some particularly severe events, such as the earthquakes in Marche in 1997, Aquila in 2009 and Amatrice in 2016, is pushing towards anti-seismic construction much more than in the past, also from a regulatory point of view. This is producing its effects: it is enough to consider that in the event of the earthquake of 2016, which extended also to Marche where, in the areas that had already suffered the earthquake in 1997 and where thus more earthquake-proof buildings had been constructed, there was less damage and no victims, as opposed to areas where such step had not occurred yet. Then, technical regulations are also moving in this direction.

Essentially, at present there are two known ways for the construction of earthquake-proof buildings.

Based on a first way, markedly stiff structures need to be built, which do not undergo swingings even in the presence of very strong forces, actually reacting to the earthquake in a completely (or almost completely) anelastic way, in order to have no kind of movement of the structure in the presence of the earthquake. Actually, the swingings produced by the earthquake on the building are almost completely absorbed by the structure, not being able to impart a significant movement.

Based on the second way, very widely used in Japan, an exactly opposite standard is followed: the resiliency of the construction work is very high and the forces released on a building constructed in this way cause very large swingings that, though, because of the resiliency of the structures themselves, even causing very marked movements, do not lead to breaks and failures in the structure and, at most, lead to the movement of objects (including furniture) contained in the rooms, though without collapses or failures.

One major problem is to be able to retrofit also structures that are not earthquake-proof yet. This is of particular importance in countries, such as Italy, where the building heritage was predominantly built before the introduction of anti-seismic measures and, additionally, is widely subjected to preservation and thus, the majority of it, cannot be demolished and rebuilt, but only adapted under the point of view of earthquake resistance.

In both cases, however, the masonries, both load-bearing and not, are poorly ductile structures, with a fragile behaviour, which little 5 and badly bear stresses other than a simple compression due to vertical loads while, in the case of an earthquake, stresses occur in many diverse directions, which require simultaneous resistance to shear, traction and bending.

In addition, masonries can even tend to react against load-bearing structures, reducing, at least in part, the ability to resist an earthquake.

Normally, masonries are built with blocks, bricks, etc. that are bound with each other with mortars, mainly based on cement, or thin-film glues: therefore, these are elements with poor ductility.

The problem underlying the invention is to offer masonry for buildings that overcomes the drawbacks mentioned above and allows obtaining improved earthquake-proof effects, by building ductile or elastic masonry, which reduces the risk of collapse in case of an earthquake. Also, it should be kept in mind that ductile or elastic masonry is suitable for being properly linked to the building load-bearing structures (beams, pillars, decks, etc.) and it would be useful if it cooperated with them in case of an earthquake, improving at the same time, the resiliency/ductility and stiffness of the construction work and further absorbing and dampening the seismic energy.

EP 3 037 599 discloses a reinforced block with reinforce bars, in order to increase its mechanical and static resistance. The block is made of light cement, via autoclave. In this patent, the insertion of undefined “pads”, inserted in the gaps between one block and another is mentioned. These pads, according to the description and drawings, have the function to cover the gaps left open between one block and another and by the hydraulic binder. In this way, they compensate for the forces generated in the case of bending of the wall. Nothing is said about the material of these pads, therefore it is unclear if they are pads made of resilient material or a stiff or semi-rigid material. It appears anyway clear that they are inserts.

US 2016/0 194 867 discloses the use of a rubber part as an insert in a structure made of bricks or anyway masonry, so as to compensate for swingings in the case of an earthquake.

Dhir Prateek Kumar et al., Construction and building materials, Elsevier, vol. 351, 6 Sep. 2022, reports data from experiments performed on masonry structures with mortar and rubber joints between the bricks, subjecting them to load cycles, to verify the energy waste due to these joints.

EP 0 005 814 discloses conjunction means for bricks, generally made of a fibrous material. Nevertheless, among the conjunction means, also polystyrene beads are considered.

EP 0 625 617 discloses the insertion of material strips suitable for improving the insulation of a building.

JP 2001-254 534 discloses the insertion of fillers for junctions made of an elastic material, for improving the seismic properties of a wall.

These objectives are reached through a construction process of masonry walls, consisting of masonry elements joined by a binder, characterised in that, at least in part of the interconnection gaps between individual masonry elements, in addition to said binder, one or more binders/adhesives (of a polymeric nature) are inserted that, once polymerised, have an elongation at break (measured according to standard DIN 53504)>30%, preferably >60%, even more preferably >90%, most preferably >150%. Dependent claims describe preferred features of the invention.

It is very important that such materials with elastic properties have a certain thickness suitable to allow a ductile behaviour of the masonry in the event of an earthquake.

Likewise, it is important that such materials have the suitable ability to make the masonry resistant to stress in every different direction, thus the ability to simultaneously withstand shear, traction and bending, in addition to compression stress.

The thickness of the elastic material is crucial since it determines, together with the resiliency degree of the material used, the ductility/resiliency of the whole masonry. Additionally, said thickness is crucial mainly for connections on the vertical plane-which, incidentally, normally are not built or are only minimally built—also to improve the transmission of the forces between the individual elements of the masonry, avoiding a concentration of loads, caused both by the irregularity of the masonry elements, and by unavoidable misalignments during the setting phase.

This can be obtained by a binder/adhesive (of elastomeric nature), that, once polymerised, has the elastic properties and suitable thickness and the ability to withstand not only vertical loads (thus compression) but also shear, traction and bending stress, which typically occur when an earthquake takes place.

Additional features and advantages of the invention anyway will be better apparent from the following detailed description of one preferred embodiment, given merely for illustrative and not for limiting purposes and illustrated in the attached drawings, wherein:

FIG. 1 shows a graph of the shift in millimetres versus shear strength for a first sample of masonry elements, obtained according to the process according to the present invention;

FIG. 1A shows data related to the test of FIG. 1;

FIG. 2 shows a graph of the shift in millimetres versus shear strength for a second sample of masonry elements, obtained according to the process according to the present invention;

FIG. 2A shows data related to the test of FIG. 2;

FIG. 3 shows an example of connection of full masonry elements, according to the process according to the present invention;

FIG. 4 emphasises cords of elastic adhesive of figure/picture 3;

FIG. 5 shows a graph of the shift in millimetres versus shear strength for the samples of masonry elements of samples 5 to 10, obtained according to the process according to the present invention;

FIG. 5A shows data related to tests of FIG. 5;

FIGS. 6 to 10 show different examples of connection on the horizontal plane and vertical plane of different types of masonry elements obtainable with elastic binders/adhesives; and

FIG. 11 shows a masonry wall, obtained according to the process according to the present invention.

As it was observed, the present invention consists in connecting the individual elements composing the masonry (blocks, bricks, etc.) to each other inserting, for a certain thickness-possibly differential in vertical connections and in horizontal ones-a binder/adhesive with elastic properties between the same. Also, such elastic material must allow to obtain adequate strengths against stresses typical of an earthquake, such as shear, traction and bending in addition to compression. The simplest and most direct method to achieve this object is to use a binder/adhesive (of elastomeric nature) having, once polymerised, elastic properties and binding properties. Such binder/adhesive will be required (mainly for the connections on the horizontal plane) when applied at a construction site and in order to have a certain thickness, that the masonry elements are kept spaced apart by specific expedients, until the binder/adhesive having an elastomeric nature, has the time to polymerise, at least to prevent its squeezing during the masonry realisation.

Needless to say that, to guarantee a good adhesion between binder/adhesive and masonry elements, it is also possible to use anchoring materials (so-called primers) or other expedients at the reach of the skilled person. For example, the setting of a certain excess of binder/adhesive, giving place to a certain squeezing with an improvement of the adhesion, in compliance with the intended final thickness of the elastic material.

Even in the known case, where tapes, strips, or elastic inserts, are inserted, among which closed-cell or mixed-cells foam materials can be mentioned, it can be advantageous to use an elastic adhesive/binder for the connections on the vertical plane, creating in fact a further embodiment of the present invention.

For withstanding earthquakes, in addition to the features of the elastic materials, which will be disclosed hereinafter assuming as main reference parameters hardness, modulus and elongation at break, also binding properties, width, length (crucial for the purpose of binding between individual blocks) and thickness (crucial for the purpose of elastic behaviour) are important.

Each practical solution displays its own advantages and requires adjustments, anyway at the reach of the skilled person.

To obtain a better collaboration aimed at the seismic resistance, the masonry composed of masonry elements and interposed elastic materials can also be properly interconnected to the load-bearing structures of the construction work by a sort of pre-compression. The above pre-compression allows better collaboration aimed at the seismic resistance, of the so-called structural components (beams, pillars, decks, etc.) with masonries. The pre-compression can be obtained by specific expedients, such as, for example, by inserting expandable materials or even by a mechanical pre-compression action, aimed at the insertion of both expanding and not expanding materials in the gaps formed or, again, at the insertion of compressed materials that, once released, cause the desired pre-compression of the masonry. Advantageously, such pre-compression must occur taking care of the polymerisation times of the elastic adhesives possibly used at the construction site. Then, a collaboration between structure and masonry is obtained.

The masonry obtained according to the present invention, having an elastic behaviour, can be usefully connected also to the ceiling (to beams and decks above) determining beneficial effects for the following reasons:

    • the elastic behaviour of the masonry, even collaborating, allows the possible bending of the decks or beams above;
    • the connection of the masonry to the ceiling allows having a box-like closure, increasing the stiffness of the construction work, without losing ductility, due to the elasticity of the masonry;
    • the connection of the masonry to the ceiling strongly contributes to prevent the overturning of the same, also in the case of forces acting perpendicularly to the masonry plane (“out of plane”).

In seismic and certain situations, considering the characteristics of the masonry elements, in the past, the insertion of elastic adhesive binders into the vertical connections was deemed unnecessary.

    • However, the homogeneity of the transmission of the stresses and the prevention of loads from concentrating in the plane, as achieved by such insertion, are very important. Furthermore, improvements are produced in this way, in terms of acoustic insulation, although outside the object of the present invention. Additionally, the insertion of elastic adhesive binders of some thickness can also be performed for groups of elements and not necessarily for every single element.

The masonry walls obtained according to the present invention are suitable to be integrated and further reinforced, according to the priori art.

For example, they can be reinforced with the most suitable materials, also taking advantage of the holes of the masonry elements, and also considering the type of rebar that is best elastically compatible with the masonry modified according to the invention, as well as, always for example, they can be connected in the most suitable ways even on angles or they can be subjected to tie rods.

Turning back to the preferred solution, it provides for the use of elastic binders/adhesives of a polymeric nature, not to be confused with the so-called elastic mortars, which actually exhibit a very modest elasticity; instead, they are adhesives that are generally used to obtain the adhesive action on surfaces that can undergo elongation and elastic deformation in general. Generally, said binder/adhesive of a polymeric nature (although it can contain also mineral filler agents and/or various kinds of additives) must have elongation at break (measured according to the standard DIN 53504)>30%, preferably >60%, even more preferably >90%, most preferably >150%. They are generally marketed compounds. Some of them are polyurethane, polysilane (or also silane-modified), silicone-based or hybrid. As it can be inferred from the research carried out, the so-called MS polymers seem to be certainly suitable. Some examples of marketed materials, merely for illustrative purpose and without expecting to be exhaustive, are: Sikaflex series by Sika Schweiz; Mapesil AC, Mapeflex MS45, Mapeflex PU 45 FT, by Mapei; MS Spray F Car by Fratelli Zucchini; SP 101 by HenkelClear Fix, Hybrifix, High tack by Den Braven; Dowsil 895, Dowsil 776, Dowsil 896 by DOW; SiMP-Seal 55, SiMP CLEAR, SiMP HIGH TACK by NPT and others. Possible materials and possible combinations of different polymeric materials also, besides additions, additives and fillers are very varied and allow to obtain products with the most suitable features in view of a particular need. To keep the individual elements spaced apart on the horizontal plane, to the desired extent, it is possible to add an elastic material with the function of a spacer, as better explained below.

Binders/adhesives or elastic adhesives with high elastic properties mean, both in the practice of the present invention and based on preferred embodiments, materials that have approximately characteristics falling within the following limits:

Shore Tensile Elongation Modulus at 100% hardness A strength N/mm2 at break % elongation Min. 10 1  50% 0.3 Max. 65 4.5 1400% 4

Wishing to identify the elasticity characteristics of suitable materials more precisely, it is sufficient to take as a reference the data of Shore hardness A (measured according to the standard DIN 53505) and modulus at 100% elongation (measured according to the standard DIN 53504) and to set the ranges, from the narrowest to the widest. Both hardness and modulus at elongation 100% scores were displayed, since they are not always homogeneous with each other, but they are certainly both characterising.

As regards hardness:

    • Shore hardness A 46 to 54
    • Shore hardness A 38 to 57
    • Shore hardness A 25 to 60
    • Shore hardness A 15 to 65.

As regards modulus at elongation 100%:

    • modulus at elongation 100% 0.9 to 3 N/mm2
    • modulus at elongation 100% 0.6 to 4 N/mm2
    • modulus at elongation 100% 0.3 to 40 N/mm2.

In further detail, FIG. 3 (exemplary picture) shows three stacked concrete blocks 1, representing masonry elements, the blocks being arranged in parallel lines on the horizontal plane and staggered on the vertical plane (see FIG. 11). The masonry elements can be clay bricks or concrete (if needed hollow) or stone, wood, or plastic material blocks, solid or, preferably, hollow, with a percentage of voids comprised between 30% and 60%, preferably between 35% and 55%, more preferably between 40% and 50%. In the example in FIG. 3, the masonry elements 1 are bound with each other by two cords (or strips) of elastic binder of a certain thickness 2.

FIG. 4 shows in an exemplary way the cords 2 of binder, inserted between the blocks 1 to create the masonry.

As regards the thickness of the elastic materials, the present invention provides the following:

    • on a horizontal plane:
    • mean thickness 1 mm to 12 mm
    • mean thickness 2 mm to 8 mm
    • mean thickness 2.5 mm to 5 mm
    • on a vertical plane
    • mean thickness from 0 mm to 6 mm
    • mean thickness from 0.5 mm to 4 mm
    • mean thickness from 1 mm to 3 mm

As it can be observed from the previously reported values, the thickness of the elastic materials is lower on the vertical plane than on the horizontal plane. Previously reported values are mean values, since blocks have a certain irregularity that is compensated by the thickness change of the elastic materials. Such thickness change, that adapts to and compensates for irregularities and setting imperfections of the masonry elements, allows an improvement in the transmission of forces in the event of an earthquake, mainly in the vertical connections, generally completely neglected, avoiding concentrated loads.

Width, surface, and thickness of the elastic adhesive binders can be adjusted, based on the features of the masonry elements, mainly hollow and shaped, and also based on the needs of resistance to earthquake, generally related to the geographic area where the building is constructed or restored, and to the masonry elements. In the case elastic adhesives are used, in the construction of masonries, it is possible to provide the use of spacers, also useful to keep the correct alignments during the building phase, possibly also made of elastic materials (with resiliency preferably falling within the scope of the parameters already reported in the scope of the present document, possibly properly differentiated to adjust the reactions to the earthquake in the different planes), to prevent the squeezing of the elastic adhesives during the construction of the wall, to be removed, if it is the case or partly removed, once setting and/or polymerisation of the elastic adhesive is completed. One advantage, resulting from the use of a binder/adhesive of a polymeric nature as compared to a traditional concrete mortar, is the considerably higher tensile strength. In fact, the tensile strength of the mentioned binders/adhesives of a polymeric nature is generally equal to about 5-10 times that of a traditional concrete mortar.

The above elastic spacers, can also consist of possibly closed-cell or mixed-cell foamed (the so-called foams) polymer materials.

Another possibility to keep the spacing between the masonry elements, at the same time avoiding squeezing, is to use binders/adhesives having high mellowness/viscosity and compactness even before polymerisation. This can be achieved either with specific products or by mixing, also at the construction site, with suitable fillers and/or bulking agents and/or additives that increase mellowness/viscosity. The construction of masonries with these products can be made with or without the previously mentioned spacers or with a different use of the same, thanks to the higher and different contribution of the binder/adhesive during the setting phase of the masonry elements. It is also possible to modify the compactness (mellowness/viscosity) of the binders/adhesives at the construction site, based on the needs. For example, the same binder/adhesive can be used to lower mellowness/viscosity at a direct contact with the materials to bind (functioning almost as a primer) and be loaded, to increase mellowness/viscosity, where it has at least partially to support or allow the alignment of the masonry elements.

Obviously, the binder can also be applied differently from what depicted in FIGS. 6 to 10, which represent only some examples, and it can be applied on the contact surface of block 1 in the most varied modes and in greater or lower width, to be selected depending on the application conditions, the geometry of the masonry element and the type of building intended to be constructed. It is also to consider that, in vertical connections, the binder/adhesive is prone to be squeezed in the intended amount, expanding, without undergoing the uncontrolled squeezing that would take place in the horizontal connections in the absence of spacers, by effect of the weight of the masonry elements.

FIG. 6 shows, in addition to cords 2, buttons 3 of elastomeric binder, in an exemplary arrangement, in which cords 2 are arranged on a (horizontal) plane and buttons 3 on a (vertical) one at 90° with it.

FIG. 7 shows cords 2 of elastomeric binder in an alternative arrangement.

FIG. 8 shows cords 2 of elastomeric binder, based on another alternative arrangement.

FIG. 9 shows buttons 3 of elastomeric binder and cords 2 of elastomeric material.

FIG. 10 shows cords 2 of elastomeric binder, according to another alternative arrangement.

Finally, FIG. 11 shows a masonry 5, obtained according to the process according to the present invention. Number and sizes of cords or strips 2 and buttons or strips both on the horizontal plane and on the vertical plane can have infinite solutions and combinations also considering the voids of the masonry elements (where hollow), sizes, structural requirements, etc. Similarly, and with highly relevant significance for the present invention, thicknesses of the elastic materials, which, as said, must be significant, mainly on the horizontal plane, can be modified as needed.

EXPERIMENTS AND TESTS

Various experiments were carried out to ascertain the resistance and deformation (or displacement) behaviour of the masonry elements connected with elastic materials.

Indeed, resistance and simultaneous deformation measurement is highly representative of the ability of a masonry to resist an earthquake where shear, traction, bending and compression forces simultaneously occur.

At the same time, the ability of the masonry to distort, absorbing and wasting the earthquake energies and returning to the original position is also essential for the resistance to earthquake.

For these experiments, as elastic adhesives, “MS polymers” were used-which have elastic properties and, at the same time, adhesive properties-changing the amount, adhesion surface, thickness, hardness degree and application direction of the shear force with respect to the arrangement of the elastic adhesive.

The aim of the tests performed was mainly to evaluate the behaviour of the elastic adhesives under extreme conditions, disregarding, in this first step of experimental tests, the characteristics of the masonry elements (blocks, bricks, etc.) and avoiding that experiments were influenced by the possible fragility of the masonry elements themselves; therefore, high-resistance solid concrete blocks were used, such as those represented in FIG. 3 and FIG. 4.

Tests were carried out glueing three 10×10×10 cm small cubes with “cords” of MS polymer, approximately as in FIG. 3.

Resistance and simultaneous deformation (or displacement) tests were performed laying two lateral blocks and pushing on the central one.

In the following and in the enclosed figures resistance will be specified as “shear strength”, since the shear strength component seems to be predominant, but there was also tension, bending and compression strength components. This is because, in performing the experiments, side blocks were simply laid and not secured and this may, in fact, have given rise to torsions with bending, traction and compression, in addition to shear, forces.

With this stated, resistance measurements carried out in the experiments (and conventionally identified, within the scope of the present document, as “shear strength”) seem highly relevant and representative of the stresses that actually occur in the various planes and in various directions as an earthquake takes place.

Various tests were carried out to verify the differences due to thickness, hardness and adhesive surface and application direction of the shear strength in comparison with the direction of the cords of MS polymer.

These disclosed are tests allowing us to ascertain the validity and reasonableness of the present invention that can be adapted, however, to a plurality of combinations, all within the reach of the expert in the field.

Sample n. 1

Using MS polymer characterized by a hardness of 43 shore A, three 10×10×10 cm concrete cubes were glued, connected with 2 cords of 10 cm in length and about 1.6 cm in width (as in FIG. 4) adhesive surface of 32 cm2 per side (equal to 32%). Thickness of the MS polymer cords 5.5 mm.

To ascertain the shear behaviour, two side blocks were secured and increasing pressure was exerted on the central block, which, consequently, resisted, but moved. Pressure was exerted parallel to the glueing cords direction. Then resistance and shift were measured (from which deformation was derived). The sample was subjected to two shear force cycles, sensing shift and thus deformation:

    • the first cycle was discontinued when the increase in shear force scores stopped at 4.8 kg/cm2 with a maximum shift of 8.1 mm. Such shift means that elastic materials have undergone a deformation of 147%;
    • after checking almost complete return to the starting position (elastic return >90%), the test was repeated, giving shear force scores similar to the first test: shear strength 4.8 kg/cm2 and shift 8.5 mm (deformation about 155%).

Also, at the end of the second cycle the central block, unbelievably, had returned almost to the starting position: elastic return >90%. Results are graphically shown in FIG. 1.

Sample n. 2

As in the case of sample n. 1, using MS polymer, characterised by hardness of 43 shore A, three 10×10×10 cm concrete cubes were glued, connected with two MS polymer cords-length 10 cm, width about 2 cm, glueing surface 40 cm2 per side (equal to 40%), thickness of the MS polymer cords 5 mm. In this case too, images of FIGS. 3 and 4 are valid as a reference.

To ascertain the shear behaviour, two side blocks were secured and increasing pressure was exerted on the central block, which consequently resisted, but moved. Pressure was exerted parallel to the glueing cords direction. Then, resistance and shift were measured (from which deformation was derived).

This second test was carried out also to evaluate a potential resistance to a plurality of earthquake cycles. To that purpose, loads were initially quite moderate and were progressively increased.

Results are reported in FIG. 2.

Initially, eleven load and unload cycles were performed, with a shear load up to 1.9 kg/cm2 and shift up to 1.6 mm (deformation 32%) with no differences observed (for simplicity, only cycle n. 11 is plotted in FIG. 2).

Subsequently, five cycles were performed (12-16), increasing the shear strength up to 2.9 kg/cm2 with a maximum shift of 2.9 mm (deformation 58%). The block always returned to its position (for simplicity, only cycle n. 16 is plotted in FIG. 2).

Then, four additional cycles (17-20) were performed, increasing the shear strength up to 3.85 kg/cm2 with a maximum shift of 4.1 mm (deformation 82%). Although deformations were increasing under stress, return was almost always close to 100% (for simplicity, only cycle n. 20 is reported in FIG. 2).

Subsequent cycle n. 21 was pushed up to 7.7 kg/cm, the maximum pressure allowed by the equipment, with a shift of 10, 37 mm (deformation 207%). For simplicity, only cycle n. 20 is illustrated in FIG. 2. After this cycle, the central block did not return to its position: upon a deformation of over 200%, the return was of about 80%.

Therefore, a new cycle up to 7.1 kg/cm2 was performed, with a shift of 11.1 mm (deformation 222%) (see FIG. 2, cycle n. 22). After this further cycle the return was of about 60%.

Sample n. 3

Using MS polymer characterised by hardness of 43 shore A, three 10×10×10 cm concrete cubes were glued, connected with three MS polymer cords-length 10 cm, width about 2 cm, adhesive surface 60 cm2 per side (equal to 60%), height of MS polymer cords 2.2 mm, consequently, distance of the blocks 2.2 mm. Glueing pattern and pictures (FIGS. 3 and 4) are still schematically valid.

To ascertain the shear behaviour, two side blocks were secured and an increasing pressure was exerted on the central block, which consequently resisted, but moved. Pressure was exerted parallel to the glueing cords direction. Then, resistance and shift were measured (from which deformation was derived).

This third sample was also subjected to the potential effect of multiple earthquake cycles. To that purpose, loads were initially quite moderate and were progressively increased.

Initially, six load and unload cycles were performed, with shear load up to 2.6 kg/cm2 with a shift up to 1.15 mm (deformation 52%). Elastic return was close to 100%.

In a second time, three cycles were performed, increasing the shear stress up to 3.2 kg/cm2 with a maximum shift of 1.4 mm (deformation 64%). Elastic return was again close to 100%.

Afterwards, eight additional cycles were performed, increasing the shear stress up to 3.85 kg/cm2 with a maximum shift of 1.75 mm (deformation 79%). Elastic return was still close to 100%.

Subsequently, three additional cycles were performed, increasing the shear stress up to 4.5 kg/cm2 with a maximum shift of 1.85 mm (deformation 84%). Elastic return remained close to 100%.

Subsequently, four additional cycles were performed, increasing the shear stress up to 5.1 kg/cm2 with a shift of 2.3 mm (deformation 104%). Elastic return was still close to 100%.

Then, three additional cycles were performed, increasing the shear stress up to 5.75 kg/cm2 with a shift up to 2.53 mm (deformation 115%). Return remained 100%.

Three more cycles were performed, increasing the shear stress up to 6.4 kg/cm2 with a shift up to 3 mm (deformation 150%). The elastic return remained close to 100%.

Three additional cycles were performed, increasing the shear stress up to 7.7 kg/cm2 with a shift up to 3.9 mm (deformation 177%). Elastic return did not depart from 100%.

With two further cycles, increasing the shear stress up to 9 kg/cm2 and with a shift up to 4.9 mm (deformation 223%), the elastic return remained close to 100%.

At the end of a further cycle, arrived at a stress of 7.3 kg/cm2, glueing failed. Therefore, it was not a deformation problem that brought the elastic binder/adhesive into crisis, but a glueing problem. On the other hand, it should be considered that a shear strength like the one found is very high and probably unrealistically overabundant for the aims of the present application.

It can be inferred that, as long as the elastic binder/adhesive used remains within 100%-200% of elongation, it can withstand many, probably a great number of seismic cycles.

Thirty-six cycles in total. No graphs were drawn because the behaviour is the same as found with the previous samples.

Sample n. 4

Using MS polymer, characterised by a hardness of 43 shore A, three 10×10×10 cm concrete cubes were glued, connected with four MS polymer cords-length 10 cm, width about 0.6 cm, adhesive surface 24 cm2 (equal to 24%) per side. Thickness of MS polymer cords 10 mm. Glueing pattern and pictures in FIGS. 3 and 4 are still valid.

To ascertain the shear behaviour, two side blocks were secured and an increasing pressure was exerted on the central block, which consequently withstood, but shifted. Pressure was exerted parallel to the glueing cords direction. Then resistance and shift were measured (from which deformation was derived).

This fourth sample was also subjected to the potential effect of various earthquake cycles. To that purpose, loads were initially quite moderate and were progressively increased.

First of all, three load and unload cycles were carried out, with a shear load up to 2.4 kg/cm2 with a shift up to 6 mm (deformation 60%). Elastic return was close to 100%.

Then, three cycles were performed, increasing the shear stress up to 3.2 kg/cm2 with a shift up to 8.4 mm (deformation 84%). Elastic return was close to 100%.

Then, two additional cycles were performed, increasing shear stress up to 3.85 kg/cm2 with a shift up to 10.9 mm (deformation 109%). Elastic return was again close to 100%.

Subsequently, a further cycle was carried out, increasing shear stress up to 4.15 kg/cm2 with a shift up to 13 mm (deformation 130%). The elastic return remained close to 100%.

Then, the test had to be discontinued, since the instruments did not allow shift readings bigger than 13 mm.

Samples 5 to 10

Using MS polymer characterised by hardness comprised between 38 and 50 shore A, three 4×4×6 cm concrete prisms were glued, connected with cords of 6 cm in length, width, thickness and adhesive surface variable as indicated in each test report. Glueing pattern and pictures (FIGS. 3 and 4) are schematically still valid although sizes are different.

To ascertain the shear/deformation behaviour, two side prisms were secured and increasing pressure was exerted on the central prism, which consequently withstood, but moved. Differently from the tests on samples 1 to 4, pressure was exerted perpendicularly to the glueing cords direction. Then resistance and shift were measured (from which deformation was derived).

In this case, the experiments of shear strength were carried out bringing the pressures to cause rupture of the glueing cords and performing readings until it was possible (FIG. 5).

From the previous description, shear strength scores, and deformation ability, it is apparent that the masonries obtained this way result, per se, particularly suitable to withstand the forces developed by an earthquake and that apply and act simultaneously in several directions on the masonries themselves.

In addition, if properly connected with the load-bearing structures, the so-constructed masonry walls are also suitable to cooperate in improving the seismic strength, both as elastic elements and as elements that, if connected with the structures, increase their stiffness, creating a sort of ribbing or box-like closure of connection between structural elements. It is apparent that, by the application of this technology, every single and simple restoration intervention may give the opportunity for improving the seismic resistance of the whole building structure. By the way, it should be expected that a building obtained with the process according to the present invention has, anyway, important earthquake-proof characteristics, even alone, to be able to resist major seismic events even in the absence of additional measures.

The present invention can be applied also to the case of restorations of already existing buildings, constructing new internal walls and floors, or demolishing and rebuilding part of the perimeter walls, with a clear increase in solidity and safety of the building heritage in terms of resistance to earthquake.

Anyway, it must be understood that the invention should not be considered limited to the particular arrangements disclosed above, which only represent some possible exemplary embodiments, but that several modifications are possible, all within the reach of a skilled person, without departing from the scope of protection of the invention itself, as defined by the following claims.

Claims

1. Construction process of masonry walls, comprising masonry elements joined by a binder, wherein, at least in a part of the interconnecting spaces between individual masonry elements, in addition to said binder, one or more binders/adhesives of a polymeric nature are interposed that, once polymerised, have elongation at break measured according to standard DIN 53504>30%.

2. The construction process as in claim 1), wherein said elastic adhesive of a polymer-based nature is selected in the group consisting of polyurethanes, polysilanes, silane-modified polymers, silicones, and MS polymers.

3. The construction process as in claim 1, wherein during the phase of masonry construction, spacers are used, in order to allow the elastic adhesive to be applied at the desired thickness and, at the same time, to fulfil the proper alignments without being squeezed, before polymerisation occurs.

4. The construction process as in claim 3), wherein spacers are also of an elastic material with elastic characteristics similar or different when compared with those of the elastic adhesive, in order to diversify the response to earthquakes in the different planes.

5. The construction process as in claim 2, wherein also an elastic binder/adhesive of a polymeric nature is used having high mellowness or viscosity, obtained by the addition of fillers and/or bulking agents and/or additives.

6. The construction process as in claim 4) wherein the elastic material interposed between the masonry elements has a polymeric nature and can be composed of closed-cell or mixed-cell foamed materials.

7. The construction process as in claim 1, wherein the mean thickness of the polymeric binders interposed between the masonry elements is:

comprised between: on the horizontal plane: 1 mm to 12 mm, on the vertical plane: 0 mm to 6 mm.

8. The construction process as in claim 1, wherein the elastic binders interposed between the masonry elements have characteristics of hardness, expressed in shore A, comprised between: 15 and 65.

9. The construction process as in claim 1, wherein the elastic binders interposed between the masonry elements have characteristics of modulus at 100%, once polymerised, comprised between:

0.3 N/mm2 and 40 N/mm2, measured according to standard DIN 53504.

10. The construction process as in claim 1, wherein the masonry obtained, whether structural or not, is connected to the other elements of the construction work, whether structural or not, by pre-compression.

11. The construction process as in claim 1, wherein said masonry elements are clay bricks or hollow concrete blocks, with a percentage of voids comprised between 30% and 60%.

Patent History
Publication number: 20260201692
Type: Application
Filed: Dec 4, 2023
Publication Date: Jul 16, 2026
Inventors: Alessandro QUADRIO CURZIO (Lecco), Paolo MORANDI (Truccazzano), Luca ALBANESI (Milano), Antonio AITELLI (Milano), Costantino QUADRIO CURZIO (Lecco)
Application Number: 19/135,244
Classifications
International Classification: E04B 2/14 (20060101); E04B 2/02 (20060101);