MX2014005823A - Seismic dissipation module made up of compression-resistant spheres immersed in a variable low density material. - Google Patents

Abstract

The present invention concerns the industry for making seismic isolators, namely devices used for isolating the load-bearing structure of buildings from the effects of an earthquake and consists of a seismic dissipation and isolation panel or module (1) made up of compression-resistant spheres (2), made of sintered alumina, bound by variable low density substances, polyurethane foams or polystyrene or other similar material (3), to be used in new buildings by placing it between a reinforced concrete bed (4) to be made on the ground (5) and the foundation structures (6) of the building (7), so that, in the event of an earthquake, there can be movements of the building independent from those of the ground on which it is built, so absorbing and isolating the seismic wave and therefore reducing the effects on the structures until, in theory, they cancel them.

Description

SEISMIC DISSIPATION MODULE ELABORATED FROM COMPRESSION RESISTANT SPHERES SUBMERGED IN A MATERIAL OF LOW VARIABLE DENSITY FIELD OF THE INVENTION The present invention relates to the industry for the manufacture of seismic isolators, ie devices used for the insulation of the load-bearing structure of buildings, the effects of an earthquake and consists of a panel or module of isolation and seismic dissipation , consisting of compression-resistant spheres, made of sintered alumina, joined by substances of low variable density, foams of polyurethane or polystyrene or other similar material, to be used in new buildings by placing them between a bed of reinforced concrete to be made in the the ground and the foundation structures of the building, so that, in the event of an earthquake, there may be movements of the building independent of those of the ground on which it is constructed, thus absorbing and isolating the seismic wave and, consequently, reducing the effects on the structures until they are canceled, in theory.

BACKGROUND OF THE INVENTION Seismic events are the cause of considerable damage to both concrete and buildings residential, with well-known consequences in the lives of many people. The buildings are anchored to the ground through various types of foundations; consequently they are totally affected by the seismic wave that propagates through the soil to the foundations and, consequently, to the building, producing forces that cause considerable stresses to the structural masses, which is tried to remedy by means of the stratification of considerable dimensions of structures and metal reinforcements that can withstand these forces as much as possible.

To contain the uncertainties due to the uncertainty of the determination of parameters of structural modeling and guarantees in the good behavior of the structures under seismic actions, specific measures must be adopted, mentioned below, in order to ensure the characteristics of ductility to the structural elements and the building in general.

When an earthquake occurs, the base of the isolated building can move in all horizontal directions compared to the foundations; consequently, after a movement, it is necessary that the building return to its original position, if the residual movements are not of small magnitude in comparison with the building. For this purpose, the base of the building must be provided with systems suitable re-centering, also called auxiliary devices, whose function is to dissipate energy and / or re-center the system and / or provide the lateral constraint of the structure.

Devices that can re-center the structure and also dissipate the energy can include hydraulic devices or devices based on the mechanical properties, in particular, of Shape Memory Alloys (SMA, for its acronym in English). These materials, typically made of nickel-titanium alloys, have the ability to "remember" their original shape, which is unusual for other types of materials.

In general, the movements experienced by the isolated structures as a consequence of the seismic action must fall within tolerable values to contain the dimensions of the structural joints and not cause problems to the connections of the installations / systems. For insulated structures, flexible connections must in fact be provided for all installations / systems that, at ground level, are connected to the superstructure.

The foundation structures must withstand the effects resulting from the response of the soil and previous structures, without permanent movements that are incompatible with the extreme state of reference.

The buildings must be provided with structural systems that guarantee rigidity and resistance to the two orthogonal-horizontal components of the seismic actions.

The foundation system must be provided with high extensional rigidity in the horizontal plane and with sufficient flexural rigidity.

The structural elements of the foundations, which must be dimensioned based on the stresses transmitted to them from the previous structure, must have non-dispersive behavior, regardless of the structural behavior attributed to the structure support below them.

By inserting insulators between the foundations and the elevation structures, the earthquake frequencies are decoupled from the frequencies of the elevation structure and thus the development of the resonance phenomenon is prevented.

In the case of seismic voltages, the insertion of insulators allows the appropriate period of vibration of the structure to be increased, thus moving away from the area of the response spectrum with greater accelerations.

This effectively causes a dynamic decoupling of the building in relation to the ground ("filter" effect), in order to reduce the transmission of energy supplied by the seismic action to the superstructure. As a consequence of the latter, the foundation-insulator-structure system can dissipate the earth's seismic energy: the dissipation is concentrated almost exclusively in the isolation devices, which dissipate the seismic energy transmitted to them from the foundations at the cost of large deformations plastic, through broad cycles of hysteresis. This allows the superstructure to have a response practically in the elastic field by remaining almost motionless compared to the movement of the ground. This considerably changes the seismic input, since, by reducing the accelerations transmitted to the building, the response capacity of the structure to the last collapse force and to the extreme state of damage is considerably increased.

In addition to protecting the load-bearing structure, these devices also protect the non-structural parts and everything they contain. In fact, as a consequence of the almost total absence of intermediate deformations of terrain (deviation), this technology allows the prevention of cracks or damage to landfills, dividing walls, installations / systems or property inside buildings, such as museums or libraries , data processing centers, etc. This allows the damage caused to the structures by a earthquake is reduced or eliminated completely, thus maintaining without change the activity contained in them, even after the occurrence of a severe earthquake.

During an earthquake, the isolated structure behaves almost like a rigid body that tends to remain even in comparison with the vibrations of the ground.

Using seismic insulators, a structure is designed that remains in elastic field even during the most violent earthquakes and maintains the dispersive energy capacity intact given the ductility.

Currently, in the case of seismic engineering, there are three categories of insulators and different types for each category.

Insulators made of elastomeric material and steel are made up of layers of elastomeric material (natural rubber or suitable artificial materials) alternated with steel plates, which have the predominant function of confining the elastomer, and are placed in the structure in order to support the actions classified horizontals and deformations through actions parallel to the position of the strata and vertical loads through actions perpendicular to the strata.

They are usually circular in design, but can also be made with a square or rectangular section. They are characterized by reduced horizontal stiffness, rigidity high vertical and adequate dispersive capacity.

Elasto-plastic insulators are made up of elements that remain elastic when there are only vertical loads but are plasticized when there are horizontal actions greater than an established threshold.

Thanks to its high dissipation capacity, elasto-plastic insulators have the task of limiting the transfer of stresses to sub-structures and thus guarantee a better response of the entire construction to a seismic event.

Sliding or rotating insulators, made respectively of steel and Teflon supports and roller supports or spheres, are all characterized by low values of resistance to friction. Therefore, although for elasto-plastic insulators and those made of elastomeric material and steel, the necessary damping is ensured to contain the relative movements of the two separated structures through the behavior with a strong presence of hysteresis of the material with which they are made , for slip insulators and for rotating insulators, it is necessary to place suitable energy dissipators, in parallel.

The dynamics of these types of insulators is complex, since the sliding process is inherently non-linear.

Some dissipators, called viscoelastic dissipators, exploit the viscous behavior of materials such as plastics, mineral oils and silicone. Other dissipators, called elasto-plastic dissipators, exploit the plasticization of metallic materials to dissipate energy in hysteresis cycles. Finally, the so-called friction dissipaters exploit the friction between properly treated metal surfaces that slide together.

In addition to the firing of elastomers (rubbers) and thermoplastic polymers (Teflon), the physical and chemical properties of the adhesives used to adhere the steel sheets to the rubber, as well as those of the linear-chain organosilicon polymers (silicone oils) and Vaseline) used in viscoelastic dissipators, possibly placed in parallel to slip or spin insulators, are also important for durability purposes.

In addition, elasto-plastic insulators and those made of elastomeric material and steel are particularly vulnerable in the case of fire and should be adequately protected from such eventuality or used in conjunction with devices that can replace them if destroyed.

In the current technique, there are also bases for ENEA seismic marble for the Bronzi di Riace.

These belong to the family of seismic isolators developed by ENEA for the protection of delicate instruments. There are non-invasive, passive and / or semi-passive seismic protection devices, formed by two superimposed blocks of marble on the internal surfaces of which, in a specular way to the two blocks, four depressions have been hollowed out whose geometry is an ellipsoid of rotation where four marble spheres are placed which, with their rotation, give the requirements of large movements, low rigidity and low friction required to maximize the seismic isolation.

When there is an earthquake, it will be the part under the base that is subject to the seismic action and will be able to move with the ground without transmitting the tensions to the top, since they are completely absorbed by the movement of the spheres within the cavities hollowed out in the marble. The movement of the spheres makes the protection system not very rigid with very low friction, characteristics that reduce earthquake tensions or make them almost nil. The new seismic marble base is particularly suitable for vertically developed states that have a very small base and, therefore, are particularly vulnerable to horizontal seismic actions, which may compromise their balance and cause them to capsize.

This type of seismic isolation can not be used for houses and apartments since the materials used for the construction of this device, if used in large areas, becomes very expensive in terms of both raw material and installation and, therefore, the Use of these seismic bases with marble spheres is limited to works of art.

The different types of heatsinks or seismic isolators on the market are very expensive and are made with a highly specialized technology and even their installation can not be carried out by an ordinary construction firm.

The mechanical rotary insulators described in the patent "MICALI" No. 1146596 are made entirely of steel or other suitable rigid material and each is formed of a pair of circular concave elements with an interposed sphere of diameter not less than the sum of the heights of the two concavities. According to this patent, when establishing the concave elements in two reinforced concrete beds or network-like structures with one resting directly on the ground and the other on the spheres, only the lower bed or structure similar to a network is forced to experience any horizontal seismic movement of the ground while the superior, thanks to the rotation of the spheres below, the inertia tranguila of the building can follow and remain almost motionless because it is forced only to experience short upwards due to the momentary movement of the lower concave elements compared to the upper ones fixed to them .

The limit of these mechanical rotation insulators considers the compressive strength of the spheres due to the small contact with the relevant concave turning seats and the consequent need for large numbers or large dimensions. O 99/07966 describes a friction sphere, made of either plastically deformable homogeneous material (lead, aluminum, brass, iron, steel, etc.) or elastomeric material, which deforms when it bears a weight; such deformation generating a frictional force that resists the turning motion in the deformed sphere.

The limit of these friction spheres considers both the expensive costs of the materials that are made as well as the low durability over time in terms of its resistance.

BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to produce a seismic insulator formed of raw materials that are easy to find in the market, which have very high costs. low but that have technical characteristics, in terms of density and resistance, that allow to have an identical response for each event in case of repeated earthquakes, and that also involve zero maintenance costs, since the components do not need to be replaced. In addition, the insulator will form excellent insulation from the damage that arises given the aggregate quality of the sintered alumina spheres.

Another object of the present invention is to produce a seismic insulator that can support a multidirectional seismic input so that, in the event of an earthquake, there can be building movements independent of those of the ground on which it is built, in order to absorb and isolate the seismic wave and reduce, therefore, the effects on the structures until they are canceled, in theory.

A further object of the present invention is to produce a seismic insulator that can avoid transmitting the seismic forces induced in the building, thus giving a reduction in the structural dimension and, at the same time, maintaining the functionality of the building.

These and other objects are achieved with the present invention which refers to a panel or module for use in new buildings, in order to be installed between a bed of reinforced concrete to be made in the ground and the foundation structures of the building, such as, for example, a bed of reinforced concrete or bed of foundation, so that, in the event of an earthquake, there may be building movements independent of those of the ground on which it is built, thus absorbing and isolating the seismic wave and reducing, therefore, the effects of the structures until they are canceled, in theory.

BRIEF DESCRIPTION OF THE FIGURES The additional features and advantages of the invention will become more readily apparent from the description of a preferred, but not exclusive, embodiment of the product that is the subject of the present patent application, illustrated by way of a non-limiting example in the figure units in which: Fig. 1 shows a plan view and a cross-sectional view of a prefabricated panel or module (1) formed of spheres (2), with a pre-established center-to-center distance between them, which changes depending on the concentrated load (acting the load on a single point of the sphere) that is desired forms the support of the sphere, made of sintered alumina, joined by substances of low variable density, foams of polyurethane or polystyrene or other similar material (3); Fig. 2 is a cross section: • of the panel or prefabricated module (1) made of spheres (2) formed of sintered alumina and joined by substances of low variable density, foams of polyurethane or other similar material (3); • the bed of reinforced concrete (4) of the foundation resting on the floor (5) and joined at the top by the "isolation interface", meaning "isolation interface" the separation surface on which it is active the insulation system; • the bed of reinforced concrete or bed of foundation (6); • Building (7) with column (8).

Figures 3 and 4 show an alternative embodiment of the panel or prefabricated module (1) in which: Fig. 3 shows a plan view and a cross-sectional view of a panel or prefabricated module (1) made of spheres (2), whose movement capacity is located within a circular area (9) and which has a distance pre-established center-to-center between them, which changes depending on the concentrated load (load acting on a single point of the sphere) that is desired to form the sphere support, made of sintered alumina, joined by substances of low variable density polyurethane or polystyrene foams or other similar material (3); Fig. 4 is a cross section: • of the panel or prefabricated module (1) made of spheres (2) formed of sintered alumina, with the ability to move within a localized area (9) and joined by substances of low variable density, foams of polyurethane or polystyrene or other similar material (3); • the reinforced concrete bed (4) of the foundation resting on the floor (5) and joined at the top by the "isolation interface", meaning "isolation interface" the separation surface on which it is active the insulation system; • the bed of reinforced concrete or bed of foundation (6); • Building (7) with column (8).

DETAILED DESCRIPTION OF THE INVENTION In the description below, the following terms will be used, of which the definition is given: - "substructure" or "first foundation", the part of the structure located below the interface of the insulation system and including the foundations, generally having negligible horizontal deformation capacity and directly subject to movements imposed by the seismic movement of the soil; "superstructure" or "second foundation" means the part of the structure located above the isolation interface and, therefore, isolated.

The polyurethane or polystyrene or other similar material (3) of the prefabricated module (1) is used to support the concrete melt of the superstructure in the first 28 days of hardening of such concrete.

The sintered alumina with which the spheres (2) of the prefabricated module (1) are made is a ceramic material resulting from the sintering of alumina, a substance present in bauxite, which consists of a thermal and mechanical process through which reduces to a compact mass of a given shape; combines the advantages of aluminum alloys and powder metallurgy.

The sintered alumina spheres are characterized by very high hardness and compressive strength and, consequently, high resistance to axial loads, in such a way that laboratory tests show that a sintered alumina sphere, approximately 5 cm in diameter, Subject to a vertical axial load of 9,000 kg, it does not show any plastic effect on its contact surface.

The advantages of aluminum alloys are: - low specific weight (approximately 2.7 g / cm3); Good corrosion resistance; remarkable mechanical properties; good wear resistance; good resistance to fatigue; The advantages of powder metallurgy are: low production costs; good tolerance control without further processing; possibility of obtaining complex forms at limited cost.

The thickness of the panel or prefabricated module (1) is equal to the diameter of the spheres (2), (example: 3-5-8 cm, etc.) with a variable surface area that is suitable for transport, (example: 3.00 x 1.50 m, etc.) or below standard sizes.

The installation of these panels or prefabricated modules (1) provides that they are placed in contact with each other on the horizontal plane, between the first and second foundation.

The sintered alumina spheres (2) should be covered with a suitable commercially available additive, a silicone release agent, to ensure that the polyurethane or polystyrene or other similar material (3) does not come into contact with the spheres (2), since they must be allowed the possibility to rotate independently of the elaborated structure of bonding material (3) that surrounds them.

The possibility of multidirectional rotation of the spheres (2) in case of an earthquake absorbs and isolates the horizontal oscillation movement of the ground (5) without transmitting tensions to the superstructure of the building (7), which, by inertia, will tend to maintain the position, thus reducing the well-known disastrous effects.

The bonding material (3), of the sintered alumina spheres (2), at low and variable density, allows its controlled rotation. The prefabricated module (1) does not experience deformations during the earthquake, since the sintered alumina spheres (2) have high resistance to compression and are without plastic consequences; consequently, the response with dispersive-insulating effect will always be the same even during the next earthquake shock, without ever having to replace the panel components (1).

For the foundation system (6), concrete of normal strength can be used, both the intradosal of the insulator as well as the backings, Rck 30, with normal loads, without plastic effects on the concrete due to the sintered alumina sphere (2) of the insulation (tests carried out in a laboratory). For particular loads on the foundation (6), a foundation concrete with adequate resistances.

The center-to-center distances between the sintered alumina spheres (2) can be adapted, in particular cases, to the requirements of the previous weights in order to optimize the concentrated load on the sphere (2).

According to a further embodiment of this panel or prefabricated module (1) for dissipation and seismic isolation, the bonding material (3) of the sintered alumina spheres (2) is configured in such a way that each sphere (2) must be moved within a localized circular area (9) that delimits its possibility of movement and, in the same way, shows its controlled rotation.

The materials and dimensions of the invention described above, illustrated in the accompanying drawings and subsequently claimed, can be varied according to the requirements. In addition, all the details can be replaced by another technically equivalent without departing for this reason from the protective scope of the present patent application of the invention.

Claims (4)

1. Seismic dissipation module to isolate the load-bearing structure of buildings, from the effects of an earthquake, consisting of a panel or prefabricated module to be installed between a bed of reinforced concrete in order to be made in the ground and the foundation structures of a building, wherein said panel or prefabricated module is formed of compression-resistant spheres, placed inside the panel or prefabricated module with a pre-established center-to-center distance between them, characterized such a prefabricated panel or module because such resistant spheres under compression they are made of sintered alumina and are joined by substances of low variable density, foams of polyurethane or polystyrene or other similar material.

2. Seismic dissipation module according to claim 1, whose sintered alumina spheres are characterized by being covered with a suitable additive in the market, such as a silicone release agent.

3. Seismic dissipation module according to claim 1, characterized in that the thickness of the prefabricated panel or module is equal to the diameter of the sintered alumina spheres, with a variable surface area that is suitable for transport.

4. Seismic dissipation module according to claim 1, whose substances of low variable density, foams of polyurethane or polystyrene or other similar material that joins the sintered alumina spheres are characterized in that they are configured in such a way that each sphere of sintered alumina must be moved within a circular area located.