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62 asperity width is the same as that used in Test 1 and Test 3. A summary of Test 5 follows. CRASH TEST 5 (474630-5) The New Jersey concrete safety shape barrier evaluated in the fifth test had asperities that were 559 mm wide and 38 mm deep. The asperity inclination angle was 90 degrees, and the asperity spacing was 203 mm. A photograph of the barrier before the test is shown in Figure 75. The barrier was impacted by a 2105-kg pickup truck at an angle of 24.5 degrees and a speed of 97.8 km/h. The barrier contained and redirected the pickup truck. The vehicle did not penetrate, underride, or override the installation. The vehi- cle remained upright during and after the collision period. The Figure 76. Barrier damage for Crash Test 5. longitudinal occupant impact velocity and ridedown accelera- tions were within acceptable limits of NCHRP Report 350. Maximum OCD was 77 mm in the left firewall area. The first bility and OCD, the research team decided to verify applica- through fifth "ribs" between asperities downstream of the im- bility of the guidelines for small passenger cars. The most pact point showed some scraping close to the edges but were severe asperity configuration evaluated in the first five tests intact after the test (see Figure 76). The crash test met the eval- was selected to evaluate small-car response. Recall that the uation criteria presented in NCHRP Report 350. asperity configuration evaluated in Test 2 generated unac- The asperity configuration in Test 5 was similar to that in ceptable OCD in the pickup. This same configuration was Test 3, except that the asperity angle was changed from 45 de- used in Test 6 with the 820C vehicle. Values for the pertinent grees to 90 degrees and the asperity spacing was increased asperity variables are given below. from 25 mm to 203 mm. The OCD values from both tests were very close (74 mm in Test 3 versus 77 mm in Test 5). Test 6: d = 13 mm, W = 178 mm, Ws = 25 mm, = Other occupant risk values were also similar between the two 45 degrees (small-car impact) tests. Simulation results, which were based on rigid asperities with a 25-mm asperity spacing, indicated that the internal CRASH TEST 6 (474630-6) energy of the floorboard was 8.4 kJ and 8 kJ for the asperity configurations evaluated in Test 3 and Test 5, respectively. The New Jersey concrete safety shape barrier evaluated in Comparison of the results from the two tests indicates that the sixth test had asperities that were 178 mm wide and 13 mm although shearing off of the concrete between asperities may deep. The asperity inclination angle was 45 degrees, and the reduce the severity of the impact, the overall effect on test out- asperity spacing was 25 mm. A photograph of the barrier come is not very significant. before the test is shown in Figure 77. Although the pickup truck is generally understood to be The barrier was impacted by an 854-kg Geo Metro at an more critical than the small car in regard to evaluating sta- angle of 19.4 degrees and a speed of 98.8 km/h. The barrier Figure 75. Setup for Crash Test 5. Figure 77. Setup for Crash Test 6.
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63 from 25 mm to 203 mm. While this prevented the concrete between asperities from shearing off in the test, the effect of asperity spacing on the preliminary guidelines established using finite element simulations with rigid barriers was not completely known. To further investigate the effect of this variable on snagging severity and OCD, additional simula- tion runs were conducted to establish the relationship between asperity depth and asperity width for an asperity spacing (Ws) of 203 mm and an asperity angle of 45 degrees. The simu- lated configurations and their corresponding results for the surrogate OCD measure are presented in Table 7. Using the previously established thresholds for the surrogate OCD, a failure line similar to the previous preliminary guidelines was established. Figure 79 shows this failure line (for Figure 78. Barrier damage for Crash Test 6. Ws = 203 mm) with the previously established failure line (for Ws = 25 mm) for the 45-degree asperities. During the course of this simulation study on asperity contained and redirected the small passenger car. The vehi- spacing, it was discovered that identical finite element mod- cle did not penetrate, underride, or override the installation. els (both barrier and truck) produced different results for the The vehicle remained upright during and after the collision truck floorboard internal energy when different binary files period. The longitudinal occupant impact velocity and ride- of LS-DYNA were used. Consequently all new simulations down accelerations were within acceptable limits of NCHRP were performed using the exact same binary files (LS-DYNA Report 350. There was no OCD, and the vehicle showed good Version 970 Release 3858) that were used in the initial stability. The third through tenth "ribs" between asperities simulation effort on which the preliminary guidelines were downstream from the point of impact showed some scraping established. The reason for this variance could not be identi- and gouging but were intact after the test (see Figure 78). The fied. However, using the same binaries that were originally crash test met the evaluation criteria presented in NCHRP used to establish the surrogate OCD thresholds eliminates Report 350. variance when comparing the simulation results associated There were no concerns related to stability or OCD with with the two different asperity spacings. the 820C small car for an asperity configuration that was It can be seen from Figure 79 that increasing the asperity unacceptable for the pickup truck. Therefore, this test veri- spacing results in an offset (i.e., upward shift) of the failure fied that the pickup truck was a more critical vehicle than the line. That is, for a given asperity width, the acceptable asper- small car in regard to establishing guidelines for aesthetic ity depth increases as the asperity spacing increases. Note that surface treatments for safety shape barriers. as the asperity width (W) decreases to a value of 200 mm or less, a significant increase in the asperity depth (d) can be Simulation Study for Wider Asperity Spacing achieved. This is because even though d is large, the larger asperity spacing (Ws) at an asperity width of 200 mm reduces To investigate the effect of asperity spacing on severity of the potential for vehicle parts to intrude into the asperity. Thus, snagging, the asperity spacing (Ws) was increased in Test 5 the opportunity for vehicle snagging and cumulative vehicle TABLE 7 Parametric study results for a 45-degree angle of asperity with 203-mm asperity spacing Asperity Asperity Truck Floorboard Width (W) Depth (d) Internal Energy Run Vehicle [mm] [mm] [J] Pass/Fail 1 Truck 559 0 1,108 Pass 2 Truck 559 51 10,300 Marginal 3 Truck 559 63.5 10,620 Marginal 4 Truck 280 0 1,108 Pass 5 Truck 280 38 9,600 Marginal 6 Truck 180 0 1,108 Pass 7 Truck 180 19 3,730 Marginal 8 Truck 180 51 3,250 Fail 9 Truck 180 76 3,050 Pass Passing Limit = 2,200 J Failure Limit = 10,700 J