ASSESSMENT OF THE EFFECTIVENESS OF METAL BARRIERS ON HIGHWAYS

International independent scientific journal №79/2025 64 TECHNICAL SCIENCES ASSESSMENT OF THE EFFECTIVENESS OF METAL BARRIERS ON HIGHWAYS Harutyunyan V. condiant of science (engineering), Associate Professor (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic Hayrapetyan A. (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic Harutyunyan A. conditant of science (engineering), Associate Professor (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic Mosikyan K. conditant of science (engineering), Associate Professor (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic National University of Architecture and Construction of Armenia University, Yerevan, Armenia https://doi.org/10.5281/zenodo.17583057 Abstract To reduce road accidents (RAs) and improve traffic management on complex roadways, barriers of various types, strengths, and materials are used. Assessing their effectiveness, or so-called functionality, helps ensure harmonious traffic flow and, in the event of RA reduces the likelihood of vehicles leaving their lane and mitigates accident consequences. The article discusses the classification of road barriers, the appropriateness of their use, and methods for evaluating their effectiveness. Keywords: road, automobile, traffic, metal barrier, stop, impact impulse, impact force. Introduction Metal barriers are a key element of road safety infrastructure. Their use significantly improves traffic regulation. Road barriers are used in all economically developed countries, and the conditions for the use of their structures are regulated by various GOSTs, in the EAEU countries by the EN 1317 standard, in the USA it is represented by the MASH and NCHRP regulatory acts, in the Republic of Armenia by the construction norms of the RA State Construction Code of the Republic of Armenia 32.01-2022 "Motorways", as well as GOST 33388-2015 and other regulatory acts. Road barriers are designed to minimize risks of vehicle run-off and collision during traffic, crossing the median, colliding with oncoming traffic, hitting obstacles and structural elements on the shoulder or in the separation layer, the risk of pedestrians falling off the road or bridge structure, as well as to regulate traffic and prevent animals from entering the roadway. Materials and methods Roadways are designed to ensure harmonious, safe, and comfortable traffic flows, with the ultimate goal of ensuring high vehicle productivity. Among the road furniture and protective structures, let's consider metal barriers. As mentioned above, they have a certain difference in their functional significance. Among roadside furniture and protective structures, this study focuses on metal barriers. As mentioned, they serve distinct functional purposes. When selecting barrier types, it is essential to justify their specific function, namely: ⚫ separation of transport flows, ⚫ preventing you from leaving the road, ⚫ Facilitating temporary blocking, ⚫ access restriction. Analysis of operating conditions is important for the selection of barriers.․ ⚫ When driving at low speeds, you should use stands made of rubber or polymer material, ⚫ vehicles moving at an average speed (50÷80 km/h) metal barriers should be used for flow, ⚫ with high speeds (≥90 km/h) in case of flows, concrete or reinforced metal barriers, ⚫ in cold climates: (galvanized) corrosion-resistant metal, ⚫ for strong winds: concrete, etc. The algorithm for selecting barriers should look like this: 1. Determine the most important purpose of protective structures. 2. Assess operating conditions. 3. Check (analytical) safety condition. 4. Give a comparative assessment of price and resource. 5. Consider current regulations. The choice of barrier depends on their functional purpose and are classified as: ⚫ permanent limiters (metal, concrete, stone, brick) ⚫ temporary limiter (plastic water, metal, removable rubber, etc.) ⚫ other types of barriers (pedestrian zone, antiparking, etc.). Let's consider side-impact road barriers, taking into account that the number of overturning road acci- International independent scientific journal №79/2025 65 dents (ADRs) is also quite high in the Republic of Armenia (an average of 310-340 ADRs per year, 40-45 fatalities, 13-14%), when cars often leave the roadway. ⚫ Metal barriers should be installed on the sides of the road [1] in areas where ⚫ the slope of the slope is greater than 1:3 and the height of the slope exceeds 2 meters, ⚫ The road runs parallel to the railway, through swamps of category III, along the banks of rivers deeper than 2 m, along the edges of valleys and gorges for a distance of less than 20 m, ⚫ roads intersect or merge at different levels, ⚫ The direction of the road changes in the plan, and the visibility distance is less than calculated. Metal barriers are placed on the sides of the road 0.5 m from the edge of the earthen embankment, 0.6 m inward. An important advantage of metal barriers is that they absorb the impact of a vehicle, are lighter than concrete, are easy to install, and require almost no maintenance, especially if made of galvanized steel. Fig. 1. Diagram of the vertical and parallel velocity components of a car after hitting a barrier. Results and Discussion Let us consider the energy absorption by the barrier during the impact of cars of different masses and the speed of the car after the impact. It is shown in Fig.․1 [2, 3, 5, 7]. It should be noted that according to statistics, 92% of traffic accidents in the Republic of Armenia involve light passenger cars. The car will have a rebound after the impact, after which the following components of the accelerations are formed: (in the direction of impact, V1 and in the direction of movement, V2)) 𝑉1=𝑉3 · sinθ where V3 is the speed of the car before the impact. Traffic in the parallel direction. 𝑉2=𝑉3 · cosθ We calculate the impulse resulting from the impact under the condition that the barrier is inelastic, in which case we calculate the impulse using the following expression: ∆𝑃=𝑚·𝑉1 where m is the mass of the car (kg), V1 is․is the normal component of the velocity (m/s). To estimate the force of the impact in the event of barrier deformation, we take the duration of the impact Δt = 0.1÷0.4 seconds. In that case, the impact force will be: F= t=m·V1 t As an example, consider a light passenger car (m=1500kg) and the forces caused by the impact of the truck (m = 15000kg). a) for light passenger vehicles, we accept V - 72 km/h (20 m/s), m=1500kg, angle of impact θ = 20° duration of the stroke Δt = 0.2 sec. Let's estimate the force of the blow: the normal component of the velocity will be: 𝑉1=20 · 𝑠𝑖𝑛 20°=6.84 𝑚/𝑠, The impulse of the blow will be: ΔP=1500 · 6.84= 10260 N, The force of the blow will be: F= 10260 0.2 =51300 N...or 51.3 kN. If we assume that the barrier is of type 11 DО , made of 3 mm thick double-walled galvanised steel, the resistance of which is 50÷100 kN. then we can be sure that the barrier will not collapse and will protect the car at the point of impact. The position of the supports and their mutual distance are also important here. For the 11 DО barrier used in the Republic of Armenia, it is 1÷3 m according to GOST 33178-2014 b) Now consider the force generated by the impact of the truck. Initial data: m = 15000 kg, V = 60 km/h ≈ 16.6 m/s, angle of impact θ = 20° duration of the stroke Δt = 0.5 sec. Let's calculate the normal component of the velocity: 𝑉1=16.6 · 𝑠𝑖𝑛 20°=5.67 𝑚/𝑠, The impulse of the blow will be: ΔP=15000 · 5.67=85050 N,or 85.05 kN. The force of the blow will be: F= 85050 0.5 =170100 N,or 170.1 kN. If we assume that the barrier is the same, made of double-walled galvanised steel (11 DО) 3 mm thick, the resistance of which is 50÷100 Kn․, then it can be confidently asserted that after the impact, the barrier will collapse, and the car will be outside the traffic lane. Analysis of traffic accident statistics in recent years shows that there are many cases, especially on the M1, M2, and M4 interstate highways, when a driver of a light passenger vehicle for some reason lost control of the vehicle, hit a road barrier, and ended up off the road. Part of the reason may be high speed, but it is known that in dangerous situations, drivers usually International independent scientific journal №79/2025 66 break their cars. This means that there is an incomprehensible reason, as a result of which the light passenger car leaves the lane and appears off the road. This means that it is necessary to study the structure of the barrier, the materials used, the installation technology and other issues. Let us consider the cases when a lightweight passenger car hits the barriers at different angles. Using formulas (1), (3), (4), we get that the impulse of hitting the barrier at a speed of 25 m/s at an angle of 30° will be 75.0 kN, in case of hitting at an angle of 45° it will be 132.0 kN, in case of hitting at an angle of 60° it will be 162.3 kN. This means that in cases when a light passenger car hits the barriers at angles of 45° and 60°, the barriers are destroyed, and the car appears outside the traffic lane. Now let's calculate the maximum angle of impact at which a car moving at a speed of 25 m/s will remain in the traffic lane. We assume the maximum impulse of the barrier resistance to be 100 kN and perform the calculation. After modifying formulas (1); (3); (4), we calculate the critical angle of attack using the following expression: sin θ= ∆𝑡·𝐹 𝑚·𝑉3 By inserting the values: m =1500 kg; Δt = 0.2 sec; V = 25 m/s; F = 100000 N; we will get: sin θ=0.2 · 100000 1500 · 25 =0.53, from which: θ ≈32°: This means that if the angle of impact of a car is greater than 32°, a car hitting it at a speed of 25 m/s will leave the traffic lane and will appear off the road. In the same way, it is possible to calculate the maximum speed at which cars moving at different speeds will hit a barrier, after which it will appear off the traffic lane. Let us consider the forces exerted by cars of different masses and speeds when they hit a barrier. Such an analysis will allow us to determine the maximum speed of the car at different points on the road. Table 1 presents the initial data and the results obtained. Table 1 Forces acting on the barrier during impact V km/hr m/sec. The normal component of speed V1 m/sec. Shock pulse, ΔP N duration of impact, sec. impact force, F kN 11DO Resistance,kN changing the state of the barrier m =1500 kg. lightweight passenger car 70 20 6,84 10260 0,2 51,3 100,0 The barrier protects 90 25 8,5 12740 0,2 63,7 100,0 The barrier protects 110 30,5 10,37 15555 0,2 77,7 100,0 The barrier protects m =15000 kg. truck 50 13,8 4,69 70350 0,5 140,7 100,0 The barrier protects 60 16,6 5,64 84600 0,5 169,2 100,0 The barrier protects 80 23,2 7,55 114740 0,5 223,5 100,0 The barrier protects Based on the data presented in Table 1, a diagram of the interaction of the specified indicators has been constructed. It is shown in Figure 2. a) Diagram showing the dependence of the normal velocity component after the automobile’s impact on the barrier. International independent scientific journal №79/2025 67 b) Diagram showing the correlation between the impact force and the normal velocity component c)Diagram showing the correlation between the impact impulse and the normal velocity component From the appearance of the diagrams, it follows that after the impact, the different values of the velocity component change according to a direct relationship (Fig. 2). The force of the impacts is almost directly proportional, but their value in the case of a truck is significantly greater than the force of the impact of a light passenger car. However, the impact momentum for a light passenger car is almost unchanged by the vertical component of the velocity, but is extremely large for a truck and increases almost too sharply. 0 2 4 6 8 10 12 0 5 10 15 20 25 30 35 V1m/sec V m/sec lightweight passenger car truck 0 50 100 150 200 250 0 5 10 15 20 25 30 35 F kN V m/sec lightweight passenger car truck 0 20000 40000 60000 80000 100000 120000 140000 0 5 10 15 20 25 30 35 shock pulse P N V m/sec lightweight passenger car truck International independent scientific journal №79/2025 68 Conclusions 1. Metal barriers are elements of road safety equipment that must be installed in accordance with regulatory requirements. 2. When choosing the type of barrier, its functional significance and operating conditions should be taken into account. 3. The increase in the number of cases of vehicles leaving the carriageway and ending up on the side of the road after hitting barriers suggests that when designing the structural elements of barriers and determining the distances between the stands, it is necessary to calculate the impact momentum of the vehicle and the force of the impact. 4. On landings, in the area of horizontal curves with a small radius, 11 DO metal barriers should be replaced with other, more effective means. References: 1. Бадоян Н.Ш., Щепетева Л.С... Путин К.Г. Обоснование применения габионных конструкций для создания барьерных ограждений при строительстве автомобильных дорог. -Russian journal of transport engineering. Пермь, 2019, № 2(том 6) ISSN 2413-907. 2. Demyanushko IV. Karpov L.A. Simulation of car hitting a road fance rack Transport Contructin, Москва 2013 № 10 стр. 16. 3. Назаров М.А. Оценка транспортно-эксплуатационного состояния автомобильных дорог. М. Транспорт 2008 г. -224 с. 4. Безносов Г.А. Диагностика и оценка состояния дорожных одежд. М. Дороги и транспорт 2005 г.-198 с. 5. AASHTO Guidefor Design of Pavement Struktures-Washington, D.G. American Association of state Highway and Transportation officials 1993. 6. SafetyCube Project (H 2020) European Commission, 2019 7. Тавшавадзе Б.Т. Разработка и обоснование методологии расчетов испитаний сертификации дорожных ограждений барьерного типа диссертация конд. тех. наук Москва 2019г 175 с. Harutyunyan Valerik, conditant of science (engineering), Associate Professor (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic, (+374)10567572, (+374)93100825, vmh[email protected], Hayrapetyan Anna (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic, (+374)91806019, annahayrap[email protected], Harutyunyan Armen, conditant of science (engineering), Associate Professor (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic, (+374)10567572, (+374)43116611, Arm.har[email protected]u, Mosikyan Karapet conditant of science (engineering), Associate Professor (RA, Yerevan) – NUACA, Chair of Construction Machinery and Organization of Traffic, (+374)94854540, karomo[email protected]