DEVICES FOR CALIBRATING THE DECELERATION OF COLLIDING VEHICLES

Abstract: Devices (A, B) providing a calibrated deceleration according to the colliding vehicle, used for the controlled displacement of road safety barriers, of the New Jersey type, installed on the sides of a bridge, and in particular those made of concrete (1, 1') or steel. The components of the devices (A, B) are fixed to the base of the modules making up the barrier and/or to the curbstone (2), and allow the displacement of the barrier, for several centimetres, notwithstanding its high weight, also in case of an impact caused by an automobile whose impact energy is less than 65-70 kJ. The purpose of said devices is that of allowing the displacement of the barrier through a reduction of the friction forces.

Description: Devices for cal ibrating the deceleration of col l iding veh i c I es Techn i ca I Field The present invention relates to devices to be mounted on road safety barriers of the New Jersey type, installed on a bridge, so that the barrier, besides redirecting the path of the col l iding vehicle towards the carriageway and ensuring the vehicle confinement to the latter, wi l l also be able to displace itself even under small energy impacts, thereby decelerating the vehicle within acceptable l imits for the passengers, and reducing to a minimum the probability of injuries. In particular, the devices can be used on concrete-made New Jersey type barriers installed on the sides of a bridge, said barriers having a considerable weight, comprised between 450 and 1200 kg/ , and providing for this reason a higher resistance to their displacement, upon impact by a vehicle; the basic concept of the invention is also more generally applicable to steel- made New Jersey barriers (about 150kg/m). Background Art It is generally known that safety barriers, in particular those to be instal led on the sides of bridges, must nowadays satisfy strict high energy absorption requirements of about 600 kJ, in order to prevent goods vehicles, having a high centre of gravity and a weight above 40 tons, from vaulting the barrier. High resistance barriers are consequently very rigid upon impact by a light vehicle (automobile with a weight of from 800 to 1500kg), even at very high speeds. In case of energies up to 70kJ, no confinement and energy absorption problems are encountered, but the decelerations acting on the passengers may be very high and fata I . Concrete-made or steel-made safety barriers, of the New Jersey type and used nowadays on the sides of a bridge, are designed to displace themselves, and are connected for this purpose to the supporting curbstone only by means of some ducti le anchor means, which must break, but in case of many accidents involving automobiles the very low energies involved are not sufficient to "trigger" the isplacement of the barrier and to deform and subsequently break the ductile anchor means by means of a traction or a shearing force. The barriers suited to retain heavy goods vehicles, with a weight comprised in the interval from 3 to 44 tons, may represent a fatal obstacle (due to their rigidity) in case of a col l ision by an automobi le whose weight is within 800 to 1500 kg. On the other hand, it is obvious however, that in the field of safety barriers for roads, and specifically in the case of barriers for bridges, the most important problem is to obtain protection and prevent vaulting, for the whole variety of vehicles circulating on the roads, which have very different masses, velocities and d imens i ons . Therefore, the current barriers of the New Jersey type to be instal led on a bridge, are not suited to provide a calibrated deceleration imparted by the barrier to a l ight vehicle, upon impact of the latter with a considerable impact angle and high velocity; the impact energy of the l ight vehicle, which is high but not extremely high, may fai l to cause a displacement of the barr i er . In practice, the vehicle path is redirected, but the passengers may be severely injured or die, due to the high decelerations transmitted during the col lision. Disclosure of invention An object of the present invention is to provide, on New Jersey barriers instal led on bridges, and in particular on those made of concrete, specific devices having the task to control the decelerations occurring during the initial period of the col l ision, and in case of impact energies up to 70 kJ (ki lojoule). A further object of the present invention is to ensure the cal ibration of the decelerations for al l kinds of impacts, both for impacts due to automobi les and those due to goods vehicles; in this latter circumstance, but also in case of extremely high energies of the automobi les, the cal ibration of the decelerations must continue, unti l the possible breakage of the screw anchors. T is wide spectrum of possibi l ities of operation, involving cal ibration of the decelerations according to the nature of the col l iding vehicle, is the essence of the i nvent i on . In order to solve the above mentioned problems, according to the present invention there are provided devices in the form of runners or sl iding shoes, which are integral with the barrier's base and possibly also with the curbstone, and which may have different friction coefficients, different extension of their surface, and may be mounted in different locations on the module's base, different mounting systems, according to the app I i cat i on . Said devices or runners are preferably formed by plates fixed to the base of the barrier's module, and by plates of corresponding shape, located below the first mentioned plates, and fixed to the support, wherein, if desired, a sheet or layer of Teflon or of different material, of e.g. 500 micron of thickness, may be interposed between said plates, faci l itating the mutual sl iding and suited to reduce friction between the contacting surfaces, could also be employed. Alternatively, said plates could be fixed at the junctions between the modules, only to the module, or both to the module and the curbstone. In particular, the plates may be continuos and extend themselves from one end to the opposite end of each module, or they may be interrupted. It is possible to arrange the runners or sl iding shoes (which may be formed by plates) at the site of the ducti le anchor means of the barrier. In any case, the runners or sliding shoes may be located (below the barrier) on the side facing the carriageway, and/or on the opposite s ide. Instead of providing a circular hole, at the foot of the barrier's module, to al low for the passage of the ducti le anchor means (e.g. screw anchors), there is provided a slotted hole, obtained by increasing its length by 3-4 cm, and the anchor means wi ll not be arranged coaxial ly with respect to said slotted hole, but, on the contrary, they wi ll be positioned adjacent to the inner side, in order to al low a displacement -of some centimetres- of the barrier, on the sliding shoes, without inducing any kind of deformation of the anchor means during the initial period of the impact. Moreover, the nut of the screw anchor wi l l not be screwed tight, that is, it wi ll remain slack, in such a way that in the event of an impact by a vehicle, said displacement wi l l occur with a minimal resistance, which wi l l be proportional to the weight of the barrier multipl ied by the very low friction coefficient of the runners. In this particular embodiment of the devices for cal ibrating the decelerations according to the kind of colliding vehicle, it is possible, by limiting the transversal extension of the runners (with respect to the barrier), to arrange for the sl iding shoe fixed to the module to "descend" from the sliding shoe fixed to the curbstone, during the initial period of the col l ision (displacement of the barrier involving no deformation of the screw anchors), in such a way that it wi ll contact the concrete body of the curbstone; then, in the second period, the displacement is influenced by the forces required for deforming the anchor means and possibly, for breaking them, and also by the forces required to overcome the friction (which is much greater than in the first period) between the device (sl iding shoe) fixed to the module, and the concrete body of the curbstone . If after the second period the col l ision has not terminated yet, that is, if the energy has not been completely dissipated, also other elements of the barrier wi l l cooperate in order to resist to the impact, and these elements wi ll displace themselves according to the same mechanisms, providing the asymoptotic gradualness necessary for the decelerations produced on the veh i c I e. The inventive concept on which the invention is based may be appl ied not only to barriers for the sides of bridges, but also to traffic dividers or lateral barriers which are simply laid on the support, without using said anchor means. Brief Description of Drawings The present invention wi l l now be i l lustrated in greater detai l, only for i l lustrative and non l imitative purposes, by describing particular embodiments thereof, which are shown in the drawings, wherein.- Fig. 1 is a cross-sectional view of a barrier to be instal led on the sides of a bridge, according to the invention, the cross-section being taken at the site of a ducti le screw anchor; Fig. 2 is a cross-sectional iew (detai l A of Fig. 1) of the devices for cal ibrating the deceleration according to the invention, located on the inner side of the barrier (impact side); Fig. 3 is a cross-sectional view (detai l B of Fig. 1) of the devices for calibrating the decelerations according to the invention, located on the outer side of the barrier; Fig. 4 shows the displacement of the barrier of Fig. 1, during the first period of the impact; Fig. 5 shows the second period of the impact and the corresponding deformation of the screw anchor; Fig. 6 is a iew of the (final) third period, in which the barrier displaces itself whi le the anchor means is broken ; Fig. 7 is a cross-section of a barrier of the New Jersey type, wherein a plate which rigidly connects to each other two contiguous modules, is of the "wrapping" kind, and forms at the same time the device for cal ibrating the decelerations according to the present invention and to this particular embodiment thereof; Fig. 8 is a view simi lar to that of Fig. 7, in which case however, in order to further reduce friction, a Teflon sheet has been appl ied between the "wrapping" plate and a second plate fixed to the curbstone below the first pi ate; Fig. 9 is an enlarged iew of the detai l C of Fig. 8 Modes for carrying out the invention Fig. 1 shows a concrete-made New Jersey barrier 1, which comprises, as usual, several modules. In the situation shown in the drawing, said modules are fixed to the support or curbstone 2 through ducti le anchor means 3, which are already known and which in this specific case are formed by screw anchors. The screw anchors 3, or in general the ducti le anchor means 3, are fixed to the concrete of the support 2, by means of the expansion of their fins 4 inside the respective conical seat, as already known in the art. The screw anchors are introduced into the recess 5 and thereafter inside the hole 6 of the prefabricated module 1. The hole 6 has not a circular shape, on the contrary it is elongated or "slotted" in a transversal direction. Usual ly the screw anchors 3 are screwed tight by means of the nut 7 which is retained by the lock nut 8. The nut 7 is screwed tight against the washer 9, and the latter -as already known in the art- rests on a plate 10 (Fig. 4) embedded inside the concrete bulk of the prefabricated module 1. This plate 10 is also provided with a hole which is not circular, but elongated, that is slotted, in the transversal direction. Usually a rubber seal 11 is provided between the washer 9 and the plate 10 embedded in the concrete , in order to prevent the accumulation of water inside the hole 6 and inside the deformation space 12 associated to the screw anchor 3 with predetermined break resistance. T is water could cause corrosion of the screw anchor 3, in particular if it contains chorides which during the winter are spread on the road pavement to cause melting of t e ice. According to the invention, the plate 10 embedded in the concrete internal ly defines an elongated hole or slot 13 for al lowing the passage of the screw anchor 3, and the washer 9 is laid -if desired through the interposition of said seal 11-on the opposite edges of the slot 13 which have the smal lest distance with respect to each other (that i s , transversa I I y with respect to the longitudinal extension of the slot). As shown, the screw anchor 3 is not located in a coaxial position inside the hole 6, on the contrary, said screw anchor is located more externally with respect to the road pavement 14, adjacent to the wall of the barrier 1. Always according to the invention, the barrier 1 is provided between its base and the curbstone 2 with devices like runners or sliding shoes, denoted A and B, which are shown in the details A and B of Fig. 2 and Fig. 3. The device A, in the present embodiment, comprises an upper plate 15a and a lower plate 15b, both made of stainless steel, wherein the upper plate 15a is fixed to the module 1, and the lower one 15b is fixed to the curbstone 2. The fixing operation may be carried out using screw anchors (as shown in the figures) or in any other way, with an interlocking system, or by means of magnets, etc. It Is to be noted that the two plates 15a, b are of the same shape, and a Teflon sheet 17 (of e.g. 500 micron) is disposed therebetween. The Teflon sheet is suited to noticeably reduce friction and may be applied indifferently to the upper plate 15a or to the lower plate 15b. The device B has an identical structure. It is formed by an upper plate 16a fixed to the module 1, and a lower plate 16b fixed to the curbstone, between which a Teflon sheet 17' is interposed in a sand i ch- I i e fashion. It is obvious that the invention is not l imited to a particular form of the runners, to the materials disclosed or to the type of connection. Moreover, it is obvious that, even if Teflon is certainly advantageous, other materials having a low friction coefficient could also be employed. Possibly, the material 17 or 17' having a low friction coefficient, may be fixed on the plate 15 or 16 made of a different material, by means of a chemical treatment which forms a layer on the plate, etc. Even if in the Figs. 1 and 4-6 the runners A and B are centered with respect to the screw anchors 3, connecting the module 1 to the support 2, the position of the devices A, B could be chosen in a different way. Moreover, it can be appreciated that the runners could extend themselves along the whole longitudinal extension of the module, or in the transversal direction, thereby covering a distance which is much greater than that shown in the Figs. 2 and 3 and in Fig. 1. Also the weight of the barrier per (l inear) meter plays a fundamental role in the choice of the materials to be used for the runners A, B and in the choice of their configuration and/or their extension. The operation of the barrier according to the present invention wi l l now be explained with reference to Figs. 1,4,5,6. Since the nut 7 of the screw anchor is not tightened, in the event of an impact, the resistance provided by the barrier unti l the position shown in Fig. 4 is reached, wi l l be minimal, above al l because of the presence of the devices A, B. In the position of Fig.4, the barrier 1 has consequently moved backwards covering a distance of some centimetres, and the head of the screw anchor 3 has therefore shifted inside the elongated hole 13, to its end position (in abutment with the right edge of the slot). Thereafter, the screw anchor wi l l start deforming itself inside the deformation space 12, due to the "push" given to it by the foot portion 18 of the barrier, upon impact by a vehicle. During this second period (Fig. 5), the two upper plates 15a, 16a have already "descended" from the lower plates 15b, 16b, that is, they have "sl ipped" beyond the latter plates, so that the further displacement of the barrier 1, from the position of Fig. 4, to the position of Fig. 5, is infl enced by the friction between the runners and the concrete, which is much greater than in the first period. Fig. 6 shows the third and last period, during which the screw anchor is sheared (this case refers to an impact by a heavy vehicle). If we consider the case of vehicles of 800-1500 kg, provided the velocity is not high and the impact angle is not great, the displacement of the barrier wi ll terminate at the end of the first period, and this in turn wi ll mean that the deceleration is cal ibrated in accordance with this type of vehicle (automobi le), and the barrier 1 wi l l not behave as a rigid barrier, in contrast with the actual behaviour of conventional barr i ers. A second embodiment of the invention, which must also be considered non- I i in i tat i ve , is shown in Figs. 7, 8, 9. These figures show a vertical cross-section of a New Jersey barrier 1' made of concrete, laid on the support 2, and wherein the cross-section is taken at the junction between two modules of the barrier 1'. The two modules may be connected to each other at the foot of the barrier 1', by means of a steel plate having two holes, each one of them being centered with respect to a hole of a respective threaded bush embedded in the concrete of each module. As shown in Fig. 7, and according to the invention, the connection plate 20 also includes a horizontal lower portion 20a, so that, in fact, it forms an angle iron or "wrapping" plate, which also extends below the barrier, and possibly (as shown) as far as the opposite side 22 of the barrier. The plate 20 is fixed to the foot of the two contiguos modules, by means of bolts 23 which are driven in the threaded bushes 24 (one for each module even if the cross-section obviously shows only one of them) . The plate 20a acts as a runner, that is, it faci l itates the displacement of the modules 1', as has already been described in the first embodiment. Obviously, in this case too, the same provisions are made with regard to the elongated hole 6, the slotted plate 10 and the position of the screw anchor 3, which is located adjacent to the inner edge of the slots. The runner 20a may also be used for a lateral barrier or a traffic divider, which are simply laid on the ground. Figs. 8 and 9 show an alternative of the embodiment of Fig. 7. In this case, the plate 20, arranged below the base of the barrier 1', is not in direct contact with the curbstone 2, on the contrary, it is in contact with a Teflon sheet 25. The Teflon sheet 25, is laid, fixed or glued to a second stainless steel plate 26 fixed to the curbstone 2. The plate 26 may have a thickness which in general is less than that of the "wrapping" plate 20. The alternative or variant of the second embodiment of the invention, shown in the Figs. 8, 9, further reduces the resistance to an impact provided by the barrier 1', with respect to the situation shown in Fig. 7. A person skil led in the art wi l l obviously appreciate that the second embodiment of the invention shown in the Figs. 7, 8, and 9 wi l l not be l imited to a particular configuration of the runner 20a, to a particular material (a metal different from steel may also be used, etc.), to a particular size of the runner, to a certain type of fixing to the curbstone 2 of the other component 26 of the runner, the particular type of appl ication of a layer of material having a very low friction coefficient (e.g. a chemical process may be employed, etc. ) . The two embodiments shown in the drawings, are only i l lustrative and could also be combined to obtain, if desired, a "mixed" real ization, or they could be modified in a suitable way by providing, for instance, only the runner A or the runner B in the first embodiment, or el iminating altogether the Teflon sheet from the runners, thereby obtaining a device of the type "steel on steel" or "steel on concrete", etc. Actually, according to the specific features of different New Jersey barriers, l ike the weight or overall rigidity thereof, it wi l l be possible to obtain in each case a control led displacement and cal ibrated decelerations, by determining the number, the surface area and the location of the runners and the Teflon sheets .

Claims: CLA I MS 1. Safety barrier for roads, having a New Jersey profi le, and made of concrete or steel, characterized in that it comprises devices or runners (A, B) for the controlled displacement of the barrier (1, 1'), which are suited to cal ibrate the decelerations according to the type of coll iding vehicle and according to the time elapsed since the beginning of the impact, wherein said devices or runners (A, B) are fixed to the base of each module of the barrier (1,1 ') and/or extend between two modules, and possibly are fixed also to the support (2), and faci l itate the backward movement of the barrier (1, 1'), also upon impact by automobi les whose impact energy is less than 65-70 kJ. 2. Safety barrier for roads, having a New Jersey profi le, and made of concrete or steel according to claim 1, characterized in that said barrier is a lateral barrier made of concrete, of the New Jersey type, which can be instal led on the sides of a bridge, or a traffic divider. 3. Safety barrier for roads, having a New Jersey profi le, and made of concrete or steel, according to claim 1 or 2, characterized in that said devices or runners (20, 20a; 25, 26) which extend between two modules, are also used to connect to each other two modules of the barrier (1). 4. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claims 1 and 3, characterized in that the barrier is connected to the support (2) by means of ductile anchor means (3), which are not tightened at the foot of the barrier (1), in order to al low a displacement of the barrier involving a minimal resistance due to friction, during the first period of the displacement, said ducti le anchor means being inserted for this purpose in a shifted position with respect to the center of the hole (6) located at the foot of the barrier (1). 5. Safety barrier for roads, having a New Jersey profi le, and made of concrete or steel, according to claim 4, characte ized in that said ducti le anchor means (3) pass through a deformation chamber (12). 6. Safety barrier for roads, having a New Jersey profi le, and made of concrete or steel, according to any of the preceding claims, characterized in that said devices or runners include an upper plate <15a; 16a; 20, 20a) fixed to each module, or to contiguos modules, and/or a lower plate (15b; 16b; 26) fixed to the support (2), and possibly also a layer or sheet of material (17, 17', 25) having a very low friction coefficient, attached to the upper or to the lower p i at e . 7. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claim 6, characterized in that the runners extend in a continuos or discontinuos way along the base of the barr i er ( 1 , 1 ' ) . 8. Safety barrier for roads, having a New Jersey profile, and made of steel or concrete, according to claim 7, characterized in that the runner (20a, 25, 26) extends transversa I I y along the whole base of the barr i er . 9. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claim 6, characterized in that after a first displacement of the barrier (1) upon impact, the upper plate (15a; 16a) "descends" from the lower plate (15b; 16b) having the same shape, and comes in contact with the support (2), in such a way that the subsequent displacement of the barrier (1) will be influenced by a higher resistance due to friction, this effect being obtained by a suitable choice of the dimension of the plates (15a, 15b; 16a, 16b), transversa I I y to the longitudinal extension of the barrier. 10. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to any of the preceding claims, characterized in that said runners are fixed to the support (2) or curbstone, or to the modules of the barrier (1; 1'), using any ind of connection system, e.g. screw anchors, magnets, glues, or res ins. AMENDED CLAIMS [received by the International Bureau on 25 October 1999 (25.10.99); original claims 1-10 replaced by new amended claims 1-8 (3 pages)] 1. Safety barrier for roads, having a New Jersey profile, used on the side of bridges or as lateral barrier, made of concrete or steel, comprising devices or runners (A, B) for the controlled displacement of the barrier (1, 1'), which are suited to calibrate the decelerations according to the type of colliding vehicle and according to the time elapsed since the beginning of the impact, wherein said devices or runners (A, B) are fixed to the base of each module of the barrier (1,1') and/or extend between two modules, and possibly are fixed also to the support (2), and facilitate the backward movement of the barrier (1, 1'), also upon impact by automobiles whose impact energy is less than 65-70 kJ, characterized in that the barrier is connected to the support (2) by means of ductile anchor means (3), which are not tightened at the foot of the barrier (1), in order to allow a displacement of the barrier involving a minimal resistance due to friction, during the first period of the displacement, said ductile anchor means being inserted for this purpose in a shifted position with respect to the center of the hole (6) located at the foot of the barrier (1). 2. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claim 1, characterized in that said devices or runners (20, 20a; 25, 26) which extend between two modules, are also used to connect to each other two modules of the barrier (1). 3. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claim 1, characterized in that said ductile anchor means (3) pass through a deformation chamber (12). 4. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to any of the preceding claims, characterized in that said devices or runners include an upper plate (15a; 16a; 20, 20a) fixed to each module, or to contiguos modules, and/or a lower plate (15b; 16b; 26) fixed to the support (2), and possibly also a layer or sheet of material (17, 17', 25) having a very low friction coefficient, attached to the upper or to the lower plate. 5. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claim 4, characterized in that the runners extend in a continuos or discontinuos way along the base of the barrier (1, 1 ' ) . 6. Safety barrier for roads, having a New Jersey profile, and made of steel or concrete, according to claim 5, characterized in that the runner (20a, 25, 26) extends transversally along the whole base of the barrier. 7. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to claim 4, characterized in that after a first displacement of the barrier (1) upon impact, the upper plate (15a; 16a) "descends" from the lower plate (15b; 16b) having the same shape, and comes in contact with the support (2), in such a way that the subsequent displacement of the barrier (1) will be influenced by a higher resistance due to friction, this effect being obtained by a suitable choice of the dimension of the plates (15a, 15b; 16a, 16b), transversally to the longitudinal extension of the barrier. 8. Safety barrier for roads, having a New Jersey profile, and made of concrete or steel, according to any of the preceding claims, characterized in that said runners are fixed to the support (2) or curbstone, or to the modules of the barrier (1; 1'), using any kind of connection system, e.g. screw anchors, magnets, glues, or resins.

Inventors: BRUSCHI STEFANO, CAMOMILLA GABRIELE, BRUSCHI, STEFANO, CAMOMILLA, GABRIELE
Applicants: AUTOSTRADE CONCESS CONST, BRUSCHI STEFANO, CAMOMILLA GABRIELE, AUTOSTRADE CONCESSIONI E COSTRUZIONI, BRUSCHI, STEFANO, CAMOMILLA, GABRIELE
Application year: 1999
Main classification: E01F15
IPC codes: E01D19, E01F9, E01F15