Description

Road Safety Barrier

Field of the art

The present invention generally refers to longitudinal road safety barriers, including those installed along the road borders, those set on the central traffic divider and those on the edge of a bridge; it also refers to impact energy attenuators.

Prior art

The performance class of a road barrier is measured through the ASI index. The acceleration severity index, ASI, is a function of time, and is calculated with the following equation:

ASI(t) = [(a , / a* _x ) ² + (a _y / a%) ² + (a_, / a*_-) ² ] ^1/2 ,

where O _x , a _y , a - are the acceleration components of a point P inside the body of the vehicle close to the center of gravity, averaged over a 50 ms mobile time window, while a*χ, a* _y , a* _z are the limit values for the acceleration components along the vehicle axes x, y, z, respectively equal to 12g, 9g and 1Og (g is the acceleration due to earth's gravity).

The maximum value reached by ASI in a collision is taken as a single measurement of the impact severity, ASI = max [ASI(t)]. The value = 1 is deemed very safe, while the value

= 1.4 is still acceptable; above this value, it is probable that there will be serious negative consequences.

A longitudinal barrier is of class A if it has an ASI <1, while it is of class B if it has an

ASI <1.4. If the barrier is characterized by a value of ASI>1.4, then it can no

longer be approved. The European standard of reference is UNI-EN 1317. A first aspect of the invention regards the longitudinal safety barriers, which constitute road safety barriers for vehicles and are installed along the borders of a road or on the central traffic divider. We will first describe the performances of the barriers of the prior art below.

A) Longitudinal safety barriers

The longitudinal safety barriers are classified on the basis of the containment level. The containment level is a function of the maximum kinetic energy that the barrier is capable of absorbing due to the impact of a vehicle. The applicant's research activity was concentrated on the road barriers of type Hl, H2 and H3, respectively characterized by a kinetic energy value of 126.6 kJ, 287.5 kJ and

462.1 kJ.

For the sake of brevity, in the following discussion only the data related to the barrier

H3 will be reported. The certification of a barrier provides that it is tested for a 100 km/h impact, which occurs with an angle of 20° with an automobile of 900 kg weight. For a comparison with the prior art, the impact simulations were executed by A.M.S. (applicant), using the Dodge Neon as automobile.

The safety barriers proposed by the applicant were compared with the safety barriers of the same performance level currently on the market (prior art).

B) Longitudinal safety barrier of type H3

The performances of the barrier H3 proposed by the applicant were compared with the lateral edge barrier H3 produced by the company Marcegaglia. The comparison is based on the calculation results of the finite element method executed by means of an explicit code, as well as on relative practical tests.

The H3 Marcegaglia safety barrier was modeled starting from the structural drawings of the same barrier which are available on-line on the Marcegaglia website. Fig. 1 shows the FE (finite element) model of the H3 Marcegaglia barrier.

In Fig. 2, the impact dynamics are reported for the Marcegaglia barrier. As is noted from Fig. 2, the double wave spacer, in the lower part of the barrier, collapses, while the spacer related to the triple wave, in the upper part of the barrier, remains practically non-deformed (see also Fig. 3). It is too rigid and makes the impact quite harmful for the motor vehicle occupants. Indeed, it is observed in Fig. 3 that the Marcegaglia barrier has a height nearly equal to that of the car and the triple wave impacts against the car posts and window, increasing the risk of physical harm to the vehicle occupants. From the preceding observations, one observes several disadvantages of the prior art with regard to the longitudinal road safety barriers.

In Figure 7, the time progressions of the ASI index for the Marcegaglia barrier and for the barrier of the presented invention are reported.

Figure 7 will be discussed below, in the detailed description of the present invention, but it is clear that the maximum 1.16 of the ASI for the barrier of the prior art approaches the maximum limit value 1.4 for safety barrier certification, hence also under this aspect it is seen that the prior art still has drawbacks. Fig. 8 shows the HIC progression (defined below in the detailed description) of an accelerometer placed inside the vehicle at the position of the driver's head, so to evaluate the damage caused to the occupants in the case of the two barriers (prior art (Marcegaglia), and present invention). Also under this aspect, the prior art can be improved.

Therefore, in a first aspect thereof, the present invention intends to provide a longitudinal road safety barrier, which for a lateral impact, on the side of the barrier itself, has the following improved characteristics: - reduced overall height of the barrier, which reduces the risk of impact of the head of the passenger against the barrier itself;

- reduced overall height of the barrier, so that the posts (of the windows) of an automobile are not affected by the impact;

- progressive deformation of the barrier during impact, so to limit the maximum value of the ASI to a much greater extent than that of the prior art;

- the car wheel remains substantially aligned in the motion direction, even after impact; - lower weight of the barrier;

- lower maximum value of the HIC parameter (see detailed description of the invention for the exact definition of the HIC parameter), in order to make the barrier safer for the vehicle occupants.

In a second aspect thereof, the present invention regards the impact energy attenuators: the attenuator can be connected to the barrier itself or it can also exist on its own, independent of the same.

An impact energy attenuator is a device placed before an obstacle in order to dampen the violence of the impact. An impact energy attenuator is placed wherever there is a fixed obstacle, not protected by safety barrier, for example, therefore, in front of: - non-pliable sign poles (portals) and lighting poles

- pillars of vehicle bridges, foot bridges, supports, etc.

- cusps in which two barrier sections are joined

- the beginning of metal barriers or cement barriers (New Jersey) or non-protected anti- noise walls - work site ends

- highway tollbooth bumpers.

The object of the present invention is that of obtaining impact energy attenuators with ASI less than 1 and which are not as long as those of the prior art. In particular, one object of the present invention is that of providing impact energy attenuators having the preceding innovative/advantageous characteristics that can both be connected to the longitudinal safety barriers and mounted on their own to protect tollbooths, art works, pillars and other objects. Then, in a second aspect thereof, the present invention in particular concerns a road barrier equipped with an

impact energy attenuator according to the present invention.

The aforesaid objects are obtained, with regard to the first aspect, as indicated in the independent claim 1.

Moreover, the objects of the invention related to the second aspect are obtained by means of the characteristics contained in the dependent claims 6-15 and the independent claim 16. The two aspects of the invention are united by the use of hexagonal cell panels, wherein said panels are arranged in a manner such that the impact of the vehicle occurs against the plane defined by the hexagonal cell panels, and not orthogonally to the plane itself. The hexagonal cell structure is made by means of a ductile metal material, having a high capacity to be inelastically deformed when the system is subjected to stresses in the hexagon plane.

Brief description of the drawings The present invention will now be illustrated by means of the drawing set, only as a non-limiting example, wherein:

FIGURE Ia is a type H3 barrier model of the prior art (Marcegaglia company), shown in cross section, in which the vehicle is approaching the barrier with an impact angle that is provided for by the certification standards;

FIGURE Ib is the barrier model shown in Fig. Ia, seen in perspective and from its rear side;

FIGURE 2 is the impact dynamics for the barrier of Figures Ia and Ib;

FIGURE 3 is a detail of the impact at time t = 0.20 s for the barrier of Figures Ia, Ib and 2;

FIGURE 4 (a, b = section, perspective rear) is a model (possible embodiment) of a longitudinal road safety barrier according to the present invention, of H3 category, and specifically a FE (finite element) model of such barrier;

FIGURE 5 shows the dynamics of the impact for the barrier H3 of the invention, illustrated in the preceding Fig. 4;

FIGURE 6 represents a detail of the impact for the barrier of H3 type of the present invention, already shown in the preceding Figures 4 and 5;

FIGURE 7 shows the time progressions of the ASI index for the barrier of the prior art (Marcegaglia, light curve) and for the barrier of the present invention (dark curve);

FIGURE 8 shows a comparison between the parameter HIC(t) (in g units) for the barrier of the prior art (light curve) and for the barrier of the present invention ("AMS": dark curve), as a function of the collision time (in seconds);

FIGURE 9 is a plan and section view of the modular impact energy attenuator of the present invention, made by means of hexagonal cell panels, in a first embodiment thereof;

FIGURE 10 is a perspective view of inside the impact energy attenuator of a longitudinal safety barrier with strips and bars (posts), the impact energy attenuator being arranged in the head part (terminal) of the safety barrier;

FIGURE 1 Ia is a side view of a traditional, non-redirective impact energy attenuator with "performance level 50";

FIGURE 1 Ib is a plan view of the traditional impact energy attenuator shown in Fig. 11a;

FIGURE 12 shows an automobile which is about to hit an impact energy attenuator model of the present invention of "performance level 50";

FIGURE 13 shows the dynamic behavior (for a collision of type TC 1.1.50) in the case of the attenuator of the present invention shown in Fig. 12;

FIGURE 14 illustrates the progression of the ASI as a function of time for the TC 1.1.50 test on the impact energy attenuator of the present invention;

FIGURE 15a is a side view of the prior art reference attenuator for "performance level 80" tests for non-redirective attenuators;

FIGURE 15b is the corresponding plan view;

FIGURE 16 is an impact energy attenuator model according to the present invention, for "performance level 80" tests.

Detailed description of the present invention

The present invention will now be described in detail, making reference to several particular and non-binding embodiments thereof, so that a man skilled in the art can reproduce it if he so desires. Those details considered as being known to the man skilled in the art will not be described/mentioned; these are thus not strictly tied to the innovative aspects of the invention.

As shown in Fig. 4a and Fig. 4b, with respect to the Marcegaglia barrier the double

wave 1 was in practice substituted with a triple wave 1', whose thickness is reduced. The spacers 2, 3 were substituted with the hexagonal cell panel 4. The introduction of the hexagonal cell panel 4 and the two triple waves I ¹ , 1" permitted reducing the overall height of the 150 mm barrier. A lower barrier reduces the risk of impact of the passenger head against the barrier itself.

In Figure 5, the impact dynamics for the barrier H3 of the invention are reported. As is known from Figures 5 and 6, the hexagonal cell panel is progressively deformed. It is also noted from Fig. 6 that the barrier of the present invention has a height such that the posts of the automobile are not affected by the impact. In addition, it is possible to observe that the right front wheel (Fig. 6) remains aligned with the direction of the motion, unlike that which occurs in the case of the Marcegaglia barrier. In Figure 7, the time progressions are reported of the ASI index for the Marcegaglia barrier and for the barrier of the present invention. It is observed from Fig. 7 that there is a reduction of the ASI of about 30%. This is an optimal result considering that the barrier, subject of the present invention, has a weight per linear meter that is 5 kg less than that of the Marcegaglia barrier. In order to evaluate the damage sustained by car occupants after impact, an accelerometer was placed inside the vehicle at the position of the driver's head. The resulting acceleration was calculated and this was then averaged over a 50 ms mobile time window. We define such parameter HIC as t+δ

HIC(t) = 1/δ I a _r (t')dt' t In Fig. 8, the progression of such parameter HIC is reported as a function of time, both for the present barrier and for the Marcegaglia barrier.

It is observed how the maximum value of the HIC for the barrier proposed by the applicant is reduced nearly 50% with respect to that of Marcegaglia. Thus, the barrier,

subject of the present patent application, is capable of simultaneously meeting the requirements of several certification classes.

The present invention was described, with regard to its first aspect, in the case of a strip and bar barrier. Nevertheless, the present inventive concept could also be applied to other barrier types, if one wishes to protect the barrier in specific points with the hexagonal cell panels arranged in a direction substantially orthogonal to the longitudinal extension of the barrier.

With regard to the second aspect of the invention (impact energy attenuator and safety barrier equipped with impact energy attenuator), this will be described with a direct comparison with the prior art, highlighting the advantages of the present finding. An impact energy attenuator is a device placed in front of an obstacle in order to dampen the impact violence. An impact energy attenuator is positioned wherever there is a fixed obstacle that is unprotected by a safety barrier: for example, therefore, in front of: * non-pliable sign poles (portals) and lighting poles

* pillars of vehicle bridges, foot bridges, supports, etc.

* cusps in which two barrier sections are joined

* the beginning of metal barriers or cement barriers (New Jersey) or non-protected anti- noise walls * work site ends

* highway tollbooth bumpers.

The applicant designed impact energy attenuators for the 50 km/h and 80 km/h speed classes, using a series of hexagonal cell panels connected with each other as element capable of absorbing the kinetic energy of the motor vehicle and transforming it into deformation energy.

In Figures 9 and 10, a drawing is reported of the elementary cell which constitutes the modular metal panel used in the impact energy attenuators of the present invention. In the attenuator model proposed by the applicant of modular type, every module or

elementary cell could be composed of four panels 11, 500 mm x 800 mm, arranged in parallel. Every module 10 could be separated from the others by means of 3 mm plates

12 (see Figs. 9 and 10).

In the tests, the directives of the UNI EN 1317-3 reference standard of 2002 were taken under consideration, borrowing, for the indications related to size and bulk of the attenuator, the TAU models of the Company Sn S.p.A. (prior art).

The finite element method calculations were executed by means of explicit, dynamic finite element commercial software.

The objective of the simulations was to obtain energy absorbers, i.e. impact energy absorbers, with ASI of less than 1 and which are not as long as those of the prior art.

The impact energy attenuator, as shown in Fig. 9, has a U-shaped portion 13 which covers the inner part of the actual attenuator (with components 10, 11, 12). The portion

13, preferably metal, is joined to the actual barrier 15 (see Fig. 10). The number 14 indicates a vehicle colliding with the impact energy attenuator. A) Performance level 50 tests for non-redirective impact energy attenuators (TC

1.1.50)

The attenuator of the invention was modeled and made starting from the impact energy absorber TAU, PARALLEL 60 model of Sn S.p.A.

The height from the ground and width were maintained unchanged, while the length was diminished, which for such model was 4200/3700 mm, while in the present invention one can start from 1500 mm (2 grating packs), before preferably reaching the optimal configuration of 2000 mm. In addition, the attenuator of the present invention is connected to the road barrier 15 (Figs. 9 and 10) while the TAU model is not. Frontally, the model of the invention has a curved triple wave, (formed by the aforesaid U-shaped portion 13), the TAU model has a plastic band of fluorescent color.

The test type TC 1.1.50. of the reference standard provides for a frontal impact with a

900 kg car impacting at 50 km/h.

The attenuator, subject of the invention, that is used for such simulations has hexagonal

cell panel modules arranged in series, having cells with progressively greater thickness: for example 1.2/1.2/1.5 mm.

In Fig. 12, the performance level 50 attenuator model proposed by the present invention is reported; Fig. 13 reports its dynamic behavior for an impact of type TC 1.1.50.

In Fig. 14, the progression of the ASI is reported as a function of time for the TC 1.1.50 test in the case of the attenuator of the invention. It is observed that the maximum value of ASI is equal to 0.56Kl. A non-redirective attenuator of class A was thus obtained, with considerable space savings in longitudinal direction with respect to the conventional case, given the same width and height.

In the following table, the size and ASI values are compared for the attenuator of the prior art (TAU) and for that proposed by the present invention (AMS).

B) Performance level 80 tests for non-redirective impact energy attenuators

The reference attenuator for the simulations and the tests was the redirective impact energy absorber TAU, PARALLEL 80 model of Sn S.p. A. whose scheme is reported in Fig. 15a and Fig. 15b. For such performance level, the standard UNI EN 1317-3 provides for four different tests:

• TC 1.1.80: frontal impact in axis with 900 kg mass

• TC 2.1.80: frontal impact with misalignment of % the width of the vehicle with

900 kg mass

• TC 1.2.80: frontal impact in axis with 1300 kg mass

• TC 3.2.80: frontal impact tilted 15° with 1300 kg mass.

After numerous attempts with four and then five modules 10 made with hexagonal cell panels, which gave ASI values greater than 1 for the tests TC 1.2.80 and TC

3.2.80, it was decided to use six modules, also inserting the hexagonal cell panels in the zone 13 (see Fig. 16) delimited by the curved part of the guardrail, obtaining an 3500 mm attenuator (see Fig. 16). The same structure was subsequently also tested for the test TC 1.1.50, in order to obtain a single product which can go well for both performance levels. All of the abovementioned tests gave optimal results, as seen in the tables related to the ASI reported below. Therefore, the attenuator that is the subject of the present invention fully meets the standards related to several certification classes as polyvalent attenuator.

The attenuator of the invention used for such simulations has grating packs (modules) 10, 10, ... , arranged in series, with panels 11 with hexagonal cells having progressive thickness: 1.2 in the curved part/1.4/1.5/1.6/1.7/1.8/2.0 mm. The maximum ASI values are reported in the following table (AMS = present invention)

AMS = resent invention

In conclusion, the attenuator model proposed by the applicant for the performance level 80 has longitudinal size equal to about half that proposed by the prior art and ensures a considerably lower ASI value than that of the prior art.