Impact Performance Evaluation of a Crash Cushion Design Using Finite Element Simulation and Full-Scale Crash Testing - MDPI
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safety Article Impact Performance Evaluation of a Crash Cushion Design Using Finite Element Simulation and Full-Scale Crash Testing Murat Büyük 1 , Ali Osman Atahan 2, * and Kenan Kurucuoğlu 3 1 Department Faculty of Engineering and Natural Sciences, Sabanci University, Main Campus, İstanbul 34956, Turkey; email@example.com 2 Department of Civil Engineering, Istanbul Technical University, Ayazaga Campus, İstanbul 34469, Turkey 3 Ulukur Plastic Traffic Products, İstanbul 34870, Turkey; firstname.lastname@example.org * Correspondence: email@example.com Received: 22 August 2018; Accepted: 25 October 2018; Published: 1 November 2018 Abstract: Crash cushions are designed to gradually absorb the kinetic energy of an impacting vehicle and bring it to a controlled stop within an acceptable distance while maintaining a limited amount of deceleration on the occupants. These cushions are used to protect errant vehicles from hitting rigid objects, such as poles and barriers located at exit locations on roads. Impact performance evaluation of crash cushions are attained according to an EN 1317-3 standard based on various speed limits and impact angles. Crash cushions can be designed to absorb the energy of an impacting vehicle by using different material deformation mechanisms, such as metal plasticity supported by airbag folding or damping. In this study, a new crash cushion system, called the ulukur crash cushion (UCC), is developed by using linear, low-density polyethylene (LLDPE) containers supported by embedded plastic energy-absorbing tubes as dampers. Steel cables are used to provide anchorage to the design. The crashworthiness of the system was evaluated both numerically and experimentally. The finite element model of the design was developed and solved using LS-DYNA (971, LSTC, Livermore, CA, USA), in which the impact performance was evaluated considering the EN 1317 standard. Following the simulations, full-scale crash tests were performed to determine the performance of the design in containing and redirecting the impacting vehicle. Both the simulations and crash tests showed acceptable agreement. Further crash tests are planned to fully evaluate the crashworthiness of the new crash cushion system. Keywords: crash cushion; crash test; simulation; LS-DYNA; EN 1317; road safety; energy absorption; linear, low-density polyethylene 1. Introduction Traffic and road safety is a serious concern worldwide, and multi-phased research has been undertaken in recent years. The United Nations General Assembly has made an important initiative to reduce the fatality rate in traffic accidents around the world by 50% and provided funds for research. In this context, Turkey has prepared a 10-year vision program covering traffic education and training, safety and enforcement, health and emergency assistance initiatives, and the improvement of traffic safety with engineering measures [1,2]. This program has been implemented by Ministries of Education, Interior, Health, and Transportation. Since 2010, serious steps have been taken regarding traffic safety in Turkey. These advances include speed control using smart detection systems, the enforcement of traffic rules through cameras, the reduction of arrival times of ambulances in an accident site, and providing traffic safety culture to students of all ages. These undertakings have resulted in a 10% Safety 2018, 4, 48; doi:10.3390/safety4040048 www.mdpi.com/journal/safety
Safety 2018, 4, 48 2 of 11 Safety 2018, 4, x FOR PEER REVIEW 2 of 11 decrease statisticalindata, fatal the accidents in Turkey; level of however, achievement according is not to statistical at the desired level data, of 15%.the level Lack ofofachievement road restraintis not at the desired level of 15%. Lack of road restraint system system utilization is one of the areas that needs to be improved . utilization is one of the areas that needs to beCrash improved . are widely used in developed countries to protect vehicles against impacts with cushions fixed, sharp, narrow,are Crash cushions andwidely used inlocated rigid objects developed countries at road to protect exit locations, vehicles tool booths, against impacts workzones, with barrier fixed, sharp, narrow, and rigid objects located at road exit locations, tool booths, ends, and trees [3,4]. As shown in Figure 1, collision with unprotected objects increases the severity workzones, barrier ends, and trees of accidents and[3,4]. As shown results in Figure in fatalities. 1, collisiontowith According unprotected predictions objects by the increases Turkish the severity statistics of institute accidents and results in fatalities. According to predictions by the Turkish statistics (TUIK), the number of fixed object accidents is on the rise, which creates concern for road-safety institute (TUIK), the number targets set byofthe fixed objectGovernment Turkish accidents is . on the rise, Crash which creates cushions in generalconcern for road-safety are designed to slow targets down and set by the Turkish Government . Crash cushions in general are designed contain the impacting vehicle in a controlled way by absorbing its kinetic energy. The Istanbulto slow down and contain the impacting Municipality Metropolitan vehicle in a controlled way by (IMM), which absorbing its is responsible forkinetic trafficenergy. The Istanbul safety within the cityMetropolitan of Istanbul, Municipality expressed interest in utilizing low-cost and nationally developed crash cushions in Istanbulinterest (IMM), which is responsible for traffic safety within the city of Istanbul, expressed due to in utilizing budget low-cost. constraints and nationally developed crash cushions in Istanbul due to budget constraints . Figure 1. Figure 1. Severity Severity of of road accidents with road accidents with narrow narrow and and rigid rigid objects. objects. The aim of of this this project projectis, is,therefore, therefore,totodevelop develop a new a newhybrid hybridcrash cushion crash system, cushion called system, the called ulukur crash cushion (UCC), made out of linear, low-density polyethylene (LLDPE) the ulukur crash cushion (UCC), made out of linear, low-density polyethylene (LLDPE) containers containers and steelsteel and plates for the plates forIMM. In this the IMM. In respect, the UCC this respect, will have the UCC low initial will have maintenance low initial and repair maintenance costs and repair with with costs reusable parts.parts. reusable The The crashworthiness crashworthiness of the system of the systemis isevaluated evaluatedboth both numerically numerically and experimentally. The The finite finite element element model model ofof the UCC is developed, and impact performance is analyzed using LS-DYNA in accordance with TSEN 1317 crash testing standard [6,7]. [6,7]. Following the simulations, full-scale crash tests were performed to validate validate the the computer computer simulation simulation results. results. Both the simulations and crash tests show acceptable agreement. Further crash tests are planned to fully crashworthiness of evaluate the crashworthiness of the the new new crash crash cushion cushion system. system. 2. Details of Ulukur Crash Cushion Developed Ulukur crash cushion (UCC) design is composed of linear, low density polyethylene (LLDPE) containers, energy-absorbing tubes, steel cables, lower plates, and and back back support support plate. plate. Geometrical Geometrical details of these materials materials areare provided providedin inFigure Figure2.2.Containers Containersare areproduced producedusing usingLLDPE, LLDPE, since since it it is is a dependableand a dependable andcost-effective cost-effectivematerial materialthatthatcould couldsustain sustain large large deformations, deformations, endure dynamic dynamic forces, forces, and andabsorb absorb kinetic energy kinetic of the energy of impacting vehiclevehicle the impacting withoutwithout crack formation. Detailed technical crack formation. Detailed information about LLDPE technical information aboutcanLLDPE be foundcaninbea found study by in aCozzi studyetbyal.Cozzi . The measurements et al. for the LLDPE . The measurements for containers the LLDPEare 500 mmare containers 500×mm long 800 long mm ×wide × 710 800 mm wide 710× mm×tall mm 8 mmtall thick. × 8 mmInthick. addition, 250 mm250 In addition, in diameter, 460 mm 460 mm in diameter, longmmenergy-absorbing tubes made long energy-absorbing outmade tubes of LLDPE areLLDPE out of utilizedareinside the containers utilized inside the to improvetothe containers crash performance improve of the design. the crash performance of the50 mm in design. 50diameter holes are mm in diameter provided holes on tubes are provided on to allow controlled air release. The number of tubes varied based on the container tubes to allow controlled air release. The number of tubes varied based on the container type. In type. In other words, as shown other words, in Figure as shown 2, the lead in Figure container 2, the with a shield lead container with aincluded two tubes, shield included whereas two tubes, all the other whereas all standard the other containers included four standard containers tubes. included This four is intended tubes. to provide This is intended toaprovide soft nose-section for vehicles a soft nose-section for with low-energy vehicles impacts. Asimpacts. with low-energy the impactAs energy increases, the impact so do energy the energy increases, so absorption do the energy capacities of the absorption UCC design. capacities Material of the properties UCC design. of LLDPE Material are provided properties of LLDPEin Table 1. are provided in Table 1.
Safety 2018, 4, 48 3 of 11 Safety 2018, 4, x FOR PEER REVIEW 3 of 11 (a) (b) (c) (d) Figure Figure 2. 2. Details Details of of ulukur ulukur crash crash cushion cushion (UCC) (UCC)(a) (a) internal internal view; view;(b) (b) energy energy absorbing absorbingtube; tube;(c) (c) top top view; and (d) assembled crash cushion view; and (d) assembled crash cushion. 1. Material Table 1. Table Materialproperties of low-density properties polyethylene of low-density (LLDPE) polyethylene used in (LLDPE) UCC used in(ulukur crash cushion) UCC (ulukur crash design [9,10]. cushion) design [9,10]. Property Value Test Standard Property Value Test Standard Density (kg/m3 ) 3 935 ASTM D 1505 Density (kg/m ) 935 ASTM D 1505 Modulus of Elasticity (MPa) 724 ASTM D 790 Modulus of Elasticity (MPa) Toughness 724 69 ASTM D 790 ASTM D 2240 Toughness Yield Strength (MPa) 69 18 ASTM D ASTM2240 D 638 Yield Strength Vicat Softening (◦ C) Temp.(MPa) 18 115 ASTM D 638 ASTM D 1525 Vicat Softening Brittleness (◦ C) (°C) Temp.Temp. −75 ASTMASTM 115 D 1525D 746 Brittleness Temp. (°C) −75 ASTM D 746 The UCC design developed in this study is composed of six containers and a frontal shield. The The UCC design developed in this study is composed of six containers and a frontal shield. The design is actually intended for 110 kph impacts, so the original design with six containers is not altered design is actually intended for 110 kph impacts, so the original design with six containers is not for 50 kph impact. Total length of the design is 3700 mm. The measurements of UCC elements are altered for 50 kph impact. Total length of the design is 3700 mm. The measurements of UCC provided in Figure 2. This design is intended to provide safe containment and redirection for 50 kph elements are provided in Figure 2. This design is intended to provide safe containment and head-on and side impacts. Since UCC has a modular nature, the design could be easily converted to redirection for 50 kph head-on and side impacts. Since UCC has a modular nature, the design could 80, 100, or 110 kph impacts by adding more containers, tubes, and steel members. Thus, the length of be easily converted to 80, 100, or 110 kph impacts by adding more containers, tubes, and steel the system can change based on target design speed. As shown in Figure 2, UCC used four 19 mm members. Thus, the length of the system can change based on target design speed. As shown in diameter steel cables (two on the bottom and two on the side), and cables are anchored to steel plates Figure 2, UCC used four 19 mm diameter steel cables (two on the bottom and two on the side), and at both ends. Bottom cables run between two 650 mm wide × 40 mm wide × 25 mm thick steel plates cables are anchored to steel plates at both ends. Bottom cables run between two 650 mm wide × 40 located under the containers. This allowed controlled deformation of containers during frontal and mm wide × 25 mm thick steel plates located under the containers. This allowed controlled side vehicle impacts. Two side cables are used to improve lateral stability of the UCC design. deformation of containers during frontal and side vehicle impacts. Two side cables are used to improve 3. TS ENlateral stability 1317 Crash of theStandard Testing UCC design. for Crash Cushion Evaluatıon 3. TSToENassess the performance 1317 Crash of crash for Testing Standard cushions Crash against Cushion vehicle impacts, Part 3 of EN 1317 standard, Evaluatıon named “road-restraint systems—part 3: performance classes, impact test acceptance criteria and test To assess methods thecushions” for crash performance of crash is followed .cushions According against to this vehicle standard,impacts, vehiclesPart 3 of EN weighing 900, 1317 1300, standard, named “road-restraint systems—part 3: performance classes, impact or 1500 kg traveling at speeds of 50, 80, 100, or 110 impact crash cushions in five different approaches.test acceptance criteria Figure 3and test all shows methods possiblefor crash test cushions”described combinations is followed . 1317 in EN According standardto this Partstandard, vehicles 3 . As shown in weighing 900, 1300, or 1500 kg traveling at speeds of 50, 80, 100, or 110 impact crash Table 2, for 50 kph tests there are only two tests, namely, TC 1.1.50 and TC 4.2.50; a 900 kg passenger cushions in five different approaches. car at impact positionFigure 1 and 31300 showskg all possiblecar passenger testatcombinations impact positon described in EN 1317 2, respectively, are standard specified. Part Both computer simulations and full-scale crash tests on UCC design are performed at 50 and 3 . As shown in Table 2, for 50 kph tests there are only two tests, namely, TC 1.1.50 kph.TC In 4.2.50; a 900 kg passenger car at impact position 1 and 1300 kg passenger car at impact positon 2, respectively, are specified. Both computer simulations and full-scale crash tests on UCC design are
Safety 2018, 4, 48 4 of 11 Safety 2018, 4, x FOR PEER REVIEW 4 of 11 other words,atimpact performed 50 kph.performance of the In other words, UCC design impact is evaluated performance of the using TC 1.1.50 UCC design and TC 4.2.50 is evaluated crash using TC tests . 1.1.50 and TC 4.2.50 crash tests . Figure 3. Crash cushion test approaches in EN 1317 Standard Standard Part Part 33 . . Table 2. Crash testing details for crash cushions in EN 1317 part 3 . Table 2. Crash testing details for crash cushions in EN 1317 part 3 . Test Speed (kph) Acceptance Tests *,,** Test Speed (kph) Acceptance Tests * ** 50 TC 1.1.50 TC 4.2.50 5080 TC 1.1.50 TC 1.1.80 TC 1.2.80 TC 2.1.80 TC 3.2.80 TCTC 4.2.50 TC 5.2.80 4.2.80 80 100 TC 1.1.80 TC 1.1.100 TC 1.2.80 TC 1.2.100 TC 2.1.80 TC 2.1.100 TC 3.2.80 TC 3.2.100 TC 4.2.80 TCTC TC 4.2.100 5.2.80 5.2.100 100 110 TC 1.1.100 TC 1.1.100 TC 1.2.100 TC 1.3.110 TC 2.1.100 TC 2.1.100 TC 3.2.100 TC 3.3.110 TC 4.2.100 TC 4.3.110 TC 5.2.100 TC 5.3.110 110 TC 1.1.100 TC 1.3.110 TC 2.1.100 TC 3.3.110 TC 4.3.110 TC 5.3.110 * TC 5.3.110 stands for test crash cushion (TC) approach (5), vehicle (3), and speed (110); ** Vehicles 1, 2, and 3 stand *forTC 5.3.110 stands for test crash cushion 900 kg, 1300 kg, and 1500 kg, respectively. (TC) approach (5), vehicle (3), and speed (110); ** Vehicles 1, 2, and 3 stand for 900 kg, 1300 kg, and 1500 kg, respectively. 4. Computer Simulation of UCC Design 4. Computer Simulation of UCC Design Before pursuing costly, full-scale crash testing, a detailed finite element simulation study was Beforeon performed pursuing costly,Afull-scale UCC design. crash testing, highly non-linear a detailed finite element and large-deformation simulation finite-element code study LS-DYNAwas performed on UCC design. A highly non-linear and large-deformation developed by the livermore software technology corporation (LSTC) was used to model the barrier finite-element code LS-DYNA and simulate developed by the livermore the vehicle-barrier impactsoftware event .technology corporation Details of the bridge rail(LSTC) wasvehicle and both used tomodels model the explained are barrier and simulate the vehicle-barrier impact event . Details of the bridge rail and both below. vehicle models are explained below. 4.1. Finite Element Model of UCC Design 4.1. Finite Element Model of UCC Design A finite element model of the UCC was developed to assess the crash test performance of A finiteThe the design. element model, model of the in as shown UCC was4,developed Figure consistedto ofassess 143,063thenodes, crash 135,389 test performance shell, andof4264 the design. solid The model, elements. as shown Shell elements in represented Figure 4, consisted the LLDPEof 143,063 members nodes, and 135,389 shell, and steel plates 4264 of the solid model, elements. while solidShell elements elements represented represented the the steelLLDPE cables.members The shelland steel plates elements of theofLLDPE the model, while solid containers and elementstubes internal represented that arethe steel cables. expected to get The in shell directelements contact of the vehicles with LLDPE containers and internalsevere and thus experience tubes that are expected deformations are to get in direct modeled with contact with vehicles full integration and thustoexperience formulation accuratelysevere deformations represent the complexare modeled with full integration formulation to accurately represent the interactions and behavior. All steel elements were modeled with default element formulation for complex interactions and behavior. All steel computational elements were modeled with default element formulation for computational efficiency. efficiency. Since containers are expected to sustain large plastic deformations and possible crushing, a Since linear piecewise containers plasticare expected material to sustain definition was large used toplastic model deformations and possible the LLDPE elements crushing, [11,12]. Since noa piecewise failure linear plastic is expected in steelmaterial members, definition was used a rigid material to modelwas modeling theused LLDPE elementsplates to represent [11,12]. andSince no cables. failure Steel is expected cables in steel were firmly members, attached to steela rigid platesmaterial modeling at both ends, wasplates and steel used were to represent securedplates and to ground cables.unfailing using Steel cables were firmly attached to steel plates at both ends, and steel plates were secured to connections. groundIn anusing unfailing actual connections. UCC installation, connections between the members, such as lower steel plates and In an actual UCC installation, containers, and steel plates to ground, connections between are established thebolts using members, and nuts.suchToas lower steel accurately plates and represent the containers, and steel plates to ground, are established using bolts and nuts. To accurately represent the behavior of these connections during full-scale crash testing, CONSTRAINED_SPOTWELD
Safety 2018, 4, 48 5 of 11 Safety 2018, 4, x FOR PEER REVIEW 5 of 11 behavior of these connections during full-scale crash testing, CONSTRAINED_SPOTWELD option in LS-DYNA option was used in LS-DYNA was. By . used definition, this option By definition, keeps members this option connected keeps members until auntil connected certain force a certain criteria is met.isThen, force criteria met. the connection Then, fails and the connection members fails can move and members canfreely. moveTofreely. determine the required To determine the force level that fails a connection, a detailed model is constructed using LS-DYNA. required force level that fails a connection, a detailed model is constructed using LS-DYNA. The behavior of The the connection behavior ofwas the examined connection under was different examinedloading under conditions. A reasonable different loading failure conditions. A criterion reasonable obtained failure from the component criterion obtained from simulation was used the component in the connection simulation was usedmodel in the. connection model . (a) (b) Figure 4. Finite element model of UCC: (a) frontal view and and (b) (b) rear rear view. view. 4.2. 4.2. Vehicle Vehicle Model Model After After the the development development of of the the UCC UCC model, model, aa small small passenger passenger car car model model was was used used to to meet meet the the EN EN 1317 standard requirements to impact the barrier. A 2002 Ford Taurus vehicle model obtained 1317 standard requirements to impact the barrier. A 2002 Ford Taurus vehicle model obtained from from the National Crash the National Analysis Crash Center Analysis (NCAC) Center was used (NCAC) was in the in used study the . studyThe mass . Theofmass the empty of thevehicle empty was adjusted to 900 kg, and it could have been increased to 1300 kg by adding extra mass vehicle was adjusted to 900 kg, and it could have been increased to 1300 kg by adding extra mass elements. This particular elements. This vehicle model particular was model vehicle used inwas many previous used in many studies with success previous studies . withAsuccess picture. of the A vehicle picture is ofshown in Figure the vehicle 5. in Figure 5. is shown Figure 5. The Figure 5. The 2002 2002 Ford Ford Taurus Taurus vehicle vehicle model model used used in in LS-DYNA LS-DYNA Impact ImpactSimulation. Simulation. 4.3. TC 1.1.50 Simulation 4.3. TC 1.1.50 Simulation After the final modifications on the vehicle model, the simulation was setup according to TC 1.1.50 After the final modifications on the vehicle model, the simulation was setup according to TC conditions specified in EN 1317 part 3 . This head-on crash test with 900 kg vehicle is performed 1.1.50 conditions specified in EN 1317 part 3 . This head-on crash test with 900 kg vehicle is to evaluate the energy-absorption capability of the UCC design and its effectiveness at reducing the performed to evaluate the energy-absorption capability of the UCC design and its effectiveness at velocity of impacting vehicle in a controlled manner, thus reducing occupant injury risks. As shown reducing the velocity of impacting vehicle in a controlled manner, thus reducing occupant injury in Figure 6, the vehicle was positioned in front of the cushion at 0 degrees impact angle. The vehicle risks. As shown in Figure 6, the vehicle was positioned in front of the cushion at 0 degrees impact speed was 50 kph. In this simulation no dummy was used. Simulation was run about 0.15 s until the angle. The vehicle speed was 50 kph. In this simulation no dummy was used. Simulation was run vehicle’s kinetic energy completely dissipated by the crash cushion and vehicle was pushed backwards. about 0.15 s until the vehicle’s kinetic energy completely dissipated by the crash cushion and vehicle was pushed backwards. As shown in Figure 7, vehicle hit the barrier; instantly, the front container began to deform and bent towards the impacting vehicle. 0.06 s after the initial impact, the kinetic energy of the vehicle was significantly reduced and the velocity of the vehicle was approximately 28
Safety 2018, 4, 48 6 of 11 As shown in Figure 7, vehicle hit the barrier; instantly, the front container began to deform and bent Safety Safety 2018, towards 4, 4, xx FOR 2018,the PEER PEER REVIEW impacting FOR vehicle. 0.06 s after the initial impact, the kinetic energy of the vehicle66 was REVIEW of of 11 11 significantly reduced and the velocity of the vehicle was approximately 28 km/h. 0.072 s after the km/h. km/h. 0.072 0.072 ss after after the the initial initial contact, the the second contact,began second container container began began toto deform deform and absorbed the rest of initial contact, the second container to deform and absorbed the restand absorbed of the kinetic the rest of energy of the kinetic the vehicle. energy kinetic energy of the of the vehicle. vehicle. Thus, 0.12 Thus, impact s after 0.12 s after the initial impact with the UCC, vehicle was the Thus, 0.12 s after the initial with the initial vehicle the UCC, impact was withbrought the UCC, to avehicle was controlled brought brought to to aa controlled controlled stop. stop. Vehicle Vehicle left left the the UCC UCC in in aa stable stable and and upright upright position. position. Energy Energy stop. Vehicle left the UCC in a stable and upright position. Energy absorption performance of the UCC absorption absorption performance performance of of the the UCC UCC was acceptable, which resulted in low low occupant risk values that was acceptable, which resulted in lowwas acceptable, occupant which that risk values resulted wereinmeasured occupant insiderisk thevalues that vehicle. A were were measured measured inside inside the the vehicle. vehicle. A A picture picture of of the the deformed deformed shape shape of of the the barrier barrier after after TC TC 1.1.50 1.1.50 picture of the deformed shape of the barrier after TC 1.1.50 simulation is shown in Figure 8. Based on simulation simulation is is shown shown in in Figure Figure 8. 8. Based Based on on the simulation thethat simulation predictions, predictions, it it was determined wascontained determined that UCC the simulation predictions, it was determined UCC design successfully andthat UCC stopped design design successfully successfully contained and containedinjury stopped and stopped 900 kg vehicle with minimal injury risk to 900 kg vehicle with minimal injury risk to occupants. occupants. 900 kg vehicle with minimal risk to occupants. Full-Scale Full-Scale Crash Crash Test Test TC TC 1.1.50 1.1.50 LS-DYNA LS-DYNA Simulation Simulation Figure Figure 6. 6. The The 900 900 kg kg car car positioned positioned in in front of UCC front of UCC barrier barrier before before TC TC 1.1.50. 1.1.50. 1.1.50. Figure 7. Cont.
Safety 2018, 4, 48 7 of 11 Safety Safety 2018, 2018, 4, x4,FOR x FOR PEER PEER REVIEW REVIEW 7 of711 of 11 Figure Figure Figure 7. 7. Sequential 7. Sequential Sequential picture picture picture comparison comparison comparison of of of UCC UCCUCC after after after TCTC TC 1.1.50 1.1.50 1.1.50 crash crash crash testtest andand simulation. simulation. Figure 8. Deformed Figure shape 8. Deformed comparison shape of of comparison UCC after UCC TC 1.1.50 after crash test and simulation. Figure 8. Deformed shape comparison of UCC after TCTC 1.1.50 1.1.50 crash crash testtest andand simulation. simulation.
Safety 2018, 4, 48 8 of 11 Safety Safety 2018, 2018, 4, 4, xx FOR FOR PEER PEER REVIEW REVIEW 88 of of 11 11 4.4. TC 4.2.50 Simulation A second secondsimulation simulationstudystudywas was also also performed performed to evaluate to evaluate side impact side impact capacity capacity of the UCCof thedesign. UCC design. As As described described by test TC by4.2.50, test TC 4.2.50, a 1300 kg acar 1300 kg car model wasmodel was positioned positioned so that so that it would it would impact impact the cushion the cushion 1/3rd of the length (see Figure 9). The vehicle contacted the barrier 1/3rd of the length (see Figure 9). The vehicle contacted the barrier at 15 degrees angle, and the velocityat 15 degrees angle, and of thethe velocity vehicle justofbefore the vehicle the impactjust was before50 the kph.impact was the Following 50 kph. initialFollowing contact, asthe initialincontact, shown Figure 10,as shown first andinsecond Figurecontainers 10, first and second began containers to deform beganthus laterally, to deform absorbing laterally, thus absorbing the impact energy of the the vehicle. impact energy As of the vehicle. the vehicle continued As totheslide vehicle continued on the to slide side of the UCC,onit the side ofmore contacted the UCC, it contacted containers more and vehicle containers and vehicle speed was further speed reduced. wass after At 0.1 furtherthereduced. At 0.1 initial impact, thes first afterfour the containers initial impact, the moderate received first four containers damage and received vehicle’s moderate velocity damage was almost and28vehicle’s kph. Asvelocity shown in was almost 28 sequential kph. As pictures shown 10, in Figure in sequential pictures in Figure 10, 0.2 s after the initial impact, cushion was able 0.2 s after the initial impact, cushion was able to contain and redirect impacting vehicle without any to contain and redirect impacting breakage ofvehicle withoutDamage the elements. any breakage to the UCC of theandelements. Damage vehicle were to theThe moderate. UCC and vehicle vehicle were left the UCC moderate. The vehicle left the UCC in a stable and upright position. Energy in a stable and upright position. Energy absorption performance of the UCC was acceptable, which absorption performance of the UCC resulted wasoccupant in low acceptable, riskwhich valuesresulted measured in low occupant inside risk values the vehicle. measured A picture inside theshape of the deformed vehicle. of A thepicture barrierof theTC after deformed shape of the 4.2.50 simulation barrierinafter is shown FigureTC11. 4.2.50 Based simulation is shownpredictions, on the simulation in Figure 11. it Based on the simulation predictions, it was determined that UCC design has was determined that UCC design has the potential to satisfy 50 kph test requirements described at EN the potential to satisfy 50 kph 1317 test part 3. requirements described at EN 1317 part 3. Figure Figure 9. 9. The The 1300 1300 kg kg car car positioned positioned in in front front of of UCC UCC barrier before TC barrier before TC 4.2.50. 4.2.50. Figure 10. Cont.
Safety 2018, 4, 48 9 of 11 Safety 2018, 4, x FOR PEER REVIEW 9 of 11 Safety 2018, 4, x FOR PEER REVIEW 9 of 11 Figure 10. Sequential pictures comparison of UCC after TC 4.2.50 crash test and simulation. Sequential pictures Figure 10. Sequential Figure pictures comparison comparison of UCC after TC 4.2.50 crash test and simulation. Figure 11. Deformed shape comparison of UCC after TC 4.2.50 crash test and simulation. Figure 11. Deformed shape comparison of UCC after TC 4.2.50 crash test and simulation. Figure 11. Deformed shape comparison of UCC after TC 4.2.50 crash test and simulation. 5. Full-Scale Crash Testing 5. Full-Scale Crash Testing After performing 5. Full-Scale two successful simulation studies for tests TC 1.1.50 and TC 4.2.50, same tests Crash Testing were performed using two After performing successful full scale crashsimulation studies cushion. Crash forwere tests testsrun TC 1.1.50 and TC in Istanbul 4.2.50, during thesame tests summer After performing two successful simulation studies for tests TC 1.1.50 and TC 4.2.50, same tests were of performed 2016. using These tests werefull scale crash intended cushion. to both verifyCrash tests werefindings the simulation run in Istanbul during theprove and conclusively summer the were performed using full scale crash cushion. Crash tests were run in Istanbul during the summer of 2016. Theseoftests acceptability UCCwere intended design to both for 50 kph verify the simulation findings and conclusively prove the conditions. of 2016. These tests were intended to both verify the simulation findings and conclusively prove the acceptability of UCC design for 50 kph conditions. acceptability 5.1. Crash TestofTC UCC design for 50 kph conditions. 1.1.50 5.1. Crash Test TC As shown 1.1.50 6 and 7, a full-scale crash test was performed on UCC design according to in 1.1.50 Figures 5.1. Crash Test TC EN 1317 part 3 TC As shown 1.1.50 conditions in Figures 6 and 7, a. The UCC full-scale crashdesign wasperformed test was installed ononconcrete pavement UCC design and the according to impactAs shown in Figures 6 and 7, a full-scale crash test was performed on UCC design according to EN 1317point, part 3asTC described in EN 1317 1.1.50 conditions .part The3, wasdesign UCC a 1991wasmodel Ford Taurus, installed on concretewhich used as and pavement the test the EN 1317 The vehicle. parttotal 3 TCmass 1.1.50ofconditions the tested . The UCC 900 vehicle design was installed on concrete kg pavement and the impact point, as described in EN 1317 part 3,was was a 1991 kg when model empty Ford and Taurus,1300which with usedtheasaddition the test impact of dummy point, as described in EN 1317 part 3, was a 1991 model Ford Taurus, which used as the test vehicle. Theandtotalmeasurement mass of the testeddevices. The was vehicle vehicle 900 positioned kg when empty in the test1300 and track kgaccelerated towards with the addition of vehicle. the The total test article at anmass of the angle tested ofdevices. zero vehicle degrees was a900 using kg when cable pullyinempty mechanismand 1300 kg with the andaccelerated impacted theaddition of barrierthe at dummy and measurement The vehicle positioned the test track towards dummy 51.5 kph.and measurement Behavior of the devices. and The vehicleare positioned in the test track accelerated towards the test article at an angle of UCC zero degrees the using vehicle a cable illustrated in Figure pully mechanism 7. As and expected,the impacted vehicle was barrier at test not article at an angle of zero degrees using a cable pully mechanism and impacted the barrier at 51.5able kph.toBehavior damage of thethe cushion UCC and significantly. the vehicle Only the first and are illustrated insecond Figure containers compressed 7. As expected, vehicle and was 51.5 kph. Behavior absorbed ofenergy the UCC andvehicle. the vehicle are illustrated in Figurein7.an Asacceptable expected, manner vehicle was not able tothe kinetic damage the cushion of thesignificantly. The vehicle Only slowed the first anddown second containers compressed and and not came able to ato damage stop. Data the cushion collected significantly. from the Only accelerometer, the first which and was second containers installed at the compressed vehicle’s and center of absorbed the kinetic energy of the vehicle. The vehicle slowed down in an acceptable manner and absorbed gravity, the kinetic energy of the vehicle. The vehicle slowed down in an acceptable manner and came towere used a stop. to calculate Data collectedthe fromoccupant injury risks. which the accelerometer, Due towas the softened installednose at thedesign of the vehicle’s barrier center of came and to aspeed low stop. of Data collected vehicle occupantfrom injury the accelerometer, risk, the valueswhich were was installed at determined to the be vehicle’s center negligible. Resultsof gravity, were used to calculate the occupant injury risks. Due to the softened nose design of the gravity, of TC 1.1.50werecrash usedtestto calculatethat the theoccupant injuryisrisks. Due to to thecontain softened andnose design of the barrier and low speed showed of vehicle occupant UCC design injury risk, soft enough the values were determined stop annegligible. to be impacted barrier vehicle andanlow speed ofmanner. vehicle occupant injury risk, the values were determined to be negligible. Results in of TCacceptable 1.1.50 crash test showed that the UCC design is soft enough to contain and stop an Results of TC 1.1.50 crash test showed that the UCC design is soft enough to contain and stop an impacted vehicle in an acceptable manner. impacted vehicle in an acceptable manner.
Safety 2018, 4, 48 10 of 11 5.2. Crash Test TC 4.2.50 After repairing damaged containers and rotating the cushion 15 degrees, a second crash test was performed on UCC design according to EN 1317 part 3 test TC 4.2.50 conditions . As shown in Figure 9, a 1320 kg Ford Taurus impacted the barrier with a speed of 51 kph and at an angle of 15 degrees. The impact point was 1.5 m away from the nose, which is equal to one third of the distance of the UCC. Following the initial contact, as shown in Figure 10, first two containers that received the impact force began to deform and absorb the initial impact loads. As the vehicle continued to slide on the side of the UCC, as in the simulation study, it contacted barriers number three and four, which reduced the vehicle speed a further 0.1 s; after the initial impact, the first four containers received moderate damage and the vehicle’s velocity was almost 32 kph. As shown in sequential pictures in Figure 10, 0.22 s after the initial impact, cushion was able to contain and redirect the impacting vehicle in an acceptable manner. Damage to the UCC and vehicle were moderate. The vehicle left the UCC in a stable and upright position. Energy absorption performance of the UCC was acceptable, which resulted in low occupant risk values measured inside the vehicle. A picture of the deformed shape of the barrier after TC 4.2.50 crash test is shown in Figure 11. As predicted by LS-DYNA simulation study, UCC design successfully passed the 50 kph test requirements described in EN 1317 part 3 . 6. Summary and Conclusions This paper deals with designing, analyzing, and testing a new, reusable, low-cost, and simple crash cushion, UCC, for roads with 50 kph speed limits. UCC design included LLDPE containers with embedded LLDPE energy-absorbing tubes as dampers. The design was strengthened by steel cables and steel plates. The crashworthiness of the system was evaluated both numerically and experimentally. Finite element analysis of the UCC design showed that the design is flexible enough to contain, and successfully stop, a 900 kg car impacting head-on and rigid enough to successfully redirect the 15 degree side impact of a 1300 kg vehicle at one third of the location of the design. Following the promising simulation study, the design was installed at a test facility and two full scale crash tests were performed on UCC to conclusively determine its performance under 50 kph vehicle impacts. Both simulation and crash test results agreed well, proving the crashworthiness and acceptability of the design at 50 kph. Damage to UCC was moderate, and the occupant risk factors were below injury threshold. Since UCC design is composed of modular elements, the design could be easily repaired and put back to service. Finally, performing further crash tests at higher speeds, such as 80, 100, and 110 kph, is recommended to fully assess the acceptability of the new crash cushion system developed. Author Contributions: A.O.A. and M.B. carried out the finite element simulations performed full-scale crash tests and constructed the manuscript. K.K. provided the crash cushion design, materials and prepared the setup to perform full-scale crash tests. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest. References 1. Istanbul Metropolitan Municipality (IMM). Istanbul Traffic Safety Strategic Plan; Technical Report IBB-3-TS04; Istanbul Metropolitan Municipality: Istanbul, Turkey, 2016. 2. TRA. Traffic Safety Handbook; Turkish Road Association, Department of Transportation: Ankara, Turkey, 2011. 3. American Association of State Highways and Transportation Officials (AASHTO). Roadside Design Guide, 4th ed.; American Association of State Highways and Transportation Officials: Washington, DC, USA, 2011. 4. FHWA. Online Guide to Crash Cushions. Federal Highway Administration, U.S. Department of Transportation, Washington, DC, USA, 2013. Available online: https://safety.fhwa.dot.gov/roadwaydept/ countermeasure/docs/CrashCushionsNov2013Safelogo.pdf/ (accessed on 6 March 2018). 5. TUİK. Vehicle data on Turkish Highways; Turkish Statistics Organization: Ankara, Turkey, 2016.
Safety 2018, 4, 48 11 of 11 6. CEN. European Committee for Standardization. European Standard EN1317, Road Restraint Systems—Part 3: Performance Classes, Impact Test Acceptance Criteria and Test Methods for Crash Cushions; Committee European de Normalization (CEN): Brussels, Belgium, 2010. 7. Livermore Software Technology Corporation (LSTC). LS-DYNA Keyword User’s Manual; Livermore Software Technology Corporation: Livermore, CA, USA, 2017. 8. Cozzi, A.C.; Briasco, B.; Salvarani, E.; Mannucci, B.; Fangarezzi, F.; Perugini, P. Evaluation of Mechanical Properties and Volatile Organic Extractable to Investigate LLDPE and LDPE Polymers on Final Packaging for Semisolid Formulation. Pharmaceutics 2018, 10, 113. [CrossRef] [PubMed] 9. Ulukur. TC 1.1.50 Crash Tests on UCC Crash Cushion; Test No. 001/ITU/17; Crash Test Facility: Istanbul, Turkey, 2017. 10. Ulukur. TC 4.2.50 Crash Tests on UCC Crash Cushion; Test No. 002/ITU/17; Crash Test Facility: Istanbul, Turkey, 2017. 11. Atahan, A.O.; Bonin, G. Numerical analysis of an H4a heavy containment level transition. Int. J. Heavy Veh. Syst. 2006, 13, 351–365. [CrossRef] 12. Vesenjak, M.; Borovinsek, M.; Ren, Z. Computational and experimental crash analysis of the road safety. Eng. Fail. Anal. 2005, 12, 963–973. 13. FEMA. Finite Element Model Archive, FHWA/NHTSA National Crash Analysis Center, Virginia, 2002. Available online: http://www.ncac.gwu.edu/vml/models.html (accessed on 6 March 2018). 14. Atahan, A.O. Vehicle crash test simulation of roadside hardware using LS-DYNA: A literature review. Int. J. Heavy Veh. Syst. 2009, 17, 52–75. [CrossRef] © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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