WO2015049248A1

WO2015049248A1 - Process for obtaining a seismic monitoring system and seismic monitoring system thus obtained

Info

Publication number: WO2015049248A1
Application number: PCT/EP2014/070974
Authority: WO
Inventors: Emanuel Manfredini
Original assignee: Area Prefabbricati S.P.A.
Priority date: 2013-10-01
Filing date: 2014-09-30
Publication date: 2015-04-09
Also published as: EP3052918A1; ITPR20130074A1

Abstract

The finding is included in the field of techniques for obtaining seismic monitoring systems and is applicable to structures pertaining to civil engineering. With the process according to the present finding, a seismic monitoring system (1) is provided which comprises a set of equipment (such as accelerometers (2a, 2b) and a central unit (3)) and software which, for functioning, requires data and specific instructions introduced by the designer of the structure (11) (at which the seismic monitoring system (1) is installed) during the installation of said seismic monitoring system (1); said data and said specific instructions render the seismic monitoring system (1) appropriate for the considered structure (11); said seismic monitoring system (1) is adapted to be used for evaluating the conditions of unfitness for use of the structure (11) and the structural damage following seismic actions that occur after the installation of said seismic monitoring system.

Description

TITLE: "PROCESS FOR OBTAINING A SEISMIC MONITORING SYSTEM AND SEISMIC MONITORING SYSTEM THUS OBTAINED"

DESCRIPTION

Known in the art are monitoring systems adapted to measure displacements and rotations of structural elements making up part of a structure. Among such monitoring systems, seismic monitoring systems are known which are adapted to identify the behavior of a structure when it is subjected to seismic actions. In particular, seismic monitoring systems are known which are adapted to provide information for evaluating the size of the damage that a structure has sustained following a seismic event.

The latter seismic monitoring systems normally comprise sensors positioned at significant points of the structure, a data collection unit, connected to the sensors and a unit for transmitting data "to outside" the structure itself. Such sensors detect displacements (such is the case of sensors based on GPS) or accelerations (such is the case of accelerometers).

Normally such data, in order to be able to extract some information therefrom, must be processed at least partly outside the seismic monitoring system, by executing calculations and/or structural analyses.

Such seismic monitoring systems often provide messages, also in the synthetic form of signals constituted by yellow light, red light and green light, which according to the various seismic monitoring systems employed assume meanings more or less precisely tied to the concepts of "no damage", "slight damage", "high damage". Such seismic monitoring systems for indicating structural damage after a seismic event have been installed in a multiplicity of structures, usually of considerable importance, such as tall buildings, bridges, etc... Such seismic monitoring systems have allowed and allow knowing important data regarding the damage sustained by the monitored buildings; nevertheless, they can have the following drawbacks.

Sometimes it is rather difficult, by means of processing subsequent to the seismic event, to identify the structural damage, damage which in any case is identified and signaled some time after the seismic event itself. The verification calculations of the structure, in this case, are carried out "with hindsight". In substance, the actions due to the seismic event are applied to a structure calculation model, and the effects of the seismic action on the structure are obtained from numerical analyses, given that it is then possible to carry out an evaluation of the sustained damage.

Such analysis procedures are often rather costly and can be subjected to criticism since, if it is true that the input data of the numerical analyses derives from measurements and therefore is "real", it is also true that the final results are obtained by means of numerical analyses, executed with hindsight by using specific mathematic models that "interpret" reality.

In addition, in many cases, in the post-seismic emergency, the identification of the various situations (associated, for example, with the aforesaid signals constituted by green, yellow and red light), with regard to the structure's unfitness for use, is strictly correlated to the damage sustained by the monitored structure.

In addition, the seismic monitoring systems according to the prior art, at the time of installation on a structure, require that an engineer provide the seismic monitoring system itself only some (fundamental) data of the structure to be monitored; normally, such data does not allow the aforesaid engineer to determine the complete management of the responses and indications that the seismic monitoring system must provide in case of earthquake. Normally, moreover, the aforesaid engineer is not the designer of the structure.

Often, in the prior art, the seismic monitoring system is installed at an existing structure, which of course is examined and studied before the installation of the seismic monitoring system itself.

US4901575 relates to a method and apparatus for obtaining dynamic structure's characteristics subject to transient loads, in order to measure changes in the structural integrity of the member and to classify transient loads by nature and type; in other words, the scope is monitoring the state of health of the structure over time. The aforesaid "transient load" is the cause exciter, which allows the apparatus to perform the analyses that identify the dynamic characteristics of the structure in the function of time and therefore allows to take advantage of any changes in these dynamic characteristics due to deteriorations or structural degrades.

The transient load can be formed by moving loads caused by vehicles passing on the structure to be monitored (bridge), the wind load, the action of a device that causes the vibration phenomena (vibrodyne).

In the present invention the scope is recording the response of the structure (mainly in terms of displacements) during a seismic event and to compare it with the threshold values, entered in the system of seismic monitoring at the time of its installation, in order to understand wheather these threshold values are or not exceeded.

In US4901575 a cause is "sought": it corresponds to the "transient load"; this cause is required to activate the apparatus claimed so that it can, as a result of analysis that it performs, detect the dynamic characteristics of the structure and any anomalies and differences compared to past situation.

On the contrary, in the present invention the seismic event is certainly not "sought" nor used to see whether over time there are deteriorations in the structure.

The monitoring system of US4901575 records the effects of the earthquake on the structure and identifies the state of damage of the structure on the basis of the data and threshold values previously set into the monitoring system itself by the engineer designer of the structure (namely at the time of its installation) ,

Each analysis carried out by the apparatus of US4901575, compares the current data with previous data it has acquired. In other words there aren't "threshold values" set at the time of installation of the device, because only variations of the status of the structure are needed, in terms of dynamic response and with respect to its installation.

US4901575 so compares the current data with the previous data.

In the present invention the generation of signals does not depend neither on what happened in the past nor on the differences between what occurred in the past and in the present; the signal's generation depend on the threshold values previously entered in the monitoring system at the time of its installation. Therefore it is compared what happened (i.e. during an earthquake) with what an structure's Engineer had previously considered as possible and acceptable.

In US4901575 the apparatus provides results (on the structural integrity) after a reasonable period of time after the installation, since it has to compare values self- measured.

In the present invention the responses of the monitoring system may be provided by the monitoring system immediately after its installation.

Another example of the prior art is the patent WO2009/063523 which describes a structural health monitoring device which has the purpose of identifying the "state of health" of the structure in which it is installed. The identification of such a "state of health" is performed by the device itself comparing the current data with data detected by the monitoring system.

The monitoring system utilizes a self-training data processing methodology aimed to recognize the typical behaviour of the structure and to exploit its time recurrent. In other words, it is an autonomous system that after having self-trained by observing the typical behavior of the structure over a certain significant lapse of time, exploits the trends of the acquired data into their recurrent time, converging and diverging components and direct and/or derivative threshold-based detection of possible structural anomalies is performed and/or a state-of-health estimation parameter is calculated through a polynomial and/or exponential combination of the evaluated exploitations.

So, the "answers" of the monitoring system are provided after a reasonable period of time since the monitoring system requires time for collecting data before their comparison.

In the present invention the responses of the monitoring system, which takes place on the basis of threshold values entered by the Engineer, may be provided by the monitoring system immediately after its installation.

WO2009/063523 describes and provides at least one tamper sensor intended to trigger an alarm message broadcast operation in case of attacks to the device integrity or functionality; the "wake -up" sensor is specifically intended to remain permanently active and "asynchronously" trigger specific data acquisition session in occurrence of fast unexpected phenomena having structural relevance.

WO2009/063523 puts emphasis also on the "architecture" of the monitoring system: few independent structural monitoring devices placed in selected locations on the structure collect data from the embedded sensors and, if required, from external wired sensors installed in the neighbourhood. Each monitoring device directly communicate with the final information recipients through the Internet by directly connecting to a standard and globally interconnected telecom network.

One object of the present finding is to obtain a seismic monitoring system for identifying the post-seismic damage of the structures that allows having, in nearly "real time", a picture of the situation regarding the structural damage, given that it is possible to simultaneously obtain data that constitutes an important decision-making aid also relative to the unfitness for use of the building.

Further object of the present finding is to ensure that the designer of the structure, who knows the structure very well, indicates, during the design of the structure itself, the most significant points of the structure (hereinbelow indicated as points of analysis) and identifies the possible deformations thereof at pre-established performance levels of the structure itself.

Further object of the present finding is to ensure that it identifies, before the seismic event, the following: the possible failure mechanisms of the structure, recalling that such mechanisms must be of ductile type; the significant points of the structure to be kept under control, for the purpose of estimating damage (such significant points are indicated with the expression "points of analysis"); the maximum "acceptable" values of displacements relative of such points of analysis. In such a manner, after the seismic event, it is possible to immediately evaluate the possible structural damage.

This and other objects are achieved by the process for obtaining a seismic monitoring system, subject of the present finding, and by the seismic monitoring system thus obtained, also subject of the present finding.

The characteristics and the advantages of the present finding will be more evident from the following description of two embodiments illustrated as a merely non- limiting example in the enclosed drawings in which:

- figure 1 illustrates, according to a plan view, the ground floor of a prefabricated industrial building, on whose structure a seismic monitoring system is installed that is obtained according to the present finding, according to a first embodiment;

- figure 2 illustrates, according to a plan view, in the same scale as figure 1, the horizontal support structure of the ceiling/roof of the prefabricated industrial building of figure 1 ;

- figure 3 illustrates, in the same scale as figure 1, a longitudinal perspective of the prefabricated industrial building of figure 1;

- figure 4 illustrates, in the same scale as figure 1 , the section along the line A-A of figure 1;

- figure 5 illustrates, in a scale larger than that of figure 1 , part according to a top view and part in cross section, the horizontal support structure of the ceiling/roof of the prefabricated industrial building of figure 1; indicated in figure 5 is a circuit diagram of the seismic monitoring system installed at the structure of the prefabricated industrial building of figure 1 ;

- figure 6 illustrates, in the same scale as figure 5, the ground floor of the prefabricated industrial building of figure 1 ;

- figure 7 illustrates, in a scale larger than that of figure 6, part of the section along the line B-B of figure 6;

- figure 8 illustrates, in a scale larger than that of figure 7, a detail of figure 7;

- figure 9 illustrates, in a scale larger than that of figure 8, a detail of figure 8 with a detail in cross section;

- figure 10 illustrates, in the same scale as figure 9, another detail of figure 8 with a detail in cross section;

- figure 11 illustrates, in the same scale as figure 9, another detail of figure 8 with a detail in cross section;

- figure 12 illustrates, in the same scale as figure 8, another detail of figure 7;

- figure 13 illustrates, in a scale larger than that of figure 12, the section along the line C-C of figure 6 and a diagram of the equipment of the seismic monitoring system installed at the structure of the prefabricated industrial building of figure 1 ;

- figure 14 illustrates, according to a plan view, the ground floor of a prefabricated industrial building, on whose structure a seismic monitoring system is installed that is obtained according to the present finding, according to a further embodiment;

- figure 15 illustrates, in the same scale as figure 14, a longitudinal perspective of the prefabricated industrial building of figure 14;

- figure 16 illustrates, according to a plan view, in the same scale as figure 14, the horizontal support structure of the ceiling/roof of the prefabricated industrial building of figure 14;

- figure 17 illustrates, according to a plan view, in the same scale as figure 14, the intermediate horizontal support structure of the front part of the prefabricated industrial building of figure 14;

- figure 18 illustrates, in the same scale as figure 16, the section along the line D-D of figure 16;

- figure 19 illustrates, in a scale larger than that of figure 14, part according to a top view and part in cross section, the horizontal support structure of the ceiling/roof of the prefabricated industrial building of figure 14; indicated in figure 19 is a circuit diagram of the seismic monitoring system installed at the structure of the prefabricated industrial building of figure 14; - figure 20 illustrates, in the same scale as figure 19, part of the intermediate horizontal support structure of the front part of the prefabricated industrial building of figure 14;

- figure 21 illustrates, in the same scale as figure 19, the intermediate horizontal support structure of the front part of the prefabricated industrial building of figure 14 and the ground floor of the rear part of the aforesaid prefabricated industrial building;

- figure 22 illustrates, in the same scale as figure 19, the ground floor of the prefabricated industrial building of figure 14;

- figure 23 illustrates, in a scale larger than that of figure 22, the section along the line E-E of figure 22;

- figure 24 illustrates, in a scale larger than that of figure 23, a detail of figure 23 with a detail in cross section;

- figure 25 illustrates, in the same scale as figure 24, another detail of figure 23 with a detail in cross section;

- figure 26 illustrates, in the same scale as figure 24, another detail of figure 23 with a detail in cross section;

- figure 27 illustrates, in the same scale as figure 24, a further detail of figure 23 with a detail in cross section;

- figure 28 illustrates, part according to a plan view and part in cross section, the third horizontal support structure of a residential building on whose structure a seismic monitoring system is installed that is obtained according to the present finding, according to a third embodiment;

- figure 29 illustrates, part according to a plan view and part in cross section, in the same scale as figure 28, the second horizontal support structure of the residential building of figure 28;

- figure 30 illustrates, part according to a plan view and part in cross section, in the same scale as figure 28, the first horizontal support structure of the residential building of figure 28;

- figure 31 illustrates, according to a plan view, in the same scale as figure 28, the ground floor of the residential building of figure 28;

- figure 32 illustrates, in the same scale as figure 28, the section along the line F-F of figure 28;

- figure 33 illustrates, in a scale larger than that of figure 28, the section along the line G-G of figure 28;

- figure 34 illustrates, in a scale larger than that of figure 33, a detail of figure 33 with a detail in cross section;

- figure 35 illustrates, in the same scale as figure 34, another detail of figure 33 with a detail in cross section;

- figure 36 illustrates, in the same scale as figure 34, another detail of figure 33 with a detail in cross section;

- figure 37 illustrates, in the same scale as figure 34, another detail of figure 33 with a detail in cross section;

- figure 38 illustrates, in the same scale as figure 34, a further detail of figure 33 with a detail in cross section.

In the present description and in the below-reported claims, with the term "designer of the structure", it is intended the engineer who designed and calculated the structure, if it is a new structure or, if such structure is an existing structure, it is intended the engineer who designed and determined the interventions on the structure for the seismic adaptation, or for the seismic improvement or in any case for the renovation of the structure itself. It is underlined that, in the case of existing structure, the engineer that has designed and evaluated the renovation of the structure has (in relation to that described in the present finding) a role analogous to that of the designer engineer, in the case of newly constructed structure.

In order to illustrate the process for obtaining a seismic monitoring system 1, obtained according to the present finding according to a first embodiment, the seismic monitoring system 1 is first described with reference to figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13. Such seismic monitoring system 1 is installed at a structure 11 of a newly constructed industrial building 10; the structure 11 is such that brittle failure mechanisms are prevented therein and only ductile failure mechanisms are possible. The structure 11 comprises eighteen precast reinforced concrete columns 20a, 20b, 20c, precast prestressed reinforced concrete beams 21, precast prestressed reinforced concrete slabs 22 and cast-in-place foundations 23 made of reinforced concrete. The columns that bear the ceiling/roof and which constitute the structural elements dedicated to resist seismic actions are the fourteen columns 20a, 20b; for this reason, hereinbelow reference will only be made to the columns 20a, 20b. The building 10 is situated in a seismic zone. The slabs 22, which are of TT type, are connected to each other and are connected with the beams 21 which support them in a manner so as to form a planking that can be considered substantially rigid in its floor. The foundations 23 comprise "cuplike" plinths and connection beams which substantially prevent the relative displacements between the aforesaid plinths. A reinforced-concrete slab is also present which forms the industrial flooring of the building 10.

It is indicated that the aforesaid structural elements are connected to each other according to resistance hierarchy criteria; the aforesaid structural elements and the joints between the structural elements themselves are obtained with criteria and with structural details such that brittle failures are prevented, thus only ductile failure mechanisms remain possible.

The cladding, on the four facades of the building 10, is constituted by horizontal reinforced-concrete panels 24, which constitute a first band of the cladding, and by sandwich panels 25, composed of two metal plates and internal insulating layer placed on top of such first band; the sandwich panels 25 are provided with suitable framework structures, for the sake of simplicity not indicated in the figures.

The seismic monitoring system 1 comprises:

- eight accelerometers 2a, 2b positioned at measurement points belonging to the structure 11 ; of such eight accelerometers 2a, 2b, the four accelerometers 2a are positioned at the top of the two columns 20a, and the four accelerometers 2b are positioned at the base of the two columns 20a themselves, in proximity to the foundations;

- a central unit 3, connected to the aforesaid accelerometers 2a, 2b; the central unit 3 continuously (signifying: uninterruptedly) receives and processes the data coming from the accelerometers 2a, 2b;

the seismic monitoring system 1, once activated, functions uninterruptedly, except for pauses due to maintenance or replacement of components, for the entire useful lifetime of the structure 11.

The seismic monitoring system 1 comprises a set of equipment and software which, for functioning, requires data and specific instructions introduced by the designer of the structure 11 during the installation of the seismic monitoring system 1 itself; the aforesaid data and the aforesaid instructions render the seismic monitoring system 1 appropriate for the considered structure 11 ; the seismic monitoring system 1 is adapted to be used for evaluating the conditions of unfitness for use of the structure 11 and the structural damage following seismic actions that occur after the installation of the seismic monitoring system 1 itself;

the seismic monitoring system 1, once installed and once the designer of the structure 11 has introduced the data and the specific instructions necessary for the functioning of the seismic monitoring system 1 itself, functions uninterruptedly and automatically; the aforesaid measurement points are included among the points of analysis (signifying that the aforesaid measurement points are included among the points of the structure 11 that are subject to analysis, i.e. the points of the structure 11 where it is desired to know the displacements) belonging to the structure 11 identified by the designer of the structure 11, at the time of installation of the seismic monitoring system 1 , as points of the structure 11 where it is necessary to know, during the seismic action, the absolute displacements in order to be able to calculate the significant relative displacements between pairs of the aforesaid points of analysis; the knowledge of the aforesaid significant relative displacements, identified by the designer of the structure 11, is necessary for evaluating the conditions of unfitness for use of the structure 11 and the damage of the structure 11 itself deriving from seismic actions; the central unit 3, for its functioning, uses the data and the instructions introduced in the central unit 3 by the designer of the structure 11 at the time of installation of the seismic monitoring system 1 ; the aforesaid data and instructions comprise:

some data relative to the structure 11, including some data typical of the dynamic behavior of the structure 11 itself;

six threshold values for each of the aforesaid significant relative displacements; - messages that the seismic monitoring system 1 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements; there are eight of such messages;

parameters adapted to identify a damage evaluation scale;

the central unit 3, which functions continuously, by means of algorithms implemented in the software inserted in the central unit 3, verifies if the signals coming from the accelerometers 2a, 2b derive from a seismic action or from other causes that must not be considered; such algorithms tend to avoid false negatives or false positives, i.e. cases in which there is a seismic event and the seismic monitoring system 1 does not recognize it as such, and cases in which the seismic monitoring system 1 recognizes as a seismic event an action which is not of seismic type; for the recognition of the seismic action, the central unit 3 also makes use of filters inserted in the central unit 3 itself, which account for the activities that can be carried out in the building 10 and the actual situation which can be characterized, for example, by the presence of a subway line that passes in proximity to the building or even by the presence of a road on which heavy traffic travels, or by the presence of an airport; the data necessary for the functioning of the aforesaid filters was inserted in the central unit 3 by the designer of the structure 11 at the time of installation of the seismic monitoring system 1 ; the central unit 3, in case of earthquake, once it has been recognized that the signals received from the accelerometers 2a, 2b are those of a seismic event, signals said seismic event and calculates the values of the displacements of the measurement points, by carrying out a double integration (in the time domain) of the values of acceleration measured by the accelerometers 2a, 2b at the measurement points; the central unit 3 also calculates the values of the displacements of the calculation points; the central unit 3, using both the values of the displacements of the measurement points and those of the calculation points, then calculates the significant relative displacements (between the aforesaid points of analysis), indicated by the designer of the structure 11 ; the central unit 3 then compares such values of the significant relative displacements with the corresponding threshold values of the aforesaid significant relative displacements, introduced in the central unit 3 by the designer of the structure 11 at the time of installation of the seismic monitoring system 1 ; the central unit 3 then communicates, to outside the building 10, the results of the aforesaid comparison and transmits the corresponding messages introduced in the central unit 3 by the designer of the structure 11 at the time of installation of the seismic monitoring system 1.

The data transmitted to outside the building 10 essentially comprises data regarding the evaluation of unfitness for use of the structure 11 , and hence of the building 10 itself, and data regarding the evaluation of the damage that the building 10 may have sustained.

It is underlined that, in the present description and in the below-reported claims, with the expression "measurement point" it is intended a point, belonging to the structure under examination, whose displacements are determined by means of an instrument positioned at the measurement point itself - such displacements due to a seismic action; the accelerometers are positioned at the measurement points.

In addition, it is underlined that, in the present description and in the below-reported claims, with the expression "calculation point" it is intended a point, belonging to the structure under examination (no measurement instrument is positioned at the calculation point), where, by means of calculations (which use the values of the displacements of the measurement points), the displacements due to a seismic action are determined.

The points of analysis, which are points of the structure where it is desired to know the displacements, comprise the measurement points and the calculation points The accelerometers 2a, 2b are of capacitive type. Each accelerometer 2a, 2b is of uniaxial type; i.e. each accelerometer 2a, 2b measures the acceleration in a single direction. It is clear that each accelerometer 2a, 2b must be installed with reference to the aforesaid direction, as a function of what is provided for in the design. With regard to the structure 11 under examination, only the accelerations on the horizontal plane are measured, since the designer of the structure 1 1 did not deem it necessary to measure the acceleration also in the vertical direction.

Each accelerometer 2a, 2b is connected to the central unit 3 and to a power supply 4 by means of a cable 5 thereof. The cables 5 are inserted within cable carrier channels 14; the channels 14 are joined together by means of connector boxes and other connector elements.

The central unit 3 comprises a master unit 7 and a computer 8 interacting with each other; the master unit 7 comprises a converter module that converts the data from analog to digital, a data communication module, and a data processing module, comprising a CPU; the data processing module processes some data, dialogues with the computer 8 and also communicates the data and the messages to outside the building 10, i.e. outside the seismic monitoring system 1.

The computer 8 increases the calculation capacity and the calculation execution speed of the data processing module of the master unit 7. It is observed that master units could also be used which are technically equivalent to the master unit 7, in which the CPU, suitably powered and provided with adequate memory, can internally perform all the calculations necessary for the seismic monitoring system 1 , such that the computer 8 is not necessary.

The seismic monitoring system 1 also comprises a continuity group 6, an electrical board 13 and a generator 12; the power supply 4, which is placed in proximity to the central unit 3, supplies power both to the accelerometers 2a, 2b and to the central unit 3; it is underlined that the accelerometers 2a, 2b are connected, by means of a junction box 9, to the central unit 3 to which they provided the detected data, and to the power supply 4. The power supply 4 is connected to the continuity group 6 which in turn is connected to the generator 12 which is connected to the general electrical board 17 of the building 10.

In case of lack of electric current supply by the external electricity network, first the continuity group 6 comes into operation; then, after a certain time period has passed (e.g. equal to ten minutes), the generator 12 automatically starts functioning, which supplies the electric current necessary for the functioning of the seismic monitoring system 1.

In figure 5, which illustrates the circuit diagram of the seismic monitoring system 1, and in figure 6, the central unit 3 is indicated for the sake of representation simplicity, even if the central unit 3 is inserted inside a cabinet 29. In figure 13, most of the equipment contained inside the cabinet 29 is schematically indicated, in particular the central unit 3.

The accelerometers 2a, 2b are integral with the columns 20a and are placed within airtight protection elements 15 fixed to the columns 20a themselves; departing from the protection elements 15 are the channels 14, within which the cables 5 are positioned. It is underlined that the seismic monitoring system 1, once activated, functions uninterruptedly, except for the pauses due to maintenance or replacement of components, for the entire useful lifetime of the structure 11.

It is specified that the seismic monitoring system 1 , in order to recognize the seismic event is based (for example) also on the duration of the dynamic phenomenon recorded by the accelerometers 2a, 2b, and on the fact that the entire structure 11 is affected by the aforesaid dynamic phenomenon, such that all the accelerometers 2a, 2b detect signals of seismic type.

The functioning of the seismic monitoring system 1 is specified hereinbelow. First of all, it is observed that the building 10 is a single-level prefabricated building, such that a single horizontal support structure is present which is that of the roof.

The number and position of the accelerometers 2a, 2b are such that they can characterize the behavior of the building 10 or, better yet, the structure 11.

It is indicated that the accelerometers 2a, 2b are of single-axial type; this indicates that they measure the acceleration only in a preset direction, which is the measurement direction. Generally, it should be noted that accelerators of three-axial type can also be used, which acquire the accelerations by detecting the three components thereof along three orthogonal Cartesian axes (one of the three components is vertical).

In the structure 11 (to be monitored), measurement points are present at which the accelerometers 2a, 2b are positioned, and calculation points are present which are placed at the top and at the base of all the other columns 20b. In the case of the structure 11 , in which eighteen columns 20a, 20b are present, there are twenty-eight points of analysis (equal to two times fourteen) since it is of interest to know the displacements of the base and of the top of each column 20a, 20b; there are eight measurement points and twenty calculation points (equal to two times fourteen minus eight). Each of the significant relative displacements, with a column 20a, 20b and a direction in the horizontal plane fixed, is equal to the difference between the displacement of the top of the column 20a, 20b and the displacement of the base of the column 20a, 20b itself.

In the central unit 3, at the time of obtainment of the seismic monitoring system 1, the designer of the structure 11 has inserted threshold values of the significant relative displacements for each column 20a, 20b; it is specified that for each column 20a, 20b, six threshold values of the significant relative displacements were inserted, for each of the two orthogonal directions (longitudinal and transverse) according to which it is assumed that the seismic action is verified. Such six threshold values of the significant relative displacements (these threshold values were indicated by the designer of the structure 11) correspond, for the column 20a, 20b itself, to the six below-indicated events. For the sake of description simplicity, it is assumed that the six threshold values relative to the longitudinal direction are equal to the six threshold values relative to the transverse direction, such that hereinbelow reference will simply be made to the six threshold values of each column 20a, 20b; of such threshold values, the first three regard the unfitness for use of the building 10, the other three (more specifically) regard the "damage state of the building".

It is recalled that the structure 11 was designed and obtained in a manner so as to prevent, in any case, the occurrence of brittle failure mechanisms, such that only ductile failure mechanisms can occur.

The first threshold value for each column 20a, 20b is the maximum value of the significant relative displacement (i.e. of the displacement of the top of the column 20a, 20b with respect to the base of the column 20a, 20b itself) in the presence of which the column 20a, 20b itself is still in a non-cracked state.

The second threshold value for each column 20a, 20b is the maximum value of the significant relative displacement (i.e. of the displacement of the top of the column 20a, 20b with respect to the base of the column 20a, 20b itself) in the presence of which the column 20a, 20b itself is still "in elastic phase" while showing cracking phenomena.

The third threshold value for each column 20a, 20b is the value of the significant relative displacement (i.e. of the displacement of the top of the column 20a, 20b with respect to the base of the column 20a, 20b itself) in the presence of which, in the column 20a, 20b itself, the reinforcements (using a suitable safety coefficient) are to be deemed non-yielded.

The fourth threshold value is the maximum value of the significant relative displacement at which the deformations of the column 20a, 20b are within the values expected for substantially zero damage. It is indicated that in the presence of the fourth threshold value, the behavior of the column 20a, 20b is normally still in elastic phase or has just exceeded the threshold of the elastic behavior.

The fifth threshold value is the maximum value of the significant relative displacement at which the deformations of the column 20a, 20b are within the values expected for small-size damage. It is indicated that in the presence of the fifth threshold value, the behavior of the column 20a, 20b is of non-linear type.

The sixth threshold value is the maximum value of the significant relative displacement at which the deformations of the column 20a, 20b are within the values expected for medium-size damage; the sixth threshold value in any case remains considerably lower than the value of the relative displacement corresponding to the limit state of collapse of the structure 1 1. It is indicated that in the presence of the sixth threshold value, the behavior of the column 20a, 20b is of decidedly non-linear type. It is also indicated that above the sixth threshold value, serious structural damage is to be expected.

It is indicated that the threshold values of the significant relative displacements, decided and introduced in the central unit 3 by the designer of the structure 11 , also account for the damage of complementary building works (such as partitioning, false ceilings, windows, etc.) and/or of installations connected to the structure 11 itself. The third threshold value is greater than the second threshold value which is greater than the first threshold value.

The sixth threshold value is greater than the fifth threshold value which is greater than the fourth threshold value.

Once the seismic monitoring system 1 has been activated, the accelerometers 2a, 2b detect and transmit to the central unit 3 the values of the acceleration of the measurement points belonging to the columns 20a; such values are continuously detected with sampling frequencies on the order of KHz.

The central unit 3, after having transformed the data coming from the accelerometers 2a, 2b from analog to digital in the converter module, divides the data into data packets and analyzes it.

Each data packet is subjected, inside the central unit 3, to a first recognition procedure which allows distinguishing the non-seismic signals from those which may be seismic.

At the end of such procedure, the central unit 3, if the data packet does not contain data deriving from seismic actions recognized as such, discards the packet itself and subsequently cancels it; if the considered data packet contains data deriving from the seismic action, such packet is identified as deriving from a possible seismic action. Immediately, the central unit 3 sends an alarm signal to preset addresses and activates suitable signals positioned in the building 10 which indicate that a possible seismic event is taking place. Such message allows the occupants of the building 10 to act as provided in pre-established procedures for conduct in the presence of seismic actions. The central unit 3 applies a second procedure for recognizing the recorded data; in case of recognition of the seismic action, the central unit 3 consecutively records other data packets; this is continued for the entire duration of the seismic tremor and also for some time afterward. It is indicated that, with the calculation procedure implemented in the central unit 3, some packets are always available "which do not detect seismic action effects" relative to data detected before the start of the seismic tremor and after the end of the seismic tremor itself. According to a possible functioning variant, the abovementioned alarm signal can be launched by the central unit 3 once the earthquake has been recognized by the above-indicated second recognition procedure.

The central unit 3, once the seismic action has terminated, first calculates the (absolute) displacements of all the measurement points which are points where the accelerometers 2a, 2b are positioned; the calculation of the displacements of the measurement points is carried out by means of double integration (in the time domain) of the values of acceleration measured by the accelerometers 2a, 2b.

It is indicated that everything described above is calculated in nearly "real time", inside the central unit 3 (and hence within the master unit 7 and the computer 8), such that the data to be processed does not "exit" from the seismic monitoring system 1. It is observed that such characteristic of the seismic monitoring system 1 constitutes an undoubted advantage also over other seismic monitoring systems already obtained in the prior art. The central unit 3 then calculates the displacements of the calculation points which, it is recalled, are the points where it is of interest to know the displacements but which are not directly instrumented by means of the accelerometers 2a, 2b. The displacements of the calculation points are calculated by the central unit 3, by means of algorithms implemented in the software inserted in the central unit 3 itself, on the basis of the values of the displacements of the measurement points and on the basis of the data and instructions supplied by the designer of the structure 11 and inserted, by the same designer, in the central unit 3. The central unit 3 then calculates the maximum values of the significant relative displacements (which are the maximum values of the relative displacements between the base and the top of each of the columns 20a, 20b); in such calculation, both the measurement points and the calculation points are used. In the embodiment described herein, the central unit 3 calculates the relative displacements between the base and the top of each of the columns 20a, 20b belonging to the structure 11. Often in the literature, reference is made to the "drift" which, with a column fixed, is equal to the difference between the value of the (absolute) displacement of the top of the column and the value of the (absolute) displacement of the base, divided by the vertical distance between the base and the top (height) of the column itself.

The central unit 3, relative to each column 20a, 20b, compares the value of the significant relative displacements as calculated above with the threshold values of the significant relative displacements themselves.

In the case of the seismic monitoring system 1, the following eight cases are possible; the first four cases (marked with the letter "i") regard the subject "unfitness for use of the building 10"; the other four cases (marked by the letter "d") regard the subject "evaluation of the damage sustained by the building 10". The damage evaluations reported below (in the cases marked by the letter "d") derive from the parameters adapted to identify a damage evaluation scale provided by the designer of the structure 11 at the time of installation of the seismic monitoring system 1 ; such parameters were introduced in the central unit 3 by the aforesaid designer of the structure 11 at the time of installation of the seismic monitoring system 1 ;

It is underlined that the designer of the structure 11 has also identified the messages that the monitoring system 1 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of said significant relative displacements.

Case li: at the end of the above-described comparison regarding the value of the relative displacements, it is found that in all the columns 20a, 20b, the value of the significant relative displacements does not exceed the first threshold value; this signifies that all the columns 20a, 20b have remained in non-cracked phase. In such case, the seismic monitoring system 1 indicates that structural damage has not been detected, and given the fact that it is assumed (considering how the structure 11 was designed and built) that brittle failure mechanisms cannot occur, it is deemed that people are allowed to stay inside the structure 11.

Case 2i: at the end of the above-described comparison regarding the value of the relative displacements, it is found that even in only one of the columns 20a, 20b, the value of the significant relative displacements exceeds the first threshold value but is less than the second threshold value; it is indicated that in each column 20a, 20b, the value of the significant relative displacements is less than the second threshold value. This means that all the columns 20a, 20b have remained in elastic phase even if cracking states are possible in the columns 20a, 20b themselves. In such case, the seismic monitoring system 1 indicates that structural damage is not expected, and given the fact that it is assumed (considering how the structure 11 was designed and built) that brittle failure mechanisms cannot occur, it is deemed that people are still allowed to stay inside the structure 11 , even if it would be opportune to schedule at least one technical examination as soon as possible.

Case 3i: at the end of the above-described comparison regarding the value of the relative displacements, even in only one of the columns 20a, 20b the value of the significant relative displacements exceeds the second threshold value but is lower than the third threshold value; it is indicated that in each column 20a, 20b, the value of the significant relative displacements is less than the third threshold value. In such case, the seismic monitoring system 1 indicates that, before allowing people to return inside the building 10, an engineer must carry out a technical inspection in order to verify if the structure 11 itself is fit or unfit for use.

Case 4i: at the end of the above-described comparison regarding the value of the relative displacements, even in only one of the columns 20a, 20b the value of the significant relative displacements exceeds the third threshold value: the building 10 is (at least temporarily) unfit for use. The seismic monitoring system 1 indicates that it is necessary to carry out accurate technical examinations in order to verify the conditions of the structure 11. It is foreseeable that it will be necessary to undertake actions for improving the situation of the structure 11 and for making it once again suitable for carrying out the activities expected at its interior.

Case Id: at the end of the above-described comparison regarding the value of the relative displacements, in each column 20a, 20b the value of the significant relative displacement does not exceed the fourth threshold value; this means that all the columns 20a, 20b have substantially remained in the elastic range. In such case, the seismic monitoring system 1 (given the fact that it is assumed (considering how the structure 11 was designed and built) that brittle failure mechanisms cannot occur) indicates that actual structural damage is not expected; the message provided by the seismic monitoring system 1 is thus the following: "it is presumable that there is no significant damage".

Case 2d: at the end of the above-described comparison regarding the value of the relative displacements, even in only one of the columns 20a, 20b, the value of the significant relative displacements exceeds the fourth threshold value but is less than the fifth threshold value; it is indicated that in each column 20a, 20b the value of the significant relative displacements is less than the fifth threshold value. In such case, the seismic monitoring system 1 (given the fact that it is assumed (considering how the structure 11 was designed and built) that brittle failure mechanisms cannot occur) indicates that a first damage level has been reached (slight damage); the message provided by the seismic monitoring system 1 is thus the following: "it is presumable that slight damage has occurred".

Case 3d: at the end of the above-described comparison regarding the value of the relative displacements, even in only one of the columns 20a, 20b, the value of the significant relative displacements exceeds the fifth threshold value but is less than the sixth threshold value; it is indicated that in each column 20a, 20b, the value of the significant relative displacements is less than the sixth threshold value. In such case, the seismic monitoring system 1 indicates that a second damage level has been reached (medium damage); the message provided by the seismic monitoring system 1 is thus the following: "it is presumable that medium damage has occurred".

Case 4d: at the end of the above-described comparison regarding the value of the relative displacements, even in one of the columns 20a, 20b, the value of the significant relative displacements exceeds the sixth threshold value. The seismic monitoring system 1 indicates that the third damage level has been reached (severe damage); the message provided by the seismic monitoring system 1 is thus the following: "it is presumable that severe damage has occurred".

In the example considered, the fourth threshold value is greater than the third threshold value; thus, the seismic monitoring system 1 , according to that which was established by the designer of the structure 11 , indicates that the structure 11 itself (and hence the building 10) is considered (at least temporarily) unfit for use (cases 3i and 4i) when actual structural damage is not yet expected (as provided in case Id); according to that indicated by the seismic monitoring system 1 , indeed, people are allowed to stay in the building 10 only after an engineer who carries out an accurate technical examination (like that required by the above-illustrated case 4i) authorizes people to stay inside the building 10, possibly after restoration works ordered by the aforesaid engineer have been carried out.

It should be noted that even in the cases li and 2i, the "reassuring" message of the seismic monitoring system 1 is only related to the seismic event that has "passed"; it is indicated that the actual decision to remain in the building 10 or not must be taken by also considering the possibility that other close-together seismic events could take place, such events following the first seismic event. It is very important to consider the seismic monitoring system 1 as an objective aid in the decision-making process, but not as a final decision-maker in itself, since the final decision, having considered the completely unpredictable nature of seismic phenomena (reference is made to the problem of strong close-together tremors), is always on man's shoulders. The seismic monitoring system 1 undoubtedly allows objectively evaluating what has taken place, by means of measurements; the decision to allow people to stay inside a building must always make reference to what is expected to occur, also accounting for possible damage sustained by the structure, and this decision lies on the shoulders of man, particularly on those of experts.

It is observed that the indications of the seismic monitoring system 1 in relation to the damage state do not refer to the technical examinations to be carried out for evaluating the damage itself; the need for the technical examinations, according to the seismic monitoring system 1, is correlated with the "unfitness for use" of the structure. It remains true that technical examinations must still be carried out, also in relation to the damage states as identified above, in order to evaluate the state of the structure 11 ; such technical examinations are made when no people are present inside the structure 11 (and hence the building 10), which has already been declared unfit for use (since the second threshold value is of course lower than the third threshold value and the third threshold value is lower than the fourth threshold value). The evaluation of the damage, carried out by means of the following messages: "no significant damage" (case Id), "slight damage" (case 2d), "medium damage" (case 3d), "severe damage" (case 4d)), is also useful for evaluating the danger in making the technical examination.

If the seismic monitoring system 1 signals damage (such as for example average or severe damage), it is necessary to carry out in-depth technical visits before then undertaking actions adapted to improve the load-bearing capacity of the structure 11 now damaged and to make it once again suitable for carrying out the expected activities therein. It is clear that, in the case of severe damage, it may also be convenient from the economical standpoint to knock down the structure 11 or carried out operations of "structural replacement".

It is indicated that the seismic monitoring system 1 is not able to signal brittle failure mechanisms. It is also indicated that the possible damage, and consequent risks for the people who inhabit the building 10, deriving from failures, collapses or excessive deformations of finishing elements (such as, for example, false ceilings, shelving or other types of structural elements) or furniture, installations or machinery are "indirectly" accounted for by the designer of the structure 11 by suitably limiting the threshold values of the significant relative displacements which were provided by the designer itself for each of the columns 20a, 20b and which were introduced by the same designer in the central unit 3 during the installation of the seismic monitoring system 1.

The seismic monitoring system 1 , immediately after the seismic event, in real time, activates the system of communication with the outside provided for in the design. In relation to the "unfitness for use" of the building 10, the seismic monitoring system 1 communicates to the outside and to outside the building 10 which from among the cases li, 2i, 3i 4i has been verified. The "communication" of the seismic monitoring system 1 with the outside of the building 10 is carried out by the central unit 3 which sends messages via Internet or sends SMS to preset addresses (such as that of the owner of the building 10 and the manager of the industrial activities that take place inside the building 10); the central unit 3 simultaneously activates suitable signals visible outside the building which can comprise lamps of different color (such as green, yellow and red) and/or other signaling systems. In the seismic monitoring system 1, the lamps have blue color if case li has been verified, green color if case 2i has been verified, yellow color if case 3i has been verified, and red color if case 4i has been verified.

In relation to the "damage forecast" of the building 10, the seismic monitoring system 1 externally communicates, outside the building 10, which from among the cases Id, 2d, 3d, 4d has been verified. It is specified that the "communication" of the seismic monitoring system 1 with the outside of the building 10 is carried out by the central unit 3 which sends messages via Internet or sends SMS to preset addresses (such as that of the owner of the building 10 and the manager of the industrial activities that take place inside the building 10 itself); the central unit 3 simultaneously activates suitable local signals.

It is indicated that the central unit 3, once the seismic event has terminated, communicates via Internet to at least one of the aforesaid preset addresses also the time history of the recorded accelerations, the time history of the displacements of the measurement points and of the calculation points. The central unit 3 stores, in the memory of the computer 8, all the data and messages that the central unit 3 itself transmits to outside the building 10.

With reference to the characteristics of the seismic monitoring system 1 the following is indicated.

In the central unit 3, a software is inserted which, in the presence of a seismic event, updates (decreasing them) the threshold values of the significant relative displacements in order to account for the variations of the characteristics and performances of the structure 11 caused by the structural damage due to possible seismic events that the structure 11 previously sustained and which are recorded by the seismic monitoring system 1.

The parameters that allow updating said threshold values of the significant relative displacements were introduced in the central unit 3 by the designer of the structure 11, at the time of installation of the seismic monitoring system 1.

In the central unit 3, a software is inserted which allows indicating, in real time, the malfunctioning of an accelerometer 2a, 2b or the lack of power supply thereof; this contributes to always maintaining the seismic monitoring system 1 with perfect efficiency.

In the central unit 3, a software is also inserted which allows, upon command or at preset time intervals, introducing virtual seismic data, adapted to verify the state of functioning of the seismic monitoring system 1. The introduction of virtual earthquakes is actuated by "artificially" inserting non-real signals in the central unit 3, then verifying the response of the seismic monitoring system 1.

The process for obtaining the seismic monitoring system 1 to install at the structure 11, being part of the building 10, comprises the operations described hereinbelow: the designer of the structure 11, during the steps of designing of the structure 11 itself, identifies all the possible ductile failure mechanisms of the structure 11 (it is recalled that the structure 11 is such that brittle failure mechanisms are prevented therein and only ductile failure mechanisms are possible) and identifies points of analysis, belonging to the structure 11, such that the knowledge of significant relative displacements, identified by the designer of the structure 11, between pairs of the aforesaid points of analysis is necessary for evaluating the conditions of unfitness for use of the structure 11 and for evaluating the damage of the structure 11 itself deriving from seismic actions; the aforesaid points of analysis comprise measurement points, at which the accelerometers 2a, 2b are positioned, and calculation points whose displacements are calculated on the basis of the displacements of the measurement points; the designer of the structure 11 then obtains, for each of the aforesaid significant relative displacements, the threshold values, which identify situations of unfitness for use and of damage of the structure; the designer of the structure 11 then establishes the messages that the seismic monitoring system 1 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values (of the aforesaid significant relative displacements); the number and the arrangement of the accelerometers 2a, 2b have been established as a function of the characteristics of the structure 11, of data provided by the designer of the structure 11 and by the number and arrangement of the points of analysis of the structure 11 ;

the accelerometers 2a, 2b are installed at measurement points belonging to the structure 11 ;

the central unit 3 is installed which is connected to the accelerometers 2a, 2b; the designer of the structure 11 introduces, into the central unit 3, the following data and the following instructions:

• some data relative to the structure 11 , including some data typical of the dynamic behavior of the structure 11;

• the threshold values for each of the aforesaid significant relative displacements;

• the messages that the seismic monitoring system 1 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements;

• the parameters adapted to identify a damage evaluation scale;

the seismic monitoring system 1 comprises a set of equipment and software which, for functioning, requires data and specific instructions, introduced in the central unit 3 by the designer of the structure 11 at the time of installation of the seismic monitoring system 1, which render the seismic monitoring system 1 appropriate for the considered structure 11 ; the seismic monitoring system 1 is adapted to be used for evaluating the conditions of unfitness for use of the structure 11 and the structural damage following seismic actions that occur after the installation of the seismic monitoring system 1 ; the central unit 3 is adapted to receive and process the data coming from the accelerometers 2a, 2b; the central unit 3, by means of algorithms implemented in the software inserted in the central unit 3 itself, is adapted to verify if the signals coming from the accelerometers 2a, 2b derive from a seismic action or from other causes that must not be considered; the central unit 3, once it has been recognized that the signals received from the accelerometers 2a, 2b are those of a seismic event, is adapted to calculate, by making a double integration (in the time domain) of the values of acceleration measured by the accelerometers 2a, 2b, the values of the displacements of the measurement points (where the accelerometers 2a, 2b are positioned); the central unit 3 is then adapted to calculate the value of the displacements of the calculation points, so as to then be able to calculate the significant relative displacements, identified by the designer of the structure 11 , in order to evaluate the state of unfitness for use and damage of the structure 11 itself; the central unit 3 is adapted to execute such calculations in nearly "real time"; the central unit 3 is also adapted to compare the values of the significant relative displacements with the corresponding threshold values introduced in the central unit 3 by the designer of the structure 11 at the time of installation of the seismic monitoring system 1 ; the central unit 3 is also adapted to communicate, to outside the building 10, the results of the aforesaid comparison and to send the messages, established by the designer of the structure 11 at the time of installation of the seismic monitoring system 1 ;

the seismic monitoring system 1 is then activated;

the seismic monitoring system 1, once installed and once the designer of the structure 11 has introduced the data and the specific instructions necessary for the functioning of the seismic monitoring system 1 itself, functions uninterruptedly and automatically.

The aforesaid process is described hereinbelow.

The designer of the structure 11 identifies the failure mechanisms (which are ductile failure mechanisms) (it is recalled that the structure 11 is such that brittle failure mechanisms are prevented therein are only ductile failure mechanisms are possible) of the structure 11 itself; such failure mechanisms are tied to the previous formation of plastic hinges at the base of the columns 20a, 20b and to the relative displacements between the top of the columns 20a, 20b and the relative bases; all the columns 20a, 20b can be considered fixed at the base and hinged at the top (it is observed that the position of the top hinges has two values: one relative to the static longitudinal frame scheme and the other relative to the static transverse frame scheme).

The designer of the structure 11 also identifies as points of analysis the top and the base of all the columns 20a, 20b.

Of interest is the value of the relative displacements between the top and the base of each of the columns 20a, 20b. The designer of the structure 11 must then identify, with reference to the relative displacement of each column 20a, 20b, the six threshold values of the relative displacement itself. The designer of the structure 11 identifies such threshold values on the basis of calculations and considerations that come from the calculation, for each column 20a, 20b, in each of the two directions (longitudinal and transverse):

of the relative maximum displacement (between the top and base of the considered column 20a, 20b) at which the considered column 20a, 20b remains in non-cracked phase,

of the relative displacement that causes, in the base section of the considered column 20a, 20b, the cracking moment,

of the relative displacement that causes, in the base section of the considered column 20a, 20b, the yielding of the longitudinal reinforcements, of the relative displacement at the collapse of the considered column 20a,

20b.

The designer of the structure 11 also introduces some general data of the structure 11 itself, such as the height of the columns 20a, 20b, and the data that defines the modal forms of the dynamic behavior of the structure 11 relative to the significant modes of vibrating the structure 11 itself.

The designer of the structure 11 introduces, into the central unit 3, also the parameters that allow updating the threshold values of the significant relative displacements in order to account for the variations of the characteristics and the performances of the structure 11 caused by the structural damage due to possible seismic events that the structure 11 previously sustained and which are recorded by the seismic monitoring system 1.

The above is applied to the case in which multiple seismic tremors occur in succession, all part of a single earthquake, or to the case in which separate seismic events occur that are spaced over time.

The accelerometers 2a, 2b are made integral with the columns 20a and are protected within the airtight protection elements 15 that are fixed to the columns 20a themselves. It is clear that the accelerometers 2a, 2b are fixed by accounting for the direction and sense of the measurement axis thereof.

In the case of the structure 11 , it is right to consider as rigid both the behavior of the foundation 23 in the plane thereof, and the behavior of the planking of the roof, where the slabs 22 are connected to each other at the wings thereof.

It is recalled that there are eight measurement points, and that there are twenty calculation points.

The central unit 3 is positioned at an easily accessible point that is if possible barycentric with respect to the position of the accelerometers 2a, 2b, in order to minimize the length of the cables 5 that connect the accelerometers 2a, 2b themselves to the central unit 3.

In proximity to the central unit 3, the power supply 4 and the continuity group 6 with the relative electrical board 13 are also installed. Also installed is the generator 12 that is connected to the electrical board 13 and to the general electrical board 17 of the building 10.

Rather important for the correct functioning of the seismic monitoring system 1 is the arrangement of the filters of the central unit 3 relative to the recognition of the seismic action by the seismic monitoring system 1 , taking into account the activities that can be carried out in the building 10.

Once again, the messages that the seismic monitoring system 1 must supply to the outside are established by the designer of the structure 11.

The seismic monitoring system 30 is described with reference to figures 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27; such seismic monitoring system 30 is obtained according to the present finding in accordance with another embodiment. The seismic monitoring system 30 is installed at a structure 41 of an existing commercial building 40; the structure 41 is (currently) such that brittle failure mechanisms are prevented therein and only ductile failure mechanisms are possible. The structure 41 comprises a rear part 41a and a front part 41b.

The rear part 41a comprises foundations 53a (of cast-in-place reinforced concrete), the (precast reinforced concrete) columns 50a, 50b 50e, (precast prestressed reinforced concrete) beams 51a, 51b, (precast prestressed reinforced concrete) slabs 52a and (precast reinforced concrete) plates 52b.

The front part 41b comprises the foundations 53b (of cast-in-place reinforced concrete), the (precast reinforced concrete) columns 50c, 50d, a ceiling/roof horizontal support structure 56 (comprising precast prestressed reinforced concrete beams and TT slabs) and an intermediate horizontal support structure 57 (comprising precast prestressed reinforced concrete beams and TT slabs and a cast- in-place composite concrete slab).

It is indicated that, in the identification of the seismic -resistant structural elements, the columns 50e may be disregarded; for such reason, hereinbelow reference is only made to the columns 50a, 50b, 50c, 50d.

The cladding, of the building 40, is constituted by horizontal panels 54 of reinforced concrete and by sandwich panels 55.

The static scheme of the columns 50a, 50b, 50c, 50d is that of rods fixed at the base and hinged at the horizontal support structures. The building 40 was designed and built in a zone originally classified as non-seismic. Subsequently, such zone was classified as seismic and such building 40 underwent a seismic adaptation carried out by means of renovation works aimed to confer, to the structure 41, the necessary characteristics (rigidity, resistance, ductility), hence also necessary for preventing the formation of brittle failure mechanisms and to only allow ductile failure mechanisms. Such operations were directed for the following, among others:

to connect together all the structural elements in an effective manner, such to comply with the resistance hierarchy criteria;

to render the columns 50a, 50b, 50c, 50d such to be provided with the necessary ductility; the interventions on the columns were such to perfectly maintain the resistance hierarchy criteria.

Between the rear part 41a and the front part 41b, there is an expansion joint 58 with transverse progression that divides the structure 41. At such joint 58, the three beams 51a belonging to the rear part 41a are abutted against the same number of brackets 46 which are integral with three of the four columns 50c.

Such joint 58 which was originally obtained with the characteristics and the size of an expansion joint was subsequently "restructured", obtaining by means of the three brackets 46 a support plane for the three beams 51a of suitable length. It is observed that, after the seismic adaptation, the beams 51a are provided with unidirectional support apparatuses which can only slide in the direction of the axis of the beams 51a themselves. The length of the support plane of each of the three brackets 46 is such that, even at the joint 58, brittle failure mechanisms are not possible.

The seismic monitoring system 30 comprises:

twenty-four accelerometers 32a, 32b, 32c, 32d, 32e (six accelerometers 32a; six accelerometers 32b; four accelerometers 32c; four accelerometers 32d; four accelerometers 32e) positioned at measurement points of the structure 41 ;

a central unit 33;

a local unit 37 connected to the accelerometers 32a, 32b;

three distance-measuring devices 38, each of which measures significant relative displacements between the two points belonging to a pair of analysis points placed one in front of the other; the three distance-measuring devices 38 are laser distance-measuring devices, placed at the joint 58, in proximity to the three brackets 46; each of the three distance-measuring devices 38 measures the relative displacements between the point at which the considered distance- measuring device 38 is positioned and the point where the laser beam is reflected; such point belongs to an angular element 59 integral with the relative beam 51a.

The central unit 33 is connected to the local unit 37, to the accelerometers 32c, 32d, 32e and to the three distance-measuring devices 38; the central unit 33 continuously receives and processes the data coming from the local unit 37 (which transmits the data detected by the accelerometers 32a, 32b), the data coming from the accelerometers 32c, 32d, 32e and the data coming from the three distance-measuring devices 38.

The seismic monitoring system 30, once activated, functions uninterruptedly, except for the pauses due to maintenance or replacement of components, for the entire useful lifetime of the structure 41.

The seismic monitoring system 30 comprises a set of equipment and software which, for functioning, requires data and specific instructions introduced by the designer of the structure 41 during the installation of the seismic monitoring system 30; the aforesaid data and the aforesaid instructions render the seismic monitoring system 30 appropriate for the considered structure 41 ; the seismic monitoring system 30 is adapted to be used for evaluating the conditions of unfitness for use of the structure 41 and the structural damage following seismic actions that occur after the installation of the seismic monitoring system 30 itself; the seismic monitoring system 30, once installed and once the designer of the structure 41 has introduced the data and the specific instructions necessary for the functioning of the seismic monitoring system 30 itself, functions uninterruptedly and automatically; the aforesaid measurement points are included among the points of analysis belonging to the structure 41 identified by the designer of the structure 41, at the time of installation of the seismic monitoring system 30, as points of the structure 41 where it is necessary to know, during the seismic action, the absolute displacements in order to be able to calculate significant relative displacements between pairs of the aforesaid points of analysis; the knowledge of the aforesaid significant relative displacements, identified by the designer of the structure 41, is necessary for evaluating the conditions of unfitness for use of the structure 41 and the damage of the structure 41 itself deriving from seismic actions; the central unit 33, for the functioning thereof, uses the data and the instructions introduced in the central unit 33 by the designer of the structure 41 at the time of installation of the seismic monitoring system 30; the aforesaid data and instructions comprise:

- some data relative to the structure 41, including some data typical of the dynamic behavior of the structure 41 itself;

six threshold values for each of the aforesaid significant relative displacements; it is indicated that among the aforesaid significant relative displacements, also the threshold values of the significant relative displacements are included, measured by the distance-measuring devices 38;

messages that the seismic monitoring system 30 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements; there are eight of such messages; parameters adapted to identify a damage evaluation scale;

the central unit 33, which functions continuously, by means of algorithms implemented in the software inserted in the central unit 33, verifies if the signals coming from the accelerometers 32a, 32b, 32c, 32d, 32e derive from a seismic action or from other causes that must not be considered; such algorithms tend to prevent false positives or false negatives; for the recognition of the seismic action, the central unit 33 also makes use of filters inserted in the central unit 33 itself which account for the activities that can be carried out in the building 40 and the presence of a trafficked road close to the building 40 on which heavy traffic travels; the data necessary for the functioning of the aforesaid filters was inserted in the central unit 33 by the designer of the structure 41 at the time of installation of the seismic monitoring system 30; the central unit 33, in case of earthquake, once it has been recognized that the signals received from the accelerometers 32a, 32b, 32c, 32d, 32e are those of a seismic event, signals the aforesaid seismic event (in a manner technically equivalent to what was described in relation to the seismic monitoring system 1) and calculates the values of the displacements of the measurement points, by carrying out a double integration (in the time domain) of the values of acceleration measured by the accelerometers 32a, 32b, 32c, 32d, 32e in the measurement points; the central unit 33 also calculates the values of the displacements of the calculation points; the central unit 33, using both the values of the displacements of the measurement points and those of the calculation points, then calculates the significant relative displacements (between the aforesaid points of analysis), indicated by the designer of the structure 41 ; the central unit 33 then compares such values of the significant relative displacements with the corresponding threshold values introduced in the central unit 33 by the designer of the structure 41 at the time of installation of the seismic monitoring system 30; the central unit 33 also receives and processes the data coming from the three distance- measuring devices 38; it is observed that the central unit 33, in the case of seismic event, detects at the end of the aforesaid seismic event the significant relative displacements (residual significant relative displacements) between the three pairs of analysis points monitored by the three distance-measuring devices 38; the central unit 33 also compares the values of the significant relative displacements measured by the distance-measuring devices 38 with the threshold values of the aforesaid significant relative displacements; it is recalled that the aforesaid threshold values were introduced in the central unit 33 by the designer of the structure 41 at the time of installation of the seismic monitoring system 30; the central unit 33 then communicates, to outside the building 40, the results of all the comparisons carried out (both those relative to the values of displacement obtained from the measurements made by the accelerometers 32a, 33b, 32c, 32d, 32e, and those relative to the values of displacement obtained by the distance-measuring devices 38) and transmits the corresponding messages introduced in the central unit 33 by the designer of the structure 41 at the time of installation of the seismic monitoring system 30.

The data transmitted to outside the building 40 essentially comprises data regarding the (possible) unfitness for use of the building 40 itself and data regarding the evaluation of the (possible) damage that the building 40 (of the structure 41) may have sustained. Each accelerometer 32a, 32b, 32c, 32d, 32e is of uniaxial type and is technically equivalent to each of the accelerometers 2a, 2b.

The six accelerometers 32a are applied at the top of the columns 50a. The four accelerometers 50b are applied at the base of the columns 50a. The five accelerometers 32c are applied at the upper end of two columns 50c. The four accelerometers 32d are applied at a median zone of the columns 50c. The four accelerometers 32e are applied at the base zone of the columns 50c.

The local unit 37, which is connected to the accelerometers 32a, 32b comprises a converter module that converts the data from analog to digital and a data communication module; the local unit 37 is connected to the central unit 33 by means of a cable placed inside an underground containment tube 36.

The central unit 33 is technically equivalent to the central unit 3.

For the sake of representation simplicity, the local unit 37 and the central unit 33 are indicated in the figures; it is clear that the central unit 33 is inserted inside a cabinet technically equivalent to the cabinet 29; it is also clear that the central unit 33 is connected to other equipment technically equivalent to that already indicated inside the cabinet 29 itself. The local unit 37 is inserted in a cabinet in which the equipment necessary for the functioning of the local unit 37 itself is also inserted. The accelerometers 32a, 32b are connected to the local unit 37 by means of cables 35; such cables 35 are positioned within cable carrier channels 44; the accelerometers 32c, 32d, 32e are connected to the central unit 33 by means of cables 35; the cables 35 are positioned within cable carrier channels 44; the three distance- measuring devices 38 are connected to the central unit 33 by means of cables 35 which are inserted in cable carrier channels 44.

The accelerometers 32a, 32b, 32c, 32d, 32e are integral with the relative columns 50a, 50c and are positioned inside airtight protection elements 45 which are fixed to the columns 50a, 50c themselves.

In the front part 41b of the structure 41, the progression of the cables 35 (and hence the progression of the cable carrier channels 44 within which the cables 35 are positioned) is mainly vertical, along the relative columns 50c; in proximity to the base of each of the two columns 50c, the cables 35 (of the accelerometers 32c, 32d, 32e installed at the column 50c itself) then pass into a well 39 where a relative underground containment tube 47 is inserted, inside of which the cables 35 themselves are positioned.

The three distance-measuring devices 38 are positioned at the three brackets 46 belonging to the relative columns 50c. Each of the three distance-measuring devices 38 is integral with the relative column 50c and measures the relative distance between the distance-measuring device 38 itself and the external face of the angular element 59 integral with the relative beam 51a; such relative distance allows immediately knowing the distance between the head of one of the three beams 51a and the face of the column 50c which sustains, by means of the relative bracket 46, the aforesaid beam 51a; in other words, the considered distance-measuring device 38 measures the distance that identifies the extent to which the beam 51a is abutted against the relative bracket 46. Each of the three distance-measuring devices 38 is connected to the central unit 33 by means of a cable 35 which has progression and arrangement rather similar to that described above with reference to the cables 35 of the accelerometers 32c, 32d, 32e.

According to a possible embodiment variant, each of the three distance-measuring devices can be constituted by a displacement transducer, for example of "flush" type which is connected to one of the three beams 51a and is itself fixed to the column 50c that sustains, by means of the relative bracket 46, the aforesaid beam 51a.

According to that stated above, the length of the slide plane is such that brittle failure mechanisms cannot occur; nevertheless it is indicated that given that there is the joint 58, it is necessary to know the values of the relative displacements between the head of each of the three beams 51a and the relative column 50c, once the seismic tremor has terminated, in order to know with certainty if the beams 51a still lie in a suitable manner on the relative brackets 46; i.e. it is necessary to know if such beams 51a abut against the relative brackets 46 in a manner such to be able to face other seismic tremors without causing pounding between the two parts of the structure 41 (i.e. between the rear part 41a and the front part 41b) and without causing the loss of support of the three beams 51a.

The functioning of the seismic monitoring system 30 is technically equivalent to that of the seismic monitoring system 1. It is observed that among the instruments that are part of the seismic monitoring system 30, also the three distance-measuring devices 38 are included. The designer of the structure 41, at the time of installation of the seismic monitoring system 30, identified and introduced in the central unit 33 also the threshold values of the distance between the end of each of the three beams 51a and the vertical face of the relative column 50c; it can be observed that such threshold values regard both an excessive approaching of the beam 51a and the relative face of the column 50c, and an excessive moving away of the beam 51a and the relative face of the column 50c. Indeed, the aforesaid excessive approaching can cause pounding phenomena between the beam 51a and the relative column 50c, while the aforesaid excessive moving away can cause the loss of support of the beam 51a.

In the case of the seismic monitoring system 30, as in the case of the seismic monitoring system 1, the eight cases (cases li, 2i, 3i, 4i, Id, 2d, 3d, 4d) already described with reference to the seismic monitoring system 1 can be verified, during the functioning of the seismic monitoring system 30 itself. The difference, in the case of the seismic monitoring system 30, consists of the fact that for each of the aforesaid eight cases it is necessary to also consider the values of the relative displacements between the beams 51a and the relative columns 50c.

The process for obtaining the seismic monitoring system 30 is technically equivalent to the process for obtaining the seismic monitoring system 1.

In relation to the aforesaid process, several clarifications are provided relative only to the fact that the seismic monitoring system 30 also comprises the three distance- measuring devices 38.

During the verification of the structure 41, the designer of the structure 41 also identifies three pairs of analysis points of the structure 41, for each of which, in case of seismic event, it is necessary to know significant relative displacements measured directly by a distance-measuring device 38 and, in particular, it is necessary to know the relative residual displacements, once the seismic event has terminated; the designer of the structure 41 then obtains, for each of said significant relative displacements, threshold values corresponding respectively to situations of unfitness for use and damage of the structure 41 ; the designer of the structure 41 then establishes the messages that the seismic monitoring system 30 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements, and following the comparison, once the seismic event has terminated, between the values of the residual significant relative displacements and the aforesaid threshold values.

The three distance-measuring devices 38 are also positioned, which are connected to the central unit 33; each of the three distance-measuring devices 38 measures the significant relative displacements between the points of one of the aforesaid three pairs of analysis points;

the designer of the structure 41 introduces, into the central unit 33, the aforesaid threshold values of the significant relative displacements and the aforesaid messages that the seismic monitoring system 30 must communicate to the outside, immediately after the seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements, and following the comparison, once the seismic event has terminated, between the values of the residual significant relative displacements and the aforesaid threshold values.

The central unit 33 is now adapted to receive and process also the data coming from the three distance-measuring devices 38; the central unit 33 is also adapted to compare the values of the significant relative displacements measured by the three distance-measuring devices 38 with the corresponding threshold values introduced in the central unit 33 by the designer of the structure 41; the central unit 33 is also adapted to communicate to outside the building 40 the results of the aforesaid comparison and to transmit the corresponding messages introduced in the central unit 33 itself by the designer of the structure 41 at the time of installation of the seismic monitoring system 30.

The three distance-measuring devices 38 are then activated.

The seismic monitoring system 60 is described with reference to figures 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38; such seismic monitoring system 60 is obtained according to the present finding in accordance with another embodiment. The seismic monitoring system 60 is installed at a structure 71 of a newly constructed residential building 70, made of cast-in-place reinforced concrete; the structure 71 of the building 70 comprises three horizontal support structures 84, 85, 86, columns 80a, 80b, walls 81a, 81b which form the stairwell, and foundations 83.

The building 70 is built in a seismic zone, hence it was designed and built following the criteria of the structures placed in a seismic zone; in particular, in such building 70 only ductile failure mechanisms are possible (brittle failure mechanisms are therefore deemed not possible).

In the figures, for the sake of representation simplicity, the external cladding and the internal partitions of the building 70 were not represented.

The seismic monitoring system 60 comprises:

- twenty-four accelerometers 62a, 62b, 62c, 62d (six accelerometers 62a; six accelerometers 62b; six accelerometers 62c; six accelerometers 62d;) positioned at measurement points of the structure 71;

eight accelerometers 62a, 62b, 62c, 62d are positioned at each of the two columns 80a; four accelerometers 62a, 62b, 62c, 62d are placed at each of the two walls 81a;

a central unit 63.

The central unit 63 is connected to the accelerometers 62a, 62b, 62c 62d; the central unit 63 continuously receives and processes the data coming from the accelerometers 62a, 62b, 62c, 62d.

The seismic monitoring system 60, once activated, functions uninterruptedly, except for the pauses due to maintenance or replacement of components, for the entire useful lifetime of the structure 71.

The seismic monitoring system 60 comprises a set of equipment and software which, for functioning, requires data and specific instructions introduced by the designer of the structure 71 during the installation of the seismic monitoring system 60; the aforesaid data and the aforesaid instructions render the seismic monitoring system 60 appropriate for the considered structure 71 ; the seismic monitoring system 60 is adapted to be used for evaluating the conditions of unfitness for use of the structure 71 and the structural damage following seismic actions that occur after the installation of the seismic monitoring system 60 itself; the seismic monitoring system 60, once installed and once the designer of the structure 71 has introduced the data and the specific instructions necessary for the functioning of the seismic monitoring system 60 itself, functions uninterruptedly and automatically; the aforesaid measurement points are included among points of analysis belonging to the structure 71 identified by the designer of the structure 71, at the time of installation of the seismic monitoring system 60, as points of the structure 71 where it is necessary to know, during the seismic action, the absolute displacements in order to be able to calculate significant relative displacements between pairs of the aforesaid points of analysis; the knowledge of the aforesaid significant relative displacements, identified by the designer of the structure 71, is necessary for evaluating the conditions of unfitness for use of the structure 71 and the damage of the structure 71 itself deriving from seismic actions; the central unit 63, for the functioning thereof, uses the data and the instructions introduced in the central unit 63 by the designer of the structure 71 at the time of installation of the seismic monitoring system 60; the aforesaid data and instructions comprise:

some data relative to the structure 71, including some data typical of the dynamic behavior of the structure 71 itself;

threshold values for each of the aforesaid significant relative displacements: messages that the seismic monitoring system 60 must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements; there are eight of such messages;

parameters adapted to identify a damage evaluation scale;

the central unit 63, which functions continuously, by means of algorithms implemented in the software inserted in the central unit 63, verifies if the signals coming from the accelerometers 62a, 62b, 62c, 62d derive from a seismic action or from other causes that must not be considered; the central unit 63, in case of earthquake, once it has been recognized that the signals received from the accelerometers 62a, 62b, 62c, 62d are those of a seismic event, signals the aforesaid seismic event (in a manner technically equivalent to that described in relation to the seismic monitoring system 1) and calculates the values of the displacements of the measurement points, by carrying out a double integration (in the time domain) of the values of acceleration measured by the accelerometers 62a, 62b, 62c, 62d at the measurement points; the central unit 63 also calculates the values of the displacements of the calculation points; the central unit 63, using both the values of the displacements of the measurement points and those of the calculation points, then calculates the significant relative displacements (between the aforesaid points of analysis), indicated by the designer of the structure 71 ; the central unit 63 then compares such values of the significant relative displacements with the corresponding threshold values introduced in the central unit 63 by the designer of the structure 71 at the time of installation of the seismic monitoring system 60; the central unit 63 then communicates to outside the building 70 the results of the aforesaid comparison and transmits the corresponding messages introduced in the central unit 63 by the designer of the structure 71 at the time of installation of the seismic monitoring system 60.

The data transmitted to outside the building 70 essentially comprises the data regarding the (possible) unfitness for use of the building 70 itself and data regarding the evaluation of the (possible) damage that the building 70 sustained.

The accelerometers 62a, 62b, 62c, 62d are connected to the central unit 63 by means of cables 65; such cables 65 are positioned within cable carrier channels 74. The accelerometers 62a, 62b, 62c, 62d are integral with the relative columns 80a and with the walls 81a and are positioned inside protection elements 75 which are fixed to the columns 80a and to the walls 81a themselves.

The progression of the cables 65 (and hence the progression of the cable carrier channels 74 inside of which the cables 65 are positioned), is mainly vertical, along the relative columns 80a; in proximity to the base of each of the two columns 80c, the cables 65 (of the accelerometers 62a, 62b, 62c, 62d installed at the column 80a) then pass inside a well 69, in which the relative underground containment tube 77 is inserted, inside of which the cables 65 are positioned.

The cables 65 of the accelerometers 62a, 62b, 62c, 62d installed at the walls 81a have an arrangement technically equivalent to that described above.

The functioning of the seismic monitoring system 60 is technically equivalent to that of the seismic monitoring system 1.

The process for obtaining the seismic monitoring system 60 is technically equivalent to the process for obtaining the seismic monitoring system 1.

A seismic monitoring system obtained according to the present finding (like the seismic monitoring systems 1, 30, 60) - once the designer of the structure, during the step of installation of the seismic monitoring system itself, has introduced in the central unit all the data and instructions necessary for the functioning of the aforesaid seismic monitoring system - functions completely automatically for the entire useful lifetime of the structure. The seismic monitoring system is temporarily deactivated only for conducting maintenance and for replacing equipment that does not function correctly.

It is clear that it is suitable to carry out, with preset frequency, the necessary controls regarding the correct functioning of the equipment that is part of the aforesaid seismic monitoring system, also actuating the procedure by means of which virtual seismic data is introduced.

A seismic monitoring system obtained according to the present finding can be applied to a structure where the possible collapse mechanisms are known beforehand - such mechanisms must be of ductile type; for such purpose, it is necessary that the compliance with the resistance hierarchy criteria is ensured, and that the structural details are correctly designed and executed (in accordance with that provided by the construction technique rules which regard the structures arranged in seismic zones), such details ensuring the ductile behavior of the structural elements adapted to resist the seismic actions.

It is observed that in the case of the structures 11 and 41, which are made with seismic -resistant precast elements having the static scheme of rods fixed at the base and hinged at the top, the possible ductile failure mechanisms provide for the formation of plastic hinges at the zones of the rods (of the columns) close to the foundations; at collapse, due to such plastic hinges, considerable relative displacements are verified between the base and the top of such rods (of the columns). The formation of plastic hinges at the ends of the columns is typical of prefabricated structures, such as the prefabricated structures 11 and 41.

It is indicated that, in the structures illustrated in the present description, the seismic- resistant structures are constituted by columns and walls; nevertheless, it is of course possible to install a seismic monitoring system obtained according to the present finding also at structures which include other types of structural elements (in addition to or in substitution of columns and walls); also in these cases, the designer of the structure identifies, with the aid of appropriate numerical analyses, the failure mechanisms of the structures, neutralizes the brittle failure mechanisms with suitable criteria (resistance hierarchy) and with suitable structural details, identifies the significant relative displacements of the structure that must be monitored and, for each of such significant relative displacements, with reference to each of the two orthogonal directions at which it is assumed earthquake can act, identifies a suitable number of threshold values (the number of such threshold values in the structures 11 and 41 is equal to six). Such threshold values identify ranges (eight ranges in the case of six threshold values of the structures 11 and 41) at which the central unit supplies messages. In addition, the designer of the structure introduces, into the central unit, the other data necessary for the functioning of the seismic monitoring system itself.

In order to ensure the continuous functioning of the seismic monitoring system even in the case of interruption of the electric current supply, it is provided to employ a continuity group (such as the continuity group 6); in addition to the continuity group, a generator can be used, connected to the continuity group, which is automatically activated when the lack of supply of electric current by the external network continues for a time interval greater than a preset value (e.g. ten minutes); the generator, therefore, allows the seismic monitoring system to function also for a long period in the absence of electric current supply by the external network.

In a seismic monitoring system obtained according to the present finding, normally two types of threshold values are inserted which refer to each of the significant relative displacements that the designer of the structure identified as essential for the description of the seismic response of the structure, and consequently, two types of messages that the seismic monitoring system must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements. This constitutes an advantage of the seismic monitoring system obtained according to the present finding with respect to the seismic monitoring systems according to the prior art, which often associate, in an inseparable manner, the "unfitness for use" subject with the "damage" subject.

The two types of threshold values of the significant relative displacements (mentioned above) are independent and one refers to the unfitness for use of the structure and one to the evaluation of the damage; the data and the instructions necessary for the formation of the aforesaid two types of threshold values were introduced by the designer of the structure at the time of installation of the seismic monitoring system. Such two types of messages allow the designer of the structure great liberty in providing for the management both of the unfitness for use of the structure and the evaluation of the damage of the structure itself. The designer of the structure can in fact calibrate the aforesaid threshold values and the consequent messages that the central unit must provide in a manner such that, following the messages of the seismic monitoring system, in case of seismic event, the unfitness for use (at least until a technician has executed an inspection of the structure and declared it fit for use) of the structure is declared well before the occurrence of damage of any extent of the structure. This is the case of the structure 41; it is observed that also for the case 3i (which provides for the unfitness for use of the structure 41 itself at least until, following a technical examination, it is recognized that it is possible to return inside the building 40), an "actual" damage state is not underlined.

A seismic monitoring system according to the present finding can be installed at the structure of a newly constructed building; in such case, the aforesaid seismic monitoring system starts functioning when the building itself has been commissioned/brought into operation.

It may happen (this is quite desirable) that the designer of the structure, during the design of the structure itself, has taken into account the future installation of a seismic monitoring system (according to the present finding) at the structure; taking into account the need to install a seismic monitoring system can be an incentive to design, for example a "regular" structure with planking provided with significant rigidity in the plane thereof and generally to design structures with simple and clear behaviors, which in addition to normally being desirable in general terms, allow the optimization both from a technical and economical standpoint of the employed seismic monitoring system.

It is underlined that a seismic monitoring system obtained according to the present finding can be installed at the structure of an existing building.

In particular, it is underlined that a seismic monitoring system obtained according to the present finding can be installed at the structure of a building which comprises precast reinforced concrete structural elements and/or precast prestressed reinforced concrete structural elements.

It is indicated that a seismic monitoring system obtained according to the present finding (like the seismic monitoring systems 1) can be installed at the structure of a newly constructed building obtained with precast reinforced concrete elements and/or precast prestressed reinforced concrete elements, such seismic monitoring system starts functioning when the aforesaid building is commissioned/brought into operation.

In the central unit of each of the seismic monitoring systems 1, 30, 60 (illustrated in the present description), software is inserted that considers the damage of the monitored structure following a succession of seismic tremors. Such software, which during the installation of the seismic monitoring system must receive data and instructions introduced by the designer of the structure, considers the damage that the structure sustains if subjected to more than one seismic tremor (of significant intensity). It is specified that, if the first seismic tremor sustained by the considered structure does not cause the cracking of the seismic -resistant structures (and thus, with reference to the structures 11 and 41, does not cause the cracking of the columns), such seismic-resistant structures have remained in elastic range (non- cracked); in the case in which such first tremor is followed by others, all of small intensity, then with the system remaining in elastic phase, there is no structural damage, nor are there appreciable variations of the performances of the seismic- resistant structures, such that the progressive damage effect is substantially nonexistent. If, however, the first seismic tremor causes the behavior of the seismic - resistant structures to depart from the elastic range, then it must be considered that seismic tremors following the first act on a structure which, at some part thereof, has already entered a non-linear range (plastic range), thus giving rise to permanent deformations and a damage state that must be accounted for.

In summary, it can be stated that a software is inserted in the central unit that, if multiple seismic events occur in succession, considers the variation of the performances of the structure (at which the considered seismic monitoring system is installed) with the increase of the structural damage that is verified as the aforesaid structure is subjected to the aforesaid succession of seismic events; the aforesaid variation of the characteristics of the structure is automatically actuated by the software, decreasing, for the tremors following the first tremor, the threshold values of the relative displacements introduced in said central unit at the time of installation of the seismic monitoring system.

The updating of the aforesaid threshold values occurs in accordance with the criteria selected by the designer of the structure.

In the case in which the seismic monitoring system pursuant to the present finding is applied to an existing building (as in the case of the building 40), before the application of the seismic monitoring system itself, it is necessary to identify all the possible failure mechanisms of the structure of the building. It is clear that this involves, among other things, the accurate knowledge of the geometric and mechanical characteristics of the structure, as well as the characteristics of the ground on which the building lies. It is then necessary to execute renovation works such to prevent the onset of all brittle mechanisms. Such works, for the sake of description simplicity referring to an industrial building belonging to the same type of building 10, can (for example) comprise the achievement of effective connections (joints) between the structural elements and the achievement of interventions that assure that the seismic-resistant structural elements (such as the columns) are provided with the necessary ductility provided by the structural calculations.

Once the existing building has been renovated and once therefore the possible brittle failure mechanisms have been eliminated, it is possible to proceed with the planning and installation of the seismic monitoring system according to the present finding which, once installed, keeps all the possible ductile failure mechanisms under control (in a manner technically equivalent to that employed in the case of "newly constructed" building built with the "antiseismic" criteria).

In the present description, reference is made to seismic monitoring systems obtained according to the present finding that do not include accelerometers which measure vertical accelerations (from which vertical displacements are obtained) due to the seismic action; nevertheless, when necessary, it is (of course) possible that a seismic monitoring system obtained according to the present finding can comprise accelerometers that measure vertical accelerations (from which vertical displacements are obtained).

The seismic monitoring system obtained according to the present finding is a useful instrument that provides objective knowledge to the owner of the building, to the manager of the activities that take place in the building (of course if this is a building with production use, or a building with commercial use, etc.), and to the engineer who carries out an inspection of the situation of the building, once the seismic event has terminated.

In particular, the measurement of the significant relative displacements between points of analysis of the structure allows knowing the maximum values of such relative displacements, maximum values which are normally correlated with the structural damage. It is observed that, in the absence of the structural seismic monitoring system, the evaluation of such maximum relative displacements is carried out, in a necessarily very approximate manner, observing "with hindsight" the effects caused by such relative displacements. It is underlined that the only way to "precisely" know the value of such relative maximum displacements is to measure them while they are occurring, i.e. during the seismic event. It is indicated that the seismic monitoring system allows knowing the values of displacements of parts of structures that remain hidden by non-structural construction elements such as finishing elements, false ceilings etc..

It is observed that each seismic monitoring system according to the present finding gives information which is only relative to the seismic event that has "passed", such that the actual decision to remain inside the building or not, even if structural damage or danger has not been signaled by the aforesaid seismic monitoring system, must be made by also accounting for the possibility that other close-together seismic events can occur that follow the first seismic event. It is important to consider the seismic monitoring system as an instrument that, by providing objective data, constitutes an objective aid in the decision-making, but is not the final decisionmaker, since the final decision - having considered the completely unpredictable nature of seismic phenomena (reference is made, for example, to the problem of significant close-together tremors) is always on man's shoulders. The seismic monitoring system undoubtedly allows objectively evaluating what has happened, by means of measurements; the decision to allow people to stay inside a building must always also refer to what is expected to occur, also considering the possible damage sustained by the structure; and this decision lies on the shoulders of man, and more precisely on the experts.

It is indicated that a seismic monitoring system obtained according to the present finding (such as the seismic monitoring systems 1, 30, 60) also supplies specific data when the central unit of the seismic monitoring system itself informs that an earthquake is taking place. Such message immediately activates signals that inform of the presence of a seismic event that affects the building.

If deemed necessary, in order to allow an engineer to inspect the structure by using a mathematical model of the structure itself, to provide, as input, the time history of the acceleration at the base that was actually sustained by the building, the central unit of the seismic monitoring system (such as the central units 3, 33, 63) immediately provides, transmitting them via Internet, the values of the accelerations on the ground that were actually recorded by the accelerometers placed in proximity to the foundations of the building. Such data allows the aforesaid engineer to reconstruct a time history of the seismic event in the two measured horizontal directions (and possibly in the vertical direction).

It is indicated that a seismic monitoring system obtained according to the present finding provides data to outside the building in nearly "real time", once the seismic event has terminated.

The central unit comprised in a seismic monitoring system according to the present finding may only include a master unit, without a computer being present that would be connected to the master unit itself; this occurs in those cases in which the CPU, which is always present in the central unit, is provided with a calculation capacity such that the external computer is not necessary.

A seismic monitoring system obtained according to the present finding can comprise, in addition to the accelerometers, also different instruments such as laser distance-measuring devices (as in the case of the distance-measuring devices 38), displacement transducers, clinometers or other instruments for the purpose of calculating displacements and/or rotations of parts of the structure.

In the central unit of a seismic monitoring system obtained according to the present finding, at the time of installation of the seismic monitoring system itself, the designer of the structure can introduce, with reference to each of the directions in which the earthquake is assumed to act, not six threshold values, for example for each of the columns or walls identified by the designer itself, but rather a higher or lower number of threshold values (such as five); in such cases (as a function of the selections of the designer of the structure), the number and also the significance of the messages that the central unit can transmit to outside the building consequently changes.

It is indicated that the designer of the structure considers the possible damage states pertaining to structural elements or to finishing elements not part of the seismic- resistant structure, correlating them with a suitable acceptable maximum value of the relative displacements of the structural elements that affect such structural or finishing elements.

In the central unit of a seismic monitoring system obtained according to the present finding (such as in the central unit of the seismic monitoring systems 1, 30, 60), a software can be inserted that allows, upon command, calculating dynamic characteristics (including the fundamental vibration periods of the structure itself) of the structure, on the basis of the measurements taken by the accelerometers relative to environmental actions; therefore, the seismic monitoring system can also be used for the purpose of providing information for the structural monitoring in general, even outside the actual seismic monitoring. It is specified that the environmental actions can for example be those due to the transit of heavy vehicles that induce vibrations (even if rather limited) in the structure, etc..

The messages that the seismic monitoring system provides can have various form and content, and these too are established by the designer. The damage messages also comprise communications via Internet that the seismic monitoring system sends to preset addresses such as, for example, the owner of the building, the director or in any case the manager of the activities that take place in the building. The messages can alternatively or additionally be sent via SMS.

In a structure typologically similar to the structure 1 1 (single-level structure), the points of analysis are positioned at the top of columns and in proximity to the base of the columns; of interest (having fixed the height and the geometric and mechanical characteristics of the column) is the value of the relative maximum horizontal displacements between the top and the base of the considered column, or the maximum value of the "drift".

In structures of this type, the drift is tied to the structural damage that the structure sustains due to the seismic events; such correlation between drift and damage is widely discussed in the literature. Therefore, knowing the value of the relative displacements between the base and top of the columns and knowing the height thereof, a reliable evaluation of the damage sustained by the structure can be obtained. Another criterion, indicated in the technical literature, for evaluating of the structural damage of a column is to consider the ratio between the value of the relative maximum displacement between the top and the base of the column during the seismic event and the value of the displacement corresponding to the yielding of the reinforcements of the base section of the column itself.

The designer of the structure, at the time of installation of the seismic monitoring system, also introduces in the central unit the parameters that allow accounting for the damage of the structure subjected to repeated actions. Such parameters, introduced by the designer of the structure, have the effect of varying the threshold values of the significant relative displacements originally introduced by the designer, valid in the case of structure that has not sustained any damage.

It is clear that the designer, in identifying the threshold values of the significant relative displacements between the points that such designer deems to be significant for identifying the damage of the structure (points of analysis), must account for, with a wide safety margin, all of the inherent uncertainties in determining the post- seismic damage of a building (and in particular of a structure) and must also account for the damage that can derive from the damage of installations, shelving and machinery present inside the building or even damage deriving from the damage of structural elements such as partitioning, false ceilings etc..

The designer of the structure, during the design or verification of the structure, considers the possible damage states pertaining to structural elements or to finishing elements not part of the seismic -resistant structure, correlating them with a suitable acceptable maximum value of the relative displacements of the structural elements that affect such structural or finishing elements.

It is indicated that a seismic monitoring system obtained according to the present finding can be considered a valid and objective instrument to take under consideration in evaluating the post-seismic damage of a building.

Indeed, such seismic monitoring system launches an alarm signal as soon as it recognizes that a seismic event is taking place, informing the occupants of the building that an earthquake is underway. After such alarm, the occupants of the building actuate those rules of conduct that were previously provided in case of seismic event.

Such seismic monitoring system, once the seismic event has terminated, gives indications regarding the unfitness for use of the building and the damage sustained by the building itself. If for example the earthquake was of small intensity, such to not cause cracking phenomena in the seismic -resistant structures of the building (the columns), the manager of the activities that take place inside the building receives from the measurements carried out by the seismic monitoring system, which assure that the structures themselves remain non-cracked during the seismic event, an important aid in his decision on whether to allow the occupants to remain inside the building itself or allow them to return thereto. If, then, according to another example the earthquake was of medium intensity, the manager of the activities, after the building has been quickly evacuated, orders that people do not return inside the building itself, until an accurate technical examination has been carried out by an engineer who can judge whether or not it is possible to recommence the activities inside the building itself.

It is observed that the data provided by the seismic monitoring system, once the seismic event has terminated, assuming that the people who were in the building escaped to outside the building itself, provides a useful decision-making aid for understanding if it is possible to return inside the building or not, and in particular if it is necessary to schedule a technical inspection before returning inside the building. The data provided by the seismic monitoring system, in this case, is data that is rather useful for the engineer who executes the inspection, such that he can correctly evaluate the damage sustained by the building. It is indicated that by examining the data provided by the seismic monitoring system, the engineer who carries out the inspection can know both the displacements of the significant points of the structure, and the stresses of the significant elements of the structure that can be obtained therefrom. In addition, the technician who carries out the inspection also knows which are the values that the designer of the structure has deemed "critical" (by considering them threshold values) for the structure itself (the significance of "critical state" varies in accordance with the extent of such relative displacements). The engineer who makes the inspection therefore has immediately available a series of "measured" and hence "objective" data that significantly support him in the decisions that he is called to make.

An important advantage of the present finding consists of the fact that it is the designer of the structure who identifies the points of analysis of the structure and hence the points that must be maintained under control; in addition, the designer of the structure inserts, in the central unit, the threshold values of the significant relative displacements; it is recalled that in embodiments 1, 30, 60, the designer of the structure, at the time of installation of the seismic monitoring system, supplied six threshold values (of the significant relative displacements) for each of the two directions (longitudinal and transverse, according to which it is assumed that the earthquake can act) and for each column (or wall). In case of seismic event, therefore, the seismic monitoring system keeps under control those structural elements that the designer of the structure has recognized as important for the seismic response of the structure and for such elements compares, in terms of relative displacements, the actual displacements obtained from the accelerations measured by the accelerometers during the seismic event with the relative threshold displacements, these too indicated by the designer.

Another advantage of the present finding consists of the fact that the seismic monitoring system obtained according to the present finding provides "exact" measurements (signifying: "effectively measured during the seismic event") of the relative displacements between significant points of the structure, indicated by the designer of the structure.

Such measurements constitute the "objective" and "certifiable" base of the damage evaluations of the structure and offer a rather useful instrument to those who must make decisions regarding the possibility of people who usually occupy the building to stay therein. A further advantage of the present finding consists of the fact that as soon as a seismic event has been verified, there is immediate (summary) knowledge of the damage sustained.

One advantage of the present finding consists of the fact that normally the accelerometers are sufficiently spread over the entire building such that the localization of the damage may not be too difficult.

A further advantage of the present finding consists of the fact that, after a seismic event, the seismic monitoring system provides data that was specifically requested by the designer of the structure who, during the design or verification of the structure itself, identified the "critical" points to be maintained under observation during the seismic event and "calculated" the effects thereof, providing various threshold values of the significant relative displacements and establishing the messages that the seismic monitoring system must communicate to the outside, immediately after the seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of the aforesaid significant relative displacements; the data provided by the seismic monitoring system is that requested by the designer of the structure, who knows the structure well (or at least better than anyone else), therefore if during the post-earthquake emergency the technician who carries out the inspection is not the designer of the structure (a very frequent occurrence), such technician who makes the inspection, even in the absence of other data, knows that the designer of the structure would have requested knowing the data that the seismic monitoring system is supplying, which is no doubt to be considered, with regard to that stated above, significant data for evaluating the situation of unfitness for use and damage of the structure. A further advantage of the present finding consists of the fact that the seismic monitoring system (this is the case, for example, of the seismic monitoring systems 1, 30, 60) can be subjected to surveillance over time in order to be able to ensure the correct functioning thereof over the course of years. Indeed, in the central unit, a software resides that allows, upon command or at preset time intervals, introducing virtual seismic data, adapted to verify the state of functioning of the seismic monitoring system. In addition, in the central unit, a software is inserted that allows indicating, in real time, the malfunctioning of an accelerometer or the lack of power supply thereof.

A further advantage of the present finding consists of the fact that in the central unit of the seismic monitoring system, a software is inserted that allows, upon command, calculating dynamic characteristics of the structure, on the basis of the measurements taken by the accelerometers relative to environmental actions; hence, the seismic monitoring system can also be used with the purpose of providing information for the structure monitoring in general, even outside the actual seismic monitoring.

A further advantage of the present finding consists of the fact that the data collected by the seismic monitoring system can be used, if coordinated and studied together with those of other "similarly monitored" buildings, for increasing the knowledge of the behavior of the structures subjected to seismic actions.

Claims

1) - Process for obtaining a seismic monitoring system to install at the structure (11, 41, 71) of a building (10, 40, 70), said structure (11, 41, 71) being such that brittle failure mechanisms are prevented therein, and only ductile failure mechanisms are possible, said process comprising the following operations:

accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) are installed at measurement points belonging to the structure (11, 41, 71);

a central unit (3, 33, 63) is installed which is connected to said accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d);

said seismic monitoring system (1, 30, 60) is activated,

such process characterized in that it also comprises the following operations:

the designer of the structure (11, 41, 71), during the steps of designing or verifying said structure (11, 41, 71), identifies all the possible ductile failure mechanisms of said structure and identifies points of analysis, belonging to said structure, such that the knowledge of significant relative displacements, identified by the designer of the structure (11, 41, 71), between pairs of said points of analysis is necessary for evaluating the conditions of unfitness for use of said structure (11, 41, 71) and for evaluating the damage of said structure (11, 41, 71) deriving from seismic actions; said points of analysis comprise measurement points, at which the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) are positioned, and calculation points whose displacements are calculated on the basis of the displacements of the measurement points; the designer of the structure (11, 41, 71) then obtains, for each of said significant relative displacements, threshold values, which identify situations of unfitness for use and damage of the structure (11, 41, 71); the designer of the structure (11, 41, 71) then establishes messages that the seismic monitoring system (1, 30, 60) must communicate to the outside, immediately after a seismic event, following the comparison between the values of said significant relative displacements that occurred during said seismic event and said threshold values (of said significant relative displacements); the number and the arrangement of the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) have been established as a function of the characteristics of the structure (11, 41, 71), of data provided by the designer of the structure (11, 41, 71) and from the number and arrangement of the points of analysis of the structure (11, 41, 71);

the designer of the structure (11, 41, 71) introduces, in the central unit (3, 33, 63), the following data and the following instructions:

• some data relative to the structure (11, 41, 71), including some data typical of the dynamic behavior of said structure;

• the threshold values for each of said significant relative displacements;

• the messages that the seismic monitoring system (1, 30, 60) must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during said seismic event and the threshold values of said significant relative displacements;

• parameters adapted to identify a damage evaluation scale;

the seismic monitoring system (1, 30, 60) comprises a set of equipment and software which, in order to function, requires data and specific instructions, introduced in the central unit (3, 33, 63) by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60), which render the seismic monitoring system (1, 30, 60) appropriate for the considered structure (11, 41, 71); said seismic monitoring system (1, 30, 60) is adapted to be used for evaluating the conditions of unfitness for use of the structure (11, 41, 71) and the structural damage following seismic actions that occur after the installation of said seismic monitoring system; the central unit (3, 33, 63) is adapted to receive and process the data coming from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d); the central unit, (3, 33, 63), by means of algorithms implemented in the software inserted in said central unit, is adapted to verify if the signals coming from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) derive from a seismic action or from other causes that must not be considered; the central unit (3, 33, 63), once it has been recognized that the signals received from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) are those of a seismic event, is adapted to calculate, by carrying out a double integration (in the time domain) of the values of acceleration measured by the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d), the values of the displacements of the measurement points (where said accelerometers are positioned); the central unit (3, 33, 63) is then adapted to calculate the value of the displacements of the calculation points, so as to be able to then calculate the significant relative displacements, identified by the designer of the structure (11, 41, 71), in order to evaluate the state of unfitness for use and damage of said structure; the central unit (3, 33, 63) is adapted to execute such calculations in nearly "real time"; the central unit (3, 33, 63) is also adapted to compare the values of the significant relative displacements with the corresponding threshold values introduced in said central unit (3, 33, 63) by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60); the central unit (3, 33, 63) is also adapted to communicate, to outside the building (10, 40, 70), the results of said comparison and to send the messages, established by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60);

said seismic monitoring system (1, 30, 60), once installed and once the designer of the structure (11, 41, 71) has introduced the data and specific instructions necessary for the functioning of said seismic monitoring system, functions uninterruptedly and automatically.

2) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that the designer of the structure (11, 41, 71) introduces, into the central unit (3, 33, 63), also the parameters that allow updating the threshold values of the significant relative displacements in order to account for the variations of the characteristics and of the performances of the structure (11, 41, 71) caused by the structural damage due to seismic events that the structure (11, 41, 71) previously sustained and which are recorded by the seismic monitoring system (1, 30, 60).

3) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that one or more local units are installed inside the building (40), such units connected to part of the installed accelerometers (32a, 32b, 32c, 32d, 32e); each of said one or more local units (37) is connected to the central unit (33) to which it is adapted to transmit the data received from the accelerometers (32a, 32b) connected to the considered local unit (37).

4) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that,

during the design or verification of the structure (41), the designer of the structure (41) also identifies one or more pairs of points of analysis of the structure (41), for each of which, in case of a seismic event, it is necessary to know significant relative displacements measured directly by a distance- measuring device (38) and, in particular, it is necessary to know the residual relative displacements, once the seismic event has terminated; the designer of the structure (41) then obtains, for each of said significant relative displacements, threshold values respectively corresponding to situations of unfitness for use and damage of the structure (41); the designer of the structure (41) then establishes messages that the seismic monitoring system (30) must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during said seismic event and the threshold values of said significant relative displacements, and following the comparison, once the seismic event has terminated, between the values of the residual significant relative displacements and said threshold values;

one or more distance-measuring devices (38) are also positioned, which are connected to the central unit (33) or to a local unit; each of said distance- measuring devices (38) measures the significant relative displacements between the points of one of said pairs of points of analysis;

the designer of the structure (41) introduces, in the central unit (33), said threshold values of the significant relative displacements and said messages that the seismic monitoring system (30) must communicate to the outside, immediately after the seismic event, following the comparison between the values of the significant relative displacements that occurred during said seismic event and the threshold values of said significant relative displacements, and following the comparison, once the seismic event has terminated, between the values of the residual significant relative displacements and said threshold values;

the central unit (33) is now adapted to receive and process also the data coming from the one or more distance-measuring devices (38); the central unit (33) is also adapted to compare the values of the significant relative displacements measured by one or more distance-measuring devices (38) with the corresponding threshold values introduced in said central unit by the designer of the structure (41); the central unit (33) is also adapted to communicate, to outside the building (40), the results of said comparison and to transmit the corresponding messages introduced in said central unit (33) by the designer of the structure (41) at the time of installation of the seismic monitoring system (30);

said one or more distance-measuring devices (38) are activated.

5) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that the designer of the structure (11, 41, 71) introduces data and instructions that allow the formation of two types of threshold values which refer to each of the significant relative displacements, and consequently of two types of messages that the seismic monitoring system (1, 30, 60) must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during said seismic event and the threshold values of said significant relative displacements; said two types of threshold values are independent and one refers to the unfitness for use of the structure (11, 41, 71) and one to the evaluation of the damage.

6) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that said seismic monitoring system (1, 60) is installed at the structure (11, 71) of a newly constructed building (10, 70); said seismic monitoring system (1, 60) is activated before said building (10, 70) is commissioned/brought into operation.

7) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that said seismic monitoring system (30) is installed at the structure (41) of an existing building (40).

8) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that said seismic monitoring system (1, 30) is installed at the structure (11, 41) of a building (10, 40) which comprises precast reinforced concrete elements and/or precast prestressed reinforced concrete elements.

9) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that the designer of the structure (11, 41, 71) considers possible damage states pertaining to structural elements or to finishing elements not part of the seismic-resistant structure, correlating them to a suitable acceptable maximum value of the relative displacements of the structural elements that affect such structural or finishing elements.

10) - Process for obtaining a seismic monitoring system according to claim 1), characterized in that it is such that the designer of the structure, during the design of said structure, considers the future installation of said seismic monitoring system at said structure.

11) - Seismic monitoring system according to the process pursuant to claim 1) installed at the structure (11, 41, 71) of a building (10, 40, 70), said structure (11, 41, 71) being such that brittle failure mechanisms are prevented therein, and only ductile failure mechanisms are possible, said seismic monitoring system (1, 30, 60) comprises:

a plurality of accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) positioned at measurement points belonging to the structure (11, 41, 71); a central unit (3, 33, 63), connected to said accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d); said central unit (3, 33, 63) continuously receives and processes the data coming from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d);

the seismic monitoring system (1, 30, 60), once activated, functions uninterruptedly, except for pauses due to maintenance or replacement of components, for the entire useful lifetime of the structure (11, 41, 71),

seismic monitoring system (1, 30, 60) characterized in that it comprises a set of equipment and software which, for functioning, requires data and specific instructions introduced by the designer of the structure (11, 41, 71) during the installation of said seismic monitoring system (1, 30, 60); said data and said specific instructions render the seismic monitoring system (1, 30, 60) appropriate for the considered structure (11, 41, 71); said seismic monitoring system (1, 30, 60) is adapted to be used for evaluating the conditions of unfitness for use of the structure (11, 41, 71) and the structural damage following seismic actions that occur after the installation of said seismic monitoring system; said seismic monitoring system (1, 30, 60), once installed and once the designer of the structure (11, 41, 71) has introduced the data and the specific instructions necessary for the functioning of said seismic monitoring system, functions uninterruptedly and automatically; said measurement points are comprised between points of analysis belonging to the structure (11, 41, 71) identified by the designer of said structure, at the time of installation of the seismic monitoring system (1, 30, 60), as points of the structure (11, 41, 71) of which it is necessary to know, during the seismic action, the absolute displacements in order to be able to calculate significant relative displacements between pairs of said points of analysis; the knowledge of said significant relative displacements, identified by the designer of the structure (11, 41, 71), is necessary for evaluating the conditions of unfitness for use of the structure (11, 41, 71) and the damage of said structure deriving from seismic actions; the central unit (3, 33, 63), for its functioning, uses the data and the instructions introduced, in said central unit, by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60); said data and instructions comprise:

- some data relative to the structure (11, 41, 71), including some data typical of the dynamic behavior of said structure;

threshold values for each of said significant relative displacements;

messages that the seismic monitoring system (1, 30, 60) must communicate to the outside, immediately after a seismic event, following the comparison between the values of the significant relative displacements that occurred during said seismic event and the threshold values of said significant relative displacements;

parameters adapted to identify a damage evaluation scale;

the central unit (3, 33, 63), which functions continuously, by means of algorithms implemented in the software inserted in said central unit, verifies if the signals coming from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) derive from a seismic action or from other causes that must not be considered; the central unit (3, 33, 63), once it has been recognized that the signals received from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) are those of a seismic event, signals said seismic event and calculates the values of the displacements of the measurement points, by carrying out a double integration (in the time domain) of the values of acceleration measured by the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) at the measurement points; the central unit (3, 33, 63) also calculates the values of the displacements of the calculation points; the central unit (3, 33, 63), using both the values of the displacements of the measurement points and those of the calculation points, calculates the significant relative displacements, indicated by the designer of the structure (11, 41, 71), between said points of analysis; the central unit (3, 33, 63) then compares such values of the significant relative displacements with the corresponding threshold values introduced in said central unit by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60); the central unit (3, 33, 63) then communicates, to outside the building (10, 40, 70), the results of said comparison and transmits the corresponding messages introduced in said central unit by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60)).

12) - Seismic monitoring system according to claim 11) characterized in that for the recognition of the seismic action, the central unit (3, 33, 63) also makes use of filters inserted in said central unit which account for the activities that can be carried out in the building (10, 40, 70) and for the actual situation; the data necessary for the functioning of said filters was inserted in the central unit (3, 33, 63) by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60).

13) - Seismic monitoring system according to claim 11) characterized in that in the presence of a seismic event, the central unit (3, 33, 63) updates the threshold values of the significant relative displacements in order to account for the variations of the characteristics and performances of the structure (11, 41, 71) caused by the structural damage due to seismic events already sustained by the structure (11, 41, 71) and recorded by the seismic monitoring system (1, 30, 60); the parameters which allow updating said threshold values of the significant relative displacements were introduced in the central unit (3, 33, 63) by the designer of the structure (11, 41, 71) at the time of installation of the seismic monitoring system (1, 30, 60).

14) - Seismic monitoring system according to claim 11) characterized in that the threshold values of the significant relative displacements, which are established and introduced in the central unit (3, 33, 63) by the designer of the structure (11, 41, 71), also account for the damage of complementary building works and/or of installations connected to said structure.

15) - Seismic monitoring system according to claim 11) characterized in that the points of analysis relative to which it is necessary to calculate the significant relative displacements, to compare with the relative threshold values, also comprise calculation points, in addition to the measurement points (at said measurement points, the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) are positioned); the central unit (3, 33, 63), by means of algorithms implemented in the software inserted in said central unit, on the basis of the values of the displacements of the measurement points and on the basis of data provided by the designer of the structure (11, 41, 71) and inserted by said designer in said central unit (3, 33, 63), calculates the value of the displacements of said calculation points.

16) - Seismic monitoring system according to claim 11) characterized in that in the central unit (3, 33, 63), two types of threshold values are inserted which refer to each of the significant relative displacements, and consequently two types of messages are inserted that the seismic monitoring system (1, 30, 60) must communicate to the outside, immediately after the seismic event, following the comparison between the values of the significant relative displacements that occurred during the aforesaid seismic event and the threshold values of said significant relative displacements; said two types of threshold values of the significant relative displacements are independent and one refers to the unfitness for use of the structure (11, 41, 71) and one to the evaluation of the damage; the data and the instructions necessary for the formation of said two types of threshold values of the significant relative displacements were introduced by the designer of the structure (11, 41, 71) at the time of installation of said seismic monitoring system (1, 30, 60).

17) - Seismic monitoring system according to claim 11) characterized in that it is installed at the structure (11, 71) of a newly constructed building (10, 70); said seismic monitoring system (1, 60) starts functioning when said building is commissioned/brought into operation.

18) - Seismic monitoring system according to claim 11) characterized in that it is installed at the structure (41) of an existing building (40).

19) - Seismic monitoring system according to claim 11) characterized in that said seismic monitoring system (1, 30) is installed at the structure (11, 41) of a building (10, 40) which comprises precast reinforced concrete elements and/or precompressed reinforced concrete elements.

20) - Seismic monitoring system according to claim 11) characterized in that it also comprises one or more local units (37) connected to part of the installed accelerometers (32a, 32b, 32c, 32d, 32e), each of said one or more local units (37) is connected to the central unit (33), to which it transmits the data received from the accelerometers (32a, 32b) connected to the considered local unit (37).

21) - Seismic monitoring system according to claim 11) characterized in that the central unit (3, 33, 63) comprises a master unit (7) and a computer (8) connected to said master unit.

22) - Seismic monitoring system according to claim 11) characterized in that the master unit (7) comprises a converter module that converts the data from analog to digital, a data communication module, and a data processing module, comprising a CPU, which processes data and also provides for the communication of the data and the messages outside the seismic monitoring system (1, 30, 60).

23) - Seismic monitoring system according to claim 9) characterized in that it also comprises one or more distance-measuring devices (38), connected to the central unit (33) or to a local unit, each of which measures significant relative displacements between the two points belonging to a pair of analysis points; the central unit (33) receives and processes the data coming from the one or more distance-measuring devices (38); the central unit (33), in the case of seismic event, detects at least at the end of said seismic event, the significant relative displacements between the one or more pairs of points of analysis monitored by said one or more distance-measuring devices (38); the central unit (33) also compares the values of the significant relative displacements measured by the distance-measuring devices (38) with the threshold values of said significant relative displacements; said threshold values were introduced in said central unit (33) by the designer of the structure (41) at the time of installation of the seismic monitoring system (30); the central unit (33) then communicates, to outside the building (40), the results of said comparison and transmits the corresponding messages introduced in said central unit (33) by the designer of the structure (41) at the time of installation of the seismic monitoring system (30).

24) - Seismic monitoring system according to claim 11) characterized in that in the central unit (3, 33, 63), a software is inserted that allows, upon command or at preset time intervals, introducing virtual seismic data, adapted to verify the functioning state of the seismic monitoring system (1, 30, 60).

25) - Seismic monitoring system according to claim 11) characterized in that in the central unit (3, 33, 63), a software is inserted that - if during the acquisition of the data coming from the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) it is found that one of said accelerometers no longer functions - automatically considers the measurement point where said no-longer-functioning accelerometer is positioned to be a calculation point.

26) - Seismic monitoring system according to claim 11) characterized in that in the central unit (3, 33, 63), a software is inserted which, in the absence of seismic events, allows indicating, in real time, the malfunctioning of an accelerometer (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d) or the lack of power supply of the same.

27) - Seismic monitoring system according to claim 11) characterized in that in the central unit (3, 33, 63), a software is inserted which allows, upon command or with a preset frequency, calculating dynamic characteristics of the structure (11, 41, 71), on the basis of the measurements taken by the accelerometers (2a, 2b, 32a, 32b, 32c, 32d, 32e, 62a, 62b, 62c, 62d), relative to environmental actions.

28) - Seismic monitoring system according to claim 11) characterized in that it also comprises a signaling unit of light or acoustic type adapted to transmit signals associated with said messages inserted in the central unit (3, 33, 63).

29) - Seismic monitoring system according to claims 11) and 28) characterized in that the central unit (3, 33, 63) can transmit light signals comprising four colors. 30) - Seismic monitoring system according to claim 11) characterized in that the central unit (3, 33, 63) is connected to a computer or telephone network and transmits said messages to preset addresses.

31) - Seismic monitoring system according to claim 11) characterized in that in the central unit (3, 33, 63), a software is inserted which, once the seismic event has terminated, communicates via Internet to one or more preset addresses also the time history of the recorded accelerations, the time history of the displacements of the measurement points and of the calculation points.

32) - Seismic monitoring system according to claim 11) characterized in that the central unit (3, 33, 63) is positioned inside the building (10, 40, 70).