WO2014057294A1 - System for the detection of seismic activity - Google Patents

Description

TITLE: SYSTEM FOR THE DETECTION OF SEISMIC ACTIVITY

The present invention is relative to a system for detecting a seismic activity and for controlling the structural layout of the building in which it is located.

The system is conceived to detect the accelerations assumed by the ground due to an earthquake or, for some specific applications, to control the structural statics behavior of buildings located in areas at high hydro- geological risk.

In particular, the system according to the present invention is a differentiated calibration system, so as to increase the resolution of the system. The system according to the present invention has a high mechanical solidity against the internal and external stresses to which the system might be subject.

Seismic activity control systems are known, which comprise a housing case, and one or more masses, which are subjected to forces caused by mechanical stresses and are arranged in proper delimiting ring nuts.

Furthermore, systems or devices are known, which provide a differentiated threshold system, in which the single masses are associated to discs featuring duly differentiated diameters, which are associated, in turn, to delimiting ring nuts, all with the same diameter.

Said ring nuts are subject to a reference common electric potential with a low voltage, normally ranging from lmV and 10 V.

The voltage is applied to the case and, subsequently, it is applied to the single ring nuts by exploiting the. conductivity of the case and of the integral connection between the ring nut and the case .

In particular, the ring nuts are fixed to the lower internal base of the case itself.

The integral connection between the ring nuts and the case is performed by means of clamping fastening means, such as, for example screws, which are normally associated to relative washers.

The system described in the Italian Utility Model IT254069 detects the contact between a disc and the ring nut by means of a measuring circuit, which is directly connected to said discs through a capillary wire. Said capillary wire is welded to a point of the upper surface of disc and is connected to a relative terminal of an electrical measuring circuit.

In order to avoid a contamination of the measurement, which can be caused by micro-seismic events occurring in a generic structure but not generated by an actual seismic micro-activity, the prior art systems do not detect local magnitude values that cannot be perceived by human sense organs .

The micro-seismic events occurring in a generic structure but not generated by a seismic activity could be caused, for example, by the nearby transit of heavy means of transport, by busy vehicle traffic, by drilling activities, by mechanical excavations, by the flight of helicopters or other aircrafts at low altitude, by high- impact thunders, by strong wind, by heavy rains, by hailstorms, etc..

For these reasons, the seismic activity detecting systems of the prior art normally need both filters to reduce the amplitude of the transduced electrical signals and frequency filters, so as to avoid the detection of high-frequency oscillations that cannot be associated to or caused by seismic activities.

Seismic activity detecting systems should preferably be arranged in places where the exposure to the risk deriving from a seismic activity is greater, and, in particular, in city centers, especially those with a high population density.

In these places, the systems or devices of the prior art are not able to operate due to frequent micro-seismic events of the anthropic or natural type.

The object of the present invention is to solve the above-mentioned technical problems by providing a seismic activity detecting system, which is not affected by the effects of the superficial micro-seismic events and, at the same time, is sensitive to the structural micro-movements of the building in which said system is applied.

The features and advantages of the present invention will be best understood upon perusal of the following detailed description of a preferred embodiment with reference to the annex drawings, which respectively illustrate what follows:

• figures 1A, IB and 1C show, in different views, the detecting system according to the present invention in two different embodiments; in particular, figure 1A shows a two-threshold system, figure IB shows a four-threshold system, and figure 1C shows a front view of the system of figure IB; • figures 2A and 2B show, in detail, a detecting system; in particular, figure 2A shows a lateral view and figure 2B shows a front view;

• figures 3A and 3B show a mass of the detecting device; in particular, figure 3A shows the mass in a front view and figure 3B shows an exploded view of the mass;

• figures 4A and 4B show, in detail, the data transferring plate in a plan view and in a lateral view respectively;

· figures 5A and 5B show the insulation plate; in particular, figure 5A shows a plan view of the plate and figure 5B shows a detail of the holding portion of the plate itself.

With reference to the above-mentioned figures, the seismic activity detecting system comprises a housing case 2, which, in turn, comprises a shell, to which at least one housing 22 is fixed; at least one mass 3, which comprises a body 31, to which a detecting element 33 is fixed, for example, by means of a connecting rod 32; and at least one measuring circuit 4. Said at least one housing is subject to a known electrical potential.

In the preferred embodiment, said detecting element 33 is a graduated disc and said housing 22 is a cylindrical ring nut .

As shown in figures 3A and 3B, said mass 3 preferably comprises a hooking portion 30, which is fixed to said body 31. Said rod 32 is fixed, in turn, to said body 31.. Said detecting element or disc 33 is fixed at the opposite end of said rod 32.

In the embodiments shown in figures 1A, IB and 1C, a plurality of housings 22 are provided, which are arranged at predetermined distances from one another, for example they are equidistant.

Said at least one mass 3 is kept suspended along a vertical axis, inside case 2, by means of at least one cable 24.

For the purpose of the present invention, the term "suspended" means that mass 3 hangs by means of said at least one cable 24, thus being suspended inside case 2.

Each detecting element 33 is arranged inside a housing 22 and is kept at a given distance from inner walls 22b of housing 22 during the state of rest.

For the purpose of the present invention, the terms " state of rest" indicates the state of the system when the latter is not subject to mechanical stresses caused by seismic activities.

Said masses 3 are preferably made of a metal material with a known mass, on which a weight acts.

In the embodiment shown in the figures, said system comprises a plurality of masses 3, each one associated to a detecting element 33 with different structural features, corresponding to different seismic activity detecting thresholds; each detecting element being adapted, in particular, to detect an acceleration of the mass above a known threshold.

In the preferred embodiment, said detecting elements are graduated discs. Each disc 33 has a different diameter corresponding to a different seismic activity detecting threshold.

The diameter of graduated disc 33 is inversely proportional to the detectable seismic activity threshold. The differentiated calibration of the system according to the present invention is a function of the diameter of graduated discs 33 used, which are connected to the lower side of masses 3, as shown for example in figure 1C.

The diameters of said discs 33 are differentiated from one another as a function of the different thresholds to be detected. Said discs 33, as mentioned above, are arranged inside relative ring nuts 22. All ring nuts 22 have the same diameter, which is larger than the diameter of disc 33 with the largest diameter. The smallest difference between the ring nut and the disc associated thereto is equal to 0.25 mm, thus detecting a seismic activity with a very low threshold. The higher the diameter difference between disc 33 and ring nut 22, the higher the seismic activity detecting threshold of the single detecting device.

Said measuring circuit 4 is adapted to detect the contact between a detecting element 33 and corresponding housing 22, in the event of an oscillation of the mass.

The contact between detecting element 33 and corresponding housing 22 occurs when a predetermined ground acceleration value is reached.

Said cable 24 is connected to said at least one measuring circuit 4, so as to conduct an electrical signal corresponding to a contact between a detecting element 33 and corresponding housing 22.

In the preferred embodiment, said measuring circuit 4, by means of a cable 24, is adapted to detect the contact between a graduated disc 33 and the corresponding ring nut 22.

Measuring circuit 4 comprises a data processing unit 42, so as to determine the extent of the seismic activity measured by determining the value of the acceleration assumed by the ground. Said data processing unit 42 is adapted both to determine which detecting element 33 has come into contact with corresponding housing 22, thus determining the corresponding threshold, and to compare said threshold with a predetermined alarm threshold.

The system according to the present invention comprises at least one alarm device 5, which is adapted to signal the presence of a potentially dangerous seismic activity, which is assumed to be occurring, for example, as a consequence of the simultaneous activation of the different activation thresholds as a function of time. If necessary, the signally takes place also when the persistence time of the seismic activity associated to the single threshold is exceeded. In any case, all the accelerating activities are filed and stored.

In the event that data processing unit 42 detects that a predetermined alarm threshold has been exceeded, the system activates said alarm device 5, which emits a light and/or sound signal, which can be perceived by human beings.

Said measuring circuit 4 is adapted to cause said housings 22 to be subject to a known electrical potential. In the preferred embodiment, said potential is equal to 9 Vcc. In an alternative embodiment, instead of applying a voltage to said housings 22, the latter are electrically connected to a reference node, for example at 0V or grounded. This last solution is preferably applied in case that said system has to be interfaced with digital electronic boards.

In the preferred embodiment, the reference potential is applied to the housing case, which is preferably made of an electrically conductor material. Said housings 22 are rigidly fixed to case 2 and are electrically connected to one another.

In the preferred embodiment shown in the figures, said housing case 2 has the shape of a regular rectangular parallelepiped. Said case is preferably manufactured with plates made of conductor materials, for example metal materials. Said plates have a thickness ranging from 5 to 10 mm. Said case, for example, has an inner height of 20 cm.

Preferably, one or more housings 22 are fixed to the lower inner base of case 2 by means of a fastening element, for example a screw and a washer. More in detail, in the preferred non-limiting embodiment of the present invention, a first hole, which is preferably non-threaded and, for example, has a diameter of 15 mm, is obtained at the center of each circular base of ring nut 22.

Said first hole is adapted to allow a first pin to be inserted therein, said pin being preferably threaded, for example a 4 mm threaded pin, and provided with a first washer, which is not integral to said first pin. Said first washer has a diameter of at least 20 mm. Under the support base of each one of said washers, in the area under the first hole, a second hole is provided, which is threaded, for example a 4 mm threaded hole, has a proper depth, and is obtained inside the thickness of case 2. The difference between the diameters of the first pin and of the first hole obtained at the center of the support base of each ring nut 22 allows the position of ring nut 22 itself to be adjusted. This adjustment allows detecting element 33 associated to mass 3, which is arranged in a vertical position, to be equally spaced from the inner walls 22b of said housing 22. This fine adjustment is performed during the installation of the system according to the present invention, the final fastening takes place after that masses 3 have been correctly arranged in their vertical position. In the preferred embodiment, this adjustment allows disc 33 to be arranged at the center of relative ring nut 22. This solution allows the achievement of a margin of error, concerning the distance of the disc with respect to inner walls 22b of the ring nut, that is lower than 0.25 mm.

Said measuring circuit 4, which comprises preferably analogue electronic devices, is housed inside case 2. Said measuring circuit 4, which is preferably manufactured on a printed circuit, has a quiescent operation.

For the purpose of the present invention, the term "quiescent operation" means that, in the state of rest of the system, there is no electrical absorption on the part of the electronic devices comprised in the system and, in particular, on the part of measuring system 4.

Said measuring circuit 4 is preferably supplied with power by means of batteries, e.g. lithium batteries, for example ranging from 7.2 to 9 Vcc . Said batteries are arranged in proper housings, which are electrically connected to the printed circuit of circuit 4, or they are connected to measuring circuit 4 by means of floating wires .

Said feature plays a very important role, since the battery life is basically infinite or, anyway, commensurate with its natural self -deterioration. Said printed circuit is preferably made of fiberglass, so as to univocally transfer the electrical signals generated by different masses 3.

Said printed circuit is installed on the upper bottom wall of case 2, parallel to the bottom wall itself, so as to guarantee the stabilization and the consequent hold of cable 24.

Possible further control devices of the system according to the present invention can be connected to the system itself by means of connecting cables or by means of wireless connections. Furthermore, said control devices can always be active, but they are preferably arranged outside of case 2.

Measuring circuit 4 preferably comprises an A/D converter, whose firmware, which is located therein, establishes a progressive and regressive control between the activation thresholds associated to said at least one mass 3. Said converter, in case of an earthquake, immediately describes the perfect increasing and decreasing diagram of the ground acceleration as a function of time. Data processing unit 42, by means of a proper processing program, is able to evaluate the actual dangerousness of the earthquake as a function of the signals received. The dangerousness of an earthquake, especially in the area close to the epicenter, is determined some moments after the first seismic waves, for example " P" waves, which precede "S" waves, have reached the ground.

"P" waves, despite producing an angle of incidence that is vertical and perpendicular to the ground with respect to the hypocenter generating them, produce thrust vectors that are oblique to the surrounding ground, due to the natural deformation of the ground, which, subsequently, generates concave and convex angles with respect to the horizon, thus causing the "P" waves themselves to create waves that are " semi -horizontal " with respect to the following "S" waves, which, as known, exclusively generate horizontal waves.

In the preferred embodiment, said cable 24 is made of steel .

Conductive wire 24 replaces the nylon wires used in the prior art to support masses 3 in a suspended manner 3.

Preferably, cable 24 has a length ranging from 1 to 10 cm, for example 4 cm, and has a section ranging from 0.55 to 0.60 mm.

Mass 3 is supported by cable 24 in a suspended manner by fixing cable 24 to the mass itself.

Preferably, cable 24 is fixed to mass 3 by means of screw fixing means, for example by means of a suited grub screw, which is preferably threaded and without head.

The fact that cable 24 is fixed to mass 3 allows an optimization of the vertical hold of the cable-mass.

In the preferred non-limiting embodiment, more in detail, a third hole is provided, which is arranged on the upper part of mass 3, for example at the center of hooking portion 30. Said third hole, for example, has a diameter of 0.75 mm and a depth of 1 cm. Furthermore, a further fourth threaded hole is provided, which is arranged in correspondence to 2/3 of the size of the above-mentioned depth of the third hole, which is vertical, and is obtained perpendicular to the height of the third hole itself. Said fourth hole is threaded and has a diameter of 3 mm as well as a depth of 7 mm. Said third vertical hole is adapted to allow cable 24 to be inserted therein. The fourth threaded hole is perpendicular to the third hole and is adapted to house a first grub screw, which is adapted to fix the cable, thus obtaining the perfect cable-mass hold. The present solution allows the cable-mass fixing to have a higher mechanical resistance against high mechanical stresses of whatever nature.

Cable 24, by exploiting its conductivity, is used as an electrically conductor cable, thus obtaining a double essential improvement. Indeed, cable 24 itself is used to transfer an electrical signal to measuring circuit 4, in the event that there is a contact between detecting element 33 and housing 22. In the preferred embodiment, said cable 24 is adapted to transfer a reference potential to said measuring circuit 4, in particular to a relative univocal terminal 40, which is comprised in measuring circuit 4 associated to corresponding mass 3. As mentioned above, the reference potential is the potential to which housings 22 are subject.

The present invention allows the elimination of the capillary conductor, which is electrically connected to detecting element 33, guaranteeing at the same time the same result. Furthermore, the elimination of said conductor helps prevent the conductor itself from jeopardizing the free oscillation of mass 3 in the presence of an acceleration or its natural return to the stillness state in the absence of a seismic activity.

Furthermore, the system according to the present invention allows the assembly of the system itself to be simplified by eliminating a difficulty affecting the assembly of the systems of the prior art, which is due to the need to correctly fix the conductor to detecting element 33 by means of welding, so as to make them integral. Furthermore, the soundness of the conductor used in the prior art could be jeopardized, especially in the presence of high stresses.

Furthermore, the present solution allows a simple identification of terminal 40 comprised in measuring circuit 4, to which cable 24 has to be connected.

Case 2 comprises at least one insulation plate 26, adapted to electrically insulate said cable 24 from the shell of housing case 2. In order to allow said at least one mass 3 to be correctly suspended inside case 2, said insulation plate 26 is used, which is made of a non- conductive material, e.g. Plexiglas.

Said plate 26 comprises at least one fixing portion

260 and at least one holding portion 261.

Said holding portion 261 comprises two holes 262, between which a groove 263 is interposed.

Said fixing portion 260 allows insulation plate 26 to be fixed to case 2. Said holding portion 261 allows said at least one mass 3 to be suspended and said cable 24 to be insulated from case 2. In detail, cable 24 is connected between a terminal 40 and corresponding mass 3. The cable is caused to pass through said holding portion 261, so that the wight of mass 3 is caused to at least partially rest on said insulation plate 26. Groove 263 is adapted to house said cable 24, thus preventing it from coming into contact with the case, insulating it, as shown in figures 5A and 5B.

The use of the insulation plate 26, with respect to the solutions of the prior art, allows the elimination of the grooves produced in the external part of the case 2 , which are suited to fix said at least one mass 3 to the case 2.

Said measuring circuit is fixed to the case 2 by means of at least one spacer 20. Said at least one spacer 20, furthermore, is suited to impart a common potential to the case 2 and to a reference node of the measuring circuit 4.

The system according to the present invention can assume different configurations as a function of the number of masses 3, of the arrangement, and of the electrical connections. Preferably, the system, also called interactive seismic warning system, assumes the following configurations: one- threshold configuration, two- threshold configuration, and multi-threshold configuration; in these configurations, the case is associated to one, two or more masses 3 respectively, which have calibrations that are differentiated from one another.

The seismic activity detecting system simplifies, with respect to the prior art, the assembly phases needed to assemble its components.

The system, furthermore, can be easily and quickly installed where it is needed. Besides the manufacturing and installing simplifications, the system features a higher mechanical solidity against high mechanical stresses, both internal and external .

The system according to the present invention has high-quality features, which are expressed in terms of high sensitivity in the detection of structural accelerations, even those that cannot be perceived by human beings.

Furthermore, the system is highly stable against superficial micro-seismic events generated by anthropic phenomena or by natural events, such as those caused by high-impact thunders, by strong wind, or by heavy rains.

The system according to the present invention enables the local performance of all the procedures needed to actually reduce panic, allowing at the same time an actual preventive behavior with respect to seismic risk; in particular, thanks to its network connection, the system according to the present invention allows the real-time performance of all the Seismic Early Warning procedures.

NUMERICAL REFERENCES

Housing case 2

Spacer 20

Housing or ring nut 22

Inner walls 22b

Cable 24

Insulation plate 26

Fixing portion 260

Holding portion 261

Holes 262

Groove 263

Mass 3

Hooking portion 30

Body- 31

Connecting rod 32

Detecting element 33

Measuring circuit 4

Terminal 40

Data processing means 42

Alarm device 5

Claims

CLAIMS :

1. Seismic activity detecting system comprising:

• a housing case (2) , which comprises a shell, to which at least one housing (22) is fixed, which is subject to a known electrical potential;

• at least one mass (3) , which is kept suspended along a vertical axis, inside the case (2) , by means of a cable (24) , and comprises a body (31) , to which a detecting element (33) is fixed, each detecting element (33) being arranged inside a housing (22) and being kept at a given distance from the inner walls (22b) of said housing (22) during the state of rest;

• at least one measuring circuit (4) , for detecting the contact between said detecting element (33) and said housing (22) , in the event of an oscillation of the mass (3) ;

characterized in that said cable (24) is connected to said at least one measuring circuit (4) , so as to conduct an electrical signal corresponding to a contact between a detecting element (33) and the corresponding housing (22) .

2. System according to claim 1, wherein said cable (24) is made of steel.

3. System according to claim 1, wherein the case comprises an insulation plate (26) , for electrically insulating said cable (24) from the shell of the housing case (2) .

4. System according to claim 3, wherein the insulation plate (26) comprises at least one fixing portion (260) and at least one holding portion (261) .

5. System according to claim 1, wherein said detecting element (33) is a graduated disc and said housing (22) is a ring nut .

6. System according to claim 5, wherein the diameter of the graduated disc (33) is inversely proportional to the detectable seismic activity threshold.

7. System according to claim 1, wherein said system comprises a plurality of masses (3) , each one associated to a detecting element (33) with different structural features, corresponding to different seismic activity detecting thresholds.

8. System according to claim 1, wherein the measuring circuit (4) comprises a data processing unit (42) , so as to determine the extent of the seismic activity measured.

9. System according to claim 8, wherein the measuring circuit (4) comprises at least one terminal (40) , to which a corresponding cable (24) is connected.

10. System according to claim 1, wherein at least one alarm device (5) is provided, for signalling the presence of a potentially dangerous seismic activity.