Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance (2022) / Chapter Skim
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19 Introduction The computer simulation analyses described here were conducted to help update the AASHTO LRFD (6) and the AASHTO Roadside Design Guide (15)
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20 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Figure 2.3. TxDOT T1W FE computer model.
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Preliminary Evaluation of AASHTO Geometric Curves 21 0.000 s 0.086 s 0.171 s 0.257 s Figure 2.4. Sequential photographs of T224 FE simulation and full-scale crash test.
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22 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0.340 s 0.426 s 0.512 s 0.597 s Figure 2.4. (Continued)
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Figure 2.5. RSVVP multichannel evaluation for TxDOT T224 crash test and simulation.
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24 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Table 2.1 shows a comparison of the occupant risk metrics, which are the occupant impact velocity (OIV) , ridedown acceleration (RDA)
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Preliminary Evaluation of AASHTO Geometric Curves 25 0.250 s 0.340 s 0.400 s 0.170 s Figure 2.6. (Continued)
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26 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance The vehicle's x, y, and z accelerations and roll, pitch, and yaw rates from the computer simulation were compared to the full-scale crash test. A quantitative comparison was performed using RSVVP.
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Figure 2.7. RSVVP multichannel evaluation for TxDOT T1W crash test and simulation.
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28 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Full-Scale Crash Test Computer Simulation Maximum Limits Roll (deg.) −15.0 −22.5 75 Pitch (deg.)
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Preliminary Evaluation of AASHTO Geometric Curves 29 Simulations were first performed with the small car impacting the TxDOT T224 bridge rail. The simulation impact speed and angle were 62.6 mph and 25.1 degrees, respectively.
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30 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0.400 s 0.450 s 0.200 s 0.300 s Figure 2.11. (Continued)
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Figure 2.12. RSVVP multichannel evaluation for TxDOT T224 crash test and simulation.
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32 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Full-Scale Crash Test Computer Simulation Longitudinal OIV (m/s) 9.6 7.6 Lateral OIV (m/s)
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0.300 s 0.400 s 0.500 s 0.200 s Figure 2.13. (Continued)
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Figure 2.14. RSVVP multichannel evaluation for TxDOT T1W crash test and simulation.
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Preliminary Evaluation of AASHTO Geometric Curves 35 vehicle. It was not deemed necessary to improve the vehicle model further based on the overall behavior of the vehicle and other occupant metrics being similar to the full-scale crash test.
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36 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance did not perform acceptably according to MASH evaluation criteria, then the line being evaluated was moved toward the opposing line. If the bridge rails performed acceptably according to MASH evaluation criteria, then the line being evaluated was adequate.
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Preliminary Evaluation of AASHTO Geometric Curves 37 The concrete post-and-beam rails were modeled as rigid material. Figure 2.18 shows an FE model of one of the concrete post-and-beam bridge rail systems.
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38 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Figure 2.19. Profile view of a deck-mounted metal post-andbeam rail showing the geometric variables.
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Preliminary Evaluation of AASHTO Geometric Curves 39 The research team selected several common dimensions for the bridge rail models. For all bridge rails, a post spacing of 10 ft.
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40 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance to be more critical in terms of vehicle snagging that can lead to high occupant risk factors. For the curb-mounted metal post-and-beam systems, a curb height of 6 in.
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Preliminary Evaluation of AASHTO Geometric Curves 41 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 2 4 6 8 10 12 Simulation Cases Post Setback Distance (in.) Ra tio o f R ai l C on ta ct W id th to H ei gh t Figure 2.26.
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42 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Figures 2.28 and 2.29 show the bridge rail configurations evaluated for deck-mounted metal post-and-beam geometrics. Figures 2.30 and 2.31 show the bridge rail configurations evaluated for curb-mounted metal post-and-beam geometrics.
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Preliminary Evaluation of AASHTO Geometric Curves 43 not possible to use bridge rail systems that would plot along the bottom curve of Figure 2.32. The points plotted in the figure show realistic bridge rail configurations for the different post setback values.
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44 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 2 4 6 8 10 12 Simulation Cases Post Setback Distance (in.) Ra tio o f R ai l C on ta ct W id th to H ei gh t Figure 2.32.
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Preliminary Evaluation of AASHTO Geometric Curves 45 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 2 4 6 8 10 12 Concrete Post and Beam Metal Post and Beam DeckMounted Metal Post and Beam CurbMounted Metal Post and Beam ParapetMounted Post Setback Distance (in.) Ra tio o f R ai l C on ta ct W id th to H ei gh t Figure 2.34.
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46 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Computer Simulation Results FE computer simulations were performed on the bridge rail models presented in the previous section. MASH Test 3-10 and Test 3-11 impact simulations were conducted on each bridge rail system.
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Preliminary Evaluation of AASHTO Geometric Curves 47 0.500 s 0.600 s 0.400 s Gut View Overhead ViewTime Figure 2.36. (Continued)
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48 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0.500 s 0.600 s 0.200 s 0.300 s 0.400 s Gut View Overhead ViewTime Figure 2.37. (Continued)
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Preliminary Evaluation of AASHTO Geometric Curves 49 Figures 2.38 and 2.39 show sequential gut and overhead views of an FE simulation performed on the MPBD-SP-System01 bridge rail. A total of 48 simulations were performed for the deckmounted metal post-and-beam rails.
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50 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0.500 s 0.600 s 0.400 s Gut View Overhead ViewTime Figure 2.38. (Continued)
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Preliminary Evaluation of AASHTO Geometric Curves 51 0.500 s 0.600 s 0.200 s 0.300 s 0.400 s Gut View Overhead ViewTime Figure 2.39. (Continued)
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52 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Gut View 0.000 s 0.100 s 0.200 s 0.300 s 0.400 s Overhead ViewTime Figure 2.40. Sequential simulation frames gut and overhead views for parapet-mounted metal post-and-beam MASH Test 3-10.
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Preliminary Evaluation of AASHTO Geometric Curves 53 0.500 s 0.600 s Gut View Overhead ViewTime Figure 2.40. (Continued)
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54 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0.500 s 0.600 s 0.300 s 0.400 s Gut View Overhead ViewTime Figure 2.41. (Continued)
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Preliminary Evaluation of AASHTO Geometric Curves 55 0.000 s 0.100 s 0.200 s 0.300 s 0.400 s Gut View Overhead ViewTime Figure 2.42. Sequential simulation frames gut and overhead views for curb-mounted metal post-and-beam MASH Test 3-10.
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56 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0.500 s 0.600 s Gut View Overhead ViewTime Figure 2.42. (Continued)
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Preliminary Evaluation of AASHTO Geometric Curves 57 0.500 s 0.600 s 0.300 s 0.400 s Gut View Overhead ViewTime Figure 2.43. (Continued)
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58 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance Overall, a total of 196 simulations were conducted. No modifications were made to the pickup truck vehicle model during the simulation runs.
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Preliminary Evaluation of AASHTO Geometric Curves 59 the results for the concrete post-and-beam bridge rail simulations. One simulation did result in a failed occupant risk metric: the lateral RDA for one of the bridge rail systems was 20.7 g's in the MASH Test 3-10 simulation, which exceeded the 20.49 g MASH limit.
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60 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 2 4 6 8 10 12 Pass Max OIV/RDA Pass Preferred OIV/RDA Fail OIV/RDA Ra tio o f R ai l C on ta ct W id th to H ei gh t Post Setback Distance (in.) Figure 2.47.
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Preliminary Evaluation of AASHTO Geometric Curves 61 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 2 4 6 8 10 12 Pass Max OIV/RDA Fail OIV/RDA Ra tio o f R ai l C on ta ct W id th to H ei gh t Post Setback Distance (in.) Figure 2.49.
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62 Evaluation of Bridge Rail Systems to Confirm AASHTO MASH Compliance 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 2 4 6 8 10 12 Pass Max OIV/RDA Pass Preferred OIV/RDA Ra tio o f R ai l C on ta ct W id th to H ei gh t Post Setback Distance (in.) Figure 2.51.
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Preliminary Evaluation of AASHTO Geometric Curves 63 The geometry of both bridge rail systems resulted in points being plotted as shown in Figure 2.53. While one system had a curb and the other was deck-mounted, both systems had the same post setback, vertical clear opening, and ratio of rail contact width to height.
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