ANTI-SEISMIC DEVICE

Abstract

Anti-seismic device for seismically isolating structure relative to ground including first support defining first support plane integrally connectable to upper portion and including two first hinges defining first constant reciprocal distance, second support defining second support plane including two second hinges defining second constant reciprocal distance, third support defining third support plane integrally connectable to lower portion and including two third hinges defining third constant reciprocal distance, and connector defining connection plane perpendicular to third support plane and including at least two first rigid bars, each defining a first non-deformable connection direction and two second rigid bars, each defining a second non-deformable connection direction. First bars transiently constrained to first hinges and second hinge so the first connection directions of first bars cross in the connection plane. Second bars transiently constrained to second hinges and third hinge so second connection directions of second bars cross in connection plane.

Description

The present invention relates to an anti-seismic device of the type specified in the preamble of the first claim.

In particular, the present invention relates to an anti-seismic joint adapted to absorb vibrations for building type structures and infrastructures in order to stabilize said structures in the presence of seismic vibrational phenomena.

As is known, a plurality of anti-seismic solutions are currently used at the construction level, also regulated by the regulations in force in each country.

At the regulatory level, for example, there are buildings characterized by a hyperstatic structure with regularity in plan and height, i.e. developing a compact and symmetrical plan and in which all the resistant vertical systems, such as frames and walls, extend throughout the height of the construction.

In addition, the masonry elements comprise metal cores that allow the structure of the building to have a predetermined deformability before reaching catastrophic collapse.

In addition, national regulations often specify that a single type of foundation should be adopted for a given elevated structure, unless it consists of independent units. In particular, the simultaneous use of pile or mixed foundations with surface foundations must be avoided in the same structure.

To ensure that the structure can resist, without major damage, seismic activities, even quite intense, seismic insulators can be used.

These are positioned between the foundations and the structures in elevation to decouple the frequencies of the earthquake from the frequencies of the structure in elevation and avoid the onset of resonance phenomena. Using seismic insulators, the structure remains elastic even during violent earthquakes and preserves the dissipative energy capacities offered by ductility.

An example of a seismic insulator is the LRB or Lead Rubber Bearings with a lead core consisting of alternate layers of steel and elastomer connected by vulcanisation which, thanks to its high dissipative capacity, can reduce horizontal displacement.

The energy dissipation provided by the lead core, through its plasticization, permits an equivalent viscous damping coefficient to be obtained of up to about 30%. Thanks to the high dissipative capacity, it is possible to reduce the horizontal displacement, compared to that of an insulation system with the same equivalent stiffness but with less dissipative capacity.

These are usually circular, but can also be made with a square cross-section, possibly with more than one lead core.

They are used on buildings, bridges or other structures, during construction or seismic adaptation. They guarantee the safety of the structure and what it contains Another type of insulator is provided by buckling-restrained axial hysteretic dissipaters for example of the BRAD® series (Buckling-Restrained Axial Dampers). These are non-linear seismic devices the behaviour of which depends essentially on displacement. They are particularly suitable for use as dissipative braces, for seismic protection by energy dissipation, and in particular for seismic adaptation, of steel frame buildings. The insertion of these devices within the structural meshes increases the dissipative capacity of the structure, and therefore significantly improves its response to the earthquake. Until yield is reached, BRAD® dissipators increase the stiffness of the structure, an effect that can be particularly useful for compliance with the regulatory requirements for limiting inter-storey movement to the Limit of Damage State, i.e. breaks allowed to the structure according to the safety margins in force.

The prior art described has several significant drawbacks.

In particular, the systems described, especially in the case of Lead Rubber Bearings, are characterized by extremely complex structures adapted to dissipate at least part of the deformation energy resulting from seismic phenomena.

These structures are therefore very onerous, in terms of cost, and make it possible to address the problem of the management of seismic vibrations only in terms of damage tolerance, i.e. tolerance of damage within the Damage Limit State, resulting from deformation phenomena sometimes even plastic.

As a result, the systems of the previous type described are reactive and irreversible beyond certain earthquake thresholds.

In fact, all the devices known to the current state of the art work only on the stiffness of the joints and support structures.

In this situation the technical purpose of the present invention is to devise an anti-seismic device able to substantially overcome at least some of the drawbacks mentioned.

Within the scope of said technical task it is an important object of the invention to obtain an anti-seismic device that is capable of seismically isolating the foundations of a building or a support structure from the ground during, for example, a seismic vibratory activity, limiting the deformations of the device.

Another important object of the invention is to make an anti-seismic device that is capable of seismically isolating a structure without only intervening on the stiffness of the support joints of said structure.

In conclusion, a further object of the invention is to realize an isolation device that makes it possible to reduce the degrees of freedom of movement to which the structure that is supported by the ground is subjected with respect to the original reference system of said structure.

The technical purpose and specified aims are achieved by an anti-seismic device as claimed in the appended claim 1.

Preferred technical embodiments are described in the dependent claims.

The characteristics and advantages of the invention are clearly evident from the following detailed description of preferred embodiments thereof, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic model of a device according to the invention in free condition;

FIG. 2 illustrates a schematic model of a device according to the invention subjected to seismic stress;

FIG. 3 is an embodiment example of a device according to the invention in free condition;

FIG. 4 represents an embodiment of a device according to the invention subjected to seismic stress;

FIG. 5 shows an example of a foundation comprising two devices according to the invention arranged in a coplanar manner;

FIG. 6 illustrates an example of a foundation comprising four overlapping devices according to the invention;

FIG. 7a represents a second embodiment of a device according to the invention in a first configuration;

FIG. 7b represents a second embodiment of a device according to the invention in a second configuration; and

FIG. 7c represents a second embodiment of a device according to the invention in a third configuration.

Herein, the measures, values, shapes and geometric references (such as perpendicularity and parallelism), when used with words like “about” or other similar terms such as “approximately” or “substantially”, are to be understood as except for measurement errors or inaccuracies due to production and/or manufacturing errors and, above all, except for a slight divergence from the value, measure, shape or geometric reference which it is associated with. For example, said terms, if associated with a value, preferably indicate a divergence of not more than 10% of said value.

In addition, where used terms such as “first”, “second”, “upper”, “lower”, “main” and “secondary” do not necessarily refer to an order, a priority relationship or relative position, but may simply be used to more clearly distinguish different components from each other.

The measurements and data presented herein are to be considered, unless otherwise indicated, as made in Standard International Atmospheres ICAO (ISO 2533).

With reference to the Drawings, reference numeral 1 globally denotes the anti-seismic device according to the invention.

The seismic device 1 is preferably adapted to seismically isolate a structure 2 with respect to the ground 3.

The structure 2 is preferably a building type structure. Therefore it can be a building, an infrastructure such as a bridge or other type.

In addition, the term “structure” 2 may be understood not only as the structure as a whole, but also as a portion of the structure.

The device 1 can in fact be housed in the foundations of the structures 2, or it can be arranged in intermediate portions thereof. In one example, the device 1 is arranged at the base of the foundations of a residential building, i.e. a house. In a second example, the device 1 is arranged below a bridge support pylon.

In a third example, the device 1 may be housed in the bridge portion comprising the coupling between the support pylon and the transit carriageway of the bridge itself.

The ground 3 may be a bottom of any type, preferably flat.

The ground 3 may be, for example, solid earth or a seabed.

In general, the device 1 is connectable to an upper portion and a lower portion.

The lower portion may consist of the ground 3. However, it need not necessarily be the ground 3, but may consist of other.

Similarly, the upper portion may consist of the structure 2, but does not necessarily consist of it.

As already mentioned above, in fact, the device 1 can assume different configurations that include, for example, the arrangement within intermediate zones of said structures 2.

The device 1 is described below in structural terms considering the constituent parts thereof following the modelling of construction science. This means that, for example, when reference is made to hinges and bars, they refer to physical elements that exhibit behaviour similar to a bar and/or a hinge, in particular in a two-dimensional plane, but without any limitation with regard to the actual physical components used.

For example, a hinge may be made by a plurality of joints, just as a rod, in terms of modelling, may refer to a bar, a beam or other elements adapted, in this case, to connect hinges or otherwise having its own stiffness.

The support 1 preferably comprises a first support 4, a second support 5 and a third support 6.

The first support 4, the second support 5 and the third support 6 preferably define similar forms.

Preferably the first support 4 defines a first support plane 4a.

The first support 4 is preferably connectable to the upper portion, e.g. to the structure 2, or, in another example, to the third support 6 of an additional device 1.

Thus, the first support plane 4a may consist of the interaction or constraint plane between the first support 4 and the structure 2.

In addition, the first support 4 comprises at least two first hinges 40.

The hinges 40, preferably, are made of mechanical joints that allow other elements to be transiently connected. Such mechanical joints may be bolts adapted to preferably allow only a degree of transience, in particular rotation around the hinge, of the other elements.

Such first hinges 40 are further preferably mutually spaced defining a first distance d′.

The first distance d′ is preferably defined along the first support plane 4a.

In addition, it is preferably constant, so the first support 4 defines a rigid rod.

Preferably the third support 6 defines a third support plane 6a.

The third support 6 is preferably connectable to the lower portion, e.g. to the ground 3 or to the first support 2 of a second device 1.

The term “lower” as well as the term “upper” used previously, is defined with reference to the ground 3 along the vertical direction defined, for example, by gravitation acceleration.

Consequently, the third support plane 6a may consist of the interaction or constraint plane between the third support 6 and the ground 3.

Further, the third support 6 comprises at least two third hinges 60.

Also the third hinges 60, preferably, are made of mechanical joints that allow other elements to be transiently connected. Such mechanical joints may be bolts adapted to preferably allow only a degree of transience, in particular rotation around the hinge, of the other elements.

Such third hinges 60 are further preferably mutually spaced defining a third distance d′″.

The third distance d′″ is preferably defined along the third support plane 6a. Further, it is preferably constant, so the third support 6 defines a rigid rod.

In addition, preferably, the distance d′″ is congruent with respect to the first distance d′. Alternatively, in the example of FIGS. 7a-7c the first distance d′ is greater, preferably by a percentage in the range of 18% to 25% and more preferably in the range of 21 to 23%, compared to the third distance d′″.

Preferably the second support 5 defines a second support plane 5a.

The second support 5 is preferably connectable to the first support 4 and to the third support 6.

As a result, the first support plane 5a is comprised between the first support plane 4a and the third support plane 6a.

In addition, the second support 5 comprises at least two second hinges 50. Preferably, in the example of FIGS. 7a-7c the second support 5 comprises four second hinges 50, two second upper hinges 50a and two second lower hinges 50b. The second hinges 50, preferably, are made, like the others, from mechanical joints that allow other elements to be transiently connected. Such mechanical joints may be bolts adapted to preferably allow only a degree of transience, in particular rotation around the hinge, of the other elements.

Such second hinges 50 are, moreover, preferably mutually spaced defining a second distance d″. Preferably, in the example of FIGS. 7a-7c the second support 5 defines a second lower distance d₁″, between said second lower hinges 50b, and a second upper distance d₂″, between said second upper hinges 50a.

The second distance d″ is preferably defined along the second support plane 5a. In addition, it is preferably constant, so the second support 5 defines a rigid rod. Preferably, the second distance d″ is not congruent with the first and third distance d′ and d′″ but is less than them.

For example, the second distance d″ can be, compared to the third distance d′″ at least 3%, more appropriately 5% less.

Alternatively, in the example of FIGS. 7a-7c the second lower distance d₁″ is less than both said first and said third distance d′ and d′″, by a percentage preferably in the range of 40% to 50% and more preferably in the range of 44 to 48%, relative to the first distance d′. Furthermore, the second upper distance d₂″ is greater than both said first and said third distance d′ and d′″, by a percentage preferably between 9% and 15% and more preferably between 11 and 13%, compared to the third distance d′″.

The device 1 then comprises connection means 7.

The connection means 7 are preferably adapted to connect the support 4, 5, 6. They preferably define a connection plane 7a. The connection plane 7a is perpendicular to the third support plane 6a. Therefore, it is substantially perpendicular to the ground 3 and vertically joins, with respect to the ground, the supports 4, 5, 6.

The connection means 7 comprise at least two first bars 70 and two second bars 71.

The first bars 70 are preferably substantially rigid. In addition, they each define a first connection direction 70a.

The first connection direction 70a corresponds to the main extension dimension of the bar 70 and therefore corresponds, for it, to the axial direction.

The first connection direction 70a is also non-deformable.

Preferably, the first bars 70 are adapted to constrain the first support 4 and the second support 5.

More specifically—the two first bars 70 are each transiently constrained to a first hinge 40 and a second hinge 50 so that the directions of connection 70a of the first bars 70 cross in the connection plane 7a.

In the example of FIGS. 7a-7c the first bars 70 are transiently attached each to a first hinge 40 and to a second upper hinge 50a and substantially define the same geometry described.

Likewise, preferably, the second bars 71 are also rigid. In addition, they each define a second connection direction 71a.

The second connection direction 71a corresponds to the main extension dimension of the bar 71 and therefore corresponds, for it, to the axial direction. The second connection direction 71a is also non-deformable.

Preferably, the second bars 71 are adapted to constrain the second support 5 and the third support 6.

More specifically, the two second bars 71 are each transiently constrained to a second hinge 50 and to a third hinge 60 so that the second directions of connection 71a of the second bars 71 cross in the connection plane 7a.

In the example of FIGS. 7a-7c the second bars 71 are transiently each constrained to a second lower hinge 50b and to a third hinge 60 and substantially define the same geometry described.

The first bars 70 and the second bars 71 are preferably congruent with each other, but may also be different.

The device 1 thus defines, substantially, preferably two similar overlapping, consequential and mirror-like structures, at least in a free condition, with respect to the second support plane 5a.

These structures are given by the first support 4, first bars 70 and second support 5 and second support 5, second bars 71 and third support 6.

In the example of FIGS. 7a-7c the distance, in the vertical direction and in an aligned configuration (FIG. 7a), between the first hinges 40 and the second upper hinges 50a is preferably very close to the first distance d′, and differs from the same preferably by less than 3%, preferably less than 1%. In addition, the distance, in a vertical direction and in the aligned configuration (FIG. 7a), between the second lower hinges 50b and the third hinge 60 is preferably greater than the third distance d′″, by a percentage preferably between 12% and 20% and more preferably between 15% and 17%.

These structures are also substantially similar to articulated quadrilaterals or “Chebyshev guides” which are used in the “straight” portion when the side bars are crossed.

As already mentioned, the device 1 preferably defines a free condition and at least one stress condition.

In the free condition, the device 1 is free with respect to seismic stresses and the first support plane 4a, the second support plane 5a and the third support plane 6a are parallel to each other. In this condition, the device 1 is adapted to support the upper structure.

In the stress condition the device 1 is, instead, stressed by means of a seismic stress defining at least one displacement x.

The displacement x is for example arranged along the third support plane 6a and parallel to the connection plane 7a so as to allow the device 1 to be moved according to a displacement x.

In detail, the first support 1 undergoes the displacement x by the seismic stress on the ground 3 and, as a result, all the supports 5, 6 arranged above are consequently moved.

Structurally, the device 1, described so far in terms of two-dimensional model, may comprise a plurality of pairs of first and second bars 70, 71.

Such first and second bars 70, 71 reciprocally coupled to other first and second bars 70, 71 are preferably parallel to the latter and arranged along parallel and spaced connection planes 7a.

In addition, the supports 4, 5, 6 may be formed or comprise a plurality of different structural elements.

For example, the first support 4 may comprise a first support bar 41, the second support 5 may comprise a second support bar 51 and the third support may comprise a third support bar 61.

The support bars 41, 51, 61 preferably rigidly connect, in this configuration, the hinges 40, 50, 60, respectively.

This configuration can be used for devices 1 that extend vertically in a two-dimensional manner, i.e. mainly along the connection plane 7a and with two first bars 70 and two second bars 71.

In particular, the device 1 may comprise adjacent pairs of first bars 70 and second bars 71 connected to adjacent pairs of support bars 41, 51, 61.

In this case the hinges 40, 50, 60 comprise spacers adapted to connect the pairs of support bars 41, 51, 61 and bars 70, 71 and the device 1 is substantially made of two structures, as described in the previous configuration, adjacent and constrained in a mirror-like manner.

Alternatively, the device 1 may comprise a first support plate, a second support plate and a third support plate.

In detail, the first support 4 may comprise the first support plate, the second support 5 may comprise the second support plate and the third support may comprise the third support plate.

The support plates are preferably coplanar with respect to the support planes 4a, 5a, 6a respectively and are adapted to respectively connect the hinges 40, 50, 60. Such support plates may further be connected by two first bars 70 and two second bars 71, or by a plurality of pairs of bars 70, 71.

Preferably, the device 1 is adapted to be used, as already mentioned, for anti-seismic foundations for building type structures.

In this case the seismic foundations comprise at least one device 1 and part, typically of the structure 2.

The device 1 can thus be arranged between two structural portions 2 or between the ground and a structural portion 2, typically the base.

The foundations comprising the device 1 may further provide for different configurations.

They may comprise a single device 1 or a plurality thereof.

For example, a foundation may comprise a plurality of devices 1 wherein all the respective third support planes 6a are all coplanar.

Preferably, moreover, all the first support planes 4a are also coplanar.

Such a configuration is, for example, shown in FIG. 5.

In addition, an anti-seismic foundation may comprise a plurality of devices 1 arranged consecutively in an overlapping manner and wherein, i.e., one of the third support planes 6a is integral with a lower portion, e.g., the ground 3, one of the first support planes 4a is integral with an upper portion, e.g., the structure 2, and the other first support planes 4a and third support planes 6a are integral with each other. In addition, preferably the devices 1 are not overlapped along coplanar connection planes 7a, but each of the devices 1 defines at least one free connection plane 7a skewed with respect to the connection planes 7a of the other devices 1 so as to allow the foundation to absorb a plurality of displacements x connected to seismic stresses in different directions along the connection planes 7a, as shown in FIG. 6. For example, preferably, a foundation may comprise four overlapping devices 1 so as to realize a column in which each device 1 defines a connection plane skewed with respect to the adjacent ones with inclination preferably equal to 45°. In this case, the devices 1 may have preferably octagonal perimeter edges.

In this way, a foundation is created that can absorb seismic stresses from the ground 3 with displacements x-within four different directions.

Even two overlapping devices 1 defining mutually perpendicular connection planes 7a can be sufficient to cushion all the coplanar forces, since the forces can always be separated along two perpendicular axes.

The functioning of the device 1 described above in structural terms, is as follows. When it is in the free condition all the support planes 4a, 5a, 6a are mutually parallel and the bars 70, 71 preferably intersect at a point comprised in the geometric axis of the device 1.

When the device 1 passes from the free condition to the stress condition due to seismic stresses that impress displacements x on the first support 4, the first support 4 is subjected to displacement x if it is parallel to the connection plane 7a. When the first support 4 moves, and typically vibrates, the crossing point of the bars 70, 71 is offset from the axis of the device 1 and the second support plane 5a tilts correspondingly to the inclination of the second bars 71.

Similarly, the first bars 70 and the first support plane 4a are tilted with respect to the second support plane 5a.

If the first support plane 4a and the third support plane 6a are integrally constrained respectively to an upper and lower portion characterized by sufficient values of moments of inertia, the limits of which are readily detectable depending on the dimensions of the device 1 from experimental tests, the first support 4 and the third support 6 remain parallel during the movement of the device 1.

In this case, the support planes 4a, 6a remain parallel and only the second support plane 5a is tilted with the bars 70, 71 which perform opposite rotations. More specifically, when the second support plane 5a rotates, the support planes can only reciprocally translate along a plane parallel to the ground 3, or along a direction perpendicular to the ground 3.

However, this latter movement is extremely limited, and negligible, for stresses with vibrations at low intensity or amplitude.

As a result, the device 1 permits a substantial “floating” effect to be obtained when a structure 2 is subjected to seismic stresses present on the ground 3. The device 1 according to the invention achieves important advantages.

In fact, the device 1 allows the stresses deriving from seismic activities to be absorbed in a dynamic and mechanical manner, i.e. without resorting to elements subject to deformations.

Consequently, the device 1 allows the movements and displacements x impressed by seismic stresses to be absorbed not only due to the rigidity of the constituent elements, but also thanks to the kinematic mechanisms included within the device 1.

In fact, in relation to the dimensions and configurations of the device 1, or of the foundations that comprise it, it is possible to completely absorb the vibration modes of the seismic stresses through the relative movement of the first support plane 4a with respect to the third support plane 6a.

This absorption takes place in a completely stable manner as the device 1 tends to return to the free condition, when not stressed. Therefore, the free condition realized by the device 1 is a stable equilibrium condition.

In conclusion, the device 1 allows the degrees of freedom of the movements to which the structure 2 is subjected to be reduced, for example with respect to the ground 3 since it is not allowed to rotate around an axis parallel to the first support plane 4a.

Variations may be made to the invention described herein without departing from the scope of the inventive concept defined in the claims.

For example, the supports 4, 5, 6 can be constrained together by means of elastic elements and/or dampers adapted to control and, if necessary, vary the dynamic response of the device 1 to seismic stresses.

Examples of embodiments of this type are shown in FIG. 3 and FIG. 4.

Preferably, such elastic elements may be common springs and the dampers may be of the hydraulic type and configurations may be provided for in which, for example, the first hinges 40 are connected by said elastic elements and/or dampers to the second hinges 50 and, in turn, the second hinges 50 may be connected to the third hinges 60.

These may be either of the passive type or active type. The device 1 could also actively compensate seismic movements.

In said sphere all the details may be replaced with equivalent elements and the materials, shapes and dimensions may be as desired.

Claims

1. An anti-seismic device for seismically isolating a structure with respect to the ground wherein it comprises:

a first support defining a first support plane integrally connectable to an upper portion, for example to said structure, and comprising at least two first hinges defining a first constant reciprocal distance (d′),

a second support defining a second support plane comprising at least two second hinges defining a second constant reciprocal distance (d″),

a third support defining a third support plane integrally connectable to a lower portion, for example to said ground, and comprising at least two third hinges defining a third constant reciprocal distance (d′″), and

connection means defining a connection plane perpendicular to said third support plane and comprising at least: two first rigid bars, each defining a first non-deformable direction of connection and adapted to constrain said first support and said second support, and two second rigid bars, each defining a second non-deformable direction of connection and adapted to constrain said second support and said third support,

said first bars each being transiently constrained to one of said first hinges and one of said second hinges so that said first directions of connection of said first bars cross in said connection plane, and

said second bars each being transiently constrained to one of said second hinges and one of said third hinges so that said second directions of connection of said second bars cross in said connection plane.

2. The device according to claim 1, wherein said first distance (d′) and said third distance (d′″) are congruent and said second distance (d″) is less than said first and third distances (d′, d′″).

3. The device according to claim 1, wherein said second distance (d″) is at least 3% less than said third distance (d′″).

4. The device according to claim 1, wherein said supports and said connection means define at least two superimposed “Chebyshev guides”.

5. The device according to claim 1, comprising a plurality of pairs of said first and second bars, which are parallel to each other along parallel and spaced connection planes.

6. The device according to claim 1, wherein said supports each respectively comprise at least one support rod respectively adapted to rigidly connect said hinges.

7. The device according to claim 1, wherein said supports each respectively comprise at least one support plate respectively coplanar with said support planes and respectively adapted to rigidly connect said hinges.

8. The device according to claim 1, comprising two pairs of two second hinges.

9. Earthquake-resistant foundations of a structure comprising a device according to claim 1 and at least part of said structure, said structure being a building-type structure.

10. The earthquake-resistant foundations according to claim 1, comprising a plurality of said devices, wherein said respective third support planes are all coplanar.

11. The earthquake-resistant foundations according to claim 1, comprising a plurality of said devices, wherein said devices are arranged consecutively overlapping, one of said third support planes being integral with a lower portion, one of said first support planes being integral with an upper portion, said other first support planes and third support planes being integral with each other, and each of said devices defining at least one said connection plane which is skewed with respect to said connection planes of said other devices so as to allow said foundations to absorb a plurality of seismic stresses in different directions along said connection planes.