crash testing and evaluation of the txdot type t8 bridge rail · austin, texas 78763-5080 14....

TTI: 407049-1

Crash Testing and Evaluation of the TxDOT Type T8 Bridge Rail

Report 407049-1 March 2008

TEXAS TRANSPORTATION INSTITUTE THE TEXAS A&M UNIVERSITY SYSTEM

COLLEGE STATION, TEXAS

TEXAS DEPARTMENT OF TRANSPORTATION

Technical Report Documentation Page 1. Report No. 407049-1

2. Government Accession No.

3. Recipient's Catalog No. 5. Report Date March 2008

4. Title and Subtitle CRASH TESTING AND EVALUATION OF THE TxDOT TYPE T8 BRIDGE RAIL

6. Performing Organization Code

7. Author(s) William F. Williams, Roger P. Bligh, and Wanda L. Menges

8. Performing Organization Report No. Report 407049-1 10. Work Unit No. (TRAIS)

9. Performing Organization Name and Address Texas Transportation Institute The Texas A&M University System College Station, Texas 77843-3135

11. Contract or Grant No. Project 407049 13. Type of Report and Period Covered Technical Report: September 2007 – January 2008

12. Sponsoring Agency Name and Address Texas Department of Transportation Research and Technology Implementation Office P.O. Box 5080 Austin, Texas 78763-5080

14. Sponsoring Agency Code

15. Supplementary Notes Project Title: Structural Analysis and Design of the TxDOT Type T8 Bridge Rail Design 16. Abstract

The Texas Type T6 was previously crash tested and evaluated under NCHRP Report 230 guidelines.

The two tests included a test with a 4500 lb passenger vehicle traveling at 61.5 mph and 27.5 degrees, and a test with a 2282 lb passenger vehicle traveling at 58.0 mph and 14 degrees. The T6 bridge rail performed acceptably during these two tests. However, with the adoption of NCHRP Report 350, TxDOT required reevaluation of the bridge rail using the 4409 lb pickup truck. Several crash tests have been performed on variations of the T6 bridge rail. No crash test to date has been successful with respect to NCHRP Report 350 TL-3 requirements. Reevaluation and redesign of the T6 post and base plate design has resulted from the previous testing.

The performance of the T6 bridge rail and the vehicle stability issues associated with this design, has led to the development of the tubular T8 bridge rail that was tested for this project. With the height increased from 27 inches to 31 inches and the stiffness of the rail element increased for the tubular thrie-beam rail element, the crash performance of the T8 was expected to be improved over the T6 bridge rail design. In addition, the similarities between the T6 and T8 bridge rails would result in a more simple and cost effective replacement for the T6 bridge railings that are currently in place on scores of off-system bridges across the state. There was concern of performance of the Texas Type T8 bridge rail, as well as concern for vehicle stability. The pickup truck test is considered to be the critical test in the evaluation of the longitudinal barriers in terms of structural adequacy, vehicle stability, barrier override, and occupant compartment deformation. Reported herein are the details of the Texas Type T8 bridge rail, and the description of the pickup truck test and the results of that test. The TxDOT Type T8 bridge rail did not perform acceptably for NCHRP Report 350 test 3-11 due to vehicle rollover. 17. Key Words Bridge Rail, W-Beam Guardrail, Tubular Thrie Beam, Concrete Cantilevered Deck, Steel Post, Roadside Safety, Crash Testing.

18. Distribution Statement No restrictions.

19. Security Classif.(of this report) Unclassified

20. Security Classif.(of this page) Unclassified

21. No. of Pages

54

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

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DISCLAIMER

The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data, and the opinions, findings, and conclusions presented herein. The contents do not necessarily reflect the official view or policies of the Texas Department of Transportation (TxDOT), Federal Highway Administration (FHWA), The Texas A&M University System, or the Texas Transportation Institute. This report does not constitute a standard, specification, or regulation, and its contents are not intended for construction, bidding, or permit purposes. In addition, the above listed agencies assume no liability for its contents or use thereof. The names of specific products or manufacturers listed herein do not imply endorsement of those products or manufacturers. The engineer in charge of the project was William F. Williams, P.E. (Texas, #71898).

ACKNOWLEDGMENTS

This research project was conducted under a cooperative program between the Texas Transportation Institute, the Texas Department of Transportation, and the Federal Highway Administration. The TxDOT project director for this research was John Holt, P.E. (BRG) who helped guide this research. Mark Steves and Jon Ries, both bridge engineers with TxDOT, also provided insightful guidance to this project. The authors acknowledge and appreciate their assistance.

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TABLE OF CONTENTS

Page LIST OF FIGURES ....................................................................................................................... vi LIST OF TABLES........................................................................................................................ vii CHAPTER 1. INTRODUCTION ................................................................................................... 1

INTRODUCTION ...................................................................................................................... 1 BACKGROUND ........................................................................................................................ 1 OBJECTIVES/SCOPE OF RESEARCH ................................................................................... 2

CHAPTER 2. CRASH TEST PROCEDURES .............................................................................. 3

TEST FACILITY........................................................................................................................ 3 TEST ARTICLE ......................................................................................................................... 3 CRASH TEST CONDITIONS ................................................................................................... 4 EVALUATION CRITERIA ....................................................................................................... 4

CHAPTER 3. CRASH TEST RESULTS ..................................................................................... 15

TEST NO. 407049-1 (NCHRP REPORT 350 TEST DESIGNATION 3-11) .......................... 15 Test Vehicle .......................................................................................................................... 15 Soil and Weather Conditions ................................................................................................ 15 Test Description .................................................................................................................... 15 Damage to Test Installation .................................................................................................. 18 Vehicle Damage.................................................................................................................... 18 Occupant Risk Factors .......................................................................................................... 18

CHAPTER 4. SUMMARY AND CONCLUSIONS.................................................................... 25

ASSESSMENT OF TEST RESULTS...................................................................................... 25 CONCLUSIONS....................................................................................................................... 27

REFERENCES ............................................................................................................................. 29 APPENDIX A. CRASH TEST AND DATA ANALYSIS PROCEDURES ............................... 31

ELECTRONIC INSTRUMENTATION AND DATA PROCESSING ................................... 31 ANTHROPOMORPHIC DUMMY INSTRUMENTATION................................................... 32 PHOTOGRAPHIC INSTRUMENTATION AND DATA PROCESSING ............................. 32 TEST VEHICLE PROPULSION AND GUIDANCE.............................................................. 32

APPENDIX B. TEST VEHICLE PROPERTIES AND INFORMATION .................................. 33 APPENDIX C. SEQUENTIAL PHOTOGRAPHS ...................................................................... 37 APPENDIX D. VEHICLE ANGULAR DISPLACEMENTS AND ACCELERATIONS.......... 39

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LIST OF FIGURES Page Figure 1. Layout of the TxDOT Type T8 Bridge Rail................................................................. 5 Figure 2. Details of the Deck of the TxDOT Type T8 Bridge Rail Test Installation. ................. 6 Figure 3. Details of the Terminals Used for the

TxDOT Type T8 Bridge Rail Test Installation............................................................. 7 Figure 4. Details of the Deck Reinforcement of the

TxDOT Type T8 Bridge Rail Test Installation............................................................. 8 Figure 5. Details of the Tubular Rail Element of the

TxDOT Type T8 Bridge Rail Test Installation............................................................. 9 Figure 6. Details of the Rebar of the TxDOT Type T8 Bridge Rail Test Installation. .............. 10 Figure 7. Details of the Post of the TxDOT Type T8 Bridge Rail Test Installation.................. 11 Figure 8. Details of the Slots in Post of the TxDOT Type T8 Bridge Rail Test Installation..... 12 Figure 9. TxDOT Type T8 Bridge Rail Before Test 407049-1. ................................................ 13 Figure 10. Vehicle/Installation Geometrics for Test 407049-1. .................................................. 16 Figure 11. Vehicle Before Test 407049-1.................................................................................... 17 Figure 12. After Impact Trajectory for Test 407049-1. ............................................................... 19 Figure 13. Installation After Test 407049-1. ............................................................................... 20 Figure 14. Vehicle After Test 407049-1. ..................................................................................... 21 Figure 15. Interior of Vehicle for Test 407049-1. ....................................................................... 22 Figure 16. Summary of Results for NCHRP Report 350 Test 3-11

on the TxDOT Type T8 Bridge Rail........................................................................... 23 Figure B1. Vehicle Properties for Test 407049-1........................................................................ 33 Figure C1. Sequential Photographs for Test 407049-1 (Overhead and Frontal Views).............. 37 Figure D1. Vehicle Angular Displacements for Test 407049-1. ................................................. 39 Figure D2. Vehicle Longitudinal Accelerometer Trace for Test 407049-1

(Accelerometer Located at Center of Gravity). .......................................................... 40 Figure D3. Vehicle Lateral Accelerometer Trace for Test 407049-1

(Accelerometer Located at Center of Gravity). .......................................................... 41 Figure D4. Vehicle Vertical Accelerometer Trace for Test 407049-1

(Accelerometer Located at Center of Gravity). .......................................................... 42 Figure D5. Vehicle Longitudinal Accelerometer Trace for Test 407049-1

(Accelerometer Located Over Rear Axle). ................................................................. 43 Figure D6. Vehicle Lateral Accelerometer Trace for Test 407049-1

(Accelerometer Located Over Rear Axle). ................................................................. 44 Figure D7. Vehicle Vertical Accelerometer Trace for Test 407049-1

(Accelerometer Located Over Rear Axle). ................................................................. 45

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LIST OF TABLES Page Table 1. Performance Evaluation Summary for NCHRP Report 350 Test 3-11

on the TxDOT Type T8 Bridge Rail........................................................................... 28 Table B1. Exterior Crush Measurements for Test 407049-1....................................................... 34 Table B2. Occupant Compartment Measurements for Test 407049-1. ....................................... 35

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CHAPTER 1. INTRODUCTION INTRODUCTION Roadside safety devices perform the important function of preventing serious injury to motorists during roadside encroachments. To maintain the desired level of safety for the motoring public, these safety appurtenances must be designed to accommodate a variety of site conditions, placement locations, and a changing vehicle fleet. As changes are made or in-service problems are encountered, there is a need to assess the compliance of the specific safety device with current vehicle testing criteria, and modify the device or develop a new device with enhanced performance and maintenance characteristics. BACKGROUND

Throughout the years, the Texas Transportation Institute (TTI) and Texas Department of Transportation (TxDOT) have worked jointly on the development, evaluation, and testing of many TxDOT standard bridge rail designs. This cooperative research has resulted in many satisfactory designs with demonstrated impact performances that TxDOT has successfully implemented. The TxDOT T6 and T8 bridge rails are two such rails that were developed and tested at TTI.

On July 16, 1993, the Federal Highway Administration (FHWA) formally adopted the performance evaluation guidelines for the highwy safety features set forth in the National Cooperative Highway Research Program (NCHRP) Report 350 as a “guide or reference” document in the Federal Register, Volume 58, Number 135. (1) FHWA has also mandated that, on projects let after October 1998, only bridge railings that have successfully met the performance evaluation guidelines set forth in NCHRP Report 350 may be used on new construction projects on the National Highway System (NHS).

Changes incorporated into NCHRP Report 350 guidelines included new design test vehicles, expanded test matrices, and revised impact conditions. Of most significance was the adoption of a 4409 lb pickup truck as the design test vehicle for structural adequacy tests. This change has necessitated the retesting and reevaluation of the impact performance of many roadside safety features. Through various pool-funded studies and research projects, FHWA has tested some of the most widely used safety appurtenances, including scores of bridge rails and transitions. However, this testing was not all-inclusive. Some bridge rails, unique to TxDOT, have not been successfully crash tested to the NCHRP Report 350 guidelines. The TxDOT T6 bridge rail is one such bridge rail design that has not been successfully crash tested with respect to NCHRP Report 350 Test Level 3 (TL-3) requirements. The Texas Type T6 was previously crash tested and evaluated under NCHRP Report 230 guidelines. (2) The two tests included a test with a 4500 lb passenger vehicle traveling at 61.5 mph and 27.5 degrees, and a test with a 2282 lb passenger vehicle traveling at 58.0 mph and 14 degrees. The T6 bridge rail performed acceptably during these two tests. However, with the adoption of NCHRP Report 350, TxDOT required reevaluation of the bridge rail using the 4409 lb pickup truck.

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Several crash tests have been performed on several variations of the T6 bridge rail. No

crash test to date has been successful with respect to NCHRP Report 350 TL-3 requirements. Reevaluation and redesign of the T6 post and base plate design has resulted from the previous testing.

The performance of the T6 bridge rail and the vehicle stability issues associated with this design, has led to the development of the tubular T8 bridge rail that was tested for this project. With the height increased from 27 inches to 31 inches and the stiffness of the rail element increased for the tubular thrie-beam rail element, the crash performance of the T8 was expected to be improved over the T6 bridge rail design. In addition, the similarities between the T6 and T8 bridge rails would result in a more simple and cost effective replacement for the T6 bridge railings that are currently in place on scores of off-system bridges across the state. OBJECTIVES/SCOPE OF RESEARCH There was concern of performance of the Texas Type T8 bridge rail, as well as concern for vehicle stability. The pickup truck test is considered to be the critical test in the evaluation of the longitudinal barriers in terms of structural adequacy, vehicle stability, barrier override, and occupant compartment deformation. Reported herein are the details of the Texas Type T8 bridge rail, and the description of the pickup truck test and the results of that test.

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CHAPTER 2. CRASH TEST PROCEDURES TEST FACILITY The Texas Transportation Institute Proving Ground is a 2000-acre complex of research and training facilities located 10 mi northwest of the main campus of Texas A&M University. The site, formerly an Air Force base, has large expanses of concrete runways and parking aprons well suited for experimental research and testing in the areas of vehicle performance and handling, vehicle-roadway interaction, durability and efficacy of highway pavements, and safety evaluation of roadside safety hardware. The site selected for construction and testing of the bridge rail transitions evaluated under this project is along an out-of-service apron. The apron consists of an unreinforced jointed-concrete pavement in 12.5 ft by 15 ft blocks nominally 8 to 12 inches deep. The aprons are over 50 years old, and the joints have some displacement, but are otherwise flat and level. TEST ARTICLE

The Texas Department of Transportation (TxDOT) Type T8 bridge rail installation consisted of a 12 gauge tubular thrie-beam bridge rail supported by W6x8.5 steel posts anchored to 6.5-inch thick concrete cantilevered deck. The height to the top of the tubular thrie-beam rail was 31 inches. The length of T8 bridge rail and cantilevered deck constructed and tested for this project was 97 ft - 9 inches. The overall length of the T8 rail installation tested for this project was 112 ft- 6 inches. The T8 bridge rail was anchored on each end using ET Plus end terminals. These terminals connected to the T8 bridge rail using 12 gauge thrie-beam to W-beam transition rail elements. TTI received detailed information regarding the concrete cantilevered deck from John Holt with TxDOT. These details were incorporated into the installation tested for this project. Details for the installation are shown in figures 1 through 8.

The W6x8.5 steel post were welded to 12 inch x9-1/2 inch x1 inch thick base plate. Two

1/4 inch x 7/8 inch slots were machine cut on the traffic side face of the posts 3/4-inch above the top of the base plate. Each steel post with base plate was anchored to the 6-1/2-inch thick simulated cantilevered deck using four 7/8-inch diameter A307 anchor bolts. Please refer to figures 7 and 8 for additional details on the W6x8.5 steel post.

The cantilevered deck was 97 ft - 9 inches in length and was 6-1/2 inches thick. The

width of the cantilevered deck was 30 inches. Top transverse steel reinforcement in the deck consisted of #5 bars spaced at 6 inches on centers in the top mat. Bottom transverse steel reinforcement in the deck consisted of #5 bars spaced at 18 inches on centers. Longitudinal steel reinforcement in the top mat of steel reinforcement consisted of #4 bars spaced at 9 inches on centers. Longitudinal steel reinforcement in the bottom mat of steel reinforcement consisted of two #5 bars spaced approximately 3-1/4 inches on centers with a third bar located approximately 17 inches from the field side edge of the deck. The specified concrete strength used in the cantilevered deck was 3000 psi compressive strength. The compressive strength of the deck concrete was 3741 psi on the day the test was performed. Please refer to figures 2, 4, and 6 for

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additional information on the concrete cantilevered deck and TxDOT Type T8 Bridge Rail installation constructed and tested for this project. Photographs of the installation are shown in figure 9.

CRASH TEST CONDITIONS

NCHRP Report 350 recommends two tests for TL-3 evaluation of longitudinal barriers such as the TxDOT Type T8 Bridge Rail:

NCHRP Report 350 test designation 3-10: This test involves an 1808-lb passenger car impacting the critical impact point (CIP) in the length of need (LON) of the longitudinal barrier at a nominal speed and angle of 62 mi/h and 20 degrees, respectively. The purpose of this test is to evaluate the overall performance of the LON section in general and occupant risk in particular.

NCHRP Report 350 test designation 3-11: This test involves a 4409-lb pickup truck impacting the CIP in the LON of the longitudinal barrier at a nominal speed and angle of 62 mi/h and 25 degrees, respectively. The test is intended to evaluate the strength of the section for containing and redirecting the pickup truck.

The test reported herein corresponds to NCHRP Report 350 test designation 3-11. The pickup truck test is considered to be the critical test in the evaluation of the longitudinal barriers in terms of vehicle stability, barrier override, and occupant compartment deformation.

The critical impact point for the barrier for test designation 3-11 was chosen according to guidelines contained in NCHRP Report 350. The target impact point was at the one-third point of the installation length from the upstream end. The impact point was 14 ft upstream of the splice near the one-third point. All crash test, data analysis, and evaluation and reporting procedures were in accordance with guidelines presented in NCHRP Report 350. Appendix A presents brief descriptions of these procedures. EVALUATION CRITERIA Researchers evaluated the crash test performed in accordance with NCHRP Report 350. As stated in NCHRP Report 350, “Safety performance of a highway appurtenance cannot be measured directly but can be judged on the basis of three factors: structural adequacy, occupant risk, and vehicle trajectory after collision.” Accordingly, researchers used the safety evaluation criteria from Table 5.1 of NCHRP Report 350 to evaluate the crash test reported herein.

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Figure 1. Layout of the TxDOT Type T8 Bridge Rail.

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Figure 2. Details of the Deck of the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 3. Details of the Terminals Used for the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 4. Details of the Deck Reinforcement of the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 5. Details of the Tubular Rail Element of the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 6. Details of the Rebar of the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 7. Details of the Post of the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 8. Details of the Slots in Post of the TxDOT Type T8 Bridge Rail Test Installation.

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Figure 9. TxDOT Type T8 Bridge Rail Before Test 407049-1.

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CHAPTER 3. CRASH TEST RESULTS TEST NO. 407049-1 (NCHRP REPORT 350 TEST DESIGNATION 3-11) Test Vehicle A 1999 Chevrolet C2500 pickup truck, shown in Figures 10 and 11, was used for the crash test. Test inertia weight of the vehicle was 4570 lb, and its gross static weight was 4570 lb. The height to the lower edge of the vehicle bumper was 16.25 inches, and it was 25.0 inches to the upper edge of the bumper. Figure B1 in Appendix B gives additional dimensions and information on the vehicle. The vehicle was directed into the installation using the cable reverse tow and guidance system, and was released to be free-wheeling and unrestrained just prior to impact. Soil and Weather Conditions The test was performed on the morning of January 11, 2008. No rainfall of significance was recorded during the 10 days prior to the test. Moisture content of the crushed limestone in which the terminals was installed was 6.6%. Weather conditions at the time of testing were as follows: Wind speed: 6-8 mi/h; Wind direction: 320 degrees with respect to the vehicle (vehicle was traveling in a southwesterly direction); Temperature: 52oF, Relative humidity: 55 percent. Test Description The 2000P vehicle, traveling at an impact speed of 62.1 mi/h, impacted the Texas TypeT8 bridge rail 32 inches upstream of post 11 at an impact angle of 25.4 degrees. At approximately 0.027 s after impact, the vehicle reached post 11, and at 0.032 s, post 11 began to deflect towards the field side. Post 10 and post 12 began to deflect toward field side at 0.034 s and 0.044 s, respectively. At 0.056 s, the vehicle began to redirect, and post 9 began to deflect toward field side. Post 13 and post 14 began to deflect toward field side at 0.075 s and 0.090 s, respectively. At 0.102 s, the vehicle contacted post 12, and at 0.199 s, post 15 began to deflect toward the field side. At 0.243 s, the vehicle began to travel parallel with the bridge rail and was traveling at a speed of 49.5 mi/h. At 0.456 s, the vehicle lost contact with the bridge rail and was traveling at a speed of 46.7 mi/h, an exit angle of 22.3 degrees, and had reached a roll angle of 38 degrees. By the end of 1.0 s, the vehicle had rolled 152 degrees. As the vehicle continued forward, the vehicle rolled about the longitudinal axis, and came to rest upright 175 ft downstream of impact and 25 ft forward of the traffic face of the bridge rail. Figures C1 and C2 in Appendix C show sequential photographs of the test period.

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Figure 10. Vehicle/Installation Geometrics for Test 407049-1.

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Figure 11. Vehicle Before Test 407049-1.

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Damage to Test Installation Damage to the installation is shown in figures 12 and 13. Post 1 was pulled downstream 1.2 inches, and posts 5 through 8 rotated clockwise 5 degrees. The galvanizing around the slots of post 8 cracked, and the front face and center flange broke on post 9. Post 10 fractured at the base and deflected toward field side 6.3 inches. The rail element separated from post 11, the post deflected toward the field side 40 degrees, the base was pushed toward field side 5.5 inches, and the galvanizing was cracked near the slots. Post 12 was deflected toward field side 40 degrees, and the base was pushed toward field side 7.3 inches. Post 13 was deflected toward field side 20 degrees, and the base was pushed toward field side 3.9 inches. Post 14 was deflected toward field side 15 degrees, and the base was pushed toward field side 2.0 inches. Posts 15-20 rotated counterclockwise 2 degrees, and post 23 was pulled upstream 0.5 inch. Length of contact of the vehicle with the rail element was 21.4 ft. Maximum permanent deflection of the rail was 1.77 ft midway between posts 11 and 12. Maximum dynamic deflection of the rail during the test was 2.44 ft. Vehicle Damage Damage to the vehicle is shown in figure 14. The right upper and lower A-arm and right frame rail were deformed. Also damaged in the initial contact with the bridge rail were the front bumper, hood, grill, right front tire and wheel rim, right front fender, right door and glass, right rear wheel rim, right rear exterior bed, and rear bumper. The remainder of the damage seen in the photographs were caused by rollover. Maximum exterior crush from the impact with the bridge rail was 12.6 inches in the frontal plane at the right front corner at bumper height. Maximum occupant compartment deformation was 5.8 inches in the right front side floor pan, some of which was caused by rollover. Photographs of the interior of the vehicle are shown in figure 15. Exterior crush measurements and occupant compartment deformation measurements are shown in Appendix B, tables B1 and B2. Occupant Risk Factors Data from the triaxial accelerometer, located at the vehicle center of gravity, were digitized to compute occupant impact velocity and ridedown accelerations. Only the occupant impact velocity and ridedown accelerations in the longitudinal axis are required from these data for evaluation of criterion L in NCHRP Report 350. In the longitudinal direction, occupant impact velocity was 19.0 ft/s at 0.119 s, maximum 0.010-s ridedown acceleration was -11.5 g’s from 0.127 to 0.137 s, and the maximum 0.050-s average was -9.8 g’s between 0.050 and 0.100 s. In the lateral direction, the occupant impact velocity was 19.7 ft/s at 0.119 s, the highest 0.010-s occupant ridedown acceleration was -12.4 g’s from 0.127 to 0.137 s, and the maximum 0.050-s average was -8.7 g’s between 0.053 and 0.103 s. Figure 16 presents these data and other pertinent information from the test. Figures D1 through D7 in Appendix D presents vehicle angular displacements and accelerations versus time traces.

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Figure 12. After Impact Trajectory for Test 407049-1.

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Figure 13. Installation After Test 407049-1.

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Figure 14. Vehicle After Test 407049-1.

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Before Test After Test

Figure 15. Interior of Vehicle for Test 407049-1.

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0.000 s 0.121 s 0.243 s 0.364 s

General Information Test Agency............................... Test No. .................................... Date ........................................... Test Article Type........................................... Name ......................................... Installation Length (ft ) ............... Material or Key Elements .......... Foundation Type ......................... Test Vehicle Designation................................ Model ......................................... Mass (lb) Curb........................................ Test Inertial............................. Dummy ................................... Gross Static............................

Texas Transportation Institute 407049-1 01-11-2008 Bridge Rail TxDOT Type T8 Bridge Rail 112.5 12 Gauge Tubular Thrie-Beam Supported by W6x8.5 Steel Posts Anchored to 6.5-inch Thick Concrete Cantilevered Deck 2000P 1999 Chevrolet C2500 Pickup 4617 4570 No Dummy 4570

Impact Conditions Speed (mi/h) .............................. Angle (deg) ................................ Exit Conditions Speed (mi/h) .............................. Angle (deg) ................................ Occupant Risk Values Impact Velocity (ft/s) Longitudinal ............................ Lateral .................................... Ridedown Accelerations (g’s) Longitudinal ............................ Lateral .................................... Max. 0.050-s Average (g’s) Longitudinal ............................ Lateral .................................... Vertical ...................................

62.1 25.4 46.7 22.3 19.0 19.7 -11.5 -12.4 -9.8 -8.7 -4.4

Test Article Deflections (ft ) Dynamic ........................................... Permanent........................................ Working Width .................................. Vehicle Damage Exterior VDS............................................... CDC .............................................. Maximum Exterior Vehicle Crush (inches)............... Interior OCDI ............................................. Maximum Occupant Compartment Deformation (inches).................. Post-Impact Behavior (during 1.0 sec after impact) Max. Yaw Angle (deg)................... Max. Pitch Angle (deg).................. Max. Roll Angle (deg) ................... Vehicle rolled after 1 sec

2.44 1.77 4.43 01RFQ3 01RFEK3 12.6 RF0201100 5.8 -32 -6 17

Figure 16. Summary of Results for NCHRP Report 350 Test 3-11 on the TxDOT Type T8 Bridge Rail.

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CHAPTER 4. SUMMARY AND CONCLUSIONS ASSESSMENT OF TEST RESULTS An assessment of the test based on the applicable NCHRP Report 350 safety evaluation criteria is provided below.

Structural Adequacy A. Test article should contain and redirect the vehicle; the vehicle should not

penetrate, underride, or override the installation although controlled lateral deflection of the test article is acceptable.

Result: The TxDOT Type T8 bridge rail contained and redirected the 2000P

vehicle. The vehicle did not penetrate, underride, or override the bridge rail. Maximum dynamic deflection of the bridge rail was 2.44 ft. (PASS)

Occupant Risk

D. Detached elements, fragments, or other debris from the test article should not penetrate or show potential for penetrating the occupant compartment, or present an undue hazard to other traffic, pedestrians, or personnel in a work zone. Deformation of, or intrusions into, the occupant compartment that could cause serious injuries should not be permitted.

Result: No detached elements, fragments, or other debris was present to penetrate

or show potential for penetrating the occupant compartment, or present hazard to others in the area. Maximum occupant compartment deformation was 5.8 inches in the right front floor pan area. (PASS).

F. The vehicle should remain upright during and after collision although

moderate roll, pitching, and yawing are acceptable. Result: The 2000P vehicle remained upright during the collision event. However,

after exiting the rail, the vehicle rolled several times and came to rest upright. (FAIL).

Vehicle Trajectory

K. After collision, it is preferable that the vehicle’s trajectory not intrude into adjacent traffic lanes.

Result: The 2000P vehicle came to rest 175 ft downstream from impact and 25 ft

toward traffic lanes. (FAIL) L. The occupant impact velocity in the longitudinal direction should not exceed

12 m/s [39.4 ft/s] and the occupant ridedown acceleration in the longitudinal direction should not exceed 20 g’s.

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Result: Longitudinal occupant impact velocity was 19.0 ft/s, and maximum

ridedown acceleration was -11.5 g’s. (PASS) M. The exit angle from the test article preferably should be less than 60 percent

of the test impact angle, measured at time of vehicle loss of contact with the test device.

Result: Exit angle at loss of contact was 22.3 degrees, which was 88 percent of the

impact angle. (FAIL) The following supplemental evaluation factors and terminology, as presented in the FHWA memo entitled “ACTION: Identifying Acceptable Highway Safety Features,” were used for visual assessment of test results. (3) Factors underlined below pertain to the results of the crash test reported herein.

Passenger Compartment Intrusion 1. Windshield Intrusion

a. No windshield contact e. Complete intrusion into b. Windshield contact, no damage passenger compartment c. Windshield contact, no intrusion f. Partial intrusion into d. Device embedded in windshield, no

significant intrusion passenger compartment

2. Body Panel Intrusion yes or no

Loss of Vehicle Control 1. Physical loss of control 3. Perceived threat to other vehicles 2. Loss of windshield visibility 4. Debris on pavement

Physical Threat to Workers or Other Vehicles

1. Harmful debris that could injure workers or others in the area 2. Harmful debris that could injure occupants in other vehicles

No debris was present.

Vehicle and Device Condition 1. Vehicle Damage

a. None d. Major dents to grill and body panels b. Minor scrapes, scratches or dents e. Major structural damage c. Significant cosmetic dents

2. Windshield Damage a. None e. Shattered, remained intact but b. Minor chip or crack partially dislodged c. Broken, no interference with visibility f. Large portion removed d. Broken or shattered, visibility

restricted but remained intact g. Completely removed (due to rollover)

27

3. Device Damage a. None d. Substantial, replacement parts b. Superficial needed for repair c. Substantial, but can be straightened e. Cannot be repaired

CONCLUSIONS The TxDOT Type T8 bridge rail did not perform acceptably with respect to NCHRP Report 350 Test 3-11 requirements, as shown in Table 1. During the test, several posts in the immediate impact area failed to activate (break away) from the base plate. Activation or “breaking away” of the posts from the posts base plates is necessary for the success of this bridge rail system. From the crash test, failure of the deck concrete at these post locations was observed as a result of the combined punching and lateral shear from the post base plates. Since the posts in the impact area failed to break away from the post base plates, this resulted in undesirable vehicle performance and contributed to the vehicle instability. This vehicular instability was largely caused by vehicular snagging on the posts in the vehicle path. Previous pendulum testing on the T8 post design revealed that the base plate and deck strength was sufficient to cause full activation of the post from lateral impact on the post at an impact height near 21 inches. This design was incorporated into the test installation for this project. However, from the full-scale crash test, the combination of longitudinal and transverse forces applied to the posts at an impact height well below 21 inches (near the approximate height of the wheel axle of 15 inches) appeared to have caused severe distress in the deck resulting in deck failure and not post activation. Additional analyses and computer simulation is needed to capture the failure mode in the deck from the full-scale crash test. Further weakening the post strength in the lateral direction by increasing the lengths of the machined slots in the tension flange will be investigated to improve the crash performance of the bridge rail design.

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Table 1. Performance Evaluation Summary for NCHRP Report 350 Test 3-11 on the TxDOT Type T8 Bridge Rail.

Test Agency: Texas Transportation Institute Test No.: 407049-1 Test Date: 01-11-2008

NCHRP Report 350 Test 3-11 Evaluation Criteria Test Results Assessment Structural Adequacy A. Test article should contain and redirect the vehicle; the

vehicle should not penetrate, underride, or override the installation, although controlled lateral deflection of the test article is acceptable.

The TxDOT Type T8 bridge rail contained and redirected the 2000P vehicle. The vehicle did not penetrate, underride, or override the bridge rail. Maximum dynamic deflection of the bridge rail was 2.44 ft.

Pass

Occupant Risk D. Detached elements, fragments, or other debris from the test

article should not penetrate or show potential for penetrating the occupant compartment, or present an undue hazard to other traffic, pedestrians, or personnel in a work zone. Deformations of, or intrusions into, the occupant compartment that could cause serious injuries should not be permitted.

No detached elements, fragments, or other debris was present to penetrate or show potential for penetrating the occupant compartment, or present hazard to others in the area. Maximum occupant compartment deformation was 5.8 inches in the right front floor pan area.

Pass

F. The vehicle should remain upright during and after collision although moderate roll, pitching, and yawing are acceptable.

The 2000P vehicle remained upright during the collision event. However, after exiting the rail, the vehicle rolled several times and came to rest upright.

Fail

Vehicle Trajectory K. After collision, it is preferable that the vehicle’s trajectory

not intrude into adjacent traffic lanes. The 2000P vehicle came to rest 175 ft downstream from impact and 25 ft toward traffic lanes. Fail*

L. The occupant impact velocity in the longitudinal direction should not exceed 12 m/s and the occupant ridedown acceleration in the longitudinal direction should not exceed 20 g’s.

Longitudinal occupant impact velocity was 19.0 ft/s, and maximum ridedown acceleration was -11.5 g’s. Pass

M. The exit angle from the test article preferably should be less than 60 percent of test impact angle, measured at time of vehicle loss of contact with test device.

Exit angle at loss of contact was 22.3 degrees, which was 88 percent of the impact angle. Fail*

*Criteria K and M preferred, not required.

29

REFERENCES 1. H. E. Ross, Jr., D. L. Sicking, R. A. Zimmer and J. D. Michie. Recommended Procedures

for the Safety Performance Evaluation of Highway Features, National Cooperative Highway Research Program Report 350, Transportation Research Board, National Research Council, Washington, D.C., 1993.

2. J. D. Michie. Recommended Procedures for the Safety Performance Evaluation of

Highway Appurtenances, National Cooperative Highway Research Program Report 230, Transportation Research Board, National Research Council, Washington, D.C., March 1981.

3. Federal Highway Administration Memorandum from the Director, Office of Engineering,

entitled: “ACTION: Identifying Acceptable Highway Safety Features,” dated July 25, 1997.

31

APPENDIX A. CRASH TEST AND DATA ANALYSIS PROCEDURES The crash test and data analysis procedures were in accordance with guidelines presented in NCHRP Report 350. Brief descriptions of these procedures are presented as follows. ELECTRONIC INSTRUMENTATION AND DATA PROCESSING The test vehicle was instrumented with three solid-state angular rate transducers to measure roll, pitch, and yaw rates; a triaxial accelerometer near the vehicle center of gravity (c.g.) to measure longitudinal, lateral, and vertical acceleration levels; and a backup biaxial accelerometer in the rear of the vehicle to measure longitudinal and lateral acceleration levels. These accelerometers were ENDEVCO® Model 2262CA, piezoresistive accelerometers with a +100 g range. The accelerometers are strain gage type with a linear millivolt output proportional to acceleration. Angular rate transducers are solid state, gas flow units designed for high-“g” service. Signal conditioners and amplifiers in the test vehicle increase the low-level signals to a +2.5 volt maximum level. The signal conditioners also provide the capability of a resistive calibration (R-cal) or shunt calibration for the accelerometers and a precision voltage calibration for the rate transducers. The electronic signals from the accelerometers and rate transducers are transmitted to a base station by means of a 15-channel, constant bandwidth, Inter-Range Instrumentation Group (I.R.I.G.), FM/FM telemetry link for recording and for display. Calibration signals from the test vehicle are recorded before the test and immediately afterwards. A crystal-controlled time reference signal is simultaneously recorded with the data. Wooden dowels actuate pressure-sensitive switches on the bumper of the impacting vehicle prior to impact by wooden dowels to indicate the elapsed time over a known distance to provide a measurement of impact velocity. The initial contact also produces an “event” mark on the data record to establish the instant of contact with the installation. The multiplex of data channels, transmitted on one radio frequency, is received and demultiplexed onto a TEAC® instrumentation data recorder. After the test, the data are played back from the TEAC® recorder and digitized. A proprietary software program (WinDigit) converts the analog data from each transducer into engineering units using the R-cal and pre-zero values at 10,000 samples per second per channel. WinDigit also provides Society of Automotive Engineers (SAE) J211 class 180 phaseless digital filtering and vehicle impact velocity. All accelerometers are calibrated annually according to the SAE J211 4.6.1 by means of an ENDEVCO® 2901, precision primary vibration standard. This device and its support instruments are returned to the factory annually for a National Institute of Standards Technology (NIST) traceable calibration. The subsystems of each data channel are also evaluated annually, using instruments with current NIST traceability, and the results are factored into the accuracy of the total data channel, per SAE J211. Calibrations and evaluations are made any time data is suspect.

32

The Test Risk Assessment Program (TRAP) uses the data from WinDigit to compute occupant/compartment impact velocities, time of occupant/compartment impact after vehicle impact, and the highest 10-millisecond (ms) average ridedown acceleration. WinDigit calculates change in vehicle velocity at the end of a given impulse period. In addition, WinDigit computes maximum average accelerations over 50-ms intervals in each of the three directions. For reporting purposes, the data from the vehicle-mounted accelerometers are filtered with a 60-Hz digital filter, and acceleration versus time curves for the longitudinal, lateral, and vertical directions are plotted using TRAP. TRAP uses the data from the yaw, pitch, and roll rate transducers to compute angular displacement in degrees at 0.0001-s intervals and then plots yaw, pitch, and roll versus time. These displacements are in reference to the vehicle-fixed coordinate system with the initial position and orientation of the vehicle-fixed coordinate systems being initial impact. ANTHROPOMORPHIC DUMMY INSTRUMENTATION Use of a dummy in the 2000P vehicle is optional according to NCHRP Report 350, and there was no dummy used in the tests with the 2000P vehicle. PHOTOGRAPHIC INSTRUMENTATION AND DATA PROCESSING Photographic coverage of the test included three high-speed cameras: one overhead with a field-of-view perpendicular to the ground and directly over the impact point; one placed behind the installation at an angle; and a third placed to have a field-of-view parallel to and aligned with the installation at the downstream end. A flash bulb activated by pressure-sensitive tape switches was positioned on the impacting vehicle to indicate the instant of contact with the installation and was visible from each camera. The films from these high-speed cameras were analyzed on a computer-linked Motion Analyzer to observe phenomena occurring during the collision and to obtain time-event, displacement, and angular data. A 16-mm movie cine, a BetaCam, a VHS-format video camera and recorder, and still cameras were used to record and document conditions of the test vehicle and installation before and after the test. TEST VEHICLE PROPULSION AND GUIDANCE The test vehicle was towed into the test installation using a steel cable guidance and reverse tow system. A steel cable for guiding the test vehicle was tensioned along the path, anchored at each end, and threaded through an attachment to the front wheel of the test vehicle. An additional steel cable was connected to the test vehicle, passed around a pulley near the impact point, through a pulley on the tow vehicle, and then anchored to the ground such that the tow vehicle moved away from the test site. A 2-to-1 speed ratio between the test and tow vehicle existed with this system. Just prior to impact with the installation, the test vehicle was released to be free-wheeling and unrestrained. The vehicle remained free-wheeling, i.e., no steering or braking inputs, until the vehicle cleared the immediate area of the test site, at which time the vehicle’s brakes were activated to bring it to a safe and controlled stop.

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APPENDIX B. TEST VEHICLE PROPERTIES AND INFORMATION Date: 01-11-2008 Test No.: 407049-1 VIN No.: 1GCGC24R3XR717251 Year: 1999 Make: Chevrolet Model: C2500 Tire Inflation Pressure: 60 psi Odometer: 085618 Tire Size: 245/75/R16 Describe any damage to the vehicle prior to test:

Geometry (inches) A 74 E 51.6 J 40.9 N 62.6 R 29.5 B 31.9 F 215.4 K 25.0 O 63.4 S 35.4 C 131.9 G 56.9 L 2.8 P 28.5 T 57.5 D 71.6 H M 16.3 Q 17.3 U 132.3

Mass (lb) Curb Test Inertial Gross Static M1 2672 2597 M2 1945 1973 MTotal 4617 4570

Mass Distribution (lb): LF: 1298 RF: 1299 LR: 978 RR: 994

Figure B1. Vehicle Properties for Test 407049-1.

• Denotes accelerometer location. NOTES: Engine Type: V8 Engine CID: 5.7 liter Transmission Type: x Auto Manual Optional Equipment: Dummy Data: Type: No dummy Mass: Seat Position:

34

>

Table B1. Exterior Crush Measurements for Test 407049-1.

VEHICLE CRUSH MEASUREMENT SHEET1 Complete When Applicable

End Damage Side Damage Undeformed end width ________

Corner shift: A1 ________

A2 ________

End shift at frame (CDC)

(check one)

< 4 inches ________

4 inches ________

Bowing: B1 _____ X1 _____

B2 _____ X2 _____

Bowing constant

X1 + X2 2 = ______

Note: Measure C1 to C6 from driver to passenger side in front or rear impacts – rear to front in side impacts.

Direct Damage Specific Impact Number

Plane* of C-Measurements

Width** (CDC)

Max*** Crush

Field L**

C1 C2 C3 C4 C5 C6 ±D

1 Front plane at bumper ht 15.7 12.6 31.5 12.6 7.9 4.7 1.6 0.8 0 -15.7

2 Side plane at bumper ht 11.8 9.4 43.3 0 1.2 --- --- 6.7 9.4 +63.0

1Table taken from National Accident Sampling System (NASS). *Identify the plane at which the C-measurements are taken (e.g., at bumper, above bumper, at sill, above sill, at beltline, etc.) or label adjustments (e.g., free space). Free space value is defined as the distance between the baseline and the original body contour taken at the individual C locations. This may include the following: bumper lead, bumper taper, side protrusion, side taper, etc. Record the value for each C-measurement and maximum crush. **Measure and document on the vehicle diagram the beginning or end of the direct damage width and field L (e.g., side damage with respect to undamaged axle). ***Measure and document on the vehicle diagram the location of the maximum crush. Note: Use as many lines/columns as necessary to describe each damage profile.

35

Table B2. Occupant Compartment Measurements for Test 407049-1.

T R U C K

OOccccuuppaanntt CCoommppaarrttmmeenntt DDeeffoorrmmaattiioonn

BEFORE AFTER(inch) (inch)

A1 34.3 33.5

A2 37.2 N/O

A3 36.8 35.7

B1 42.9 37.4

B2 37.6 32.8

B3 41.9 36.1

C1 54.1 53.5

C2 ----- -----

C3 53.9 N/O

D1 12.7 12.4

D2 6.0 5.4

D3 12.0 11.2

E1 62.4 60.8

E2 62.5 61.8

F 57.9 56.1

G 57.9 56.5

H 41.7 43.3

I 41.7 N/O

J* 60.0 59.0*Lateral area across the cab from driver’s side kickpanel to passenger’s side kickpanel.

37

APPENDIX C. SEQUENTIAL PHOTOGRAPHS

0.000 s

0.060 s

0.121 s

0.182 s Figure C1. Sequential Photographs for Test 407049-1

(Overhead and Frontal Views).

38

0.243s

0.303 s

0.364 s

0.424 s Figure C1. Sequential Photographs for Test 407049-1

(Overhead and Frontal Views) (continued).

39

APPE

ND

IX D

. VE

HIC

LE

AN

GU

LA

R D

ISPLA

CE

ME

NT

S A

ND

AC

CE

LE

RA

TIO

NS

Roll, Pitch, and Yaw Angles

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-100

-50

0

50

100

150

200

Time (s)

Ang

les

(deg

rees

)

Test Number: 407049-1Test Date: January 11, 2008Test Article: Texas Type T8 Bridge RailTest Vehicle: 1999 Chevrolet C2500 PickupTest Inertial Mass: 4570 lbImpact Speed: 62.1 mi/hImpact Angle: 25.4 degrees

Roll Pitch Yaw

Figure D1. Vehicle Angular Displacements for Test 407049-1.

Axes are vehicle-fixed. Sequence for determining orientation:

1. Yaw. 2. Pitch. 3. Roll.

40

X Acceleration at CG

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-15

-10

-5

0

5

10

Time (s)

Long

itudi

nal A

ccel

erat

ion

(g's

)


Time of OIV (0.1204 sec) SAE Class 60 Filter

Figure D2. Vehicle Longitudinal Accelerometer Trace for Test 407049-1 (Accelerometer Located at Center of Gravity).

41

Y Acceleration at CG

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-15

-10

-5

0

5

10

Time (s)

Late

ral A

ccel

erat

ion

(g's

)


Time of OIV (0.1204 sec) SAE Class 60 Filter

Figure D3. Vehicle Lateral Accelerometer Trace for Test 407049-1 (Accelerometer Located at Center of Gravity).

42

Z Acceleration at CG

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-15

-10

-5

0

5

10

15

Time (s)

Vert

ical

Acc

eler

atio

n (g

's)


SAE Class 60 Filter

Figure D4. Vehicle Vertical Accelerometer Trace for Test 407049-1 (Accelerometer Located at Center of Gravity).

43

X Acceleration over Rear Axle

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-15

-10

-5

0

5

10

Time (s)

Long

itudi

nal A

ccel

erat

ion

(g's

)


SAE Class 60 Filter

Figure D5. Vehicle Longitudinal Accelerometer Trace for Test 407049-1 (Accelerometer Located Over Rear Axle).

44

Y Acceleration over Rear Axle

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-15

-10

-5

0

5

10

Time (s)

Late

ral A

ccel

erat

ion

(g's

)


SAE Class 60 Filter

Figure D6. Vehicle Lateral Accelerometer Trace for Test 407049-1 (Accelerometer Located Over Rear Axle).

45

Z Acceleration over Rear Axle

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-15

-10

-5

0

5

10

15

Time (s)

Vert

ical

Acc

eler

atio

n (g

's)


SAE Class 60 Filter

Figure D7. Vehicle Vertical Accelerometer Trace for Test 407049-1 (Accelerometer Located Over Rear Axle).

crash testing and evaluation of the txdot type t8 bridge rail · austin, texas 78763-5080 14....

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