NCHRP REPORT 350 TEST 3-11 OF THE STEEL-BACKED ......NCHRP Report 350 recommends two crash tests on...

TEXAS TRANSPORTATION INSTITUTETHE TEXAS A & M UNIVERSITY SYSTEMCOLLEGE STATION, TEXAS 77843

NCHRP REPORT 350 TEST 3-11 OF THESTEEL-BACKED TIMBER GUARDRAIL

by

D. Lance Bullard, Jr., P.E.Associate Research Engineer

Wanda L. MengesAssociate Research Specialist

and

Sandra K. SchoenemanResearch Associate

Contract No. DTFH61-99-C-00035Project No. 405181-2

Sponsored byU.S. Department of TransportationFederal Highway Administration

June 2001

DISCLAIMER

The contents of this report reflect the views of the authors who are solely responsible forthe facts and accuracy of the data, and the opinions, findings and conclusions presented herein. The contents do not necessarily reflect the official views or policies of the U.S. Department ofTransportation, Federal Highway Administration, the Texas A&M University System, or TexasTransportation Institute. This report does not constitute a standard, specification, or regulation.In addition, the above listed agencies assume no liability for its contents or use thereof. Thenames of specific products or manufacturers listed herein does not imply endorsement of thoseproducts or manufacturers.

KEY WORDS

Guardrail, aesthetic, timber guardrail, crash testing, roadside safety

Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

NCHRP REPORT 350 TEST 3-11 OF THE STEEL-BACKEDTIMBER GUARDRAIL

5. Report Date

June 2001 6. Performing Organization Code

7. Author(s)

D. Lance Bullard, Jr., Wanda L. Menges and Sandra K. Schoeneman 8. Performing Organization Report No.

405181-2 9. Performing Organization Name and Address

Texas Transportation InstituteThe Texas A&M University SystemCollege Station, Texas 77843-3135

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-99-C-0003512. Sponsoring Agency Name and Address

Office of Safety and TrafficOperations Research and DevelopmentFederal Highway Administration6300 Georgetown PikeMcLean, VA 22101-2296

13. Type of Report and Period Covered

Revised Test ReportSeptember 1999 - January 200114. Sponsoring Agency Code

15. Supplementary Notes

Research Study Title: Guardrail Testing Program IVName of Contacting Officer’s Technical Representative (COTR): Mr. Charles F. McDevitt (HRDS-4)16. Abstract

The steel-backed timber guardrail is a semi-rigid barrier consisting of rough sawn timber rail backed by asteel plate mounted on rough sawn posts and blockouts. The steel-backed timber guardrail was designed tobe aesthetically pleasing and structurally sound but had not been tested and evaluated to the guidelinesspecified in National Cooperative Highway Research Program (NCHRP) Report 350, RecommendedProcedures for the Safety Performance Evaluation of Highway Features.

This report presents the details of the steel-backed timber guardrail, the results of NCHRP Report 350 test 3-11, and the evaluation of the guardrail’s performance according to the guidelines of NCHRP Report 350. Thesteel-backed timber guardrail met the required criteria specified for test designation 3-11 of NCHRP Report350.

17. Key Words

Guardrail, aesthetic, timber guardrail, crash testing,roadside safety

18. Distribution Statement

No restrictions. This document is available to thepublic through the National Technical InformationService, 5285 Port Royal Road, Springfield,Virginia 22161.

19. Security Classif. (of this report)

Unclassified20. Security Classif. (of this page)

Unclassified21. No. of Pages 22. Price

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

ii

SI* (MODERN METRIC) CONVERSION FACTORS

APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITSSymbol When You Know Multiply by To Find Symbol Symbol When You Know Multiply by To Find Symbol

LENGTH LENGTH

inftydmi

inchesfeetyardsmiles

25.40.3050.9141.61

millimetersmetersmeterskilometers

mmmmkm

mm m m km

millimetersmetersmeterskilometers

0.0393.281.09

0.621

inchesfeetyardsmiles

inftydmi

AREA AREA

in2

ft2

yd2

acmi2

square inchessquare feetsquare yardsacressquare miles

645.20.0930.8360.4052.59

squaremillimeterssquare meterssquare metershectaressquare kilometers

mm2

m2

m2

hakm2

mm2

m2

m2

ha km2

square millimeterssquare meterssquare metershectaressquare kilometers

0.001610.7641.1952.47

0.386

square inchessquare feetsquare yardsacressquare miles

in2

ft2

yd2

acmi2

VOLUME VOLUME

fl ozgalft3

yd3

fluid ouncesgallonscubic feetcubic yards

29.573.7850.0280.765

millilitersliterscubic meterscubic meters

mLLm3

m3

mL L m3

m3

millilitersliterscubic meterscubic meters

0.0340.26435.711.307

fluid ouncesgallonscubic feetcubic yards

fl ozgalft3

yd3

NOTE: Volumes greater than 1000 l shall be shown in m3.

MASS MASS

ozlbT

ouncespoundsshort tons (2000 lb)

28.350.4540.907

gramskilogramsmegagrams (or “metric ton”)

gkgMg (or “t”)

g kg Mg (or “t”)

gramskilogramsmegagrams (or “metric ton”)

0.0352.2021.103

ouncespoundsshort tons (2000 lb)

ozlbT

TEMPERATURE (exact) TEMPERATURE (exact)

EF Fahrenheittemperature

5(F-32)/9 or(F-32)/1.8

Celciustemperature

EC EC Celciustemperature

1.8C+32 Fahrenheittemperature

EF

ILLUMINATION ILLUMINATION

fcfl

foot-candlesfoot-Lamberts

10.763.426

luxcandela/m2

lxcd/m2

lx cd/m2

luxcandela/m2

0.09290.2919

foot-candlesfoot-Lamberts

fcfl

FORCE and PRESSURE or STRESS FORCE and PRESSURE or STRESS

lbflbf/in2

poundforcepoundforce persquare inch

4.456.89

newtonskilopascals

NkPa

N kPa

newtonskilopascals

0.2250.145

poundforcepoundforce persquare inch

lbflbf/in2

*SI is the symbol for the International System of Units. Appropriate (Revised September 1993) rounding should be made to comply with Section 4 of ASTM E380.

iii

TABLE OF CONTENTS

Section Page

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1PROBLEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

TECHNICAL DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3TEST PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Test Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Test Article – Design and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Test Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Evaluation Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

CRASH TEST 405181-2 (NCHRP REPORT 350 TEST NO. 3-11) . . . . . . . . . . . . . . . 9Test Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Soil and Weather Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Impact Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Damage to Test Article . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Vehicle Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Occupant Risk Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19ASSESSMENT OF TEST RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

APPENDIX A. CRASH TEST PROCEDURES AND DATA ANALYSIS . . . . . . . . . . . . . 23ELECTRONIC INSTRUMENTATION AND DATA PROCESSING . . . . . . . . . . . 23ANTHROPOMORPHIC DUMMY INSTRUMENTATION . . . . . . . . . . . . . . . . . . 24PHOTOGRAPHIC INSTRUMENTATION AND DATA PROCESSING . . . . . . . 24TEST VEHICLE PROPULSION AND GUIDANCE . . . . . . . . . . . . . . . . . . . . . . . . 24

APPENDIX B. TEST VEHICLE PROPERTIES AND INFORMATION . . . . . . . . . . . . . 27

APPENDIX C. SEQUENTIAL PHOTOGRAPHS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

APPENDIX D. VEHICLE ANGULAR DISPLACEMENTSAND ACCELERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

iv

LIST OF FIGURES

Figure Page

1 Details of the steel-backed timber guardrail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Steel-backed timber guardrail prior to testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Vehicle/installation geometrics for test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Vehicle before test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Vehicle trajectory after test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Installation after test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Vehicle after test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Interior of vehicle for test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Summary of results for test 405181-2, NCHRP Report 350 test 3-11 . . . . . . . . . . . . 17

10 Vehicle properties for test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2711 Sequential photographs for test 405181-2

(overhead and frontal views) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3112 Sequential photographs for test 405181-2

(rear view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3313 Vehicular angular displacements for test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . 3514 Vehicle longitudinal accelerometer trace for test 405181-2

(accelerometer located at center of gravity) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3615 Vehicle lateral accelerometer trace for test 405181-2

(accelerometer located at center of gravity) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3716 Vehicle vertical accelerometer trace for test 405181-2

(accelerometer located at center of gravity) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3817 Vehicle longitudinal accelerometer trace for test 405181-2

(accelerometer located over rear axle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3918 Vehicle lateral accelerometer trace for test 405181-2

(accelerometer located over rear axle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4019 Vehicle vertical accelerometer trace for test 405181-2

(accelerometer located over rear axle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

v

LIST OF TABLES

Table No. Page

1 Performance evaluation summary for test 405181-2, NCHRP Report 350 test 3-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2 Exterior crush measurements for test 405181-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Occupant compartment measurements for test 405181-2 . . . . . . . . . . . . . . . . . . . . . 29

1

INTRODUCTION

PROBLEM

Research has developed railings to withstand impact loads from vehicles of ever-increasing size. However, aesthetic considerations have been overshadowed by safety andstructural requirements. Engineers and architects are beginning to focus more attention onrailings and other crashworthy structures that are aesthetically compatible with the localenvironment. Stone wall and timber guardrails in park areas are examples of such structures.

The steel-backed timber guardrail is a semi-rigid barrier consisting of rough sawn timberrail backed by a steel plate mounted on rough sawn posts and blockouts. The steel-backed timberguardrail was designed to be aesthetically pleasing and structurally sound but had not been testedand evaluated to the guidelines specified in National Cooperative Highway Research Program(NCHRP) Report 350, Recommended Procedures for the Safety Performance Evaluation ofHighway Features.(1)

BACKGROUND

The Federal Highway Administration (FHWA) adopted NCHRP Report 350 as theofficial guidelines for performance evaluation of roadside safety hardware. NCHRP Report 350specifies the required crash tests for longitudinal barriers such as bridge rails, guardrails, andtransitions for six performance levels, as well as evaluation criteria for structural adequacy,occupant risk, and post-test vehicle trajectory for each test. FHWA further mandated that allroadside safety features installed under new construction on the National Highway System(NHS) meet NCHRP Report 350 performance evaluation guidelines. Implementation of thisrequirement for breakaway devices, longitudinal barriers (except weak-post W-beam guardrail),crash cushions, and W-beam guardrail terminals on new construction went into effect on October1, 1998. Guardrail to bridge rail transitions are required to meet the NCHRP Report 350requirements by October 1, 2002. It is necessary to test new and/or some existing roadside safetyfeatures to evaluate their performance under these guidelines.

OBJECTIVES

The objective of the test reported herein was to crash test and evaluate the performanceof the steel backed timber guardrail in accordance with the guidelines presented in NCHRPReport 350 test 3-11: a 2000-kg pickup truck impacting the critical impact point (CIP) of thelength of need (LON) at a nominal impact speed and angle of 100 km/h and 25 degrees.

NCHRP Report 350 recommends two crash tests on the length of need of a longitudinalbarrier, or bridge rail, to evaluate the performance to test level 3 (TL-3). These crash testsinclude: 1) NCHRP Report 350 test 3-10: an 820-kg passenger car impacting the CIP of the

2

LON at a nominal impact speed and angle of 100 km/h and 20 degrees, and 2) NCHRP Report350 test 3-11: a 2000-kg pickup truck impacting the CIP of the LON at a nominal impact speedand angle of 100 km/h and 25 degrees.

This report presents the details of the steel-backed timber guardrail, the results ofNCHRP Report 350 test 3-11, and the evaluation of the guardrail’s performance according to theguidelines of NCHRP Report 350.

3

TECHNICAL DISCUSSION

TEST PARAMETERS

Test Facility

The test facilities at the Texas Transportation Institute’s Proving Ground consist of an809-hectare complex of research and training facilities situated 16 km northwest of the maincampus of Texas A&M University. The site, formerly an U.S. Air Force base, has large expansesof concrete runways and parking aprons well suited for experimental research and testing in theareas of vehicle performance and handling, vehicle-roadway interaction, durability and efficacy of highwaypavements, and safety evaluation of roadside safetyhardware. The site selected for placing of the steel-backed timber guardrail is along a wide out-of-serviceapron/runway. The apron/runway consists of anunreinforced jointed concrete pavement in 3.8 m by 4.6 mblocks (as shown in the adjacent photo) nominally 203-305 mm deep. The aprons and runways are about 50years old and the joints have some displacement, but areotherwise flat and level. The steel-backed timber guardrail was installed in NCHRP Report 350standard soil. Further details of the installation follow.

Test Article – Design and Construction

The steel backed timber guardrail is constructed of wood post and wood rail elements toprovide a more rustic appearance than a conventional steel or concrete barrier. A steel plate ismounted to the backside of each wood rail element to provide the tensile strength needed for thesystem. The timber guardrail in some applications is attached to a stone masonry guardwall. The stone masonry guardwall is constructed from concrete core-wall barriers veneered withnative stones that blend with the surrounding environment. The test installation was anchored atone end to a stone masonry guardwall parapet and terminated at the upstream end with a steelbacked timber guardrail, Type FAT-9 terminal. The details of the entire test installation arepresented hereafter.

All wood in the steel backed timber guardrail was specified to conform with AmericanAssociation of State Highway Traffic Officials (AASHTO) M168. The wood used for the testpresented herein was southern pine. All steel and hardware were weathering steel conforming toAASHTO M 222M for structural shapes and plates, American Society of Testing andMeasurement (ASTM) A606 type 4 for the rail elements and AASHTO M 164M type 3 for thefasteners.

4

The transition section of the guardrail installation was 6 m long and consisted of 10 mmthick, double steel plates mounted to the rear of the wood rail elements between posts 2 through5. In addition, a two-piece wood rub rail (100 mm x 150 mm x 4500 mm and 100 mm x 150 mmx 1650 mm) rough sawn was mounted from the stone masonry guardwall parapet to post 5. Therub rail was blocked-out with 100 mm x 225 mm x 300 mm rough sawn blocks at the first fourposts only. The first four wood posts in the transition were 250 mm x 300 mm x 2400 mm roughsawn. The last post in the transition (post 5) and the remaining length-of-need posts were250 mm x 300 mm x 2100 mm rough sawn. The wood rail elements were 150 mm x 250 mm x2990 mm rough sawn and were blocked-out using 100 mm x 225 mm x 300 mm blocks. Type A,as tested, is the designation for a blocked-out rail and Type B designates a non-blocked-outsystem. Each rail element in the length-of-need section was backed with a 10 mm x 150 mm x2930 mm steel plate bolted to the timber rail with nine M16 x 100 mm lag screws. Thecomposite rail elements were contiguously attached together at each post location using a 10 mmx 150 mm x 750 mm steel splice plate. A splice plate was attached to each post with an M16 x380 mm carriage bolt with a plate washer and nut. Each end of a rail element was attached to oneside of a splice plate using four M20 x 215 mm carriage bolts with hex nut and washer. Theoverall rail height was 685 mm. The rail installation was terminated with a Type FAT-9terminal. The FAT-9 terminal is constructed using the same rail and splice components as thestandard length-of-need rail section but is flared both laterally and vertically and anchored belowgrade. The lateral flare rate was 13:1. A 675 mm x 675 mm x 750 mm concrete anchor blockwas placed 100 mm below grade for attaching the last rail element. Figure 1 illustrates theconstruction details of the steel-backed timber guardrail transition to the stone masonryguardwall parapet, the length-of-need section and Type FAT-9 terminal.

Test Conditions

According to NCHRP Report 350, two tests are recommended to evaluate longitudinalbarriers, such as guardrails and bridge rails, to test level four (TL-3) and are as described below.

NCHRP Report 350 test designation 3-10: An 820-kg passenger car impacting thecritical impact point in the length of need of the longitudinal barrier at a nominal speedand angle of 100 km/h and 20 degrees. The purpose of this test is to evaluate the overallperformance of the LON section in general, and occupant risks in particular.

NCHRP Report 350 test designation 3-11: A 2000-kg pickup truck impacting the CIPin the LON of the longitudinal barrier at a nominal speed and angle of 100 km/h and25 degrees. The test is intended to evaluate the strength of section in containing andredirecting the pickup truck.

5

Figu

re 1

. D

etai

ls o

f the

stee

l-bac

ked

timbe

r gua

rdra

il.

6

Figure 2. Steel-backed timber guardrail prior to testing.

7

The crash test reported herein corresponds to the pickup truck test, NCHRP Report 350test designation 3-11. The CIP chosen for this test was selected using the information in NCHRPReport 350, and was determined to be 1.5 m upstream of the post/splice nearest the one-thirdpoint.

The crash test and data analysis procedures were in accordance with guidelines presentedin NCHRP Report 350. Appendix A presents brief descriptions of these procedures.

Evaluation Criteria

The crash test performed was evaluated in accordance with the criteria presented inNCHRP Report 350. As stated in NCHRP Report 350, “Safety performance of a highwayappurtenance cannot be measured directly but can be judged on the basis of three factors:structural adequacy, occupant risk, and vehicle trajectory after collision.” Safety evaluationcriteria from table 5.1 of NCHRP Report 350 were used to evaluate the crash test reportedherein.

9

CRASH TEST 405181-2 (NCHRP REPORT 350 TEST NO. 3-11)

Test Vehicle

A 1996 Chevrolet 2500 pickup truck, shown in figures 3 and 4, was used for the crashtest. Test inertia weight of the vehicle was 2000 kg, and its gross static weight was 2075 kg. Theheight to the lower edge of the vehicle front bumper was 395 mm, and to the upper edge of thefront bumper was 600 mm. Additional dimensions and information on the vehicle are given inappendix B, figure 10. The vehicle was directed into the installation using the cable reverse towand guidance system, and was released to be free-wheeling and unrestrained just prior to impact.

Soil and Weather Conditions

The crash test was performed the morning of December 11, 2000. Ten days before thetest 2 mm of rainfall was recorded and five days before the test an additional 6 mm wasrecorded. Moisture content of the NCHRP Report 350 soil in which the test article was installedwas 9.9 percent, 10.4 percent, and 10.2 percent at posts 4, 6, and8, respectively. Weather conditions at the time of testing were asfollows: wind speed: 27 km/h; wind direction: 10 degrees withrespect to the vehicle (vehicle was traveling in a northwesterlydirection); temperature: 13 EC; relative humidity: 69 percent.

Impact Description

The 2000P vehicle, traveling 98.7 km/h, impacted the steel-backed timber guardrail at animpact angle of 24.5 degrees, 1.35 m upstream of post 6. Posts 6 and 5 moved at 0.012 s and0.019 s, respectively. The vehicle began to redirect at 0.067 s. At 0.077 s, the left front tirereached post 6, and at 0.090 s post 7 moved. The rear of the vehicle contacted the rail element at0.249 s. The vehicle was traveling parallel with the guardrail at 0.254 s at a speed of 67.5 km/h.At 0.510 s the vehicle lost contact with the guardrail and was traveling at a speed of 58.2 km/hand an exit angle of 9.5 degrees. Brakes on the vehicle were not applied and the vehiclesubsequently came to rest 50.3 m downstream of impact and aligned with the front face of theguardrail. Sequential photographs of the test period are shown in appendix C, figures 11 and 12.

10

Figure 3. Vehicle/installation geometrics for test 405181-2.

11

Figure 4. Vehicle before test 405181-2.

12

Damage to Test Article

The steel-backed timber guardrail sustained minimal damage as shown in figures 5 and 6.The rail was fractured on the tension side of the member at the point of maximum deflectionbetween post 6 and 7. The upstream terminal showed no sign of movement and posts 3 through 5were only disturbed. Post 6 was pushed rearward 245 mm and pulled upward 50 mm; post 7 waspushed rearward 155 mm and pulled upward 110 mm; and post 8 was disturbed and pulledupward 95 mm. Length of contact of the vehicle with the guardrail was 2.2 m. Maximumdynamic deflection of the timber guardrail during the test was 580 mm and maximum permanentdeformation after the test was 315 mm.

Vehicle Damage

Damage to the vehicle is shown in figure 7. Structural damage was imparted to the left tierod ends and A-arms, stabilizer bar and left front of the frame. The windshield received stresscracking and the floor pan was buckled. Also deformed was the front bumper, grill, hood, leftfront quarter panel, left front tire and wheel, left door, left rear side of the bed and the left reartire and wheel. Maximum exterior crush to the vehicle was 380 mm to the left front corner atbumper height. Maximum occupant compartment deformation was 88 mm in the center floor panarea over the transmission tunnel. Photographs of the interior of the vehicle before and after thetest are shown in figure 8. Exterior vehicle crush and occupant compartment measurements areshown in appendix B, tables 2 and 3.

Occupant Risk Factors

Data from the triaxial accelerometer, located at the vehicle c.g., were digitized tocompute occupant impact velocity and ridedown accelerations. The occupant impact velocityand ridedown accelerations in the longitudinal axis only are required from these data forevaluation of criterion L of NCHRP Report 350. In the longitudinal direction, occupant impactvelocity was 5.1 m/s at 0.130 s, maximum 0.010-s ridedown acceleration was -12.1 g’s from0.152 to 0.162 s, and the maximum 0.050-s average was -6.5 g’s between 0.112 and 0.162 s. Inthe lateral direction, the occupant impact velocity was 5.4 m/s at 0.130 s, the highest 0.010-soccupant ridedown acceleration was 16.4 g’s from 0.157 to 0.167 s, and the maximum 0.050-saverage was 8.0 g’s between 0.149 and 0.199 s. These data and other information pertinent to thetest are presented in figure 9. Vehicle angular displacements and accelerations versus time tracesare shown in appendix D, figures 13 through 19.

13

Figure 5. Vehicle trajectory after test 405181-2.

14

Figure 6. Installation after test 405181-2.

15

Figure 7. Vehicle after test 405181-2.

16

Before test

After test

Figure 8. Interior of vehicle for test 405181-2.

17

0.000 s 0.188 s 0.281 s 0.586 s

General InformationTest Agency . . . . . . . . . . . .Test No. . . . . . . . . . . . . . . . .Date . . . . . . . . . . . . . . . . . . .

Test ArticleType . . . . . . . . . . . . . . . . . .Name . . . . . . . . . . . . . . . . . .Installation Length (m) . . . . .Material or Key Elements . .

Soil Type and Condition . . . .Test Vehicle

Type . . . . . . . . . . . . . . . . . .Designation . . . . . . . . . . . . .Model . . . . . . . . . . . . . . . . . .Mass (kg)

Curb . . . . . . . . . . . . . . . . .Test Inertial . . . . . . . . . . .Dummy . . . . . . . . . . . . . .Gross Static . . . . . . . . . . .

Texas Transportation Institute405181-212/11/00

GuardrailSteel Backed Timber Guardrail49.2Steel-Backed Timber Guardrail AttachedtoStone Masonry Guardwall ParapetStandard Soil, Dry

Production2000P1996 Chevrolet 2500 pickup truck

18992000 752075

Impact ConditionsSpeed (km/h) . . . . . . . . . . . . . . . .Angle (deg) . . . . . . . . . . . . . . . . .

Exit ConditionsSpeed (km/h) . . . . . . . . . . . . . . . .Angle (deg) . . . . . . . . . . . . . . . . .

Occupant Risk ValuesImpact Velocity (m/s)

x-direction . . . . . . . . . . . . . . . .y-direction . . . . . . . . . . . . . . . .

THIV (km/h) . . . . . . . . . . . . . . . .Ridedown Accelerations (g's)

x-direction . . . . . . . . . . . . . . . .y-direction . . . . . . . . . . . . . . . .

PHD (g’s) . . . . . . . . . . . . . . . . . . .ASI . . . . . . . . . . . . . . . . . . . . . . .Max. 0.050-s Average (g's)

x-direction . . . . . . . . . . . . . . . .y-direction . . . . . . . . . . . . . . . .z-direction . . . . . . . . . . . . . . . .

98.724.5

58.2 9.5

5.1 5.425.4

-12.1 16.4 18.0 0.97

-6.5 8.0-5.8

Test Article Deflections (m)Dynamic . . . . . . . . . . . . . . . .Permanent . . . . . . . . . . . . . . .Working Width . . . . . . . . . . .

Vehicle DamageExterior

VDS . . . . . . . . . . . . . . . . . .CDC . . . . . . . . . . . . . . . . .

Maximum ExteriorVehicle Crush (mm) . . . . .

InteriorOCDI . . . . . . . . . . . . . . . . .

Max. Occ. Compart.Deformation (mm) . . . . . . .

Post-Impact Behavior(during 1.0 s after impact)Max. Yaw Angle (deg) . . . . . .Max. Pitch Angle (deg) . . . . .Max. Roll Angle (deg) . . . . . .

0.5800.3150.760

11LFQ211FLEK2&11LYEW2

380

LF0100000

88

33 -5 8

Figure 9. Summary of results for test 405181-2, NCHRP Report 350 test 3-11.

19

SUMMARY AND CONCLUSIONS

ASSESSMENT OF TEST RESULTS

An assessment of the test based on the applicable NCHRP Report 350 safety evaluationcriteria is provided below.

! Structural Adequacy

A. Test article should contain and redirect the vehicle; the vehicleshould not penetrate, underride, or override the installationalthough controlled lateral deflection of the test article isacceptable.

Result: The steel-backed timber guardrail contained and redirectedthe 2000P vehicle. The vehicle did not penetrate, underride,or override the installation. Maximum dynamic deflectionwas 580 mm.

! Occupant Risk

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

Result: No detached elements, fragments, or other debris werepresent to penetrate or to show potential for penetrating theoccupant compartment, or to present undue hazard to othersin the area. Maximum deformation of the occupantcompartment was 88 mm.

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

Result: The vehicle remained upright during and after the collisionperiod.

! Vehicle Trajectory

K. After collision, it is preferable that the vehicle’s trajectory notintrude into adjacent traffic lanes.

Result: The vehicle came to rest 50.3 m downstream of impact andin line with the face of the guardrail.

20

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

Result: Longitudinal occupant impact velocity was 5.1 m/s andlongitudinal ridedown acceleration was -12.1 g’s.

M. The exit angle from the test article preferably should be less than60 percent of the test impact angle, measured at time of vehicleloss of contact with the test device.

Result: Exit angle at loss of contact with the guardrail was9.5 degrees, which was 39 percent of the impact angle.

The following supplemental evaluation factors and terminology, as presented in theFHWA memo entitled “Action: Identifying Acceptable Highway Safety Features,” were used forvisual assessment of test results:

— PASSENGER COMPARTMENT INTRUSION

1. Windshield Intrusion

a. No windshield contactb. Windshield contact, no damagec. Windshield contact, no intrusiond. Device embedded in windshield,

no significant intrusion

e. Complete intrusion intopassenger compartment

f. Partial intrusion into passengercompartment

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.

21

— VEHICLE AND DEVICE CONDITION

1. Vehicle Damage

a. Noneb. Minor scrapes, scratches or dentsc. Significant cosmetic dents

d. Major dents to grill and bodypanels

e. Major structural damage

2. Windshield Damage

a. Noneb. Minor chip or crack (stress only)c. Broken, no interference

with visibilityd. Broken and shattered, visibility

restricted but remained intact

e. Shattered, remained intact butpartially dislodged

f. Large portion removedg. Completely removed

3. Device Damage

a. Noneb. Superficialc. Substantial, but can be

straightened

d. Substantial, replacement partsneeded for repair

e. Cannot be repaired

CONCLUSIONS

The steel-backed timber guardrail met the required performance criteria specified for testdesignation 3-11 of NCHRP Report 350, as shown in table 1.

22

Table 1. Performance evaluation summary for test 405181-2, NCHRP Report 350 test 3-11.

Test Agency: Texas Transportation Institute Test No.: 405181-2 Test Date: 12/11/2000NCHRP Report 350 Evaluation Criteria Test Results Assessment

Structural AdequacyA. Test article should contain and redirect the vehicle; the

vehicle should not penetrate, underride, or override theinstallation although controlled lateral deflection of thetest article is acceptable.

The steel-backed timber guardrail contained andredirected the 2000P vehicle. The vehicle did notpenetrate, underride, or override the installation.Maximum dynamic deflection was 580 mm.

Pass

Occupant RiskD. Detached elements, fragments, or other debris from the

test article should not penetrate or show potential forpenetrating the occupant compartment, or present anundue hazard to other traffic, pedestrians, or personnelin a work zone. Deformations of, or intrusions into,the occupant compartment that could cause seriousinjuries should not be permitted.

No detached elements, fragments, or other debriswere present to penetrate or to show potential forpenetrating the occupant compartment, or topresent undue hazard to others in the area.Maximum deformation of the occupantcompartment was 88 mm.

Pass

F. The vehicle should remain upright during and aftercollision although moderate roll, pitching, and yawingare acceptable.

The vehicle remained upright during and after thecollision period. Pass

Vehicle TrajectoryK. After collision, it is preferable that the vehicle's

trajectory not intrude into adjacent traffic lanes.The vehicle came to rest 50.3 m downstream ofimpact and in line with the face of the guardrail. Pass*

L. The occupant impact velocity in the longitudinaldirection should not exceed 12 m/s and the occupantridedown acceleration in the longitudinal directionshould not exceed 20 g's.

Longitudinal occupant impact velocity was5.1 m/s and longitudinal ridedown accelerationwas -12.1 g’s. Pass

M. The exit angle from the test article preferably shouldbe less than 60 percent of test impact angle, measuredat time of vehicle loss of contact with test device.

Exit angle at loss of contact with the guardrail was9.5 degrees, which was 39 percent of the impactangle.

Pass*

*Criterion K and M are preferable, not required.

23

APPENDIX A. CRASH TEST PROCEDURES AND DATA ANALYSIS

The crash test and data analysis procedures were in accordance with guidelines presentedin 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 tomeasure 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 back-up biaxialaccelerometer 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 toacceleration. 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 an R-Cal orshunt calibration for the accelerometers and a precision voltage calibration for the ratetransducers. The electronic signals from the accelerometers and rate transducers are transmittedto a base station by means of a 15 channel, constant bandwidth, Inter-Range InstrumentationGroup (I.R.I.G.), FM/FM telemetry link for recording on magnetic tape and for display on a real-time strip chart. Calibration signals, from the test vehicle, are recorded before the test andimmediately afterwards. A crystal controlled time reference signal is simultaneously recordedwith the data. Pressure-sensitive switches on the bumper of the impacting vehicle are actuatedprior to impact by wooden dowels to indicate the elapsed time over a known distance to providea measurement of impact velocity. The initial contact also produces an “event” mark on the datarecord to establish the instant of contact with the installation.

The multiplex of data channels, transmitted on one radio frequency, is received anddemultiplexed onto separate tracks of a 28 track, (I.R.I.G.) tape recorder. After the test, the dataare played back from the tape machine and digitized. A proprietary software program (WinDigit)converts the analog data from each transducer into engineering units using the R-cal and pre-zerovalues at 10,000 samples per second per channel. WinDigit also provides SAE J211 class 180phaseless digital filtering and vehicle impact velocity.

All accelerometers are calibrated annually according to SAE J211 4.6.1 by means of anENDEVCO 2901, precision primary vibration standard. This device and its support instrumentsare 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, usinginstruments with current NIST traceability, and the results factored into the accuracy of the totaldata channel, per SAE J211. Calibrations and evaluations are made any time data are suspect.

24

The Test Risk Assessment Program (TRAP) uses the data from WinDigit to computeoccupant/compartment impact velocities, time of occupant/compartment impact after vehicleimpact, and the highest 10-ms average ridedown acceleration. WinDigit calculates change invehicle velocity at the end of a given impulse period. In addition, maximum averageaccelerations over 50-ms intervals in each of the three directions are computed. For reportingpurposes, the data from the vehicle-mounted accelerometers are filtered with a 60-Hz digitalfilter and acceleration versus time curves for the longitudinal, lateral, and vertical directions areplotted using TRAP.

TRAP uses the data from the yaw, pitch, and roll rate transducers to compute angulardisplacement 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 initialposition and orientation of the vehicle-fixed coordinate system being initial impact.

ANTHROPOMORPHIC DUMMY INSTRUMENTATION

An Alderson Research Laboratories Hybrid II, 50th percentile male anthropomorphicdummy, restrained with lap and shoulder belts, is placed in the driver's position of 820C testvehicles. The dummy is uninstrumented. Use of a dummy in the 2000P vehicle is optionalaccording to NCHRP Report 350 and there was no dummy used in the tests with the 2000Pvehicle.

PHOTOGRAPHIC INSTRUMENTATION AND DATA PROCESSING

Photographic coverage of the test included three high-speed cameras: one overhead witha field of view perpendicular to the ground and directly over the impact point; one placed behindthe installation at an angle; and a third placed to have a field of view parallel to and aligned withthe installation at the downstream end. A flash bulb activated by pressure-sensitive tape switchesis positioned on the impacting vehicle to indicate the instant of contact with the installation andis visible from each camera. The films from these high-speed cameras were analyzed on acomputer-linked Motion Analyzer to observe phenomena occurring during the collision and toobtain event time, displacement, and angular data. A 16-mm movie cine, a BetaCam, a VHS-format video camera, and still cameras were used to document conditions of the test vehicle andinstallation before and after the test.

TEST VEHICLE PROPULSION AND GUIDANCE

The test vehicle was towed into the test installation using a steel cable guidance andreverse tow system. A steel cable for guiding the test vehicle is 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 is connected to the test vehicle, passed around a pulley near the impactpoint, through a pulley on the tow vehicle, and then anchored to the ground so the tow vehicle

25

moves away from the test site. A two-to-one speed ratio between the test and tow vehicle existswith this system. Just prior to impact with the installation, the test vehicle was released to befree-wheeling and unrestrained. The vehicle remains free-wheeling, i.e., no steering or brakinginputs, until the vehicle clears the immediate area of the test site, at which time brakes on thevehicle are activated bringing it to a safe and controlled stop.

27

APPENDIX B. TEST VEHICLE PROPERTIES AND INFORMATION

Figure 10. Vehicle properties for test 405181-2.

28

X1 % X22

'

Table 2. Exterior crush measurements for test 405181-2.

VEHICLE CRUSH MEASUREMENT SHEET1

Complete When Applicable

End Damage Side Damage

Undeformed end width Bowing: B1 X1

Corner shift: A1 B2 X2

A2

End shift at frame (CDC) (check one)

< 4 inches $ 4 inches

Bowing constant

Note: Measure C1 to C6 from Driver to Passenger side in Front or Rear impacts–Rear to Front in Side impacts.

SpecificImpactNumber

Plane* of C-Measurements

Direct Damage

FieldL**

C1 C2 C3 C4 C5 C6 ±DWidth **

(CDC)

Max***

Crush

1 Front bumper 750 380 700 380 350 250 150 70 30 -350

2 700 mm above ground 750 240 940 0 80 N/A N/A N/A 240 +1440

Wheel Well

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, atbeltline, 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 theindividual 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.

Table 3. Occupant compartment measurements for test 405181-2.

29

T r u c kO c c u p a n t C o m p a r t m e n t D e f o r m a t i o n

BEFORE AFTER

A1 867 857

A2 879 879

A3 910 910

B1 1077 1082

B2 1068 980

B3 1070 1070

C1 1378 1367

C2 1255 1255

C3 1375 1375

D1 325 347

D2 159 155

D3 317 317

E1 1597 1600

E2 1593 1623

F 1460 1460

G 1460 1460

H 900 900

I 900 900

J 1529 1480

31

0.000 s

0.188 s

0.281 s

Figure 11. Sequential photographs for test 405181-2(overhead and frontal views).

0.094 s

APPENDIX C. SEQUENTIAL PHOTOGRAPHS

32

0.422 s

0.821 s

1.173 s

Figure 11. Sequential photographs for test 405181-2(overhead and frontal views) (continued).

0.586 s

33

0.000 s

0.188 s

0.281 s

Figure 12. Sequential photographs for test 405181-2(rear view).

0.586 s

0.821 s

1.173 s

0.094 s

0.422 s

35

Figure 13. Vehicular angular displacements for test 405181-2.

APPE

ND

IX D

. VE

HIC

LE

AN

GU

LA

R D

ISPLA

CE

ME

NT

SA

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 1.0-40

-30

-20

-10

0

10

20

30

40

Time (sec)

Ang

les

(deg

rees

)

Test Article: Steel backed timber guardrailTest Vehicle: 1996 Chevrolet 2500 pickup truckInertial Mass: 2000 kgGross Mass: 2075 kgImpact Speed: 98.7 km/hImpact Angle: 24.5 degrees

Roll Pitch Yaw

36

Figure 14. Vehicle longitudinal accelerometer trace for test 405181-2(accelerometer located at center of gravity).

X Acceleration at CG

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-30

-20

-10

0

10

20

30

Time (sec)

Long

itudi

nal A

ccel

erat

ion

(g's

)


SAE Class 60 Filter

37

Figure 15. Vehicle lateral accelerometer trace for test 405181-2(accelerometer located at center of gravity).

Y Acceleration at CG

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-30

-20

-10

0

10

20

30

Time (sec)

Late

ral A

ccel

erat

ion

(g's

)


SAE Class 60 Filter

38

Figure 16. Vehicle vertical accelerometer trace for test 405181-2(accelerometer located at center of gravity).

Z Acceleration at CG

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-30

-20

-10

0

10

20

30

Time (sec)

Vert

ical

Acc

eler

atio

n (g

's)


SAE Class 60 Filter

39

Figure 17. Vehicle longitudinal accelerometer trace for test 405181-2(accelerometer located over rear axle).

X Acceleration Over Rear Axle

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-30

-20

-10

0

10

20

30

Time (sec)

Long

itudi

nal A

ccel

erat

ion

(g's

) Test Article: Steel backed timber guardrailTest Vehicle: 1996 Chevrolet 2500 pickup truckInertial Mass: 2000 kgGross Mass: 2075 kgImpact Speed: 98.7 km/hImpact Angle: 24.5 degrees

SAE Class 60 Filter

40

Figure 18. Vehicle lateral accelerometer trace for test 405181-2(accelerometer located over rear axle).

Y Acceleration Over Rear Axle

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-30

-20

-10

0

10

20

30

Time (sec)

Late

ral A

ccel

erat

ion

(g's

)


SAE Class 60 Filter

41

Figure 19. Vehicle vertical accelerometer trace for test 405181-2(accelerometer located over rear axle).

Z Acceleration Over Rear Axle

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0-30

-20

-10

0

10

20

30

Time (sec)

Vert

ical

Acc

eler

atio

n (g

's)


SAE Class 60 Filter

43

REFERENCES

1. H. E. Ross, Jr., D. L. Sicking, R. A. Zimmer and J. D. Michie, Recommended Proceduresfor the Safety Performance Evaluation of Highway Features, National CooperativeHighway Research Program Report 350, Transportation Research Board, NationalResearch Council, Washington, D.C., 1993.

NCHRP REPORT 350 TEST 3-11 OF THE STEEL-BACKED ......NCHRP Report 350 recommends two crash tests on...

Documents

Transcript of NCHRP REPORT 350 TEST 3-11 OF THE STEEL-BACKED ......NCHRP Report 350 recommends two crash tests on...