FR2845156A1 - Vehicle weighing method, especially for a vehicle about to cross a bridge or other weight-limited structure, wherein the weight applied by each axle is measured by the deflection of a structure and then the axle weights summed - Google Patents

Abstract

Device for measuring the weight of a vehicle crossing onto a bridge or similar comprises detectors (11d, 11g) for measuring the vertical deflection of supports (2d, 2g) for one end of the bridge apron (1). The deflection of the supports is measured for each axle to give a weight for each axle. The total of the weights for each axle equals the vehicle weight. If this exceeds a predetermined limit an alarm or other action can be triggered. An Independent claim is made for a method for measuring the weight of a vehicle crossing onto a bridge or similar.

Description

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  METHOD AND DEVICE FOR MEASURING THE WEIGHT APPLIED TO THE GROUND BY AT LEAST ONE AXLE

  The present invention relates to a method for measuring the weight applied to the ground by at least one vehicle axle. The present invention also relates to a device for measuring the weight applied to the ground by at least one vehicle axle. The increasing powers of commercial road vehicles allow increasingly heavy vehicles to circulate in an apparently normal way on the road network. This results in increasing demands on the road infrastructure, and a risk of accelerated aging or even rupture of certain equipment. Bridges are particularly exposed to this type

of risk.

  The authorities are currently carrying out checks consisting, for example, of installing a scale on a parking area on which vehicles intercepted by the traffic police can be passed through traffic at very low speed. This process gives precise results but its implementation for a series of controls is tedious. For a road carrier, the risks of being intercepted in the event of overloaded traffic are extremely low. The protection of road infrastructure is therefore not

not insured.

  We have also imagined installing special road elements that would be sensitive to the stress resulting from the passage of an axle. Even by imposing a slowdown on the 30 vehicles, the results obtained have been extremely imprecise because the complex deformation of a road element is translated by strain gauges into a dome-shaped signal which is very difficult to interpret in terms of load. applied. The object of the invention is to propose a method and / or a device which considerably facilitates the control of the weight of road vehicles, and if necessary the initiation of appropriate measures in the event of overtaking.

an authorized limit.

  According to a first aspect of the invention, the method for measuring the weight applied to the ground by at least one vehicle axle is characterized in that the sudden action is detected

  variation undergone by a vertical dimension of a structure of a bridge below an extreme support line materialized by one end of an apron of the bridge when the axle crosses said extreme support line in the course of the 10 traffic.

  When a vehicle axle approaches the first support line of a bridge, the weight that the axle applies to the ground is suddenly transferred from an essentially rigid mass and fixed to an apron of the bridge. When the axle crosses the last support line, the weight it applies to the ground is suddenly transferred from an apron (the same as before

  or another) to an essentially rigid and fixed bed.

  The concept of "extreme support lines" of the bridge must therefore be understood as designating the two horizontal transverse lines of the roadway between which the weight applied by the axles is transferred to the structure of the bridge, which can deform relative to the between which the bridge stretches. According to the invention, the abrupt dimensional variation undergone by the underlying structure is exploited.

  the end of the bridge deck when a vehicle axle is supported on this end corresponding to the first support line of the bridge, or, in the other direction of traffic, when a vehicle axle unloads the bridge deck 30 when it exceeds the last support line of the bridge.

  It has been found according to the invention that there is thus a remarkably pure indication of the load represented by the axle in question. The deck serves as a direct transmission member between the axle and the infrastructure 35 supporting the end of the deck. According to the invention, a dimensional variation is directly translated into an applied load measurement. This is distinguished from the prior art where we

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  wanted to measure a stress distribution in space and time to try to deduce an applied load value from it. The method according to the invention does not require the vehicles to slow down. So it can be constantly

  operational. Consequently, if, for example, the presence of the measuring system is announced upstream of the bridge, the bridge is unlikely to be more or practically more crossed by overloaded vehicles and / or exceeding the tonnage limit for which the bridge in question is authorized to the circulation.

  To detect the sudden variation in dimension

  vertical, a variation in the vertical dimension of a support interposed between the bridge deck and a bridge abutment supporting said end of the deck is preferably detected.

  It is also possible to detect a variation in vertical dimension of a bridge support, in particular a

  bridge, supporting the end of the deck.

  When the supports are of a relatively flexible type, for example made of neoprene, the sensitivity may be sufficient if the variation in vertical dimension of the support is simply detected. On the other hand, in the case of relatively stiff supports, such as metallic, the reduction in height of the support during the passage of an axle, even when heavily loaded, can be very small. According to the invention, it is therefore preferable to detect the

  variation of vertical dimension along the height of the bridge support, for example over a few meters in height below the deck. Detection may include both the support and a portion of the height of the bridge support such as the abutment.

  The method is particularly advantageous if, to detect the dimensional variation, use is made of a detection mode with instantaneous appearance and transmission without dead time, of a detection signal between the detection site at the end of the apron and the treatment site. Such a detection mode is preferably of the type using the alteration of a light signal. Particularly contemplated detectors are

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  optical fibers which exploit the particularity that optical fibers have of attenuating the transmitted light when they are stretched. EP-B 0264 622 describes such a detector which can measure a variation in spacing between two distant points 5, for example several meters. EP-B-0649 000 describes such a

  very robust detector with respect to fatigue stresses and capable of detecting very small dimensional variations between two points which can be relatively close together, by transforming the dimensional variations into 10 variations of curvature of the optical fiber.

  In this kind of detector, a light power

  constant is applied to one end of the fiber and the light power received at the other end constitutes an input signal indicating in real time and without delay the dimensional variations undergone by the detector.

  Thus, according to the invention, the end of the bulkhead immediately and directly undergoes the variation in load due to the passage of an axle on the first or the last corresponding support line, and the immediate dimensional variation which results therefrom is immediately transformed into an input signal for processing processing of appropriate measurement and / or control and action signals, in particular in the event of exceeding the authorized limits. Furthermore, this absence of dead time between the event and its consequence in terms of detection automatically eliminates the influence of parasitic effects, in particular those due to the

  possible deformation of the deck and its inertia.

  It is thus possible to make recordings which correspond with great precision to the dimensional variations undergone by the bridge at said end on the one hand and the time scale on the other hand. It is further provided, according to the invention, to collect a video recording for the movement of vehicles on said end of the bridge, with a time scale using the same clock as that associated with the aforementioned recording of dimensional variations. It is therefore possible, in case of doubt or dispute, to check which vehicle has caused a train

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  determined sudden dimensional variations, and to determine whether, during this period, a particular phenomenon has

could disturb the measurement.

  In particular when the apron rests on the support by at least two supports, it is advantageous to detect the dimensional variation at at least two points different from the width of the end of the apron, each point being

  preferably adjacent to one of the supports.

  Particularly preferably, the dimensional variation is detected by associating a deflectometer with each

support of the end of the deck.

  For a carriageway with two lanes of traffic, the distribution of the dimensional variation on both supports indicates on which lane the vehicle is traveling, the axle of which produces the dimensional variation. Two vehicles

  rolling substantially side by side can be distinguished from this distribution. An axle of a given vehicle produces a simultaneous variation on the two supports but with a distribution which is characteristic of the track along which this axle travels.

  One can calculate in a very simple way the weight applied by the axle according to the elastic stiffness of each support and the vertical deformation of each support. In practice, use is preferably made of calibration curves or laws of correspondence which give the applied load as a function

  of the detection signal generated by the corresponding vertical deformation of the support. Such correspondence laws are established prior to the commissioning of the device.

  They make it possible in particular to take into account the dynamic effects which can have the consequence that the deformation undergone by a support during the passage of a moving axle may be greater or less than the deformation which would be due to an equal weight, but motionless on the end of the apron. They also make it possible to take into account any hyperstaticity of the deck on its supports.

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  Different correspondence laws can be provided for different passage speeds. In this case, the method provides for an evaluation of the speed of movement of the axle having produced the sudden dimensional variation. The speed can be evaluated according to the time which separates the abrupt successive dimensional variations due to the passage of a vehicle, or also by a means of speed measurement, for example with doppler effect placed above the road, or according to the slope of the dimensional variation from the high level of the jump corresponding to the sudden dimensional variation considered to correspond to the passage of an axle. In fact, during the sudden dimensional variation, the high level corresponds to the presence of the axle on the bulkhead and the low level to its absence. From the high level, the axle moves away from the end towards the center of the apron and the stress on the support decreases at a speed (slope of the timing diagram of the deformation detection signal) which is a function of the speed movement of the vehicle. In the other direction of travel, the stress increases until the axle reaches the end of the bulkhead (last line of support), at which point

  the stress due to this axle suddenly disappears.

  Depending on the speed determined for the vehicle, or on the speed range within which the vehicle speed is situated, the appropriate law of correspondence is chosen to match a measured axle weight to a sudden

  dimensional variation detected.

  In some cases, the actual law of correspondence between the abrupt dimensional variation and the weight of the axle 30 can drift over time. For example, neoprene supports can become less eléatique. It can also happen that the road joint between the end of the deck and the road on dry land deteriorates over time, which can modify the dynamic effect when the axle passes. The response curve of the detectors can itself drift over time. It is provided according to the invention to keep, preferably automatically, at least one statistic on the evaluations

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  of weight performed. If, for example, the average weight recorded has a difference in excess of a predetermined setpoint exceeding a predetermined value, it is deduced therefrom that a recalibration is necessary. Such recalibration can be carried out automatically as a function of the difference observed and the

sense of this gap.

  In a preferred version of the method according to the invention, the trains of dimensional variations are identified which are

  caused by successive axles in the same vehicle.

  We can thus calculate the total weight of a vehicle by adding the weights applied to the ground by its different axles. According to a second aspect of the invention, the device for measuring the weight applied to the ground by at least one vehicle axle, is characterized in that it comprises: - input means for receiving at least one signal from input representative of a deformation as a function of time and - processing means which transform a value 20 of abrupt variation of the input signal, into at least one output representative of an at least partial weight applied by a vehicle. Other features and advantages of the invention

  will emerge further from the description below, relating to nonlimiting examples.

  In the accompanying drawings - Figure 1 is a schematic view, partially in perspective with cutaway, showing an end of the bridge being crossed by a utility vehicle; - Figure 2 is an elevational view of the bridge of Figure 1, with illustration of part of the measuring device according to the invention; - Figure 3 is a view of the left end of the bridge of Figure 2, in an alternative embodiment of the device;

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  - Figure 4 is a cross-sectional view of the end of the bridge during the passage of two vehicles traveling side by side in the same direction; - Figure 5 is a timing diagram of the detection signal 5 of the vertical support compression recorded by a detector of the device according to the invention in the situation of Figure 1; FIG. 6 is a timing diagram of the vertical compression detection signal after the whole vehicle has crossed the first support line of the bridge; FIG. 7 is a timing diagram of the signal for detecting the vertical compression at the other end (last support line) of the apron after this other end has been crossed by the same vehicle - FIG. 8 shows, on a time scale more small, the chronogram of the trains of variation of the detection signals produced by three vehicles having successively crossed the first support line of a bridge; FIG. 9 is a view associating the two timing diagrams relating to the signals for detecting the compressions of the two supports of the same end of the apron during the simultaneous passage of two vehicles, one on the left lane and the other on the right lane, respectively; and FIG. 10 is an example of a simplified flow diagram 25 for processing the input signals and for developing the

  device control and output signals.

  In the example shown in Figures 1 and 2, a road bridge comprises a deck 1 whose upper surface is constituted by a roadway 9d. In the example, it is assumed that the roadway has a width corresponding to two traffic lanes. Still by way of simple example, the two lanes are assumed to be intended for the same traffic direction. The length of the deck 1 is its dimension measured parallel to the direction of circulation, and the width of the deck 1 its horizontal dimension perpendicular to the direction of circulation.

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  At each end of its length, the deck 1 rests

  by two supports 2 on a shoulder 3 of the abutment 4 of the bridge.

  The end of the deck 1 which is crossed first (FIG. 1 and left part of FIG. 2) by a vehicle such as the utility vehicle 6d, traveling in the intended direction, constitutes the first support line of the bridge. More specifically, 2d is called the support located under this first end and near the right longitudinal edge, relative to the direction of circulation, of the deck 1. We call 2g the support located under 10 this same end of the deck 1 but close to its left longitudinal edge. The other end of the deck 1 (right part of Figure 2) constitutes the last support line of the bridge. Beyond the ends of the deck 1, the pavement 9p of the deck 1 continues with a pavement 9av before the bridge and by a pavement 9ap after the bridge, the pavements 9av, 9p and 9ap

  together constituting "pavement 9".

  In accordance with the invention, a respective detector 11 has been installed between the underside of the deck 1 and the shoulder 3, along each support 2, 20 11. The detector associated with the support 2d is called more particularly lld, and calls llg the detector associated with the 2g support (figure 1). Each detector it is, for example, in accordance with EP 0 649 000, and in particular of a type transforming a dimensional variation into a modulation of the light power restored by an optical fiber. The detectors 11 are installed so as to detect the variations undergone by the vertical dimension of the supports 2

  with which they are respectively associated.

  In the variant shown in FIG. 3, which relates more particularly to the case of supports 2 having a great stiffness, the detector 11 is an optical cord preloaded to extension, for example according to EP 0 264 622, arranged vertically on a few meters in height between an anchor 12 on the underside of the deck 1 and an anchor 13 in the front face 35 of the abutment 4 of the bridge. With this arrangement, the deformation in vertical compression detected includes the compression of the support 2 and the compression of the abutment between the shoulder 3 and a horizontal plane passing through the anchor 13. An increase in vertical compression produces a reduction in the prestressing extension of the optical fiber and therefore an increase in the light power restored by the optical fiber. The device according to the invention comprises a processing unit 14 comprising inputs 16 for receiving the signals coming from the detectors such as lld, llg, and one or more outputs 17 connected to a video screen 18 10 for displaying the measurement, to a camera with flash 19 for taking pictures of infringing vehicles, or others, such as audible or visual alarm, automatic barrier closure, etc. The processing unit 14 comprises means 15 for developing from the signals received on the inputs 16 one or more signals on the output 17 which are representative of the weights transmitted to the roadway by the vehicles crossing

the end of the bridge.

  FIG. 5 is a timing diagram of the signals 20 representative of the dimensional variations recorded by one of the detectors lld or lg, for example the detector lld,

  in the situation shown in Figure 1.

  We called ti the instant when the wheels of the front axle 21 of the vehicle 6d crossed the first support line to come to rest on the bulkhead 1. We suppose that before the instant t1 the compression noted was zero , that is to say that the origin of the deformations is the compression state of the support 2 of the deck 1 under the weight of the deck 1 when none

  vehicle is not on deck 1.

  When the axle 21 is supported, this causes a sudden dimensional variation designated by BV1. In theory, this variation in deformation is equal to

Q * PE21 / K

  expression in which Q is a factor, between 0 and 1, representing the fraction of the weight of the axle which relates to the support considered; il 2845156 PE21 is the weight of the vehicle which is transmitted to the ground by the axle 21; and

  K is the elastic constant of the support 2 considered.

  If the variations in deformation of the two supports 2d and 2g are simultaneously measured, we can add up these two deformations and consider that then the total deformation is equal to

PE21 / K

  Knowing K on the one hand, and knowing on the other hand the law of correspondence between the levels at the signal and the levels of deformation of the supports, this formula makes it possible to

  determine the weight PE2 directly, theoretically.

  The above calculations assume that the deck 1 is isostatically supported on the two supports 2d and 2g. In addition, their implementation requires, in most cases, calibrations concerning the value of K for the two supports 2d and 2g and concerning the response of each of the two detectors lld and llg to a given dimensional variation. Furthermore, the calculation is only precise if the value of K is the same for the two supports, and if the dynamic effects are negligible. This is why it is preferred, according to the invention, to carry out a prior calibration in order to establish at least one law of correspondence between each axle weight and the detection signals which account for the corresponding deformations on the two supports, when the vehicle is in the right lane and when the vehicle is in the left lane. In other words, according to the invention, it is preferable to pass detection signals directly, for example a variation of restored light power, to a weight evaluation, without necessarily seeking to know or the deformation

  real nor especially the corresponding real constraint.

  It is also preferred according to the invention, to establish a different correspondence law for each of several ranges of speeds of crossing the end of the deck

1 per vehicle.

  Thus, whether in a more or less theoretical manner or preferably on the basis of a prior calibration, the amplitude of the abrupt variation BV1 of the signal makes it possible to evaluate a weight transmitted to the ground by the front axle 21 of the vehicle. Then, as shown in FIG. 5, the deformation undergoes a progressive decrease phase VP, which corresponds to the fact that the front axle 21 moves away from the end of the apron 1 in the direction of the other end of the apron 1. The slope of this progressive decrease phase is substantially proportional to the speed of movement of the vehicle. This slope therefore constitutes an indication of the speed of movement of the vehicle and this indication makes it possible to select the law of correspondence between the abrupt 15 dimensional variations such as BV, and the axle weights in the case where several laws of correspondence have been pre-established.

  each associated with a range of traffic speeds.

  At time t2, the rear axle 22 of the tractor of the road combination 6d in turn comes to rest on the end 20 of the deck 1 and this results in a new abrupt variation BV2 (FIG. 5) in the direction of l increase in level of

support compression.

  FIG. 6 represents the situation a few moments later, when the entire road assembly 6d has engaged on the bulkhead 1. The three rear axles of the

  trailer 23, 24, 25 have each successively created sudden dimensional variations BV3, BV4, BV5. Like the abrupt variation BV1, each of the abrupt variations BV2, BV3, BV4, BVs is followed by a progressive decrease VP2, VP3, VP4, 30 vp ,.

  The signal thus collected for the entire vehicle comprises as characteristic elements, independent for example of the speed of the vehicle, the number of abrupt variations, the respective amplitude of each of the abrupt variations and their relative spacings parallel to the axis of the chronogram time. A set of characteristics of the signal generated by the

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  passage of the vehicle. This signature makes it possible to know the type of vehicle and therefore to refer to the total weight

  maximum driving allowed for this type of vehicle.

  Furthermore, as shown in FIG. 7, when the same vehicle arrives at the other end of the deck 1, there is a progressive dimensional variation VP1 as the axle 21 approaches the last support line and load progressively the corresponding end of the apron 1 until, at the instant t1j, the front axle 21 leaves the apron 1 and abruptly discharges said corresponding end thereof. This results in an abrupt dimensional variation BV1, which is in theory in an equal relation (or other if the law of correspondence is different) with the variation BV1 of FIG. 6, but occurring in the opposite direction. We will thus witness abrupt decreasing variations BV2, BV3, BV4, BV5 theoretically of the same amplitude as (or of amplitude for example proportional to) those of FIG. 6, and with the same time intervals between them if the speed of vehicle has not varied, or with time intervals proportional to those in Figure 6 if the vehicle speed has varied. When the last axle 25 leaves the apron 1, the dimensional variation as noted by the detector (s) returns to level 0

  corresponding to the rest of the deck 1 on its supports 2.

  It is provided according to the invention that the processing unit 14 having recorded the signature of the vehicle when it enters the apron 1 (FIG. 6) then recognizes this signature when the vehicle leaves the apron 1 (FIG. 7), compares the weights measured for each axle in both cases and produces a refined weight measurement. For example, the processing unit 14 takes as a refined measure of the weight applied by an axle the smaller of the two measured values, or the average of the two measured values, or the more likely or the

more usable of the two measures.

  If, for example, one of the two measurements was disturbed by the simultaneous presence of another vehicle, for example if an axle of one of the vehicles crossed one of the lines

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  extreme support of the bridge exactly at the same time as an axle of the other vehicle, the signature of a vehicle with n axles is then constituted by the abrupt n-1 variations which are not disturbed. For the n-th axle, the one of the two measurements is used which is not disturbed. FIG. 8 shows on a tighter time scale the sudden variations generated by three successive vehicles, namely the train T6d generated by the vehicle 6d, a train T26d generated by a private car or a light utility vehicle, and a train T36d generated by a second heavy commercial vehicle having a signature different from the

vehicle 6d.

  Analysis of this succession of signals makes it possible to determine time intervals corresponding to trains 15 T6d, T26d, T36d, during which abrupt variations follow one another with a variable time difference "e" but which never exceeds a determined value relatively weak. The processing device interprets each period during which abrupt variations follow one another, separated by such reduced time intervals, as corresponding to

  the duration of the crossing of the same vehicle, respectively.

  Between these durations, the processing device detects longer time intervals E corresponding to spaces between vehicles. According to the evaluation of the speed of circulation of the vehicles, obtained for example from the slope of the progressively variable parts VP of each signal train, or by a measuring means acting above the road, the the processing unit chooses a duration threshold between successive sudden variations beyond which it considers that there are two distinct vehicles. And in particular we give

  at this threshold a value which decreases when the speed of circulation increases. Thus, the maximum distance between two successive axles considered to belong to the same vehicle can be made constant and independent of the speed of movement of the vehicles.

  When the speed of circulation decreases and reaches very low values (case of a traffic jam), it is frequent

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  that the vehicles follow each other very close to one another and the distance between the last axle of one vehicle and the first axle of the next may even become smaller than the maximum possible distance between two successive axles of the same vehicle. In this case, you must either give up measuring the total weight of each vehicle, and only measure its weight applied to the ground by each axle, or use other means to distinguish the sudden variations that can be associated with each vehicle. It is also possible that even when the circulation speed is higher the progressively variable parts VP of the signal are too distorted

  to totally allow an evaluation of the speed.

  To remedy all this, it is proposed according to the invention

  presence detection means having a field of action above the roadway 9.

  For this purpose there is shown in Figure 4 and in part in Figures 1 and 2 a gantry 28 disposed above the end of the deck 1 and carrying in the center of its crossbar, a few meters above the longitudinal axis 20 of roadway 9, two presence detectors 29d and 29g, the detection axes of which are oriented one towards the left longitudinal edge of the roadway, the other towards the right longitudinal edge of the roadway, both towards the bottom and (Figure 2) backwards. The detection axis 31d of the detector 29d is cut by the vehicle 6d traveling on the right lane while the axis 31g of the detector 29g is cut by a vehicle 6g (FIG. 4) traveling on the left lane. Thanks to the tilt backwards (FIG. 2), very small differences, for example between the cab of the tractor of a vehicle such as 6d and the semi-trailer coupled to this tractor are not

  detected and are therefore not interpreted as an interval between two different vehicles. Tilting forward, relative to the direction of travel, would produce the same result. The result of the detection can be sent to the processing unit 14 by a third of the inputs 16.

  When the detection axis 31 of a detector is not cut, the processing unit 14 considers that there is an interval between

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  two successive vehicles. Consequently, the processing unit 14 assigns to the same vehicle, subject to the means which will be described below to discriminate vehicles traveling side by side on the two lanes of roadway 9, the sudden variations in stress / deformation which follow one another without being interrupted by an interval between vehicles. We will now describe with reference to FIG. 9 the means for discriminating between two vehicles traveling side by side. FIG. 9 shows one above the other the vehicles 6d and 6g in their relative positions as far as the longitudinal direction is concerned. Graph dd shows the stress / strain variations recorded by the right detector lld and graph dq the stress / strain variations recorded by the left detector llg. As the vehicle 6d travels on the right lane, it mainly carries its weight on the support 2d on the right, while the vehicle 6g traveling on the left mainly carries its weight on the support 2g on the left. Each axle passage 20 produces an abrupt simultaneous variation on the two detectors 11d and 11g. However, when the axle producing the abrupt variation belongs to the vehicle on the right 6d, the abrupt variation recorded is greater on the graph dd than on the graph d. On the contrary, when the axle 25 belongs to the vehicle on the left 6g, the sudden change is

  stronger on graph d. as on the graph dd. The processing unit therefore assigns to one or the other vehicle each axle and the associated weight as a function of a comparison between the sudden variation detected by the detector 11g and that detected by the detector 11d.

  FIG. 10 shows a schematic flowchart which can be implemented in the unit of

treatment 14.

  In a step 41, the presence of an abrupt variation in the signals arriving by the inputs 16 is detected.

  Step 42 consists in finding whether the sudden variation detected is greater on the 2d support or on the support

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  2g, to determine the traffic lane used by the vehicle whose axle produced the sudden change (step 43). In a step 44, the speed of circulation of the vehicle is determined, for example for an effect device

  Doppler having a field of action above the road.

  In step 46, the weight applied by the axle is determined by selecting in a memory 47 for the laws of correspondence the law corresponding to the speed evaluated in step 44. The weight applied by an axle traveling on the left track and PEd the weight applied by an axle traveling on the right track. The determination takes into account the two signals dd and d. One can for example add the two charges corresponding to the two abrupt 15 variations respectively if there is a law of correspondence for each support. As a variant, there may be for each speed range a single law of correspondence, but more complex, giving a weight for each combination of two

  sudden variation values on the two detectors.

  In step 48, the evaluated weight PEd or PE9 is communicated, for example so that it is displayed on the screen 18 in FIG. 1. In step 49, a test determines whether the weight calculated for the axle exceeds a predetermined PELIM limit. If yes, an "alarm / action" step 51 is carried out, consisting of

  example to trigger the camera 19. If no, or again if yes but after step 51, step 52 adds the axle weight PEg or PEd to the value of a parameter PTg or respectively PTd representative of the total weight of the vehicle passing the end of the bulkhead.

  Then, a test 53 determines whether the axle whose weight

  has just been evaluated is the last axle of the vehicle. One of the methods described above is used for this. If not, we return to step 41 while waiting for the next axle.

  If on the contrary the axle which has just been measured is the last of the vehicle, we go to a step 54 of communication of the total weight PT9 OR PTd of the vehicle, for example for

display on the screen 18.

  A step 56 calculates the new average (M (PT)) of the total weights of the vehicles having crossed the bridge, for example in the last three months. A test 57 checks whether the new average has a deviation greater than or equal to a predetermined value Ec with respect to a setpoint C. If yes, we conclude that there has probably been a drift of the device and we initiate a self-calibration step 10 58 which modifies the laws of correspondence contained in the memory 47. In addition, we reach the negative output of the test 57 to go to another test 59 which checks whether the total weight PTg or PTd exceeds a total weight limit PTLIM authorized on the bridge. And if so, an "alarm / action" step 62 15 is carried out, consisting for example of an activation of the camera 19. If the weight limit PTLIM is not exceeded, or after step 61 s '' it is exceeded, the parameter PTg or PTd is set equal to zero and we return to step 41

  wait for the next sudden change.

  Of course, the invention is not limited to the examples

described and represented.

  For example, one could evaluate the speed of movement of vehicles based on the time between two sudden variations belonging to the same variation train. 25 In the software, if the speed of the vehicle is determined by an analysis of the peculiarities of the train of dimensional variations, the elaboration of the measurement must be slightly delayed in time compared to the collection of the

detection signal.

  In general, the invention has the merit of having discovered that the end of the deck of a bridge can serve as a means of direct transmission of vertical forces between a vehicle axle and a load-bearing structure which the invention uses like a dynamometer. As a bridge, the invention encompasses works which would consist of a very short deck installed on supports above a hollowed-out part of the underlying infrastructure for the sole purpose of measuring the weight of the vehicles. in circulation. It is also part of the invention to mount the device on a bridge-type structure located upstream of a more fragile structure so that overloaded vehicles can be intercepted before reaching the structure

  more fragile. It is also within the scope of the invention to equip a device according to the invention with several works located on different possible routes between two sites, to prevent overloaded vehicles from making detours 10 to avoid an equipped bridge.

  Within the meaning of the invention, the weight measurement can consist of a simple binary signal, the low level of which corresponds to a weight in accordance with the regulations and the high level of a weight exceeding an authorized limit. 15

Claims (25)

  1 - Method for measuring the weight applied to the ground by at   minus one axle (21-25) of the vehicle (6d, 6g), characterized in that the sudden dimensional variation is detected (BV1, ...   BV5) undergone by a vertical dimension of a structure of a bridge below an extreme support line materialized by one end of an apron (1) of the bridge, this sudden variation being produced when the axle crosses said line support 10 extreme in the course of road traffic.   2 - Method according to claim 1, characterized in that   that in order to detect the dimensional variation, a variation in vertical dimension is detected of a support (2, 2d, 2g) interposed between the deck (1) of the bridge and a bridge abutment (4) 15 supporting the end of the deck.   3 - Method according to claim 1 or 2, characterized in that a variation in vertical dimension of a bridge support is detected, in particular a bridge abutment (4),   supporting the end of the deck (1).   4 - Method according to one of claims 1 to 3,   characterized in that, to detect the dimensional variation, a detection mode using an instantaneous appearance and transmission of a detection signal is used between a detection site at the end of the apron and a signal processing site.   - Method according to claim 4, characterized in that said detection mode uses the alteration of a light signal.   6 - Method according to one of claims 1 to 5, 30 characterized in that the dimensional variation is detected in   at least two sites different from the width of the roadway (9)   along the extreme support line.   7 - Method according to claim 6, characterized in that the dimensional variation is detected by associating a deflectometer (lld, llg) with each press (2d, 2g) of the end   of the deck (1) embodying the extreme support line. 21 2845156   8 - Method according to claim 6 or 7, characterized in that one detects the presence of two vehicles (6d, 6g) rolling side by side according to a different distribution of the abrupt dimensional variation generated by their respective axles in the one and the other detection site, respectively.   9 - Method according to one of claims 1 to 7,   characterized in that the detection above the roadway (9)   presence of two vehicles (6d, 6g) traveling side by side.   - Method according to one of claims 1 to 9, 10 characterized in that by analysis of signal representative of the   dimensional variation the speed of passage of the vehicle is determined. II - Method according to claim 10, characterized in that   that the vehicle speed is evaluated according to the duration between successive abrupt dimensional variations (BV1, ..., BV5).   12 - Method according to claim 10, characterized in that   that the speed of the vehicle is evaluated according to the slope of the timing diagram of the dimensional variation signal (VP1, ... 5) created by the displacement of the axle on the area of the bulkhead (1) 20 adjacent to said end of the apron.   13 - Method according to one of claims 1 to 12,   characterized in that on the basis of a preliminary calibration the weight measurement is corrected as a function of the speed of the vehicle (6d, 6g).   14 - Method according to one of claims 1 to 13,   characterized in that one automatically recalibrates (58) a law of correspondence between a signal (BV1, ..., BV5) received as representative of the abrupt dimensional variation and an output (PEg, PEd) produced as representative of weight measurement.   - Method according to claim 14, characterized in that at least one statistic (M (PT)) relating to the   successive measurements carried out, and recalibration (58) is carried out as a function of the difference between the statistic (M (PT)) and a setpoint (C).   16 - Method according to one of claims 1 to 15,   characterized by a train identification step (T6d, T26d, 22 2845156   T36d) of dimensional variations as being caused by   successive axles (21, ..., 25) of the same vehicle (6d).   17 - Method according to claim 16, characterized in that one identifies as corresponding to an interval between two successive vehicles a time interval (E) sufficiently   large without abrupt dimensional variation.   18 - Process according to claim 17, characterized in that   that a time threshold beyond which a time interval is considered to be sufficiently long is varied as a function of the estimated speed of the vehicle.   19 - Method according to claim 16, characterized in that by detection means (29d, 29g) having a detection field above the roadway (9) the presence of a vehicle is detected above said end of the bulkhead (1) and for the identification step, the stress variations having their origin on a traffic lane are assigned to the same vehicle while the presence of the same vehicle is detected there.   - Method according to one of claims 16 to 19, 20 characterized in that the total weight of the vehicle is measured by   dealing additively with the values (PE., PEd) each obtained in response to one of the abrupt variations   dimensional (BV, ..., BV5) of the train (T6d).   21 - Method according to one of claims 16 to 20, 25 characterized in that:   - there is a first line of support on the bridge with a signature of a vehicle (6d) approaching the bridge, composed of elements (BV1, ..., BV5) characteristic of the dimensional variations caused by the passage of the successive axles 30 (21-25) of the vehicle; - the passage of the same vehicle is detected at a last support line on the bridge according to a corresponding signature; - we take into account the detections carried out at both   support lines to develop a refined measure of the weight applied by each axle.   22 - Device for measuring the weight applied to the ground by at least one axle (21, ..., 25) of the vehicle (6d, 6g), characterized in that it comprises - input means (16) for receiving at least one input signal representative of a dimensional variation as a function of time; and processing means (14) which transform a   abrupt variation value of the input signal, in at least one output (PEd, PEgI PTD, PTg) representative of an at least partial weight applied by a vehicle.   23 - Measuring device according to claim 22, characterized in that the device comprises association means for associating several abrupt variations with the same vehicle, means (52) for adding the weights (PEd, 15 PEg) applied by the successive axles (21, ..., 25) of the same vehicle, and means (54) for providing at least one   output representative of the total weight of a vehicle.   24 - Measuring device according to claim 23, characterized in that the association means comprise means for analyzing the input signal between the abrupt variations. - Measuring device according to claim 24, characterized in that the analysis means take into account   the durations (e, E) between sudden variations.   26 - Measuring device according to claim 24, characterized in that the association means take into   counts the signal slopes between abrupt variations.   27 - Measuring device according to one of claims   23 to 26, characterized in that the association means 30 comprise presence detection means (29d, 29g)   intended to be installed to have a field of action above the roadway (9).   28 - Measuring device according to one of claims   22 to 27, characterized in that the at least one representative output 35 comprises a binary signal, and the device comprises alarm and / or action means (19) sensitive to one of the levels of the binary signal. 24 2845156   29 - Measuring device according to one of claims   22 to 28, characterized in that the input means receive at least two input signals (dd, dg) and the processing means (14) take account of the sudden simultaneous variations 5 of the two input signals to evaluate the weight applied by an axle.   - Measuring device according to claim 29, characterized in that the processing means produce signals representative of the respective weights of two vehicles 10 (6d, 6g) substantially simultaneous by forming two sums (PTd, PT.) In each of which are added the values corresponding to the sudden variations which are distributed substantially in the same proportion between the two signals input (dd, dg).   31 - Measuring device according to one of claims   22 to 30, characterized in that it comprises means self-calibration (58).   32 - Measuring device according to claim 31, characterized in that the self-calibration means (58) 20 modify a law of correspondence in the event of deviation exceeding a predetermined value (Ec) between a statistic (M (PT) ) sure   the weights recorded and a pre-established setpoint (C).