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Field of the invention

The invention relates to the construction of road safety systems, in particular of side barriers arranged along the roads to retain vehicles within the carriageway in the event of accidents.

Prior art

Side safety barriers are installed along roads of various type and category to keep vehicles within the carriageway in the event of accident. Side protection barriers, also commonly named guardrails, must be certified in order to be installed along roads. In Europe, such certification is the CE marking. In order to obtain the latter, a road safety barrier must have some minimum requirements, among which there are: passing crash tests according to EN1317-1 /2 relative to the type of crash and involved vehicles, assembly performed according to the executive drawings of the elements constituting the protective barrier and production of the device according to a detailed production and control plan. In almost all European countries, in the installation of the barrier on the road, the stretch of the installed barrier must not be shorter than the stretch of the barrier which was subjected to real-scale crash tests and the type and quality of the barrier supports must be similar to those of the support used during the tests. The latter requirement is very difficult to guarantee during the step of installing on the roads because all the supports, both the barriers embedded into the ground and those anchored onto the curbs, are different from those used in the test. The problem is even more serious in cases in which the side barriers are installed on stretches of road on embankments, which are normally built using backfill soil. The consistency of this type of ground is thus different from, and almost always lower than, that of the ground of the test fields, which is normally flat, consisting of stabilized and well-compacted material. It is also worth noting that the support material in real cases, even when it is different from the soil, has a different consistency with respect to the deeper layer of ground on which the road is built. In order to overcome this problem, it is necessary to resort to costly, disruptive and often very complicated operations. The most common operations consist in: modifying the configuration of the ground, which is replaced by material having higher mechanical properties, elongating the barrier poles in part embedded in the ground and/or increasing the contrast surface of the pole. All these solutions, in addition to being very expensive and disruptive on the road structure, do not always guarantee that the behavior of the safety barrier in real installation configuration will be similar to that of the same barrier determined during the crash test. Although elongating the pole means anchoring it to the deeper layers, which are certainly more compact and consistent, in doing so it is not possible to guarantee that its behavior will be similar to that it had during the crash test.

The need is thus felt to find a technical solution which is cost-effective to make, the assembly of which is not excessively complex or costly, which can ensure a barrier road behavior compatible with that found during the crash tests in the certification procedure. This also in the case when the barrier is installed on ground which is morphologically different from that used for the tests.

Summary of the invention

It is the main object of the present invention to provide an anchoring device to the deeper layers of the road paving for the poles of road restraint systems which is cost-effective and simple to install.

These and other objects are achieved by means of an anchoring device to the non- superficial layers of the road paving for a safety road barrier supporting pole having its own longitudinal direction, wherein the device comprises a coupling element, adapted to be fixed at a predetermined height between base and top of said supporting pole when it is driven into a ground near a road, at last one rigid elongated element having a first proximal portion fixed to the coupling element and a second distal portion, with a surface provided with surface protrusions or with an increased friction roughness surface, adapted to be either immersed or driven under a road paving, in a direction either transversal or orthogonal to the longitudinal direction of the safety road barrier.

These and other objects are achieved thanks to another aspect of the invention which provides an assembly method of the aforesaid anchoring device having the features set forth in claim 7.

By virtue of the anchoring device solution to the ground for safety road barrier poles of the invention, the initial construction costs are greatly reduced, due to the simplicity of the device and to the limited number of elements which form it, and so are the installation costs, due to its simplicity.

Indeed, the installation procedure of the ground anchoring device of the invention can be performed with machines which are very common and could be easily performed manually, whereby reducing costs while guaranteeing a high degree of safety of the barrier which has supporting poles anchored with the device of the invention. The anchoring device can be easily installed on a safety barrier both during the first construction or renovation of a road or when it is necessary to reinforce pre-existing safety barriers along stretches of road which may be located on land of low consistency, guaranteeing in all cases a considerable increase in the retaining capability of vehicles, in particular in incidents in which a very high force component is released transversely onto the safety barrier, i.e. in particular in those cases in which the vehicle crashes are very close to the angular values of 90 ° with respect to the direction of the safety barrier.

The present invention allows to transfer onto the road the same ideal installation conditions obtained in tests without necessarily having to resort to the costly and disruptive operations described above (increase of the resistant surface of the pole/ground system and/or redevelopment of the road margin).

Among the advantages of the invention there is an increase in the capability of the safety barrier to withstand high-intensity stresses, above all those directed transversely, or even orthogonally to the safety barrier which tend to pull it out from the ground, and this advantage is obtained even when the safety barrier is driven into less compact or consistent soil. This is because the anchoring device of the invention allows a coupling to the non-superficial layers of the road paving, under the carriageway, which are made of materials of higher consistency and quality, or to the deeper soil layers underneath and thus having superior mechanical properties to those of the surface ground flanking the carriageway.

By virtue of the device of the invention, in case of a crash of a vehicle on the safety barrier with a very strong component transverse to the safety barrier, the forces are not released only on the ground which holds the supporting pole but are also transmitted to the deeper layers of the road paving (bed, base and foundation levels) being the elongated rigid elements or the bars planted transversely to the longitudinal direction of the safety barrier. In general, the bars are arranged in an inclined manner in respect to the horizontal or to the plane of the carriageway as is shown in the figures. This arrangement increases the crash resistance capability of the supporting poles reinforced by an anchoring device of the invention. However, they may be planted horizontally, if the ground so allows, without departing from the scope of the invention. In this manner, the supporting pole bends in the zone in which the anchoring device is fixed, plastically deforms and dissipates the energy of the crash. This prevents the supporting pole embedded in yielding ground, having poor mechanical properties, from rotating rigidly and being pulled out as a result of the action consequent to the transverse crash or to the high transverse component. The low consistency of the ground, in the absence of the device which is the object of the present invention, is not an effective constraint for the pole. Accordingly, the latter does not apply its crash resistance function in a transverse direction as provided in design. On the other hand, the use of the anchoring device ensures the correct operation of the safety barrier and the formation of the plastic hinge at the height provided by the designer. The bending point is higher, the higher the coupling element of the anchoring device.

The solution offered by the invention can be made at low costs with regard to manufacturing and to installation and maintenance. It can be used on newly built systems and on systems already present in situ.

Another non-irrelevant advantage is to provide a minimum visual impact and practically zero dimensions on the road surface, which is not at all changed because the coupling element may be fixed very low onto the supporting pole or even on ground level or even underground, but in all cases close to the road. The coupling element of the anchoring device which is the object of the present invention does not require any replacement, disassembly or modification of the poles already installed or of parts of them.

The distal portion of the rigid elongated element or bar is usually either driven or immersed under the road paving transversely to the direction of the safety barrier because in this manner the anchoring device of the invention can withstand the crash components in an optimum manner caused by vehicles crashing in transverse direction, in particular when the crash is orthogonal or nearly orthogonal to the direction of the safety barrier. It is disadvantageous to arrange the rigid element or the bar with an angle of small value, or even more so equal to 0 °, with respect to the longitudinal direction of the safety barrier since this arrangement provides a low resistance to transverse crash forces.

The elongated element is generally a round section bar provided with an external thread on the surface to facilitate screwing into the ground and to increase the force needed to extracting it from the ground and arranged in a transverse to the direction of the safety barrier, or substantially orthogonal is pushed or embedded almost always under the carriageway itself. It may also be a bar provided with hooks or discs or surface projections of different shape to a thread, but also to increase the grip in the carriageway or in the ground to increase the force needed to extract it. It can also be a bar with outer surface free of macroscopic added protrusions but left untreated so as to facilitate the friction with the ground into which it is driven.

The elongated element may also not be single, but even two or more can be installed, as needed, according to the structural needs of the road safety barrier. The dependent claims refer to preferred embodiments of the invention.

The object of the present invention relates to one or more contrast systems placed at the point in which the formation of the plastic hinge and the increase in the resistance to thrusts or impacts with high value transverse components is necessary for the correct operation of the restraint device.

Brief description of the figures

Further features and advantages of the invention will be more apparent in view of the detailed description of a preferred, but not exclusive, embodiment of a pole anchoring device illustrated by way of non-limiting example, with the aid of the accompanying drawings, in which:

Figure 1 shows a diagrammatic, axonometric view of an anchoring device according to the invention;

Figure 2 shows a vertical section view of an anchoring device according to the invention;

Figure 3 shows a plan view of an anchoring device according to the invention;

Figures 4, 5, 6, 7, 8, 9 show various contrast systems of the anchoring device according to the invention. Figures 10, 1 1 , 12, 13, 14, 15, 16, 17, 18 (tie-rods) show variants of the anchoring systems with screws or the like;

Figures 19 and 20 (cross section 1 and 2) show two different types of installation (one with screwing tie-rods and one with abutting tie-rods with examples of tie-rods with and without protrusions) of the anchoring device according to the invention. Same reference numbers in the various figures correspond to the same elements or components.

Detailed description of example embodiments of the invention

Figure 1 , in particular, shows a safety barrier indicated as a whole by reference numeral 1 , commonly also named guardrail, which comprises a longitudinal bar 2, of the type well known in the road construction art and a pole 3 onto which the longitudinal bar 2 is fixed by means known in the field of technique, for example, but not exclusively, by means of screws, bolts, welding. The pole 3, by means of its end 3' is intended to be fixed to the ground by the sides of the road carriageway. The pole 3 may be fixed to the ground by driving, pushing or hammering or by immersion in the casting of cement or asphalt or other material with which the road superstructure is made.

Fig. 1 and fig. 3 show only a very short stretch of a road safety barrier, it being quite apparent to a person skilled in the art that for understanding the invention it is sufficient to refer to a short stretch as shown in the figures because the invention may also be applied to barriers without any limitation of length. Generally, these types of safety barrier are also commonly called guardrails. Such safety barrier defines a longitudinal direction, which is generally parallel to the lane of the road along which it is built.

The anchoring device, indicated as a whole by reference numeral 10 and generally made of metal, in particular steel alloy, comprises a bracket 13, or a tie or collar and, advantageously, two tie-rods 1 1 and 12. The number of tie-rods may be reduced to only one and in case of particular types of materials constituting the road superstructure they could be in number greater than two, without departing from the scope of the invention. The length of the tie-rods may be chosen as a function of the needs, generally it should be sufficient to reach the ground layers which are more compact, as well as the shape, which can be either entirely straight or provided with curved portions.

The tie-rods 1 1 , 12, made of any material or alloy or any metal section, are connected at one end with the bracket 13, e.g. by means of nuts 14', 14" screwed onto a thread provided at least on the end portion of the tie-rod. It is not excluded that the tie-rods 1 1 , 12 are welded to the bracket 13, if the assembly of the anchoring device permits, e.g. in those cases in which it is immersed in the concrete casting during the road construction.

The bracket 13, instead of a simple plate, may also be advantageously made in the form of a ring, the bar 30, yoke, etc. also to take the size and shape of the cross section of the pole 3 into account. The bracket 13 may have different shapes or sections, e.g. C-shaped (element 13"'), U-shaped (element 13"), L-shaped (element 13') and can also be a cord 31 of any material having the necessary strength, can be a hollow or solid cylindrical element. Holes are provided in the elements 13, 13', 13", 13"' to allow guiding and correctly mounting the tie-rods or bars in the ground in the direction transverse to the longitudinal direction of the safety barrier, see figs, from 4 to 9. The bracket 13 may also be formed by a plate and a counter-plate, as in fig. 8, connected to each other by means of two elements.

A particularly advantageous embodiment of the anchoring device consists of two tie-rods 1 1 , 12, or more in general of two bars of cross section which may be as varied as possible, L-shaped, C-shaped, H-shaped, etc. which may be provided with surface protrusions of various kinds to promote the grip on the material of the ground or the paving layers in which they are immersed with the surface of the tie-rods. Particularly, these surface protrusions in radial direction may consist of a thread formed on the surface of the tie-rods 1 1 , 12: this thread may be advantageously formed as a spiral surface with thin but very high thread, since the anchoring device must be always screwed into the ground or into materials which are not very compact, non-limiting examples are shown in Figs, from 1 to 4.

The tie-rods 1 1 , 12 can also be helical or half-helical screws, micropiles or steel tubes or other alloys and materials which guarantee adequate resistance to tensile loads. Other types of sections made of steel or any other material or alloy can be used without departing from the scope of the invention.

Other embodiments of the tie-rods are anchor-shaped or hook-shaped on the tip as shown in figs. 10, 1 1 , 13, 14, 18, or C-shaped or U-shaped portions, or the spiral may be formed by winding a further bar of any diameter on the tie-rod along part of the length or along the entire length, as shown for example in figs. 10, 1 1 . The tie-rods can also be cords or have elements such as plates, half-plates and the like, as shown in figs. 12, 15, 16, 17, of the fixed type or which open once inserted into the ground in order to promote more grip. Other embodiments which increase the grip of the tie-rods 1 1 , 12 with the ground are possible, such as the use of resins, either expanding or not, which grip the surrounding ground when they dry. Some other alternative forms of fixing to the ground of the tie-rods 1 1 , 12 are shown in Figs. 19 and 20

It is apparent that such surface protrusions must not have a radial size such as to prevent the driving into the ground by hammering or screwing, it being preferable to promote the production of a sufficient grip of the tie-rods for withstanding the traction by virtue of the careful selection of the length of the part immersed in the ground. Naturally, the choice of the length and diameter of the tie-rods 1 1 , 12, is determined by the morphology and type of ground into which poles are driven, the shape of the tie-rods and the mechanical properties of the lower layers of the road paving and/or the ground below the paving and the ability to produce sufficient friction between ground and surface of the tie-rods 1 1 , 12, both when they are inserted by hammering or when they are screwed, as is well known to the person skilled in the art.

The anchoring device is intended to be mounted along the pole at an appropriate height with respect to the road surface and with a suitable angle of inclination with respect to the horizontal which can be comprised between 0 ° and 70 ° approximately, to allow an effective reinforcement of the constraint imposed by the ground, e.g. as is shown in fig. 2. If it is necessary and desired, the bracket 13 may also be arranged below the level of the ground, so as not to be visible from the outside e.g. as in figures 19 and 20.

The anchoring device 10 for poles, after assembling a safety barrier on the poles 3, in case of a crash of a vehicle with the barrier allows to transfer most part of the stresses to the road superstructure, as can be easily understood from the pattern of distribution of the forces shown in figure 2. The force caused by the crash of the vehicle on the barrier 1 , indicated by the arrow 20, is transferred to the ground with a pair of forces which may be approximately indicated with arrows 21 and 22. The force shown by arrow 21 is released as tensile force on the tie-rods 1 1 and 12, which are constrained to the non-superficial layers of the paving 15, which can absorb such traction better than the backfill ground of the embankment 16 does, while the strength represented diagrammatically by arrow 22 is released as compressive force on the backfill ground which transfers it to the road superstructure. In all cases, tie-rods 1 1 and 12 of the anchoring device prevent the pulling out of pole 3 from the ground that the force 20 would tend to cause if it were not for the tie-rods 1 1 and 12.

The assembly of the anchoring device is easy, whether it be done during the initial installation of the safety barrier or during an operation intervention following the installation of the safety barrier.

The anchoring device is inserted by screwing the tie-rods into the material of the superstructure or by insertion by means of hammering devices or the like, or alternatively holes can made preliminarily in the road superstructure to facilitate the embedding of the tie-rods possibly with the aid of hardening material, such as mortar, resins, etc.

The length of the tie-rods 1 1 , 12 is chosen so that it is sufficient to make their distal end, considered in a direction transverse to the direction of the safety barrier, be fixed in a layer of ground which is known to have sufficient compactness, e.g. a layer placed under the road carriageway at the end of the driving operation, to ensure a sufficient resistance against the extraction forces which would occur in the case of crash of a vehicle onto the safety barrier. Naturally, according to the consistency of the ground, it is possible to use combinations of methods described hereto without departing from the scope of the invention.