Patent Description:
The invention concerns the so-called "bearings" which constitute particular elements of support on which the structures are laid.

In fact, suitably sensorized, these support elements can provide a number of information that can be used in various areas: both to highlight the status of the viaducts themselves, and to monitor their operation.

Almost all bridges and viaducts are placed on structural elements known as "bearings". The theories of the construction science, which are not explored here, but which offer a decidedly mature and consolidated theoretical support, highlight how there are some structural, construction and maintenance advantages in concentrating the unloading of the weight of the entire structure of a bridge or viaduct in a limited number of points, in which the constraint can be considered, with good approximation to a simple support. Therefore, these "bearings" are real structural elements, designed to withstand over time the strong stresses transmitted from the deck to the pylons of the structures. They are very expensive elements, precisely due to the characteristics of mechanical strength and durability that they must have, and they are mainly made up of mechanical components in stainless steel with surfaces normally coated in Teflon (to reduce friction in the relative movements between the various steel components).

Due to the relative movement between the various components and their positioning, which exposes them to frequent washout and aggression of water percolating from the deck, these "bearings" are subject to degradation over time, therefore, different levels of inspection and verification are foreseen: from the visual inspection, to the verification of the corrosive state and to the lifting of the support beams, and up to the eventual replacement with a totally new "bearing".

Monitoring the state of degradation of the "bearings", and their consequent maintenance, is an activity of great importance for the subject who manages the road. All these activities, in addition to being expensive, have important impacts on traffic and the risk of accidents caused by the presence of temporary construction sites.

In some cases (see for example <CIT>) the known technique proposes particular vehicles that allow the workers to perform some inspection or maintenance in a particularly advantageous, fast and safe way; however, these are always expensive and not always feasible operations.

As for the pure monitoring of the wear state of the "bearings", the most recent known technique also offers a large number of innovative solutions based on the introduction of particular sensors. In fact, although they may appear as mechanically simple elements, since they only need to be sufficiently resistant to oppose a very concentrated constraint reaction to the enormous weights of the structures of a viaduct, the state of one of these "bearings" can be defined through a plurality of state variables, which can be correlated to various quantities, some of which are subject to very small variations, but which can still be appreciated with modern sensors. <CIT> discloses a system of sensorized bearings.

A family of considerations, aimed at monitoring the state of the "bearings", can be conducted on the basis of the analysis of the overheating dynamics of the "bearings" themselves, therefore temperature measurements can be made, for which various technologies are available to create special sensors.

Other analyzes may be based on the detection of changes in electrical properties (for example impedances offered between appropriate pairs of points of the monitored element), as these changes can be correlated with the physical integrity of the material. Other considerations may be based on the analysis of the vibrations to which the "bearing" is subject, in fact, even the frequency response of the element can highlight its degradation. Still other analyzes can then be based on the measurement of the deformation of the "bearing".

It is not the case, here, to review the great variety of sensors that can be integrated into the "bearing" in order to monitor its status, just take note that such monitoring is useful and it is also possible from the technical point of view.

Furthermore, and as already explained, the "bearings" for bridges and viaducts are elements subject to wear and, therefore, they are elements whose replacement is substantially foreseen. Gradually over time, then, taking advantage of the necessary replacements, it will be convenient to spread sensorized "bearings", and it is foreseeable that in the medium term a large number of viaducts will be supported on sensorized "bearings".

Although the state of degradation of the "bearings" appears as the information of greatest interest, and therefore may justify the widespread introduction of sensorized "bearings", it is observed that the availability of information obtained with measurements performed on these "bearings" may have also other uses, and the elaborations that can be drawn from such information, can give rise to analyzes of equal interest.

In particular, information that can certainly be made available by a sensorized "bearing" is the information, over time, of the weight downloaded over the single "bearing". This weight is a variable quantity over time as each "bearing", in addition to supporting the bridge, or viaduct, contributes to supporting the weight of the vehicles that cross this bridge or viaduct.

While the weight of the bridge, or viaduct, is substantially known and constant over time (at least in observation intervals of medium duration), the weight of the vehicles obviously varies rapidly over time depending on the transit of vehicles.

The main purpose of the present invention, therefore, is to exploit in a new way the availability of data measured on the sensorized "bearings" installed on bridges and viaducts. In particular, the present invention teaches to realize a system, which takes advantage of the load information that can be obtained from the presence of said sensorized "bearings" and, by integrating further information regarding the transit of vehicles, aims to define an analysis method, which allows to calculate the weight of vehicles passing over a bridge or viaduct, in which particular sensorized "bearings" are installed.

A further object of the present invention is to indicate the overall system that must be implemented on bridges and viaducts in order to achieve the main object.

Finally, the present invention defines a method for estimating the weight of vehicles passing over a bridge or viaduct in which the overall system taught in the present invention has been implemented.

This main objective can be achieved by means of a system implemented on a bridge or viaduct, and this system includes a plurality of sensorized "bearings", installed in said bridge or viaduct, suitable to perform a series of measurements, over time, of the vertical load exerted on each of said sensorized "bearings", and a video coverage system suitable for identifying, over time, the number of vehicles and their position on the trait of road corresponding to said bridge or viaduct; furthermore, said system makes use of suitable computing means configured for processing the information produced by said sensorized "bearings" and by said video coverage system, in order to estimate the weight of said vehicles passing on said stretch of road corresponding to said bridge or viaduct.

The weight of the vehicles is estimated using the knowledge of the mathematical structural model of the bridge or viaduct, implemented by said computing means, as it is previously programmed on them.

Through the application of said mathematical structural model of the bridge, or viaduct, a plurality of equations can be produced in which the unknown variables are the weights of the vehicles which are in the stretch of road corresponding to said bridge or viaduct.

In fact, having fixed an instant of time <t *>, for each "bearing", the mathematical structural model of the bridge, or viaduct, allows you to write the formula to calculate the total load on this "bearing", given the position and the number of vehicles that download their weight, at least in part, on this "bearing". This formula will have as unknown values only the weights of individual vehicles, as all the other quantities expressed in the produced equations are known or can be obtained by other means.

The result of this formula will be set equal to the load measured by the sensors, which each "bearing" is equipped with, thus obtaining an equation with as many variables as the number of vehicles that are passing over the stretch of road corresponding to said bridge or viaduct, in the considered instant of time.

It is observed that it is possible to write a large number of equations, as a different equation can be written for each "bearing", and for each instant of time.

As regards the number of "bearings", it is observed that in a span of a viaduct there must be a minimum of four "supports" (but generally there are more); while, with regard to the different measurements in temporal succession, it is observed that the vehicles move quickly going to burden differently, from instant to instant, on the different "bearings", and, moreover, in the stretch of road considered, vehicles continually exit and new ones enter. It is clear that the obtained system of equations can also be of considerable complexity, as the model of propagation of the weights on the bearings must be very accurate, and the number of equations can also be very high, however it can be solved with known methods of numerical computation and implemented on said computation means.

It is noted that, for the identification, over time, of the number of vehicles, determining their position in the stretch of road corresponding to said bridge or viaduct, it is possible to use, in addition to a video coverage system, any other subsystem able to detect the position, over time, of the vehicles passing on that stretch of road.

The main advantage of the present invention consists in the fact that its teachings allow to satisfy all the main objectives for which it was conceived.

This invention also has further advantages, which will become more evident from the following description, from some examples of practical embodiments which illustrate further details, from the attached claims which form an integral part of the present description, and from the attached figures in which:.

The representation offered in all the proposed figures is simplified and the proportions are not realistic. These are figures conceived essentially for the purpose of highlighting, each one, some characterizing elements; therefore, many details, which do not concern the characteristics that are intended to be described, are omitted or represented in an approximate way.

<FIG> presents an axonometric view of a stretch of road on a viaduct. The number <NUM> indicates the pylons that support the viaduct. The stretch of road between two groups of pylons, corresponding to a span of the viaduct, is indicated with the number <NUM>.

In the example of the road represented in <FIG>, four pylons are assumed: two in one cross section of the road, and two others in another section. It is also assumed that the stretch of road <NUM> rests on four "bearings" corresponding to the four pylons <NUM>.

It is observed that in real cases, different support architectures can also be implemented, also providing a greater number of pylons per section, and a greater number of "bearings" per pylon; however, all the possible structural and architectural variants do not substantially influence the inventive concept underlying the present invention.

Therefore, assuming the simplest case in which a viaduct span rests on four "bearings", the four points on the road surface in correspondence with the vertical above each physical "bearing" are highlighted with the numbers <NUM>, <NUM>, <NUM> and <NUM> (being under the road, the physical "bearings" are not visible in the figure).

It is observed that these "bearings" are constructed in such a way as to concentrate the support in a very small surface, so much so that the "punctual" approximation of the support, and consequently of its projection on the road surface, is a widely acceptable approximation: in fact , said "bearings" can be modeled as "punctual" elements for the transmission of loads, so they lend themselves to returning (by means of suitable sensors) an important data about the structure of the viaduct, and a measure of the constraint reactions associated with this.

<FIG> shows a top view of the stretch of road <NUM> included in a span of a viaduct and, as in the example of <FIG>, said stretch of road <NUM> is supported on four "bearings" whose projection on the surface is, once again, marked with an "X" and indicated with the numbers <NUM>, <NUM>, <NUM> and <NUM>.

Only one vehicle, indicated by the number <NUM>, is depicted on this stretch of road <NUM>. The transit of said vehicle <NUM>, whose weight is not known, will determine a variation of the constraint reaction on said four "bearings" on which the stretch of road <NUM> is laid. This constraint reaction variation, in addition to depending on the unknown weight of the vehicle <NUM>, also depends on its position, and in particular on the distance of said vehicle <NUM> from the four points <NUM>, <NUM>, <NUM> and <NUM>.

Approximately, the weight of the vehicle <NUM> is distributed over the four "bearings" underlying the points <NUM>, <NUM>, <NUM> and <NUM>, and it will typically weigh more on the closest bearing, and to a lesser extent on the more distant ones. In general, the variation of the constraint reaction on each of the "bearings" underlying the four points indicated with the numbers <NUM>, <NUM>, <NUM> and <NUM>, can be formally calculated using the mathematical modeling of the viaduct structure.

In the following we will indicate with the string "D1-<NUM>", the difference between the constraint reaction on the "bearing" below the point <NUM> when the road is not traveled by any vehicle, and when it is instead occupied by the vehicle <NUM>. Similarly, with the strings "D2-<NUM>", D3-<NUM>" and "D4-<NUM>", the analogous differences of constraint reaction on the "bearings" underlying points <NUM>, <NUM> and <NUM> will be indicated. It is noted that the real values of "D1-<NUM>", "D2-<NUM>", "D3-<NUM>" and "D4-<NUM>", are variable over time, depending on how the vehicle <NUM> moves, and can be measured using appropriately sensorized "bearings"; therefore, the formulas for the calculation of these constraint reaction variations (which can be written for each constraint, knowing the mathematical model of the viaduct) can be set equal to the real measured values.

As noted above, these formulas will depend on the weight of the vehicle <NUM> and its position throughout the transit. While the weight of the vehicle <NUM> is actually an unknown value, its position over time can instead be measured quite easily, and therefore such formulas, expressing the constraint reaction differences on the "bearings" underlying points <NUM>, <NUM> and <NUM> ("D1- <NUM>", "D2-<NUM>", "D3-<NUM>" and "D4-<NUM>"), may contain a single unknown value, or at most two unknowns, in case it is relevant to take into account also the speed of the vehicle <NUM> in order to calculate the propagation of its weight on each "bearing".

<FIG> shows, in an axonometric view, the example presented in <FIG>, in which a vehicle <NUM> passes through the stretch of road <NUM>.

In addition to what is shown in <FIG>, <FIG> also shows a video recording system, indicated with the number <NUM>. Said video recording system <NUM> performs the function of determining the position of the vehicle <NUM> over time. It should be noted that the function of determining the position of a vehicle on a road can be performed using numerous systems, including those based on technologies other than video recording technology; in fact, the following invention requires a generic system capable of detecting the position, over time, of vehicles passing on a stretch of road corresponding to said bridge or viaduct. However, the solution which, to determine the position of a vehicle on a road, is based on the analysis of a video image, appears, at the state of the art, as one of the preferred solutions, especially since the video images of a road can also be used for other purposes, such as traffic surveillance and monitoring.

Some improvements, to speed up and to make the calculation of the information about the position more precise, can resort to the installation on said stretch of road <NUM>, in the field of view of the video recording camera, of easily recognizable reference tags placed in known positions, such as, for example, poles similar to that indicated with the number <NUM> in <FIG>, placed along the edge of the stretch of road <NUM>, or else other types of reference can be marked on the road.

Ultimately, it can be stated that the position, over the time, of a vehicle transiting on a stretch of road <NUM> is easily detectable using various systems, including video recording systems suitable for taking images of the stretch of road <NUM>. Consequently, given an instant of time <t *>, it is possible, for each "bearing", to write an equation in which only the weights of the vehicles, and possibly their speeds, appear as unknown values. The speed of the vehicles appears in the case in which the model of propagation of the weight of the vehicles on the "bearings" depends significantly on the speed of the same; and in the event that these speeds are calculated by the video analysis, they would appear as known values and not as variables. It is observed that a very precise and accurate modeling of the dynamics, which the constraint reactions exerted by the "bearings" are subject to, must take into account the speed of the vehicles; it is also true that the speed of the vehicles, as well as the position, is a datum that can be easily calculated through the 'video analysis. Therefore, in the preferred implementations of the present invention, they will be used just equations in which only the weight of the vehicle appears as unknown, since its position and speed can be measured.

<FIG>, shows a top view of the stretch of road in which there are two vehicles, and the stretch of road shown is longer than the stretch included in a span of a viaduct. <FIG> allows to specify some further details regarding the construction of the equations associated with the computation of the constraint reaction on each "bearing".

Firstly, even if it is obvious, it must be said that a plurality of vehicles can travel on a given stretch of road, and therefore the constraint reaction exerted by each bearing must balance the weight contribution of a plurality of vehicles.

Secondly, the vehicles that stress each "bearing" are all those located in the two contiguous spans on both sides of the cross section determined by the pylons <NUM>. In the example presented in <FIG>, the same case shown in <FIG> is shown, but the stretch of road represented is longer, therefore, in addition to vehicle <NUM>, which weighs on the "bearing" below points <NUM>, <NUM>, <NUM> and <NUM>, there is also a second vehicle, indicated with the number <NUM>, which weighs, in part, on the "bearings" underlying the points <NUM> and <NUM>, while it does not burden (at least not as a first approximation) on the "bearings" underlying the points <NUM> and <NUM>.

Therefore, in the end, given an instant of time <t*>, for each "bearing" the equation that describes the constraint reaction load on this "bearing" must be written by adding all the contributions determined by all the vehicles that go to burden on this "bearing".

Ultimately, given a stretch of road on a viaduct (or on a bridge), it is possible to write a considerable number of equations based on the calculation, carried out through the application of a mathematical model, of the constraint (support) reaction on a "bearing". The number of equations that can be written, as mentioned, is considerable, as an equation can be written for each "bearing" and for each instant of time. In fact, the equations are different in every moment as the vehicles move, weighing differently on the various "bearings", moreover new vehicles continually enter and leave the stretch of road under observation. Realistically, therefore, it is possible to write a number of equations greater than the number of vehicles transiting, in the observation time interval, on said stretch of road under observation: therefore, it is possible to write a system whose unknown values are the weights of the vehicles. This system can be solved with known numerical methods, and the solution will provide an accurate estimate of the weights of the vehicles that have passed, in the observation time interval, on a stretch of road equipped with the system indicated in the present invention. The accuracy of the estimate will obviously depend on the quality of the sensors applied on the "bearings" (obviously, the more precise the measurements, the more accurate the system result will be), however the accuracy of the estimate can also be refined by increasing the number and frequency of measurements over time, in fact increasing the number of measurements will have the effect of reducing the statistical error. Obviously, increasing the frequency of measurements corresponds to increasing the number of equations, and then the complexity of the system.

Here we do not intend to provide details about the resolution of the systems that can be written using the mathematical model of the infrastructure (bridge or viaduct) together with the availability of the measurements produced by the sensorized "bearings". However, for the resolution of such systems, the iterative methods of numerical analysis are suggested, even if this family of methods is not the only one that can be used.

In particular, iterative methods allow to converge towards the solution of the system, through successive corrections, at each iteration, of an approximate previous solution. Furthermore, the solution of this system with iterative methods of numerical computation can be speeded up, even considerably, by resorting to particular iterative computation methods, also known as "warm start methods", being able to start from starting solutions close to the convergence solution of the system. In fact, video analysis, in addition to providing the position, and possibly the speed, of the vehicles, can recognize some types of vehicles, and can therefore provide a hypothetical approximate weight of the same; therefore, through video analysis of the images produced by the video coverage system <NUM>, a first approximate starting solution of the system can be easily determined. In this way the calculation iterations of the system will certainly be able to converge directly and quickly towards the optimal solution of the system.

The computing power that is made available by the technology of actual computers is, already today, widely adequate to support the calculations necessary for the implementation of the present invention, and it is also continuously growing: therefore, also taking into account the computational efficiency of the "warm start methods", for carrying out the calculations, the size of the systems of equations resulting from the application of the present invention is not to be considered a critical factor for the implementation of the invention itself.

Therefore, in the various forms of implementation of the present invention, the construction of the system can be carried out considering, even particularly long road sections, with many "bearings" and many vehicles, producing frequently repeated measurements, for relatively long-time intervals: ultimately very large systems, with many equations, can be built. The choice of large systems, and the use of a large number of measurements, in space and time, allows to reduce measurement errors, and, therefore, it is a choice that improves measurement accuracy, at the expense of the calculation complexity that, however, for the above considerations, it should not be considered a problem.

From what has been said so far, it therefore clearly emerges that by means of a system installed on a bridge or viaduct that includes sensorized "bearings", capable of returning a series of measurements over time of the vertical load exerted on the bearing itself, and a video coverage system suitable for identifying, over time, the number of vehicles and their position in the stretch of road corresponding to said bridge or viaduct, it is also possible to define a method for estimating the weights of the vehicles transiting on that stretch of road corresponding to said bridge or viaduct.

In particular, said vehicle weighing method comprises at least the following steps.

Finally, it is reiterated that this method of estimating the weights of vehicles transiting on a stretch of road placed over a bridge or viaduct is based on measurement and monitoring elements that can also be used for other purposes; and the accuracy of the estimate can be refined purely through calculation processes, which can make use of repeated measurements, in order to considerably reduce statistical errors.

It is observed that the weight of vehicles passing on the roads is a very interesting information for various reasons:.

The dynamic weighing systems proposed today (WIM - Weigh In Motion systems) are based on the preliminary preparation of a cross-section of a road so that the weight of the axles is detected as the vehicles pass over, then reconstructing the weight of the entire vehicle with appropriate calculation algorithms. The system proposed by the present invention represents an evolution of the current dynamic weighing systems: instead of having a single road cross section prepared for weighing the axles as the vehicles pass, in this case, they are made "m" measurements over time, consisting of "n" punctual weight values, each corresponding to the "n" constraint reactions on the "n" sensorized bearings comprised in the overall system. With modern computing powers, the number "m" can be very high and in any case increased until the "m" weighted with "n" constraint reactions univocally converge to define the single "p" traveling loads with great precision.

The video camera (or video cameras) included in the video coverage system are typically positioned in correspondence with the extrados of the bridge or viaduct and, in addition to detecting the positions over time of the various "p" traveling vehicles, they can also easily detect their license plates, and consequently allow to intercept any overweight vehicles.

In general, the weighing system according to the invention can be used in all situations where it is necessary, or useful, to accurately weigh moving vehicles. For example, in approach to toll stations, perhaps to match the tariff to the real weight of the vehicles with great precision.

It is observed that one of the great advantages of the system is given by the fact that it requires two subsystems whose usefulness is evident also for other applications:.

The invention just described can be implemented by resorting to different numerical methods for the solution of the systems of equations produced, and the size of the system itself can vary since the calculation method is applicable considering road traits of different length and with a different number of sensorized "bearings.

Ultimately, the system of "intelligent bearings" according to the teachings of the present invention, appears to be very efficient in supporting the needs of control of the loads transiting on the roads, in the name of the growing sensitivity with respect to the themes of structural control of infrastructures, of their use and, ultimately, their management and maintenance.

In general, then, the present invention lends itself to numerous variations while maintaining the claimed prerogatives. In fact, it can be developed using different technologies for the realization of the "bearings" and for their "sensorization", as well as the systems for determining the position over time of the vehicles can be based on various technologies, and can resort to various measures to create visible references that facilitate the estimation of the detection of vehicle positions. The invention itself can then be partially realized as all the details described can be replaced by technically equivalent elements. Basically, and as previously mentioned, the use of specific technologies and materials does not constitute an essential part of the present invention. Therefore, if in the future the sector of materials for the realization of "bearings" and of the technologies used in the overall system were to make available new technologies, more advantageous than those available today, in order to implement the present invention more efficiently, they could be made further improvements without changing the inventive nature and the principles that inspired the invention itself.

Other possible variants for the present invention may be linked not only to the evolution of the technologies that constitute it, but also to how the so-called ITS (Intelligent Transport System) sector will evolve, which provides for the progressive computerization of roads and the introduction of vehicles more connected toward the external way, suitable to the exchange of information of all kinds.

Claim 1:
A system of "intelligent bearings" for bridge of viaduct structures, wherein said system comprises at least:
i. a plurality of sensorized " bearings ", installed in said bridge or viaduct, suitable to perform a series of measurements, over time, of the vertical load exerted on each of said sensorized " bearings ",
ii. a subsystem capable of detecting the position, over time, of vehicles transiting on a trait of road (<NUM>) corresponding to said bridge or viaduct, and
iii. suitable computing means configured for processing the information produced by said sensorized "bearings" and by said subsystem capable of detecting the position of said vehicles;
and said computing means are:
a. configured to implement a previously programmed mathematical model of the structure of said bridge or viaduct, and
b. programmed to produce a plurality of equations in which each value of said series of measurements, over time, of the vertical load exerted on each of said sensorized "bearings", is expressed as a function of said position, over time, of the vehicles transiting on that trait of road corresponding to said bridge or viaduct, and of their weight, being the weights of said vehicles expressed as unknowns in these equations,
c. moreover, said computing means are programmed to solve systems of equations composed of said equations produced in the previous point "b." in order to estimate the weight of each of said vehicles transiting on said trait of road corresponding to said bridge or viaduct.